The company I work for uses many steel and aluminum parts that are made to specification and powder coated. One new part in particular is a powder-coated, die-cast aluminum part. How can we specify the properties of the powder coat to be of sufficient quality for our application (office furniture)?
Q. The company I work for uses many steel and aluminum parts that are made to specification and powder coated. One new part in particular is a powder-coated, die-cast aluminum part. How can we specify the properties of the powder coat to be of sufficient quality for our application (office furniture)?
For instance, the first parts that we received clearly had adhesion problems. The powder was coming off in large flakes when lightly scratched with a small knife. The second set of samples for this part are clearly better and appear to be sufficient. However, there is no process in this company to measure these characteristics and we receive powder-coated products from many different suppliers.
Where does one find the industry standards for testing and specifying the physical properties of the applied powder coating? I have subsequently learned of a cross-hatch method to determine adhesion but I do not have any access to documentation of the procedure. A.N.
A. Unfortunately, the coatings industry is not as sophisticated as the steel or aluminum industry. In the latter, steel and aluminum materials are designated by ANSI standards. When you specify ANSI 1018 steel, all the features about that material are fully known. You know the tensile strength, the modulus of elasticity, the metallurgical composition and so on. The powder coating industry has yet to evolve to this level of predictability.
Powder coating properties need to be specified to ensure that the coating looks, feels and performs up to expectations. Every powder material has, at one time or another, been custom-formulated to meet a defined list of properties. You can select a coating based on the properties published by the powder formulator or write your own specifications and let your powder supplier evaluate their product line to determine the best choice. In either case, the physical properties of the powder coating need to be evaluated as much as the color or gloss.
A typical list of powder coating properties and ASTM test methods is available in the Powder Coating Institute’s Powder Coating, The Complete Finisher’s Handbook. But finding the list is the easy part of your effort. Determining the specific properties of the coating you need is much more involved. For instance, do you need 160 inch-lb of direct impact resistance, or will 110 inch-lb be sufficient? How about hardness, flexibility, abrasion resistance, chemical resistance, or corrosion resistance properties?
This kind of effort can be pretty daunting, and this is where you can obtain help from a qualified independent consultant to address these design specific issues.
Yours truly can be reached at 800-97-POWDER.
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