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Etchant for aluminum plating

I was told that 20% sulfuric acid heated is better than 60% nitric acid room temperature for etching aluminum before zincating. Please advise. I also have zinc in my nitric acid tank from the first zincate strip. Will this affect the quality of the acid and if so when should it be replaced. Should the zinc be removed before acid neutralization begins?

Angie Molnar
- Canada
2001

Angie,

Over many years I have found that 50 %/vol nitric acid works great. I never have heard of utilizing 20 % sulfuric while zincating. Sulfuric is difficult to rinse off any substrate. Heating adds cost anyway. Depending on the alloy, sulfuric could leave a smut, interferring with the zincate step.

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan
2001

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