Wrinkles in Powder Coating

Q.We would like to introduce ourselves as a leading compressor manufacturer in India. Sir, in our compressor parts we are powder coating our sheet metals. We have totally four approved powder suppliers who supply the powder to our approved powder coating vendors. The problem which we are facing is the WRINKLE pattern which we call it as STRUCTURE finish. As we want to compete globally, we have to stabilize the wrinkle pattern. In this regard can you tell us how can we freeze the pattern of wrinkle? Is there any standard method to regularize or international test method so that we can ask our powder supplier to follow the
same? S.K.

A. The powder coating industry has come a long way in the last 40+ years. However, there are no international standards for much more than the color of a powder coating (i.e. RAL color standards). There are test standards to evaluate many of a coating’s attributes (i.e. ASTM), but these are a long way from using a “standard” that depicts a numerical value for a specific powder like ANSI standards are used for steel (i.e. 1018 steel). If you buy steel anywhere in the world and just specify 1018, everyone will know what you are talking about. Oh I know that the ANSI standards are not used worldwide, but the international steel standards have exact equivalents to ANSI, making conversion simple. In the coatings industry everyone’s requirements are usually much different from each other’s, so we provide the testing methodology and let you choose the results you want. So as they say in the USA: “You are S.O.L.”

The wrinkle in a powder coating is developed by the particular chemistry formula, the applied powder coating film thickness, and the oven characteristics used to cure the coating. Since you have no hope of specifying or controlling any of these, I recommend that you establish a proprietary visual standard to set parameters for your coating’s “look and feel”. You accomplish this by selecting the wrinkle finish you like and coat numerous test panels the same exact way. Keep a couple for yourself, in a vault for safekeeping, and send the rest to your suppliers with the following statement: “All powder coated parts are to match this color and smoothness standard, without exception, when viewed at an angle of X degrees from a distance of Y meters under a light of Z lumens.” I’ll leave the XYZ parameters up to you to fill out. Notice that I used SI (international) units. (In the USA, we use feet and foot-candles.) Good Luck.