Corrosion Rulebook

Table of Contents

Object of the Game
Components
Setup
Overview of the Game's Resources
Playing the Game
Phase 2: Main action
- Play 1 engineer from your hand
- Actions of the starting engineers
Turn your corrosion wheel
Phase 1 and 3: Maintenance
Secondary Actions
- Complete machines
- Perform extra steam actions
Phase 4: End of turn
Example turn: Play 1 engineer from your hand
Example turn: Turn your corrosion wheel
End of the Game
- Additional notes
Overview of the Machines and Engineers
Solo Mode
Credits

Object of the Game

To be successful, you must think carefully about when to deploy your engineers and when to turn your corrosion wheel. Whoever manages this best and scores the most points with their machines and awards wins the game.

Components

1 display board (front: multi-player side; back: solo side)
4 player boards (1 for each player)
4 factory boards (1 for each player)
48 engineer cards:
- 24 starting engineers (4 sets of 6 cards each — sets A, B, C, D)
- 24 qualified engineers
30 chrome machines:
- 12 basic chrome machines
- 18 advanced chrome machines
22 one-shot machines
20 turning machines
16 award tokens (8 with a watch chain, 8 without a watch chain)
8 watch tokens
1 wrench (to mark the active player)
24 chrome gears
24 medium gears
24 small gears
20 water tokens
60 point markers (green: 24 x 1-point, 12 x 2-point, 12 x 3-point, and further denominations)
36 special point markers
1 score pad

Before your first game, attach a corrosion wheel to each factory board with a rivet.

Setup

Below, you can find the setup for 2 to 4 players. For solo mode, see the Solo Mode section.

1 Place the display board, multi-player side up, in the middle of the table and set up the general display:

Shuffle the 18 advanced chrome machines and place them as a refill stack, uncompleted side up, above the refill stacks label in the top left of the display board.
Shuffle the 24 qualified engineers and place them as a face-up refill stack below the refill stacks label in the bottom left of the display board.
Shuffle the 12 basic chrome machines and place them as a refill stack, uncompleted side up, above the advanced chrome machine refill stack.
Shuffle the 22 one-shot machines and place them as a refill stack, uncompleted side up, below the qualified engineer refill stack.
Shuffle the 20 turning machines and place them as a face-up refill stack below the one-shot machine refill stack.

2 From each of these 5 refill stacks, take the top 3 tokens/cards and display them (without turning them over) in a row to the right of their stack, forming 3 columns running through the windows of the display board (windows A, B, C).

3 Depending on the player count, place a number of special point markers directly above the chrome machines as the special point supply:

In a 2-player game, place 22 markers and return the remaining 14 to the box.
In a 3-player game, place 29 markers and return the remaining 7 to the box.
In a 4-player game, place all 36 markers.

Afterwards, add 1 marker from this special point supply to each of the 2 rightmost chrome machines above window C.

4 To the left of the general display, set up the award supply:

Shuffle the 8 award tokens with 'A's on their backs face down. Draw as many as indicated below, and place them face up in a column:

In a 2-player game, display 4 tokens.
In a 3-player game, display 5 tokens.
In a 4-player game, display 6 tokens.

Return the spares to the box.

Then take the other 8 award tokens (with a chain on their front). Find among them the duplicates of the tokens displayed and place each duplicate face up to the left of its match. Return the spares to the box.

5 Shuffle the 8 watch tokens and place a random token face up on the chain of each left award token. Return the spare watch tokens to the box.

6 Each player:

Place a player board in front of you.
In its top right corner, place a factory board. If possible, make sure that on each side of your factory board, there is plenty of free table space (about the size of your palm). Make sure that the X of your corrosion wheel is pointing towards you.
Take the 6 starting engineers of one set (A, B, C or D) and put them in your hand. The starting engineers of each set are identical in their actions and grades. Only their suits are different.

Return any spare player boards, factory boards and sets of starting engineers to the box.

7 In easy reach of all players, set up the general supply of the resources: 24 chrome gears, 24 medium gears, 24 small gears, 20 water tokens, and the green point markers.

8 Each player:

Take 1 chrome gear and 3 green 1-point markers from the general supply and place them above your player board in your reserve.
Take 1 medium gear and 1 small gear and place them onto your factory board in sector 3.
Take 3 water tokens. Place 1 of them in the hot half of your boiler and the other 2 in the cold half.

Note: Your factory board has 4 sectors. Throughout the game, each sector is named according to which quarter of the corrosion wheel is currently in that sector. For example, at the start of the game one quarter marks sector 3 and one marks sector X. This will change whenever you turn your corrosion wheel.

9 Place the score pad ready for later.

10 Determine a starting player (for example, whoever is first to spot a rusty object) and give them the wrench.

Overview of the Game's Resources

The main resources in this game are gears and steam, which are mostly needed to complete one-shot machines and chrome machines. Gears and steam (and point markers) are primarily produced by activating certain machines and performing the actions of engineers.

Steam

Steam is simulated by moving the water tokens in your boiler up and down between its upper hot half and its lower cold half:

Moving a water token up is called generating steam.
Moving it down is called consuming steam.

The most common icons mean:

Generate 1 steam.
Consume 1 steam.
Generate maximum steam — by moving all "cold" water tokens to the hot half of your boiler.
Gain 1 water token from the general supply and add it to the hot half of your boiler.

If you have all your water tokens in the hot half of your boiler, you cannot generate any more steam. If you have all your water tokens in your cold half, you cannot use any actions or effects that consume steam.

One steam icon refers solely to water tokens in the hot half of your boiler.
Another steam icon refers to all of your water tokens, whichever halves they're in.

Small gears and medium gears

Whenever you produce small or medium gears, take them from the general supply and place them directly onto your factory board in sector 3. There is no limit to how many gears you may have in any sector. However, you may never move them from one sector to another.

Whenever you spend small or medium gears (e.g. to complete a machine), return them from any of your sectors to the general supply.

The most common icons mean:

Produce 1 small gear.
Produce 1 medium gear.
Produce 1 small or 1 medium gear.
Produce 2 gears in any mix of small and medium gears.
Spend 1 small gear.
Spend 2 medium gears.
Spend 1 small or 1 medium gear.
Spend 2 gears in any mix of small and medium gears.

Chrome gears

Whenever you produce chrome gears, take them from the general supply and place them in your reserve above your player board. Whenever you spend chrome gears, return them to the general supply. There is no limit to how many chrome gears you may have in your reserve.

The most common icons mean:

Produce 2 chrome gears.
Spend 1 chrome gear.
Produce 1 chrome gear by spending 1 small or 1 medium gear AND consuming 1 steam.

Point markers

There are 2 types of point marker: special point markers and green point markers in different denominations. The special point markers are distinct from the green because when the special point supply runs out, the end phase of the game begins (see End of the Game).

