Metal finishing Q&As since 1989

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Amonium Bifloride, Muric Acid, Cleaning Solution for Plastics

I have heard that if you mix Bifluoride with Muriatic Acid you can remove rust from painted soft plastics without damaging the paint. Is this true? What is the mixture ration to use? Would it be Sodium Bifluoride or Ammonium Bifluoride? I think it is the later.

Any help out there?

Alan Geary
electronics - Santa Clara, California, USA
2001

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The chemical you are probably talking about Ammonium Bifluoride or ABF. It is a powder that when added to acids creates Hydrofluoric Acid. Although it is somewhat safer than HF, it is still very serious stuff. Anything that eats your bones from the inside (tying up the calcium) and etches glass is not something I like to spend time around.

I don't want to sound like your mother but please be careful in the lab playing with ABF.

As for the rust, I don't have much experience working around plastics but I have always found citric very mild but effective on removing rust. It is slower but nice and safe... at least on metal. Citric also loves heat. As with most chemicals, the power doubles with every 20 degree increase in temperature, or so the old tales go.

Please let us know what worked for you in the final tally.

Todd Turner
- Monroe, Louisiana
2001

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I think what you want is called Barkeepers Friend [on eBay or Amazon]. Hope this helps.

Ryan Palmer
- Denton, Texas
2001