6 Finishing Flaws Powder Coaters Don't Have to Accept
Echo Engineering & Production Supplies, Inc.
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Have you ever been powder coating and experienced issues like overspray, re-tapping threaded holes, or the dreaded "fisheye" effect? More often than not, powder coaters accept flaws they could quickly eliminate. We’ve curated a list of common issues powder coaters sometimes overlook and provided simple fixes for each one.
Powder Coating Overspray
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.
Masking to Prevent Powder Overspray
The simple answer to preventing overspray is to mask the surfaces that must be kept clear of paint. This can be done in several ways, including masking tape, caps, plugs, and/or custom silicone masking options.
Bridging (Powder Build Up)
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.
Preventing Powder Build-up
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 and 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.
Re-Tapping Threaded Holes
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.
How To Prevent Having To Re-Tap Threads After Powder Coating
To avoid having to re-tap a threaded hole, your best option?is to use a?masking plug?before coating. A?push plug is ideal for threaded blind holes, while a pull plug works best for through holes. Whether masking a blind hole or a through hole, creating a tight seal on the leading threads will be vital to?keeping all threads clean.
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Fisheye Caused by Silicone Residue
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.
Other Potential Causes of Powder Coating "Fisheye" or "Craters"
While many powder coaters believe their fisheye issue stems from using silicone caps or plugs, in most cases, the reason stems from something else. A few areas to look into include:
Masking Tape Baking Onto Surface
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 remove cleanly.
The Fix
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:
Paint Flaking Off of Masks
Quality issues can sometimes be caused by the paint sticking to masking materials and then flaking off after removal.
The Fix
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.