Powder Reject Rates

Question: I have read your clinic on many occasions and appreciate the information.


I have read your clinic on many occasions and appreciate the information. I am looking for any information on published or recognized normal internal and/or external reject rates for medium to large coaters. We feel we have a great number, but with nothing to compare it to but our past numbers, it may not be as good as we think. Thanks for any help. S.J.


Most well-run powder coating operations have reject rates in the 2-8% range. This applies to standard visual and performance quality testing criteria matched to general industrial applications. However, those companies that have stringent visual and performance criteria may have much higher reject rates (10-25%). The opposite is true for those shops that have low visual standards (0.25-1%). Combine a high visual standard with a process that is difficult to control or a substrate that is unstable and you can get reject rates that are astronomical (15-40%). All this brings up some important points:

•Quality standards must be commensurate with the industry the products are used. For instance, electrical control cabinets are not jewelry; and high-end electronics are not lawn furniture. Having realistic quality standards is a must for success.

•Unstable substrates (castings, die-castings, plated items, hot-dipped galvanized items, etc.) will influence the defect rate, even though a process is held to tight process control standards. These are considered high-risk substrates and come with a higher defect rate.

•Spraying clear coats, metallics, hammer tones, etc. will often yield a higher defect rate, since these coatings are considered high risk.

You are probably asking, "What does all this have to do with my question?" Your defect or reject rate is directly related to the reliability of your process equipment, the success of your process control, the training level of your operators, the "tightness" of your quality standards, the type of coatings you spray, and the industry your products serve. As a result, comparing your defect rate with another industry might not be practical. Therefore, judging your process by the rise or fall of your own defect rate may be the best way to measure your success.