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"Powder Coating : Master Coupon vs Actual Item"

September 8, 2016

Q. Dear All,
I am facing some issues with powder coating gloss. We have tested with color coupons and gloss was within spec. Then we sprayed onto the actual parts with same temperature heat, time and thickness but the gloss was below spec.
Then we tried to spray the color coupon together with actual part and put into same oven with exactly temperature and time. The color coupons were meeting spec but the actual item was below spec. FYI, color coupon thickness was 1.5 mm and actual was 6 mm.
Can anyone tell me is it still correct if color coupon meets spec even if actual part were out?

Zakaria Abdullah
- Perai, Malaysia

September 2016

Hi Zakaria. Obviously the intent of the coupons is to simulate actual parts, so you want the actual parts, not just the coupons, to exhibit the required gloss. But to answer the question of whether you are meeting the spec or not, you would need to carefully review the wording of the purchase order and the spec.

The reason I especially like this question is that it reminds me that people who do chemical treatments on aluminum know that there is no way their actual parts could possibly pass salt spray requirements, but they carefully shop for sample coupons that will (see letter 47907). When a spec conditions us towards gradually compromising our integrity, we should keep fighting against such specs -- so let us know what the spec says :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
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