Whenever you gain point markers, place them in your reserve. Whenever you spend green point markers, return them to the general supply. At any time, you may exchange green point markers in your reserve for ones of equal value in the general supply to gain different denominations. However, you may never spend or exchange special point markers.

The most common icons mean:

Gain 3 green points (in any denominations).
Spend 1 green point.
Gain 1 marker from the special point supply.
Gain either 1 marker from the special point supply or 1 green point.

Unlike the special point supply, the general supply is limitless. If you run out of any item there, use something else as a replacement.

Playing the Game

The starting player begins the game by taking a turn. Then play proceeds clockwise with the players taking one turn each until the end phase of the game begins (which happens when the special point supply or the award supply has almost run out — see End of the Game).

At the beginning of your turn, take the wrench from the player on your right and place it in front of you. This is to indicate that you are the active player. Then carry out the following phases in this order:

Phase 1: Maintenance
Phase 2: Main action
Phase 3: Maintenance
Phase 4: End of turn

Phases 1 and 3 are maintenance phases in which you may perform secondary actions and must clear sector X of your factory board (explained in detail below).

Phase 2: Main action

Perform one of these two actions:

EITHER Play 1 engineer from your hand — Playing engineers mostly gains you new machines and qualified engineers. Other players can copy your engineer's action by playing an engineer of a higher grade.

OR Turn your corrosion wheel — Turning your corrosion wheel puts your machines to work and returns engineers to your hand. It also causes old gears and machines to rust.

Each engineer card shows a suit, a grade, and an action.

Play 1 engineer from your hand

Step 1: Choose 1 engineer from your hand, play her face up in front of you and announce her suit and grade. Then perform her action once.

Step 2: Afterwards, in a clockwise direction, each of the other players may choose to copy the action of the engineer that you just played. To copy it, the player must play an engineer from their hand that has the same suit as yours and a higher grade. They place that engineer face up in front of them and perform the action printed on the engineer that you played.

Step 3: Once everyone has had a chance to copy, place your engineer beside your factory board in the sector that corresponds to her grade. Here she waits for her shift to end (which will happen when she's in sector X). If you have multiple engineers in one sector, keep them in an overlapping row, so that you can see their grades. Any player who played an engineer to copy yours places their engineer likewise in their factory (in the sector that corresponds to the grade of their engineer). Afterwards, proceed to your phase 3 ("Maintenance").

There are three main suits: blue, green and orange. In addition, there is a gray suit and a wild suit among the qualified engineers. An engineer of the wild suit can be played to copy the action of a lower-grade engineer of any of the three main suits but not of the gray one.
Conversely, if you play an engineer of the wild suit on your turn, the other players can copy her action with a higher-grade engineer of any of the three main suits or the wild suit.
The grade 4+ engineer is considered the highest-grade engineer and thus can copy grade 4 engineers.
Played engineers of grade 4 or 4+ must be placed in sector X. Turn them upside-down to show that they have not yet ended their shift. When the X of your corrosion wheel leaves their sector, turn them upright again.

Actions of the starting engineers

Hire a qualified engineer: From the general display, choose 1 of the three qualified engineers below windows A, B, C and put her in your hand. Then refill the empty spot by sliding any cards on its left one spot to the right and placing the top card of the refill stack below window A.

Attention: Hiring an engineer of grade 4 or 4+ has an additional cost of 1 point (green!) AND 1 steam. If you cannot pay that cost, you cannot hire her.

Build a one-shot machine: From the general display, choose 1 of the three one-shot machines below windows A, B, C and place it, uncompleted side up, in its slot in your sector 3. Then refill the empty spot by sliding any one-shot machines on its left one spot to the right and placing the top token of the refill stack in the vacant spot below window A.

If you have several one-shot machines in one sector, line them up in a row. There is no limit to how many you may have.
One-shot machines have their name because they can only be activated once (when they reach sector X). But you will only be able to activate a one-shot machine if you manage to complete it first (see "Complete machines").

Build a turning machine: From the general display, choose 1 of the three turning machines below windows A, B, C and place it face up in its slot in your sector 3. Then refill the empty spot by sliding any turning machines on its left one spot to the right and placing the top token of the refill stack in the vacant spot below window A.

If you have several turning machines in one sector, line them up in a row. There is no limit to how many you may have.
Turning machines are already completed when you build them. You can activate them whenever you turn your corrosion wheel.

Build a chrome machine: From the general display, choose 1 of the six chrome machines above windows A, B, C and take it. If you choose either of the machines above window C, also take all special point markers on that machine and place them in your reserve.

Place the machine itself, uncompleted side up, on your player board: either in your free storage spot or on the drive space of its type. The 3 types of drive space are cog-wheel drive, piston drive, and chain drive. If there is already a machine or a stack of machines on that drive space, place the new machine on top of them. You are not allowed to change the order of the stacked-up machines on any of your drive spaces.

After placing the chrome machine, refill the empty spot in the general display by sliding any chrome machines on its left one spot to the right and placing the top chrome machine of the refill stack in the vacant spot above window A. Afterwards, add 1 marker from the special point supply to the rightmost chrome machine (above window C) of that row.

Your storage spot: To the left of your player board, you have a storage spot for one uncompleted chrome machine. If this storage spot is unoccupied when you build a new chrome machine, you can place it here. If it is occupied, you can vacate it at any time by moving the occupying uncompleted machine (without flipping it over) to the matching drive space on your player board, covering any machines below it. Once a chrome machine has entered its drive space, it remains there for the rest of the game.

Generate up to 2 steam.

Produce 1 small or 1 medium gear. (Whoever copies this action has the same choice between 1 small and 1 medium gear, of course.)

You can find an overview of the engineers in the Engineers section.

Turn your corrosion wheel

Turn your corrosion wheel 90 degrees clockwise. This switches on all of the following machines:

Your turning machines, whichever sectors they're in.
Your completed one-shot machines in sector X.
Your visible completed chrome machines showing the "turn corrosion wheel" icon.
Your visible prototype machines, but only if sector X is at the bottom, i.e. the X of the corrosion wheel is pointing towards you.

Prototype machines are printed on your player board. The visible ones are switched on whenever the X of the corrosion wheel is turned to the bottom sector.

Now, in the order of your choice, activate each of these switched-on machines once (i.e. use its effect).

At any time between these activations, you may complete any of your uncompleted one-shot machines and chrome machines (see "Complete machines"). If this includes one-shot machines in sector X or chrome machines with the "turn corrosion wheel" symbol, they are immediately switched on as well and thus can be activated in this phase. You cannot use "extra steam actions" (see "Perform extra steam actions") in this phase.

You may forfeit any activations that you cannot or do not want to use during this phase.

Exception: Whenever the "special point" prototype machine is switched on, you must activate it (gain 1 marker from the special point supply).

