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  for Metal Finishing since 1989
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Street light mfgr. needs pickling process prior to powder coating

Dear Sir,

Our customer produces Lighting columns for outdoor applications(street lighting), I brought to his attention recently your product,he showed some interest. The process will be as follows:-My company has manufactured 2 pickling tanks which are quite large,the size of the tanks are 18 meters long x 2.meters high x 1.meters wide for pickling with Hydrochloric acid or the debate go's on about using Hydrofluoric acid which as you know is a very harmful and the regulations in the UK as in the USA are stringent.The process is to put the columns through a shot blast machine and then into the pickling tanks they have been told by someone else to use Hydrofluoric Acid this process is prior to powder coating the column, and I was reading your specification on citric acid s whether it would work in this high volume production set up,with the above acids HF & HC this would leave the material with a pitted effect(a keyed surface) would your product give a good keyed surface for powder coating? could you please advise.The column thickness are 3 mm & 5 mm.

I hope you can assist in this matter, also could you tell me what type of extraction would be needed?

Regards,

Mel Moore
Director - West Midlands, UK
2003

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Hydrofluoric acid is by far the nastiest of the acids. It should be used only where it is imperative. Per common knowledge, HF corrodes glass; from a science or production standpoint, it dissolves silicon. If you are dealing with castings that have silicon in them, or stainless steels, it may be that only HF can pickle it (or more correctly, only fluoride can pickle it).

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey