Why did this rust?

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C10SLEY

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Whilst bleeding my brakes, I left the lid off and brake fluid went everywhere. Sure. Fine. Whatever. I cleaned it up.
Couple days later I found this:

Why??
Should I tape and paint??
 

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nvrenuf

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Brake fluid can remove paint so if you try to paint the m/c be careful to never spill a drop on it.

Your m/c most likely rusted because either the brake fluid or the cleaner you used removed the protective coating that keeps it from rusting in the box on the shelf.

Most m/c's have a rusted surface.
 

Grit dog

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First, bare cast iron oxidizes on the surface as quick as any steel.
Brake fluid itself won’t cause it to corrode ( but it eats paint). But the moisture that brake fluid absorbs (and traps) will make it corrode since brake fluid is hygroscopic.
Short answer, yes just paint it if you don’t like the rusty look.
 

fast 99

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Brake fluid will melt spray paint. Although I haven't tried it would think Por 15 might work.
 

C10SLEY

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I had no idea brake fluid would dissolve paint and absorb water. That is great to know.
As for POR15, I am getting some soon for the cab floor, so maybe I will do that, then I wouldn't have to tape anything, just hand paint it.
Will post updates here in a few months when i do paint. Just went through a MAJOR hassle of running new lines to the MC, and it's new MC, booster, hard lines to the proportioning valve and soft lines. Almost done except I'm struggling finding the right rod end to fix to the brake arm from the booster. Nevertheless, I'm close to having this project complete.
 

TPISly-C10

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Whilst bleeding my brakes, I left the lid off and brake fluid went everywhere. Sure. Fine. Whatever. I cleaned it up.
Couple days later I found this:

Why??
Should I tape and paint??
thats why i change it for this one! :)
 

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ali_c20

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You need really tough paint. Many 2k paints are chemical resistant and withstand brake fluid. They often are available in small rattle cans.
Brake caliper paint should work too.
 
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