Attention: If a chrome machine says "at end of turn", it cannot be activated during the main action but only in phase 4 of that turn (see Phase 4: End of turn).

Once you've activated all the switched-on machines that you wanted once, proceed to phase 3 ("Maintenance").

Phase 1 and 3: Maintenance

Step 1: First, you may perform as many secondary actions as you want and can afford in the order of your choice (see Secondary Actions for the types).

Step 2: Afterwards, check if your sector X is empty. If it is not, you must immediately clear it (as its machines and gears have rusted and its engineers have ended their shifts):

a Discard any one-shot machines from sector X, completed side up, onto the one-shot machine discard pile of the general display (whether or not those machines have been completed and whether or not they've been activated).
b Discard any turning machines from sector X face down onto the turning machine discard pile of the general display.
c Return any gears from sector X to the general supply.
d Return any engineers from sector X to your hand. Exception: Engineers that have a grade of 4 or 4+ remain in this sector if the X of the corrosion wheel has not left it since they were placed here (they should be upside-down to mark this). They will only end their shift once all quarters of the corrosion wheel have passed them.

Secondary Actions

Complete machines

Chrome machines and one-shot machines are uncompleted when you build them. In order to activate them, you must complete them first by means of this action.

To complete one of your chrome machines, it must be either in your storage spot or on top of its drive space. Pay the gears shown at the top of its uncompleted side. Then flip it and place it on top of its matching drive space (if it's not there already), covering up any machines below it. The effects of covered machines cannot be used for the rest of the game. However, at the end of the game, you will get the points printed at the top of each completed chrome machine.

To complete one of your one-shot machines, pay the cost printed at the top of its uncompleted side. This cost may include:

Spending gears.
Consuming steam.
Discarding 1 qualified engineer face down to the engineer discard pile of the general display. This engineer can either come from your hand or any sector of your factory.

After paying the cost, flip the one-shot machine. It can be activated when it enters sector X.

Perform extra steam actions

There are 2 types of extra steam actions:

Discard an item from the general display: Consume 1 steam and choose the engineer OR the one-shot machine OR the turning machine below window C and discard it to its discard pile. Then refill the empty spot by sliding the items on its left one spot to the right and placing the top item of its refill stack in the vacant spot below window A.

Speed up an item in your factory: Consume 1 steam and move 1 of your engineers OR 1 of your one-shot machines (completed or uncompleted) OR 1 of your turning machines to the next sector in a counter-clockwise direction. If it is already in sector X, you cannot move it. Moving it has no further effect except in the following cases:

Whenever you move a turning machine, immediately activate it once.
Whenever you move a completed one-shot machine to sector X, immediately activate it once.

Note: You only carry out maintenance on your own turns, never on other players' turns.

Phase 4: End of turn

You may now activate any "end of turn" chrome machines that you switched on in your main action phase. To do so, pay any costs and perform their additional action (turning the corrosion wheel or playing an engineer). This is done in the same way as in the main action phase and is then followed by another maintenance phase.

Attention: These "end of turn" actions are considered additional actions, not main actions — so you cannot perform them in an infinite loop. However, if you have both of these completed chrome machines, you may activate them one after the other in the order of your choice (with a maintenance phase between them).

Once you have completely finished your turn, pass the wrench to the player on your left.

Example turn: Play 1 engineer from your hand

1) Maintenance

a First, you choose to perform an extra steam action by consuming 1 steam and moving the orange engineer from sector 1 to sector X.
b Afterwards, you clear sector X by returning the orange engineer to your hand.

2) Main action

Step 1:

c You play the orange engineer (that you just returned to your hand) in front of you and
d perform her action by taking the chrome machine above window C along with the 2 special point markers on it.
e You place the points in your reserve and the chrome machine in your storage spot.
f Then you refill the display and
g add a marker from the special point supply to the now rightmost chrome machine of that row.

Step 2:

In a clockwise direction, each of the other players may now copy your engineer's action: The player to your left does not want to copy.

h The third player chooses to copy the action by playing an orange engineer of grade 4.
i That player takes the chrome machine above window B from the top row,
j then refills the display and
k adds a marker from the special point supply to the rightmost chrome machine of that row.

The fourth player does not want to copy either.

Step 3:

As your engineer has a grade of 3, you place her in your sector 3. The third player places their grade 4 engineer in their sector X (and turns her upside-down to mark that she has not ended her shift yet).

3) Maintenance

Since you do not want to perform any secondary actions and your sector X is empty, you skip maintenance.

4) End of turn

You end your turn by passing the wrench to the player on your left.

Example turn: Turn your corrosion wheel

1) Maintenance

a First, you choose to perform an extra steam action by consuming 1 steam and moving a turning machine from sector 2 to sector 1.
b This produces a medium gear that you place in sector 3.

Since sector X is empty, you don't need to clear it.

2) Main action

c You turn your corrosion wheel.
d First, you choose to activate your turning machine, which produces 1 medium gear
e that you place in sector 3.

Since the X of your corrosion wheel is in your bottom sector, you then choose to activate each of your visible prototype machines:

f You produce 1 small gear,
g 1 medium gear and
h gain a marker from the special point supply.
i Then you choose to complete the chrome machine in your storage spot by paying its cost (2 medium gears, 2 small gears and 1 chrome gear).
j You flip that chrome machine and place it onto its drive space. Since you're still in the phase in which you turned your corrosion wheel, this machine is also immediately switched on. So you choose to activate it (generating 1 steam).

3) Maintenance

k You choose to complete the one-shot machine in sector 2, which costs your remaining gears.
l Then you choose to perform two extra steam actions by consuming 2 steam and moving that one-shot machine from sector 2 to sector X, where you immediately activate it once (gaining 3 points and adding a water token to your boiler).

Afterwards, you clear sector X by discarding the turning machine and the one-shot machine.

4) End of turn

You end your turn by passing the wrench to the player on your left.

End of the Game

The end phase of the game begins when at the end of any player's turn one or both of the following conditions are met:

There are 3 or fewer markers left in the special point supply.
There are 3 or fewer award tokens left in the award supply.

In the end phase, play proceeds clockwise as before. However, on each of your turns, you must decide whether you want to:

a) take that turn as usual, OR b) pass for good.

Taking your turn as usual costs green points from your reserve. Your first turn in the end phase costs 1 point, your second costs 2 and your third costs 3. Once you've taken 3 turns, you must pass for good on your next turn.

When you pass for good, carry out one more maintenance phase (but no main action). Afterwards, your turn is skipped for the rest of the end phase and you are not allowed to copy engineer's actions.

Once all players have passed for good, the game ends. Now, take the score pad and carry out the final scoring:

First, any player may spend spare chrome gears: For every 2 chrome gears that you return from your reserve to the general supply, gain 1 green point.

