Pretreating Parts for Liquid Coating

I’ve spilled a lot of ink touting the importance of pretreatment before powder coating, which is why the following statement may come as a surprise to some readers: Kaser does not pretreat parts before liquid coating them.

Wash bays take up space. They require walls, drainage, and various hookups. We didn’t install one when we were designing the liquid coating shop over a decade ago, and now it’s too late. There’s no room.

Would parts benefit from pretreatment before being painted? Absolutely. In a perfect world, we’d be degreasing, creating a conversion coating, and drying parts off in an oven before painting them, just like we do in the powder shop. If our liquid coating output were as high as our powder coating output, we would make that happen. Instead, we do it all by hand, and it works well for our purposes.

Our main objective is to remove greases and oils before painting. At Kaser, we achieve this through MEK, blasting, or a combination of the two.

I want to be clear that blasting is not a substitute for pretreatment. It’s not even a subsection of pretreatment. Pretreatment encompasses any chemical process aimed at cleaning or creating a conversion coating. Blasting, on the other hand, falls squarely under the category of surface preparation, along with sanding, grinding, and any other mechanical process that removes material from the part’s surface. 

Despite the fact that blasting is not meant to clean parts, it does a great job of removing most greases and oils. Blasted parts are well on their way to being ready for liquid coating. 

If we do not blast the parts, we always wipe them down with a rag soaked in MEK. This is very effective for removing surface contaminants and in most cases, is all the pretreatment we need for liquid coating.

Small shops, take heart: you don’t need a full wash bay in order to adequately prepare a part.  A well thought out multi-stage pretreatment process is definitely the best way to go. But if that isn’t feasible, a rag and some chemical will work. 



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