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Powder coating and infra red curing time

I have just completed an oven check on a client's electric Infra Red oven. Although our white TGIC free polyester powder appeared to be fully cured and it passes 500 hours ASTM B117 with a proprietary pre-treatment. However, the figures for time and temperature appear to be very low i.e. 4.25 minutes at MT 130°C é air temp was 180°C. I can not find any comparison or suggestions what is considered to be the norm anywhere on the web. The customer informed me that any higher MT or longer duration in the oven then yellowing will occur. My thoughts are if it works don't interfere. Just thought I would post this item to see what other coaters are doing.

Terry Hickling
Birmingham, United Kingdom
May 15, 2008

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May 16, 2008

Terry:
What metal was it ? Aluminium? What thickness?

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

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IR's don't produce metal temp the way convection does, it would be a mistake to try and cure the parts using the convection mindset and methodology. Testing will have to be done for all substrate thicknesses used and for the range of paints light to dark, no generalized oven temp/line speed like a convection oven, it's one of the drawbacks to IR tech. I think you hit the nail on the head though, if it is producing the desired results, don't mess with it. The MT is good for white and cure time is good for IR, write the process to fit the system and call it a day. The salt spray results are from a steel substrate and sound correct, aluminum would be higher.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
May 19, 2008