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Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Problem of adhesion failure of Zinc Primer only when topcoated

July 24, 2008

Hallo sir,

Very Good Morning

I am facing very big problem on Zinc Primer, when I coat Zinc Primer on GI Sheet, after that we coat White Tex(TGIC FREE POWDER ON TOP COAT) on Zinc Primer (GI sheet). Then 40 kgcm impact fail and flexibility fail with 5mm.There is very good adhesion with Zinc Rich primer when I coat on GI SHEET and also very good adhesion wtih tex white coat on GI SHEET without Zinc Primer coat . please advice what should I do.

* ZINC CONC. 26.55%
* RESIN 40 % AND HARDNER IS 10%

SAT PANCHAL
TECHNICAL MANAGER - BANGLORE, INDIA

Hi, Sat. I think I understood the question but I am not entirely sure. So let me rephrase it in my words and you tell me if I got it right. You have found that your zinc primer by itself adheres fine to your GI sheet. You have also found that your topcoat by itself adheres fine to your GI sheet. But if you prime the sheet and then topcoat it, the two different layers of paint are so fundamentally incompatible with each other that the coating peels off?

You are using GI sheet, so you already have the fine galvanic protection that it offers. If the topcoat sticks to the GI sheet fine, why do you need a primer?

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 24, 2008

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