Thread: Removing rust with Citric Acid - test results

Good work Dengy. Five hours seems a long time - were you doing it at room temp (although that's a little elevated in your neck of the woods)? I usually do it at about 70 deg. That seems to be enough for one cycle, then give it a nuke in the microwave for the next lot (yeah, I'm a scab, even with my $5 per 500 grams bulk CA ).

Also, I noticed that your solution didn't turn green as mine habitually does.

For heavily rusted pieces I often take them out after a little while and give them a brush to get rid of the new loosened layer - seems to accelerate things.

You should see how CA cleans up Carbide - stunning! Maybe not a great idea to soak router bits in it - just use a plastic brush. BobL has a concern about the CA possibly weakening the glue between the carbide and the steel.

Hi FF, I started out with boiling hot water, and then it cooled down gradually over the next hour or so. I took the pieces out every hour and wire brushed them by hand to remove the oxides formed and expose the next layer of rust.

I used electrolysis ages ago on an old rusted 10" saw blade with TCT teeth, it works perfectly, no apparent affect on the teeth, still cutting strongly even after a couple of sharpenings at the local tool shop

Right, just very heavy rust then.

Right, just very heavy rust then.

Too right it was, if you look at the first pic, there was some pretty heavy wire brushing on the right, just to get it to manageable levels. Even then it took 5 hours, which is still quicker, and a cleaner result, than electrolysis. Probably cleaner because I don't wirebrush the item during electrolysis, but also because the rust with electrolysis is converted to this black stuff that is not easily removed.

Great stuff, thanks for posting Dengy, I've got a few things that need rust removal. Might go in this direction.

If you want quick (like 15-30 minutes) rust removal, you really can't go past hydrochloric acid.

A note for any users of any acid based rust removal - if the part is high carbon steel (springs or chisels or anything over about 30Rc), it's a good idea to bake it in the oven (200 degrees C for four hours) immediately after rinsing off the acid to avoid hydrogen embrittlement. (maybe pop it on the shelf below the Sunday roast to stop it getting all rosemary and garlic smelling...) Time will also (apparently) cure hydrogen embrittlement, but we are talking 6-12 months.