Letter 047

Alternative to ammonium bifluoride to etch aluminum

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I'm a aluminum anodizer looking for a alternative to ammonium bifluoride to matte (or satin) etch aluminum without a lot of metal loss. We anodize a lot of close tolerance optical components but want to eliminate the fluorides so we can use titanium racking. Customers want a uniform satin appearance and we need to maintain .0005.   Any ideas?  

Mark Dewitt
Rochester, NY      

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We anodize with titanium racks and go through an ammonium bifluoride desmutter. I didn't know that it is a problem.      

Ken Rosenblum
finishing shop - Minneapolis, Minnesota

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We enter a 12-15% volume and water to achieve a dull etch.The ammonium bifluoride etches aggressively the titanium. Try it. It works. We don"t want to be replacing racks. The finish is nice, but it kills our racks. Is it our chemistry? Do we need an inhibitor of some sort? This is not a proprietary product but a home brew.      

Mark Dewitt
Rochester, NY

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The standard aluminum desmutter that I'm familiar with is 30% nitric acid, 30% sulfuric acid and 1 lb/gal ammonium bifluoride.  

Ken Rosenblum
finishing shop - Minneapolis, Minnesota

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