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topic 12242

Surface treatment for a Al-Si alloy with high Si content


We have some problems with one of our injected Al-Si alloy parts. The part consist of a small frame with very thin wall thicknesses (1.5mm), so we must use an aluminium alloy with high Si content (10%).

After injection, the parts must have a first coating. The coating must have following characteristics at the same time: - To be electric conductive. - To protect the aluminium against oxidation. - Good adhesion of the final paint.

The coating we use is Alodine. The problem with an alloy with high Si content is the very poor adhesion between aluminium and the cromating treatment (we can separate them after painting).

Now we have substituted the Alodine by a chemical descaling, and it works but not too god, due to the aggressiveness of the treatment for a very thin thicknesses.

There is any surface treatment similar to Alodine for a high Si content?

Thank you in advance,

Roberto Clemente
Zaragoza, Spain


Have you tried a phosphate coating?

tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania



Subramanian Ramajayam
Subramanian Ramajayam
Bangalore, Karnataka, India

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