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TSA paint not adhering on galvanized sheets
Q. We are manufacturing TSA Black paint for one of our customers. They are coating this paint on Galvanized sheets.
Now the problem is poor adhesion of film on Galvanized sheets. If etch primer is applied, adhesion is very good. But customer is not ready to apply the etch primer. They are directly applying TSA Black paint on Galvanized sheet.
How to improve the adhesion properties (Subject to coating on Galvanized sheet) in TSA coating system?
Soundararajan Ranganathan
paint company - Coimbatore, Tamilnadu, India
July 13, 2009
A. Hi, Ranganathan. "TSA" is a bit ambiguous to me. In the metal finishing field it might mean Thermally Sprayed Aluminum or Tartaric-Sulfuric Anodizing, but I am guessing you mean for it to indicate Thermosetting Acrylic?
The galvanized sheets should be pretreated by zinc hosphatization. The use of a Galvanized Metal Primer
[affil links] is a sometimes acceptable alternative for situations where phosphating isn't practical for some reason. If the customer will neither pretreat the galvanized sheets as is the right practice, and not even apply a self-etching primer as plan B, I think it is unreasonable to expect the paint to adhere. But I suppose you could suggest that they at least dip or spray with vinegar
[in bulk on
eBay or
Amazon] as an etch as plan C. I'd give an F to the attempt to reformulate a finish coat so that it will also etch and phosphatize galvanizing :-)
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2, 2009
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