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Why the Powder Painting Peel Off From the Galvanized Metal?

September 27, 2008

This is Juan Bravo SQE

We have a situation on some metal cabinets that we are receiving from vendor.

We are observing bubbles on the painting surface and said bubbles
can be removed easily by hand..and also rust can be seen over the affected area

Would like to know the root cause or at least the possible causes.

Powder painting is use on said cabinets.

Thanks

Juan Bravo
Supplier Quality Eng. - Reynosa, Tamaulipas , Mexico

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First of two simultaneous responses -- October 2, 2008

Powdercoating on galvanized steel is notoriously difficult. To be successful an appropriate pretreatment is required, but it is possible to powdercoat with NO pretreatment, and there is no visual difference on the first day, but it does not last.

If your steel is galvanized, it is unusual to see rust, that suggests a galvanizing fault. A bare patch or something.

If the powder is lifting and the galv is intact underneath, that suggests wrong or missing pretreatment.

Ask you applicator what pretreatment they do. If none, find another coater. The more stages of pretreatment they do the better (up to say 10)

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

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Second of two simultaneous responses -- October 2, 2008

Dear Juan,
The short and simple answer is that prior to applying the powder, it is possible that no recognised and essential pretreatment was carried out.
Galvanized substrates are the most difficult to PC and obtain adhesion, therefore require extra care and attention.
Terry

Terry Hickling
Birmingham, United Kingdom