Then, on the score pad, tally each player's score in the following categories:

Sum the values of the point markers in your reserve (special and green combined).
Take all chrome machines from your player board and line them up in front of you without flipping them over. Sum the points at the top of each completed chrome machine.
Sum the points you get from any award tokens you have collected during the game.

Finally, total the points of the 3 categories. Whoever has the most points wins the game. In the case of a tie, the tied player who has more special point markers wins. If there is still a tie, the victory is shared.

Additional notes

Whenever you must refill a vacant spot below window A but the refill stack is empty, shuffle the corresponding discard pile and place it as the new refill stack. Then refill the vacant spot.
In the unlikely case that there is no discard pile, any vacant spots remain empty. Refill them immediately as soon as any new discards become available.
If either of the chrome machine refill stacks run out, refill the vacant spot with a chrome machine from the other chrome machine stack.
If the special point supply runs out during the end phase of the game, use green 1-point markers from the general supply instead.

Overview of the Machines and Engineers

One-shot machines

There are 12 types of one-shot machine (for icons that are not explained here, see the resource overview):

(1x) Gain 1 green point. Then move to any of your sectors: any number of your turning machines, any number of your uncompleted one-shot machines, and any number of your completed one-shot machines that you have not yet activated. If you move completed one-shot machines to sector X, activate them immediately (in any order). You do not activate turning machines when you move them.
(1x) Go through the discard piles of the general display and choose 1 item from them. If it's an engineer, put her in your hand. (Pay the usual additional cost if she's an engineer of grade 4/4+.) If it's a one-shot or turning machine, place it in sector 3 as usual.
(2x) Complete one of your uncompleted chrome or one-shot machines free of charge.
(1x) Gain 3 green points. Then return all your engineers from your factory board to your hand.
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 2 green points for each of your completed one-shot machines (including this one).
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 2 green points for each different type of turning machine in your factory.
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 1 point for each water token in the hot half of your boiler.
(1x) Produce as many gears (in any mix of small and medium) as you have water tokens in your entire boiler.
(6x) Choose one of the award tokens in the award supply and place it face up in front of you. If there is a watch token attached to it, take it too and use its effect immediately. Then discard the watch token to the game box.

Award tokens give you points during the final scoring depending on how well you have fulfilled their tasks. There is no limit to the number of award tokens you can collect. You can have tokens with identical tasks. Both will give you their points when scored. There are 8 tasks.

There are 4 types of watch token (for their effects, see the resource overview): 2x, 2x, 2x, 2x.

Turning machines

There are 4 types of turning machine (for their effects, see the resource overview): 6x, 6x, 5x, 3x.

Chrome machines

You can only use the effects of chrome machines that are both completed and visible. As soon as you cover a chrome machine, its effect is immediately lost for the rest of the game. (For the effects of icons that are not explained here, see the resource overview.)

Whenever you play your engineer of grade 1 or a qualified engineer of grade 2 (even when you use it to copy), produce 1 small or 1 medium gear.
Whenever you play an engineer of grade 2 (even when you use it to copy), generate 1 steam.
This applies whenever you play an engineer (even when you use it to copy). For example, engineers of grade 4 are placed in sector 3, your engineer of grade 1 in sector X.
Whenever you build a turning machine, immediately activate its effect once. Then place it in sector 3 as usual.
(Grade doubler) For example, if you use this engineer's action, you can consume 2 steam to produce 6 gears. This does not apply to the gray engineer of grade 3.
Whenever you complete a chrome machine, generate maximum steam. (This does not apply to this machine itself.)
Whenever you complete a one-shot machine, you may immediately move it to sector X (if it's not already there), activate it once and gain 1 green point.
Whenever you complete a one-shot machine, gain 2 green points.
Whenever you complete a chrome machine, gain 3 green points. (This does not apply to this machine itself.)
Whenever you hire a qualified engineer, you may take the one on top of the refill stack instead of any of those below the windows (paying the usual cost if it's an engineer of grade 4/4+). Whenever you build a machine, you may take the one on top of its refill stack instead of any of those above/below the windows. If you take the top machine of a chrome machine stack, don't forget to add a special point marker to the rightmost chrome machine of that row.
This machine is switched on whenever you play your engineer of grade 1 or a qualified engineer of grade 2 as your main action. At the end of that turn, you may turn your corrosion wheel and proceed as you do when you turn it as your main action (see "Turn your corrosion wheel"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).

The following chrome machines modify copy effects:

For example, if a player plays an orange engineer of grade 2, you can copy that engineer's action by playing a grade 3 (or 4) engineer of the blue, green, orange, gray or wild suit.
For example, if a player plays an orange engineer of grade 2, you can copy that engineer's action by playing an orange engineer of grade 2.
For example, if a player plays an orange engineer of grade 4, you can copy that engineer's action by playing an orange engineer of grade 2 and an orange engineer of grade 3. Each of these engineers then goes to the sector that corresponds to her grade.

Naturally, you can use all of these copy effects in combination.

The following chrome machines reduce completion costs:

Whenever you pay the cost of a chrome machine while completing it, that cost is reduced by 1 chrome gear.
Whenever you pay the cost of a one-shot or chrome machine while completing it, that cost is reduced by up to 2 medium gears. This reduction also applies to machines with a steam cost.
Whenever you pay the cost of a one-shot or chrome machine while completing it, that cost is reduced by up to 2 small gears. This reduction also applies to machines with a steam cost.

All of the following completed chrome machines are switched on whenever you turn your corrosion wheel (see "Turn your corrosion wheel"):

You may activate once more up to two separate turning machines that you have already activated this phase.
If there are at least 2 engineers of grade 2 in your sector X, you may consume 1 steam to gain 3 green points.
At the end of your turn, you may consume 1 steam to turn your corrosion wheel again. Proceed in the same way as in your main action (see "Turn your corrosion wheel"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).
At the end of your turn, you may consume 1 steam to play 1 engineer from your hand. Proceed as though you had played her as your main action (see "Play 1 engineer from your hand"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).

Engineers

For icons that are not explained here, see the resource overview and the main action rules. There are starting engineers (sets A, B, C, D) and qualified engineers.

Some qualified engineer actions:

Without actually turning the corrosion wheel, activate any of your turning machines and visible completed chrome machines in any order as though you had, following the rules described in "Turn your corrosion wheel". (This includes being able to complete machines in between.) One-shot machines and prototype machines cannot be activated this way.
Move any number of your one-shot machines (completed and/or uncompleted) to any sectors of your factory board. If you move completed one-shot machines to sector X, activate them immediately (in any order).
Return up to 2 engineers from any of your sectors to your hand. (You cannot return this one.)
Build either a turning machine or a one-shot machine. (Whoever copies this action does not have to build the same type of machine, of course.)

Solo Mode

Hello! Do you want to play Corrosion alone? I'm happy to step in as your opponent.

