Metal finishing Q&As since 1989

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Zincate Etchant/Stripper

Does anyone know of a zinc etch that won't attack aluminum. I have purchased a zincate solution from a plating kit supplier and it gives me a nice even deposit on the pads of an integrated circuit. However, if I wish to rework or double zincate the acids which I have been trying; hydrochloric, phosphoric and nitric, all have been etching away the underlying 5000¦ of aluminum in as little as 1 minute. The phosphoric appears to be the slowest of the bunch but that is a visual observation and may be erroneous.

Patrick Franklin
- Santa Barbara
2000

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Nitric acid is surely the best non-proprietary zincate stripper.

The issue of double-zincating is a complex one, and many researchers have described the mechanism by which they feel it improves adhesion. But, the bottom line is that it may not be strictly necessary, especially on high purity aluminum, and it sounds like stripping the first zincate layer may introduce more problems in your instance than just going with a single zincate.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2000

Since you gave no specifics, the normal way to slow down an attack on the aluminum is to use a weaker percent acid, a cooler temperature or less time. When you double zincate, it is desirable to leave a tiny bit of the original zincate.It sort of acts like a "seed" coatand also tends to be in the microscopic crevices. It sounds like you could not be leaving any.

James Watts
- Navarre, Florida
2000