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Metal giftware is rusting before painting

 

We're a small company who produce metal gifts. We're using %0,3 phosphoric acid and %0,1 nonionic solution to cleaning rust and degreasing on metal (iron) surface by wiping (not rinsing) before painting. But after then application when it dry, we have a big problem on surface with yellow rusting. I want to your help about solving this problem.

Sincerely,

Arda SARIHAN
AS METAL - Ankara, TURKEY

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Dear Mr. SARIHAN,

There are few solutions to your problem , it worth trial:

A. You can add 50 ppm of Sodium Molybdate to your solution and while the part is drying you will get probably Iron Phosphate coating.
B. Rinse the metal surface with water , and force dry at 40-50 °C (With hair dryer ⇦ on eBay or Amazon [affil link] for example) and paint .
C. Use citric acid ⇦ on eBay or Amazon [affil link] instead of Phosphoric with higher concentration (10-20 grams per liter) , and you will have better results.
D.In case of no rusted parts , clean with alkaline or neutral cleaner and rinse with water , no rust will appear after drying.
E. Wipe with solvent instead of water solution compound , like Trichloro Ethylene , dry and paing.

I recommend you to try all my suggestions and choose the best solution for you.

Yehuda Blau
YB Plating Engineering and Quality - Haifa Israel

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