Leave The "Brake Cleaner" On The Shelf
Q. I powder coated this frame more than two months ago, and the job looked flawless. Now, it has these spots that are in various places and growing. Any ideas what would cause this? The frame (4130 Chromoly steel) was bright cadmium plated, steel wooled, and cleaned extensively with brake cleaner/metal cleaner that I use most of the time with good results. This was the first time I chose cadmium as a base instead of zinc for this type of job. After applying the translucent red powder I was very pleased with the results until now. What happened? C.
A. Contrary to popular belief, “brake cleaner” is not the best chemical to remove all soils from a part before powder coating. This solvent-rich aerosol solution is used by auto mechanics to clean brake parts before reassembly when performing a brake job. I bet if you read the can carefully you will not see any reference to using it to clean parts before powder coating. Granted, it will dissolve any petrochemical-based soils on the part and carry them off the surface provided you use enough of it. But is won’t prepare a chrome plated surface for powder coating.
The spots you are seeing are blisters formed from the salts on the surface before powder coating. These salts combine with the moisture that has penetrated the coating and, through osmotic pressure, eventually lift the coating. Salts on the surface of plated objects are very common and must be removed by a series of cleaning chemicals and neutralizers. Deionized water can be very effective as a final rinse before powder coating plated objects.
You have two choices now: Continue to watch the spots grow in number and size or strip the part and start over using the right combination of cleaning chemistries and neutralizers. For help on what chemicals to use, I recommend that you contact one of the many companies that serve the powder coating industry with pretreatment and cleaning chemicals to select the materials that can work in your process. Good luck and leave the “brake cleaner” on the shelf until you do your next brake job.
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