diy rust removal

[vlad01]

yes, as its acidic it will donate protons to the metal, infiltrating the structure and forming molecular hydrogen inside voids and grain boundaries.

Mild steel should be ok, it more of an issue with carbon steel and high carbon alloy steel, used in such parts as fasteners, springs, some suspension parts.

its also not good for cast iron as the gas will accumulate in the graphite nodules and react and product high pressure methane which also leads to brittleness and micro fracturing. This is called hydrogen attack.

I have put few cast iron parts in before and they all fucked up big time, turned into brittle chalky mess, could pick at the metal with your finger nails.

Panels are generally ok, later model stuff probably will become somewhat brittle as they are made of a carbon steel for strength so they can be made thinner. Old cars used low carbon steel hence why the panels are butter soft and dent super easy despite being much thicker, also why they grind, file and cut easy as. Very soft.

[ejukated]

that's for that - good to know.

So I guess then the best bet is media blasting or possibly that Evaporust which is PH neutral.

[pman92]

I soaked parts in white vinegar years ago to remove rust (similar idea to molasses)
Does an incredible job of removing the rust, but as vlad said I found the cast iron became very soft.
Had a similar thing happen soaking cast iron in degreaser. It ended up with a thin layer of vey soft metal that was much darker grey in color and I could actually scrape it off with my finger.
I've also learnt the hard way about leaving oil on parts. Put some engine oil on some cast iron brake drums to prevent them rusting while they weren't being used (just a smear of oil), when I ended up using them even after a very good degrease and clean with brake cleaner, the oil had soaked into the iron and came back out and ended up mixing with the brake dust and causing alll sorts of problems

[Gareth]

Wax or cavity wax is the only successful way of preserving cast iron I have found.

[brindo]

What about using electrolysis to remove the rust? Does that affect cast iron?

[vlad01]

it does work, but also produces hydrogen gas. All chemical or electrochemical processes to remove rust as far as I know with either donate protons (+ hydrogen ions) or produce gas directly.


If you got a good oven with precise temp control, like an external thermal couple temp controller you can do a bake out at about 195ºC for 6-24 hours.

It really depends on the part and the metal its made from. Aluminium does not suffer from it, so acid clean it to your heats desire. Use phosphoric acid though, HCl will destroy it lol, not sure about sulfuric acid, I think its ok as they use it in anodizing. Mild steel it fine and anything that isn't really much critical or load bearing.

Even ok on control arms, diff housings and stuff like that as its all soft ductile mild steel which doesn't get effected. Just don't use it on suspension/brake/steering bolts, springs, drive shafts or rotors.

I have done a few brake caliper brackets, though I avoid it now with this knowledge, but they are cast steel and are ductile to a good degree.

When I get stuff plated critical bits I get de-gased via the bake out, the plater does this. I have been told by what would be the biggest plater in vic, if not oz that for 8.8 class fasteners its a bit overkill for the bake out and never seems to cause an issue, 8.8 is relatively a low tensile steel. I'm still a bit wary of this but hey, these are automotive industry experts. 10.9 and 12.9 for sure need bake out and even they don't really want to do that stuff even with bake out as its not guaranteed, just reduces the risk to very low.

This is why I am trying to get new bolts sorted for my cars where they get the delta/geomet coating (via a different company) as its hydrogen free and safe. I am getting rotors done in that coating too becasue fuck you rust !

[ejukated]

This is why I am trying to get new bolts sorted for my cars where they get the delta/geomet coating (via a different company) as its hydrogen free and safe. I am getting rotors done in that coating too becasue fuck you rust !

could you share more details on this?

[vlad01]

which one, the coating or the bolts?

[ejukated]

the coating

[vlad01]

http://www.adhesivecoatingservices.com.au/