Pretreatment is neither the most visible nor the most glamorous part of the coating process. It doesn’t involve color, it doesn’t photograph well, and it makes for less-than-ideal social media content. It’s no wonder, then, that most customers don’t prioritize pretreatment as they should when they’re shopping for a powder coating service provider – none of us know what we don’t know.
But when it comes to pretreatment, what you don’t know could cost you. Literally. As your friendly neighborhood powder coating professional, I recommend that you ask your shop the following questions:
Question 1: “How many stages is your pretreatment process?”
The worst possible answer to this is a blank stare. If the powder coating shop doesn’t have a multi-stage pretreatment process, or if their pretreatment process is to simply wipe your parts down with a damp rag, you can pretty much assume that any coating applied will fail much more quickly than you’d like it to.
Ideally, shops will say that they have a 3- or 5-stage pretreatment process. Some shops offer both, and the chemicals involved will differ based on the part’s substrate. A typical 3-stage pretreatment process for steel is as follows: alkaline cleaner to degrease, followed by a city water rinse, followed by an iron phosphate treatment to build a barrier against moisture. A 5-stage pretreatment process will involve an additional water rinse, and some sort of sealing agent (i.e., zirconium). Whether it’s 3- or 5-staged, the purpose of the pretreatment process is to build a preliminary barrier, protecting your part before the powder coating is even applied.
Question 2: “Where do you do your pretreatment?”
If the answer is “outside” or “right here in the middle of the shop,” this could be a red flag. Ideally, pretreatment will happen in its own dedicated space. Water should always be kept away from powder coating, which needs to stay dry at all times. Additionally, pretreatment runoff should not be dumped willy-nilly into nature. I would strongly advise against doing business with shops that aren’t conscientious in their disposal of chemicals.
Question 3: “Is your pretreatment process automated or manual?”
Either answer is acceptable. An automated process involves hanging parts up on a line, and running them through pretreatment mechanically, much like a car wash. If the shop tells you they do manual pretreatment (which is what Kaser offers), follow up by asking what kind of equipment they use. If the answer is “a wet rag,” run away. A good answer should involve mention of a pressure washer or pressure wand. Pressure is essential to proper pretreatment.
Additional considerations:
Pretreatment Time: If the shop rubs parts with a rag before coating them, the pretreatment process will take no time at all. The longer the pretreatment process takes, the more confidence you can have that your shop does a thorough job.
Pretreatment Temperature: Any reputable pretreatment process will involve a little heat. An oily part cannot be fully cleaned with cold water.
Pretreatment Concentration: Honestly, if a general public customer asked me about Kaser’s chemical concentrations in the pretreatment booth, I would simply assure them that our proprietary concentrations are adequate for the job. If, however, a large industrial customer requests a tour of Kaser’s facility (as they often do when vetting new powder coating providers for a long-term business relationship), I will be far more willing to break down the nitty-gritty detail of which chemicals are used, and at which concentrations. Bear in mind that if you’re on a tour of a powder coating facility and you can’t smell any of the pretreatment chemicals when you’re near the wash bay, it’s possible that their concentrations are too low to be effective.
If you’re seeking a powder coating provider that will offer good coating value for your money, consider asking a few pointed questions about pretreatment. The answers will tell you a lot about the shop’s commitment to coating quality.
Jase Kaser has a BS in Mechanical Engineering and is the General Manager of Kaser Blasting & Coatings in Lincoln, NE. They provide abrasive media blasting, powder coating, and liquid coating services throughout the Midwest and beyond. Connect with him on LinkedIn for more articles and resources or check out his blog on www.kaserblasting.com.
