Muriatic Acid... Ailuminum... Uh?

[Lynx331]

Muriatic Acid... Aluminum... Uh?

Has anyone ever used muriatic acid to clean anything aluminum? I soaked one of my engine brackets in it diluted today, and now the finish is very grey. Now what? Id like to get it to look as polished as possible.. but it seems like that acid may have took me back a step. Anyone?

 

[RacEoHolic330]

When i polish stuff, i clean it with brake cleaner, then hit it with a wire wheel, then sand the crap out of it about 3783495094 times, and then buff with tripoli and finish with white rouge

 

[bdazzgt]

That is what my dad uses to clean stamped concrete with, it is very potent stuff, i wouldnt use it for aluminum, i had some rubber soled boots on and it ate into the heel of it as we cleaned it off the concrete. I think i would just sand and buff like he said

 

[Michael Yount]

The color change you see is due to a chemical reaction between the acid and the aluminum. Muriatic acid is basically hydrochloric acid. Some acids are used in the aluminum annodizing process -- nitric, phosphoric, chromic, etc. The process of soaking the aluminum in the muriatic acid likely created a coating of aluminum chloride on the surface of the part and gave off some hydrogen during the process. If you leave the aluminum in undiluted hydrochloric acid long enough it will 'clean' it so well that it will be completely invisible.

Stiff wire brush or abrasive-tool of choice (sand paper, etc.) will probably be required to get through whatever you've created by soaking the piece in the acid.

From our high school chemistry class:

aluminum + hydrochloric acid = aluminum chloride + hydrogen.
2Al(s) + 6HCl(aq) = 2AlCl3(aq) + 3H2(g)