Metal finishing Q&As since 1989

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Hydrofluoric acid substitute

2007

We operate plating facilities in several parts of the world plating nickel/silicon carbide deposits onto high silicon aluminum castings. Typically, during the pre-treatment, we "de-smut" (acid etch) using a nitric acid/hydrofluoric acid solution prior to zincating.

We are about to open a new facility in a location where hydrofluoric acid acid is not available, so I need to find a substitute that will work as well as (or better than) HF.

Any ideas please?

Geoff Slater
plating shop owner - Weston-super-Mare, England

Do a search of this site for ammonium bifluoride for the amount to equal the HF. Infinitely more safe than HF, but it is an additive to nitric acid or sulfuric acid for etching.

James Watts
- Navarre, Florida
2007

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Depending on the amount of Si you are talking about, you might try a Ammonium Bifluoride/Nitric Acid mixture. If memory serves me correctly (I don't work with cast Al anymore) I believe we used 8oz/gal concentration.

Marc Green
anodizer - Boise, Idaho
2007

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These guys are right - use ammomium bifluoride. It can be obtained from most of the better chemical supply houses in the UK

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007

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Geoff
All good advice
Just make sure that any spec you are operating permits bifluoride.
Remember, it is much safer to handle but you still need calcium gluconate gel available and appropriate first aid training.

Geoff Smith
Hampshire, England
2007

Hi my name is Frank Klodner I work in a plant that makes car care products and am looking for a HF replacement, we use it as a wire wheel cleaner but with everyone going green would like to go green myself.

Frank Klodner
Car care Products - Toronto ontario
May 20, 2009