How to Determine if Coating is Powder or Liquid

Q. How can I tell if a metal part is powder coated or liquid painted? A test I found on-line (wipe it with MEK, and if the color transfers to the Q tip or rag it is paint) was inconclusive. I tested my part and the color transferred and then I tested a part that I know is powder coated and the color transferred on that as well. Is there a definite test?—CK

A. It is usually possible to tell if a coating is powder based on visual properties and certain physical properties. The chemical rub test you performed will only identify the chemical resistance of the coating and not tell you if it is powder or liquid. First, do a visual inspection. Powder will likely have more texture than liquid and be more rounded at the edges than liquid paint. Measure the film thickness if you can. There are gauges made for that purpose. If you do not have a thickness gauge you may be able to take your part to a coating shop and have them do it for you.

A typical liquid coating (single coat) will be anywhere between 0.5 mils and 1.5 mils. A typical powder coating will be 1.5 to 4.0 mils. You can also apply a liquid coating stripping solution. You can find a stripping solution at your local hardware store in the paint department. Many liquid coatings (not all) can be broken down fairly quickly with an aggressive stripping solution. Powder is more resistant to chemical strip and will take longer to break down. Chemical analysis could be used to tell more about the coating, but I suspect that you can tell based on texture, thickness and resistance to a chemical stripping solution. You may want to take it to a powder coating shop and have someone experienced look at it. An experienced powder coater will have a pretty good idea if the coating is powder.