Setup

Set the game up as described in the Setup section, making the following changes during these steps:

1 Place the display board with the solo side up.

3 Place all 36 special point markers in the special point supply.

4 In the award supply, display 3 random award tokens and their duplicates. Then take from the remaining award tokens one with an 'A' on its back, one with a 'B' on its back and one with a 'C' on its back. Place these face down in front of the three award rows to mark them as rows A, B, C. Return the rest to the game box.

6 Take the cards of set D and put them in your hand as your starting engineers. Then shuffle the 18 cards of sets A, B and C to form a combined deck. Place this deck face down to the right of the display board as my draw deck. Then flip the top card and place it face up beside it. This is my discard pile.

Playing the game

You and I take alternating turns. You are the starting player. Carry out your turn as usual (the only difference is that I will never copy your engineers' actions).

When it is my turn, carry out these steps for me in this order:

1) Flip 2 cards

Flip the top card of my draw deck and place it face up on my discard pile. Then flip the next card of my draw deck and place it also face up on my discard pile. That second card is my action card.

2) Perform my discard action

According to the icon shown on my action card, remove an item from the general display:

Remove the engineer/one-shot machine/turning machine from below the window that matches the letter on top of my draw deck. Discard that engineer/machine to its discard pile in the display. Then refill the display as usual.

There is one exception: If you remove this type of one-shot machine, place it, completed side up, below my draw deck. Take 5 water tokens from the supply and place them onto that one-shot machine. (This is to track when an award token will be removed from the award supply — see step 4.)

Remove a chrome machine from the display, according to the letter and arrow shown on top of my draw deck:

If it's an up arrow, remove the upper chrome machine from above the window of the matching letter.
If it's a down arrow, remove the lower chrome machine from above the window of the matching letter.

Discard the chrome machine to the game box, along with any special point markers on it. Then refill the display as usual (including placing a special point marker on the rightmost chrome machine).

If it is either of the two "no discard" icons, nothing is discarded.

3) Copy the action of my action card

Next, you may choose to copy the actual printed action of my action card, following the usual rules in "Play 1 engineer from your hand".

4) Check for award token removal

If there are any of these one-shot machines below my draw deck, return 1 water token from each of them to the general supply. Whenever you remove the last water token from such a one-shot machine, discard that machine to its discard pile in the display and immediately do the following:

Remove from the award supply the leftmost face-up award token in the row that matches the letter on top of my draw deck. Discard that award token to the game box, along with any watch token attached to it.

If that row is already empty, check the arrow on top of my draw deck: If it's an up arrow, remove the leftmost award token from the remaining row that is farther up. If it's a down arrow, remove the leftmost award token from the remaining row that is farther down.
If there is only one row left, remove the leftmost token from it.
If all award tokens are gone, this type of one-shot machine has no effect any more.

Then it's your turn again.

Note: Whenever my draw deck runs out (which happens every nine turns when flipping the first card), mark this by placing a water token from the supply onto the leftmost free reshuffle space in the upper right corner of the display board. Then shuffle my discard pile and place it as my new draw deck. Flip its top card as the second card of this turn to form my new discard pile. Then proceed as usual.

End of the game

The end phase of the game begins when my draw deck runs out for the 4th time. Reshuffle the deck one last time and finish my turn as usual. Then proceed with your turn as described in the End of the Game rules (spend points or pass for good). If you choose to carry out your turn as usual, also carry out my turn afterwards and so on. When you finally pass for good, the game ends.

Tally your score as usual. How well did you do?

Less than 30 points — Sorry! I'm sure you can do much better.
30+ points — It seems you are still a little rusty. Try again!
50+ points — Satisfactory! That was pretty good.
70+ points — Now we're talking business! Nice job!
90+ points — What an unbelievable feat! You should be named "Business Person of the Year"!
100+ points — This is the kind of entrepreneurial spirit that legends are made of.

Credits

Game design: Stefan Bauer. Artwork: Dennis Lohausen. Development: Viktor Kobilke, Peter Eggert. Editing, rule book and rule book layout: Viktor Kobilke. Rule book revision: Neil Crowley.

Corrosion Rulebook

Table of Contents

Object of the Game
Components
Setup
Overview of the Game's Resources
Playing the Game
Phase 2: Main action
- Play 1 engineer from your hand
- Actions of the starting engineers
Turn your corrosion wheel
Phase 1 and 3: Maintenance
Secondary Actions
- Complete machines
- Perform extra steam actions
Phase 4: End of turn
Example turn: Play 1 engineer from your hand
Example turn: Turn your corrosion wheel
End of the Game
- Additional notes
Overview of the Machines and Engineers
Solo Mode
Credits

Object of the Game

Components

1 display board (front: multi-player side; back: solo side)
4 player boards (1 for each player)
4 factory boards (1 for each player)
48 engineer cards:
- 24 starting engineers (4 sets of 6 cards each — sets A, B, C, D)
- 24 qualified engineers
30 chrome machines:
- 12 basic chrome machines
- 18 advanced chrome machines
22 one-shot machines
20 turning machines
16 award tokens (8 with a watch chain, 8 without a watch chain)
8 watch tokens
1 wrench (to mark the active player)
24 chrome gears
24 medium gears
24 small gears
20 water tokens
60 point markers (green: 24 x 1-point, 12 x 2-point, 12 x 3-point, and further denominations)
36 special point markers
1 score pad

Before your first game, attach a corrosion wheel to each factory board with a rivet.

Setup

Below, you can find the setup for 2 to 4 players. For solo mode, see the Solo Mode section.

1 Place the display board, multi-player side up, in the middle of the table and set up the general display:

Shuffle the 18 advanced chrome machines and place them as a refill stack, uncompleted side up, above the refill stacks label in the top left of the display board.
Shuffle the 24 qualified engineers and place them as a face-up refill stack below the refill stacks label in the bottom left of the display board.
Shuffle the 12 basic chrome machines and place them as a refill stack, uncompleted side up, above the advanced chrome machine refill stack.
Shuffle the 22 one-shot machines and place them as a refill stack, uncompleted side up, below the qualified engineer refill stack.
Shuffle the 20 turning machines and place them as a face-up refill stack below the one-shot machine refill stack.

3 Depending on the player count, place a number of special point markers directly above the chrome machines as the special point supply:

In a 2-player game, place 22 markers and return the remaining 14 to the box.
In a 3-player game, place 29 markers and return the remaining 7 to the box.
In a 4-player game, place all 36 markers.

Afterwards, add 1 marker from this special point supply to each of the 2 rightmost chrome machines above window C.

4 To the left of the general display, set up the award supply:

Shuffle the 8 award tokens with 'A's on their backs face down. Draw as many as indicated below, and place them face up in a column:

In a 2-player game, display 4 tokens.
In a 3-player game, display 5 tokens.
In a 4-player game, display 6 tokens.

