Yellowing of Stainless Steel
I read your April 2007 article with great interest, as we have a similar problem with powder coated Type 430 stainless steel and we have also been seeing yellowing. Unfortunately, at this time I can’t give you the powder coating composition, but could that be the source of our problem? Or is it simply that Type 430 stainless is a bad grade and we should be using Type 210 or 304?
Q. I read your April 2007 article with great interest, as we have a similar problem with powder coated Type 430 stainless steel and we have also been seeing yellowing. Unfortunately, at this time I can’t give you the powder coating composition, but could that be the source of our problem? Or is it simply that Type 430 stainless is a bad grade and we should be using Type 210 or 304? I appreciate any light you can shed on this matter. G.L.
A.The article you reference discusses yellowing of a hybrid powder coating that was used in an outdoor environment. If your product is coated with a hybrid or epoxy powder coating and is used outside, then changing the formula to an outdoor-durable (UV-resistant) powder coating is in order, as the previous article states.
However, if the yellow you see is a stain, then look at the possibility that you have oil contamination on the part before coating. Yellowing can also be caused by over-curing the powder coating (too much time, temperature, or both).
What is not causing the yellowing is the grade of stainless steel you are selecting for the substrate.
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