Acid rust removal and dissolving brass

[Guest 36chev]

There have been a number of threads addressing using acid, molasses and other chemicals for rust removal. But what would be the best acid for removing rust from small sheet metal parts AND dissolving brass? I have a couple of old aftermarket turn signals that had tiny brass machine screws holding on the covers. But many of the screws broke off flush rather than backing out when trying to disassemble (after repeated soakings of PB Blaster for several days). So, what would be:

1) A good, readily available acid to de-rust sheet metal and eat away the remains of the brass screws? Would the brass contaminate the acid?

2) A readily available retail store (Lowe's, etc.) to find that of type acid?

Thanks!

[Luv2Wrench]

I've used Phosphoric Prep and Etch ( http://www.homedepot.com/h_d1/N-5yc1v/R-100406369/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=phosphoric )

It will turn the rust black but you still have to wire brush that off. It is better than just removing the rust with a wire brush.

I don't think it will be any help for getting rid of the brass screws, however, it could loosen them up. I'd try heat on the brass screws and then try to back them out. I don't know of anything strong enough to get rid of the brass without making a big mess of your sheet metal (and limbs). That isn't to say there isn't something else...

[Guest 36chev]

I've used Phosphoric Prep and Etch ( http://www.homedepot.com/h_d1/N-5yc1v/R-100406369/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=phosphoric )

It will turn the rust black but you still have to wire brush that off. It is better than just removing the rust with a wire brush.

I don't think it will be any help for getting rid of the brass screws, however, it could loosen them up. I'd try heat on the brass screws and then try to back them out. I don't know of anything strong enough to get rid of the brass without making a big mess of your sheet metal (and limbs). That isn't to say there isn't something else...

Thanks for the information and might try this acid. I can sandblast them in a cabinet but was hoping to get rid of the brass screw remains with acid while de-rusting. The screws are itsy, bitsy, miniscule in size (1/32 or maybe up to 1/16 in diameter), so trying to drill out and re-tap could be difficult. There is nothing to grab to remove.

[Bhigdog]

I believe metallic mercury will amalgamate with brass. Might take awhile and elemental mercury is getting hard to find............Bob

[Luv2Wrench]

OK, I better understand the screw problem. I've seen a video where a guy welded a bolt unto a bolt that had snapped off flush. The heat from welding made it easy to remove the bolt that was stuck. Obviously this will be a little tricky considering the size of your screws, but... I think it is something that can be accomplished with a small torch or bottle of Mapp gas.

I've also heard of drill bits that are reverse threaded (so to speak) and you can put them in your drill, run it in reverse and as it drills into the screw it tends to catch and cause the screw to back out.

I don't envy your situation. Stuck bolts/screws are a pain and more so when they are tiny. Best of luck!!

[Guest 36chev]

OK, I better understand the screw problem. I've seen a video where a guy welded a bolt unto a bolt that had snapped off flush. The heat from welding made it easy to remove the bolt that was stuck. Obviously this will be a little tricky considering the size of your screws, but... I think it is something that can be accomplished with a small torch or bottle of Mapp gas.

I've also heard of drill bits that are reverse threaded (so to speak) and you can put them in your drill, run it in reverse and as it drills into the screw it tends to catch and cause the screw to back out.

I don't envy your situation. Stuck bolts/screws are a pain and more so when they are tiny. Best of luck!!

Thanks again for the responses, and I could always use the luck! If I don't find an acid, then will probably drill them out and if unable to re-thread just use small sheet metal screws. Most of the screws loosened ok, but I think about six broke off.