Return the spares to the box.

5 Shuffle the 8 watch tokens and place a random token face up on the chain of each left award token. Return the spare watch tokens to the box.

6 Each player:

Place a player board in front of you.
In its top right corner, place a factory board. If possible, make sure that on each side of your factory board, there is plenty of free table space (about the size of your palm). Make sure that the X of your corrosion wheel is pointing towards you.
Take the 6 starting engineers of one set (A, B, C or D) and put them in your hand. The starting engineers of each set are identical in their actions and grades. Only their suits are different.

Return any spare player boards, factory boards and sets of starting engineers to the box.

7 In easy reach of all players, set up the general supply of the resources: 24 chrome gears, 24 medium gears, 24 small gears, 20 water tokens, and the green point markers.

8 Each player:

Take 1 chrome gear and 3 green 1-point markers from the general supply and place them above your player board in your reserve.
Take 1 medium gear and 1 small gear and place them onto your factory board in sector 3.
Take 3 water tokens. Place 1 of them in the hot half of your boiler and the other 2 in the cold half.

9 Place the score pad ready for later.

10 Determine a starting player (for example, whoever is first to spot a rusty object) and give them the wrench.

Overview of the Game's Resources

Steam

Steam is simulated by moving the water tokens in your boiler up and down between its upper hot half and its lower cold half:

Moving a water token up is called generating steam.
Moving it down is called consuming steam.

The most common icons mean:

Generate 1 steam.
Consume 1 steam.
Generate maximum steam — by moving all "cold" water tokens to the hot half of your boiler.
Gain 1 water token from the general supply and add it to the hot half of your boiler.

One steam icon refers solely to water tokens in the hot half of your boiler.
Another steam icon refers to all of your water tokens, whichever halves they're in.

Small gears and medium gears

Whenever you spend small or medium gears (e.g. to complete a machine), return them from any of your sectors to the general supply.

The most common icons mean:

Produce 1 small gear.
Produce 1 medium gear.
Produce 1 small or 1 medium gear.
Produce 2 gears in any mix of small and medium gears.
Spend 1 small gear.
Spend 2 medium gears.
Spend 1 small or 1 medium gear.
Spend 2 gears in any mix of small and medium gears.

Chrome gears

The most common icons mean:

Produce 2 chrome gears.
Spend 1 chrome gear.
Produce 1 chrome gear by spending 1 small or 1 medium gear AND consuming 1 steam.

Point markers

The most common icons mean:

Gain 3 green points (in any denominations).
Spend 1 green point.
Gain 1 marker from the special point supply.
Gain either 1 marker from the special point supply or 1 green point.

Unlike the special point supply, the general supply is limitless. If you run out of any item there, use something else as a replacement.

Playing the Game

Phase 1: Maintenance
Phase 2: Main action
Phase 3: Maintenance
Phase 4: End of turn

Phases 1 and 3 are maintenance phases in which you may perform secondary actions and must clear sector X of your factory board (explained in detail below).

Phase 2: Main action

Perform one of these two actions:

OR Turn your corrosion wheel — Turning your corrosion wheel puts your machines to work and returns engineers to your hand. It also causes old gears and machines to rust.

Each engineer card shows a suit, a grade, and an action.

Play 1 engineer from your hand

Step 1: Choose 1 engineer from your hand, play her face up in front of you and announce her suit and grade. Then perform her action once.

There are three main suits: blue, green and orange. In addition, there is a gray suit and a wild suit among the qualified engineers. An engineer of the wild suit can be played to copy the action of a lower-grade engineer of any of the three main suits but not of the gray one.
Conversely, if you play an engineer of the wild suit on your turn, the other players can copy her action with a higher-grade engineer of any of the three main suits or the wild suit.
The grade 4+ engineer is considered the highest-grade engineer and thus can copy grade 4 engineers.
Played engineers of grade 4 or 4+ must be placed in sector X. Turn them upside-down to show that they have not yet ended their shift. When the X of your corrosion wheel leaves their sector, turn them upright again.

Actions of the starting engineers

Attention: Hiring an engineer of grade 4 or 4+ has an additional cost of 1 point (green!) AND 1 steam. If you cannot pay that cost, you cannot hire her.

If you have several one-shot machines in one sector, line them up in a row. There is no limit to how many you may have.
One-shot machines have their name because they can only be activated once (when they reach sector X). But you will only be able to activate a one-shot machine if you manage to complete it first (see "Complete machines").

If you have several turning machines in one sector, line them up in a row. There is no limit to how many you may have.
Turning machines are already completed when you build them. You can activate them whenever you turn your corrosion wheel.

Your storage spot: To the left of your player board, you have a storage spot for one uncompleted chrome machine. If this storage spot is unoccupied when you build a new chrome machine, you can place it here. If it is occupied, you can vacate it at any time by moving the occupying uncompleted machine (without flipping it over) to the matching drive space on your player board, covering any machines below it. Once a chrome machine has entered its drive space, it remains there for the rest of the game.

Generate up to 2 steam.

Produce 1 small or 1 medium gear. (Whoever copies this action has the same choice between 1 small and 1 medium gear, of course.)

You can find an overview of the engineers in the Engineers section.

Turn your corrosion wheel

Turn your corrosion wheel 90 degrees clockwise. This switches on all of the following machines:

Your turning machines, whichever sectors they're in.
Your completed one-shot machines in sector X.
Your visible completed chrome machines showing the "turn corrosion wheel" icon.
Your visible prototype machines, but only if sector X is at the bottom, i.e. the X of the corrosion wheel is pointing towards you.

Prototype machines are printed on your player board. The visible ones are switched on whenever the X of the corrosion wheel is turned to the bottom sector.

Now, in the order of your choice, activate each of these switched-on machines once (i.e. use its effect).

You may forfeit any activations that you cannot or do not want to use during this phase.

Exception: Whenever the "special point" prototype machine is switched on, you must activate it (gain 1 marker from the special point supply).

Attention: If a chrome machine says "at end of turn", it cannot be activated during the main action but only in phase 4 of that turn (see Phase 4: End of turn).

Once you've activated all the switched-on machines that you wanted once, proceed to phase 3 ("Maintenance").

Phase 1 and 3: Maintenance

Step 1: First, you may perform as many secondary actions as you want and can afford in the order of your choice (see Secondary Actions for the types).

Step 2: Afterwards, check if your sector X is empty. If it is not, you must immediately clear it (as its machines and gears have rusted and its engineers have ended their shifts):

a Discard any one-shot machines from sector X, completed side up, onto the one-shot machine discard pile of the general display (whether or not those machines have been completed and whether or not they've been activated).
b Discard any turning machines from sector X face down onto the turning machine discard pile of the general display.
c Return any gears from sector X to the general supply.
d Return any engineers from sector X to your hand. Exception: Engineers that have a grade of 4 or 4+ remain in this sector if the X of the corrosion wheel has not left it since they were placed here (they should be upside-down to mark this). They will only end their shift once all quarters of the corrosion wheel have passed them.

