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Plating over aluminum starts peeling

We plate aluminum mags in volume. It has an alloy composition of 50% virgin material and 50% scrap. Our process starts with electrocleaner, etching, desmutting, zincate1, zinc strip, zincate2, copper-nickel-chrome. After 1-2 months plating peel-off starts to occur. What do you think is the cause of our problem? What can you suggest to improve our plating adhesion?

Zenaida R. Adorable
plating services - Cubao, Quezon City, Philippines
2006

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First of two simultaneous responses -- 2006

Hi,
I don't shore what you mean with scrap, but the most of aluminium has alloy element and I belive you mean you plating is on casting aluminium alloy.

On casting alloy you should avoid to do two zincate pretreatment, because the etching will build make same small pore in the aluminium and then when you plate, will the plating build some bridge over this por and in this will the preatments acid stay left and occure at the deposit bubbles after.

That's also important to know the aluminium alloy elements so your pretreatmen is the right for the alloy element.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

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Second of two simultaneous responses --

The cause of your plating peel off has probably to do with base metal porosity more than anything. Aluminium has a high affinity for oxygen. You might be successful if you avoid the copper plating and use an electroless nickel strike instead.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2006

Try eliminating you copper plating and just go straight into electro nickel after zincate. it seems to work for me.

Frank DeGuire
- St. Louis, Missouri, USA
2006