Topic: maximum Al content in etching tanks?

Hi there,

Does anyone
know what the maximum Al content in alkaline etching should be to avoid
galvanized appearance (also known as spangling) in anodized (type II, natural,
10u) 6063 T6 extrusions. I have found conflicting advice on this. Some sources say that
Al conc should not be allowed to grow beyond 20-25 g/L while others state that
it can be kept as high as 120 g/L without detrimental effects. Hope someone in
the forum can help me. I work in Al extrusion, live in Argentina, and do not
have whom to ask here. Many thanks for your reply!


Re: maximum Al content in etching tanks?

Hello,The spangling is not caused by the aluminum disolved in solution, it is caused by the zinc contained in the solution. It is a good idea to use a poly sulphur to eliminate the problem.

It is a common practice in zinc plating baths. I used to use it in my etch tank and the spangling was eliminated.

There are other problems associated with high aluminum, however, spangling is not.

Marcos Cielak