Secondary Actions

Complete machines

Chrome machines and one-shot machines are uncompleted when you build them. In order to activate them, you must complete them first by means of this action.

To complete one of your one-shot machines, pay the cost printed at the top of its uncompleted side. This cost may include:

Spending gears.
Consuming steam.
Discarding 1 qualified engineer face down to the engineer discard pile of the general display. This engineer can either come from your hand or any sector of your factory.

After paying the cost, flip the one-shot machine. It can be activated when it enters sector X.

Perform extra steam actions

There are 2 types of extra steam actions:

Whenever you move a turning machine, immediately activate it once.
Whenever you move a completed one-shot machine to sector X, immediately activate it once.

Note: You only carry out maintenance on your own turns, never on other players' turns.

Phase 4: End of turn

Attention: These "end of turn" actions are considered additional actions, not main actions — so you cannot perform them in an infinite loop. However, if you have both of these completed chrome machines, you may activate them one after the other in the order of your choice (with a maintenance phase between them).

Once you have completely finished your turn, pass the wrench to the player on your left.

Example turn: Play 1 engineer from your hand

1) Maintenance

a First, you choose to perform an extra steam action by consuming 1 steam and moving the orange engineer from sector 1 to sector X.
b Afterwards, you clear sector X by returning the orange engineer to your hand.

2) Main action

Step 1:

c You play the orange engineer (that you just returned to your hand) in front of you and
d perform her action by taking the chrome machine above window C along with the 2 special point markers on it.
e You place the points in your reserve and the chrome machine in your storage spot.
f Then you refill the display and
g add a marker from the special point supply to the now rightmost chrome machine of that row.

Step 2:

In a clockwise direction, each of the other players may now copy your engineer's action: The player to your left does not want to copy.

h The third player chooses to copy the action by playing an orange engineer of grade 4.
i That player takes the chrome machine above window B from the top row,
j then refills the display and
k adds a marker from the special point supply to the rightmost chrome machine of that row.

The fourth player does not want to copy either.

Step 3:

3) Maintenance

Since you do not want to perform any secondary actions and your sector X is empty, you skip maintenance.

4) End of turn

You end your turn by passing the wrench to the player on your left.

Example turn: Turn your corrosion wheel

1) Maintenance

a First, you choose to perform an extra steam action by consuming 1 steam and moving a turning machine from sector 2 to sector 1.
b This produces a medium gear that you place in sector 3.

Since sector X is empty, you don't need to clear it.

2) Main action

c You turn your corrosion wheel.
d First, you choose to activate your turning machine, which produces 1 medium gear
e that you place in sector 3.

Since the X of your corrosion wheel is in your bottom sector, you then choose to activate each of your visible prototype machines:

f You produce 1 small gear,
g 1 medium gear and
h gain a marker from the special point supply.
i Then you choose to complete the chrome machine in your storage spot by paying its cost (2 medium gears, 2 small gears and 1 chrome gear).
j You flip that chrome machine and place it onto its drive space. Since you're still in the phase in which you turned your corrosion wheel, this machine is also immediately switched on. So you choose to activate it (generating 1 steam).

3) Maintenance

k You choose to complete the one-shot machine in sector 2, which costs your remaining gears.
l Then you choose to perform two extra steam actions by consuming 2 steam and moving that one-shot machine from sector 2 to sector X, where you immediately activate it once (gaining 3 points and adding a water token to your boiler).

Afterwards, you clear sector X by discarding the turning machine and the one-shot machine.

4) End of turn

You end your turn by passing the wrench to the player on your left.

End of the Game

The end phase of the game begins when at the end of any player's turn one or both of the following conditions are met:

There are 3 or fewer markers left in the special point supply.
There are 3 or fewer award tokens left in the award supply.

In the end phase, play proceeds clockwise as before. However, on each of your turns, you must decide whether you want to:

a) take that turn as usual, OR b) pass for good.

When you pass for good, carry out one more maintenance phase (but no main action). Afterwards, your turn is skipped for the rest of the end phase and you are not allowed to copy engineer's actions.

Once all players have passed for good, the game ends. Now, take the score pad and carry out the final scoring:

First, any player may spend spare chrome gears: For every 2 chrome gears that you return from your reserve to the general supply, gain 1 green point.

Then, on the score pad, tally each player's score in the following categories:

Sum the values of the point markers in your reserve (special and green combined).
Take all chrome machines from your player board and line them up in front of you without flipping them over. Sum the points at the top of each completed chrome machine.
Sum the points you get from any award tokens you have collected during the game.

Additional notes

Whenever you must refill a vacant spot below window A but the refill stack is empty, shuffle the corresponding discard pile and place it as the new refill stack. Then refill the vacant spot.
In the unlikely case that there is no discard pile, any vacant spots remain empty. Refill them immediately as soon as any new discards become available.
If either of the chrome machine refill stacks run out, refill the vacant spot with a chrome machine from the other chrome machine stack.
If the special point supply runs out during the end phase of the game, use green 1-point markers from the general supply instead.

Overview of the Machines and Engineers

One-shot machines

There are 12 types of one-shot machine (for icons that are not explained here, see the resource overview):

(1x) Gain 1 green point. Then move to any of your sectors: any number of your turning machines, any number of your uncompleted one-shot machines, and any number of your completed one-shot machines that you have not yet activated. If you move completed one-shot machines to sector X, activate them immediately (in any order). You do not activate turning machines when you move them.
(1x) Go through the discard piles of the general display and choose 1 item from them. If it's an engineer, put her in your hand. (Pay the usual additional cost if she's an engineer of grade 4/4+.) If it's a one-shot or turning machine, place it in sector 3 as usual.
(2x) Complete one of your uncompleted chrome or one-shot machines free of charge.
(1x) Gain 3 green points. Then return all your engineers from your factory board to your hand.
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 2 green points for each of your completed one-shot machines (including this one).
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 2 green points for each different type of turning machine in your factory.
(1x) Gain either a marker from the special point supply or 1 green point. Then gain 1 point for each water token in the hot half of your boiler.
(1x) Produce as many gears (in any mix of small and medium) as you have water tokens in your entire boiler.
(6x) Choose one of the award tokens in the award supply and place it face up in front of you. If there is a watch token attached to it, take it too and use its effect immediately. Then discard the watch token to the game box.

Award tokens give you points during the final scoring depending on how well you have fulfilled their tasks. There is no limit to the number of award tokens you can collect. You can have tokens with identical tasks. Both will give you their points when scored. There are 8 tasks.

There are 4 types of watch token (for their effects, see the resource overview): 2x, 2x, 2x, 2x.

