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Should zinc phosphate conversion coatings rub off?

We are doing Zinc phosphate Coating on Fasteners but here the problem is that while rubbing on a piece of paper the coating left its place partially. I mean that excessive coating. Is this a feature of Phosphate conversion coating?

Aattir Arfi
Plating Shop Employee - Karachi
October 4, 2011

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November 24, 2011

If the cleaner is not properly rinsed off prior to the phosphating stage the adhesion to the substrate will be very poor. I have seen this many times over my extensive career. The pH of the residual cleaner promotes the formation of the coating bypassing the usual route of slightly etching the substrate surface which changes the pH at the interface promoting phosphate film formation.

The residual cleaner is hard to detect and it does not take much, but the results are quite evident.

I was once employed by a major pretreatment manufacturer as an on-site technical service representative for a large automotive manufacturer. On my first day on the job I attached a panel to one of the vehicles going through the treatment process let it get e-coated and the folded it in a very generous radius and to the amazement of those around me the treatment was on the paint side not the substrate side after a virtually complete delamination. The plant's largest quality problem was paint chipping off on the assembly line.

Ronald Zeeman
Coil Coating - Brampton, Ontario, Canada

Thanks dear sir. I hope it makes quite better results for our requirements. Thanks once again.

Aattir Jamal Arfi
- Karachi, Pakistan
November 26, 2011