There’s nothing worse than realizing you’ve made a mistake in the wash bay after the part is coated. You may not realize that you didn’t thoroughly rinse your degreaser, for instance, until the powder coating is flaking off in sheets. Luckily, you can monitor your progress in the wash bay (and avoid late-stage disasters) by focusing on the three pillars of pretreatment: time, temperature, and concentration.
Let’s talk about the three pillars of pretreatment.
Good pretreatment takes time.
A shop that’s committed to long-term powder coating adhesion will spend time pretreating parts. We can argue about the number of pretreatment stages required, but hopefully everyone agrees: pretreatment should not be rushed or skipped over completely. Whether you’re manually degreasing the part with MEK or putting it through several stages of chemical in your wash bay, it’s going to take you a while to get the part clean.
Good pretreatment requires some heat (temperature).
Anyone who has washed a dish knows that you need hot water to combat grease. The same is true of metal parts. There’s room for discussion around how hot the water should be – I don’t believe, for instance, that you need to be using steam. However, if there’s no heat involved in the process, I would question how clean your parts are getting.
Good pretreatment relies on proper chemical concentrations.
Most powder coaters (self included) use a proprietary blend of chemicals that we’ve developed, tested, and proven effective with our city’s water supply and environmental conditions. You should expect to smell a distinct chemical odor near your wash bay or pretreatment area. If there’s no smell, the chemicals might be too diluted. On the other hand, if the smell is overpowering, you might be using more chemical than you need.
Successful pretreatment lies in the interplay of time, temperature, and concentration. If your chemical concentrations are low, for instance, you’ll need to spend more time. If you’re not able to get good heat, you might need stronger chemicals. I get into more concrete details here:.