6 Finishing Flaws Powder Coaters Don't Have to Accept

Regarding powder coating, overspray happens when powder is applied but lands on areas you want to keep paint-free. Overspray can occur because of improper use of the powder coating gun, too much air pressure, and/or the angle of the powder application. However, the primary source of overspray finishing flaws is a lack of masking.

The simple answer to preventing overspray is to mask the surfaces that need to be kept clear of paint. This can be done in several different ways, including masking tape, caps, plugs, and/or custom silicone masking options.

Bridging happens when the paint/powder accumulates against the mating point of the masking and the part that's being coated.  The GIF shown here demonstrates what this looks like.

One option for reducing bridging is to create a feathering effect and take advantage of the Faraday Cage effect. This is where the charge helps push the powder away from the area so that it tapers towards the parts so that the edge is as slight as possible.

One of the most efficient solutions to help reduce bridging is to implement a custom mask that protects the grounding area of the transitional spot. Several designs achieve this protection, but a common solution is to design a mask with a flange wrapped around at an angle like an umbrella or a skirt. (See featured plug below)

Incorrect or inadequate masking causes threaded holes to need to be re-tapped. Any time paint gets onto threads and has to be re-tapped, labor increases, quality is at risk, and profits decrease.

All powder coaters fear "Fisheye" or powder craters. While there are several different causes of this, one that we hear about a lot is silicone. Low-quality silicone masking products can be the source, but luckily, there's not as much to worry about today.

At Echo, we use a high-heat post-curing system to remove residue, odor, and toxins from our silicone masking parts. For more extreme scenarios, we can also use platinum-cured silicone, which has no by-products.

An issue powder coaters encounter is that the masking tape they're using can’t withstand the curing temperature, resulting in the adhesive baking onto the surface. This can be very labor-intensive and hard to cleanly remove.

The simple fix is switching to a higher temperature-resistant masking tape.  Here is what we suggest for when you're running into issues with green or blue poly tapes:

• Rusty Red Tape (425F) - Slightly higher temperature rating at a lower price than the other options below
• Red Poly Tape (437F) - Great alternative to blue poly due to thin backing and higher temperature rating
• Glass Cloth (500F) - Great for thicker coats and more extreme temperatures
• Polyimide Tape (500F) - Great for clean masking lines and extreme temperatures

Cleaning your masking caps and plugs will remove paint from previous processes, reducing the chances of paint flake issues. A vibratory tumbler does this well. 

You may also need to switch masking materials. Red iron oxide silicone can provide excellent results in place of standard silicone in high-temperature paint applications. Paint bonds better to red iron oxide silicone, reducing the risk of paint flaking.