Consider Avoiding These Simple Powder Coating Habits As They'll Usually End Up Costing You More Time And Money.
In the past we've mentioned some powder coating habits or steps that you should be doing, but in this article, we're going to mention a few that should be avoided.
1. Hot Flocking
The first is one we've mentioned a few times before but is worth mentioning again - no more hot coating (hot flocking). It's not that the "hot flocking" technique is completely wrong, but its fraught with risks that should make it an absolute last resort. It is far better to rely on a properly set up spray gun and a well-honed technique. Doing so will force the coater to better read and understand the powder's behavior and then make the appropriate adjustments. It's a skill developed over time, there are no shortcuts! Only when all other options have been exhausted, or if the equipment is not up to the task should hot flocking be considered and done carefully.
2. using Torches as a cleaning method
Refrain from using butane or other torches to burn lint from parts. Many people are tempted to use butane torches after wiping down or degreasing parts to burn off lint from rags. The problem is, torches do not burn 100% clean and can deposit contaminants on to the part you just tried to clean; resulting in defects in the finish.
3. relying on automatic gun settings
Don't rely on automatic gun settings or manufacturer programmed presets. Many of todays higher end spray guns have manufacturer programmed presets (usually 3) for different coating situations such as, re-coat or top coat, metallic, etc. These presets can make coating easy for a lot of situations, but they are not a cure-all and have their limitations. Sometimes the voltage presets are set too high for some scenarios. Get familiar with the manual mode of your spray gun and learn to adjust voltage and micro amps on your system. It may be necessary to contact your gun manufacturer if you do not have your systems manual.
4. Using Dirty Equipment
Don't use dirty hooks. Powder build-up on hooks or racks even after one use can create grounding problems which can result in numerous coating issues such as back ionization, over charging (KV Burn), poor transfer efficiency etc. Always use clean hooks, and make sure your racks are clean too. You need clean metal on metal contact from the part all the way to the ground in order to coat effectively. Dust that has settled onto your coating rack or nearby shelving can be disturbed by a slight breeze invisibly depositing these particles in to your coating.
5. Relying Exclusively on Acetone
Consider using a solvent other than acetone for degreasing and prepping parts. Acetone can absorb moisture from the air which can change how effective it is at cutting grease and oils depending on the humidity of the environment. This can result in undesired moisture on your parts even after the solvent has been flashed off. Instead try mineral spirits or denatured alcohol if your environment has excessively high humidity levels.
6. Don't Guess on Cure Times
Don't make guess work out of your cure times. While there is a fair amount of overbake stability in most powders, there is little to no tolerance for under baking. Powder coating MUST achieve the manufacturers stated combination of time and temp in order to obtain a full cure, anything less will result in an under cured finish. Use IR temperature guns to gauge part metal temp. Thermal probes can give faulty readings by giving you the ambient air temp which can be different than the part metal temp.
- Always check your work, never assume you got it right.
- Remove parts from the oven and inspect them after the powder flows out.
- Check for light spots in the finish, use a flashlight if necessary.
- Check for color consistency (especially with transparent colors).
- Lastly: Don't make assumptions
Many touch-up fixes can be done on localized areas rather than respraying the whole part, if caught in time. If the powder bakes too long and the powder begins to cross link, you will have to spray the whole part to correct any mistakes. Hopefully, some or all of these tips will help improve your workflows and ultimately lead to a superior finish. Happy Coating!