I'm looking at purchasing some engine parts (basically a whole 13B disassembled) from someone nearby in a few days. Their ad states that the parts were "chemical dipped" at a shop, but it's been a few years since so there is some surface rust.

I need to see the rust in person to assess whether it's fatal of course (the seller indicates there is no pitting), but in the photos it looks like it will clean up fine on the parts I am interested in (irons).

What I'm more concerned about is whether it's safe to chemically dip our engine parts. The housings are aluminum and look pretty oxidized, but I imagine if the chrome is okay and they meet spec they could be re-used. But is it okay to chemically dip irons? I know they have a nitride coating that is important to keep intact, but I'm not well versed on metallurgy so I don't know if the chemical dip would damage the coating.

Thanks, Chris.

 

depends on the chemical, most seem totally fine. there are a few that damage bearings and freeze plugs, in a piston engine you're replacing this stuff anyways

 

Not sure what exact chemical dip was done, but it probably involved water which will rust iron/steel. Surface rust than can be removed using electrolysis. Google DIY electrolysis rust removal.

Alkaline works great at removing grease. Just need to be careful using on aluminum, chrome and painted surfaces. I'm currently using Super Clean to clean bike parts. That stuff is nearly 14 pH . I dilute it 1:2 (or 30% SC) and don't let it sit on the surface too long (a minute or two). A lesser pH will of course be safer. You can check pH values on MSDS.

Acid will neutralize alkaline. I wash parts cleaned in alkaline in a 50% vinegar solution. May not be necessary, but i had the vinegar.

 

I'll end up replacing those either way. It isn't worth trying to save $20 on freeze plugs just for the headache it causes later to replace them, and I don't think I'll be using the bearings either since Rx8 gears (with bearings) are cheap and available.

It looks like it's just surface rust in the pictures, but then it's not sharp enough to really zoom in. My concern is that there's pitting, but I don't know that for sure until I see the parts in person. I've never tried electrolysis for rust removal, only for electroplating. Maybe I'll give it a try I can use the parts I'll be unlikely to reuse (e-shaft, stat gears) as test pieces.

 

If there's not a lot of rust, may be easier to use elbow grease. Steel wool, etc

 

Completely depends, I've chemical dipped rotors to the point where they lose their cadmium coating, and they'll quickly surface rust but when in use they're perfectly fine.