Never has the saying “Trash In, Trash Out” ever been so true than in the coating industry!
Over the last decade I have been in countless meetings discussing powder coated production parts problems. The meetings usually include a purchasing manager, quality control manager, production manager, and me, the guy responsible for the application of the powder coating. They usually ask questions along these lines: “Dallas, what do you think this is and how do we prevent it?” as they point to what appears to be a defect with the powder coating. This article discusses the most common issues and the solutions.
Because every part starts as a design in some program, here are some questions to ask yourself before the part goes into production:
Is there a hole to hang the part by with a metal hook? The powder coating process will require the part to be grounded (a negative) and suspended in air in order to apply the powder. This is usually achieved by a metal hook.
Will the part hold water in the pre-treat process? If you were to hold the part in your shower, would the water run off, or would it build up in corners, areas not welded solid, tubing etc.? This can be an issue as powder coating and water do not mix.
Does the part have any crazy angles? Powder coating is an electrostatic process and any corners 90 % or less can present problems coating the corner. You should also have your powder coating expert look at the drawing to determine if it’s “powder coating friendly” to save you time and money in the long run.
Now that your part is in production, here are key items to look for:
Is the part rusting or oxidized? This may seem obvious but unless the part is going to be media blasted before powder coating, it is imperative to keep rust or oxidization off the parts. We suggest putting on additional water-soluble oil if you feel the parts might get rusty before coating.
“If you feel it, you will probably see it!” This rule of thumb holds true on weld seams, weld splatter, gashes in the metal, or any raised or lowered surface imperfections.
Does the part have mill scale? Mill scale is a loose coating of oxide which forms on iron or iron products when heated. If this is not removed before coating, it will make for poor adhesion.
“What is on the surface?” Some big “no-no”s are using weld splatter spray, silicone, or sticker glue on the parts since the substance is mostly clear and will not be removed in the pretreatment stage but will bleed through the coating.
Is the part a casting? Cast parts sometimes present a problem in the powder coating process, depending on the quality of the cast. If the cast is of poor quality, the pockets will “out-gas” in the curing cycle, causing pin-sized holes on the surface.
Do you have metal overlapping metal without being welded solid? This is the most common problem that we see. Exposed surfaces are needed to apply powder coating since powder coating will only cover what you can see. This is commonly misunderstood because the process is electrostatic.
By answering these questions before your next powder coating job, you will most certainly ensure quality and save time and money.
By: Dallas Cooley – Vice President of Sales – Georgia Powder Coating INC. – dallas@georgiapowdercoating.com
For More Information Visit www.georgiapowdercoating.com