Turning machines

There are 4 types of turning machine (for their effects, see the resource overview): 6x, 6x, 5x, 3x.

Chrome machines

Whenever you play your engineer of grade 1 or a qualified engineer of grade 2 (even when you use it to copy), produce 1 small or 1 medium gear.
Whenever you play an engineer of grade 2 (even when you use it to copy), generate 1 steam.
This applies whenever you play an engineer (even when you use it to copy). For example, engineers of grade 4 are placed in sector 3, your engineer of grade 1 in sector X.
Whenever you build a turning machine, immediately activate its effect once. Then place it in sector 3 as usual.
(Grade doubler) For example, if you use this engineer's action, you can consume 2 steam to produce 6 gears. This does not apply to the gray engineer of grade 3.
Whenever you complete a chrome machine, generate maximum steam. (This does not apply to this machine itself.)
Whenever you complete a one-shot machine, you may immediately move it to sector X (if it's not already there), activate it once and gain 1 green point.
Whenever you complete a one-shot machine, gain 2 green points.
Whenever you complete a chrome machine, gain 3 green points. (This does not apply to this machine itself.)
Whenever you hire a qualified engineer, you may take the one on top of the refill stack instead of any of those below the windows (paying the usual cost if it's an engineer of grade 4/4+). Whenever you build a machine, you may take the one on top of its refill stack instead of any of those above/below the windows. If you take the top machine of a chrome machine stack, don't forget to add a special point marker to the rightmost chrome machine of that row.
This machine is switched on whenever you play your engineer of grade 1 or a qualified engineer of grade 2 as your main action. At the end of that turn, you may turn your corrosion wheel and proceed as you do when you turn it as your main action (see "Turn your corrosion wheel"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).

The following chrome machines modify copy effects:

For example, if a player plays an orange engineer of grade 2, you can copy that engineer's action by playing a grade 3 (or 4) engineer of the blue, green, orange, gray or wild suit.
For example, if a player plays an orange engineer of grade 2, you can copy that engineer's action by playing an orange engineer of grade 2.
For example, if a player plays an orange engineer of grade 4, you can copy that engineer's action by playing an orange engineer of grade 2 and an orange engineer of grade 3. Each of these engineers then goes to the sector that corresponds to her grade.

Naturally, you can use all of these copy effects in combination.

The following chrome machines reduce completion costs:

Whenever you pay the cost of a chrome machine while completing it, that cost is reduced by 1 chrome gear.
Whenever you pay the cost of a one-shot or chrome machine while completing it, that cost is reduced by up to 2 medium gears. This reduction also applies to machines with a steam cost.
Whenever you pay the cost of a one-shot or chrome machine while completing it, that cost is reduced by up to 2 small gears. This reduction also applies to machines with a steam cost.

All of the following completed chrome machines are switched on whenever you turn your corrosion wheel (see "Turn your corrosion wheel"):

You may activate once more up to two separate turning machines that you have already activated this phase.
If there are at least 2 engineers of grade 2 in your sector X, you may consume 1 steam to gain 3 green points.
At the end of your turn, you may consume 1 steam to turn your corrosion wheel again. Proceed in the same way as in your main action (see "Turn your corrosion wheel"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).
At the end of your turn, you may consume 1 steam to play 1 engineer from your hand. Proceed as though you had played her as your main action (see "Play 1 engineer from your hand"). However, this is considered an additional action, not a main action (see Phase 4: End of turn).

Engineers

For icons that are not explained here, see the resource overview and the main action rules. There are starting engineers (sets A, B, C, D) and qualified engineers.

Some qualified engineer actions:

Without actually turning the corrosion wheel, activate any of your turning machines and visible completed chrome machines in any order as though you had, following the rules described in "Turn your corrosion wheel". (This includes being able to complete machines in between.) One-shot machines and prototype machines cannot be activated this way.
Move any number of your one-shot machines (completed and/or uncompleted) to any sectors of your factory board. If you move completed one-shot machines to sector X, activate them immediately (in any order).
Return up to 2 engineers from any of your sectors to your hand. (You cannot return this one.)
Build either a turning machine or a one-shot machine. (Whoever copies this action does not have to build the same type of machine, of course.)

Solo Mode

Hello! Do you want to play Corrosion alone? I'm happy to step in as your opponent.

Setup

Set the game up as described in the Setup section, making the following changes during these steps:

1 Place the display board with the solo side up.

3 Place all 36 special point markers in the special point supply.

Playing the game

You and I take alternating turns. You are the starting player. Carry out your turn as usual (the only difference is that I will never copy your engineers' actions).

When it is my turn, carry out these steps for me in this order:

1) Flip 2 cards

Flip the top card of my draw deck and place it face up on my discard pile. Then flip the next card of my draw deck and place it also face up on my discard pile. That second card is my action card.

2) Perform my discard action

According to the icon shown on my action card, remove an item from the general display:

Remove a chrome machine from the display, according to the letter and arrow shown on top of my draw deck:

If it's an up arrow, remove the upper chrome machine from above the window of the matching letter.
If it's a down arrow, remove the lower chrome machine from above the window of the matching letter.

Discard the chrome machine to the game box, along with any special point markers on it. Then refill the display as usual (including placing a special point marker on the rightmost chrome machine).

If it is either of the two "no discard" icons, nothing is discarded.

3) Copy the action of my action card

Next, you may choose to copy the actual printed action of my action card, following the usual rules in "Play 1 engineer from your hand".

4) Check for award token removal

If that row is already empty, check the arrow on top of my draw deck: If it's an up arrow, remove the leftmost award token from the remaining row that is farther up. If it's a down arrow, remove the leftmost award token from the remaining row that is farther down.
If there is only one row left, remove the leftmost token from it.
If all award tokens are gone, this type of one-shot machine has no effect any more.

Then it's your turn again.

Note: Whenever my draw deck runs out (which happens every nine turns when flipping the first card), mark this by placing a water token from the supply onto the leftmost free reshuffle space in the upper right corner of the display board. Then shuffle my discard pile and place it as my new draw deck. Flip its top card as the second card of this turn to form my new discard pile. Then proceed as usual.

End of the game

Tally your score as usual. How well did you do?

Less than 30 points — Sorry! I'm sure you can do much better.
30+ points — It seems you are still a little rusty. Try again!
50+ points — Satisfactory! That was pretty good.
70+ points — Now we're talking business! Nice job!
90+ points — What an unbelievable feat! You should be named "Business Person of the Year"!
100+ points — This is the kind of entrepreneurial spirit that legends are made of.

Credits

Game design: Stefan Bauer. Artwork: Dennis Lohausen. Development: Viktor Kobilke, Peter Eggert. Editing, rule book and rule book layout: Viktor Kobilke. Rule book revision: Neil Crowley.