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Additional test failed of powder coating zinc-plated material

cold rolled material(MS) are ZINC plated and baked at 200 degree temperature for 30 minutes, then applied brown powder coating and baked it at 180 degree temp.for 40 mintues but after completion of process we got failed additional tests,the layer of powder coating get easily removed from the surface of the material by applying blade, please tell me how can we get the success test.

Ranjeet Singh Dhaliwal
employee - Chandigarh, UT, India
April 15, 2008

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First of two simultaneous responses --

What pretreatment did you do before applying powder? You don't mention any.
If none, then the result is expected. Chromate, phosphate or silane pretreatment required on zinc surfaces.

And you mention "cold rolled" steel. How thick? If thin (1-3mm) then perhaps 40 mins is too long to cure polyester powder?

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

April 18, 2008

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Second of two simultaneous responses --

Unfortunately, you inform us of the problems you are experiencing but no more. What type of powder, I presume it is not coffee or cocoa-powder:-)? What type of powder? What metal temperature do you achieve (not oven temp)? What film weight is being achieved? Once those bits of information are provided then you may get some answers from the experts. On my part I will then contact you direct (a long analysis) with a shorter version for this forum.

Terry Hickling
Birmingham, United Kingdom
April 19, 2008