Paint Adhesion to Plated Plastic

am the senior engineering manager in charge of product development execution. The problem comes about after a translucent paint is applied over a chrome-plated polycarbonate/ABS plastic substrate. I’m assuming that the chrome plating must be prepared (cleaned or etched) before paint application, but I need some recommendations to forward to the factory.

Q. I am the senior engineering manager in charge of product development execution. I received your name from a NASF member in Dayton, OH. We’re a contract manufacturer and I’m troubleshooting a paint adhesion issue on a custom part. I’m not sure if you can help me, but if you know how I can locate a consultant or other resource to help resolve a production issue, I would greatly appreciate the assistance.

The problem comes about after a translucent paint is applied over a chrome-plated polycarbonate/ABS plastic substrate. I’m assuming that the chrome plating must be prepared (cleaned or etched) before paint application, but I need some recommendations to forward to the factory. Thanks in advance for your time and assistance. D.K.

A. The short answer is, “Poor surface preparation is the greatest single cause of paint failures.” You already know this because you are trying to solve the problem by asking how to pretreat the part. Hopefully, your supplier has a good working relationship with the manufacturer of the chrome-plated parts. He could ask him if he applies a protective coating over the chrome-plated parts for damage resistance during shipping and, if so, what to use to remove it. Such a coating could act as an interference coating, similar to oily soils, causing adhesion problems and film defects.

Your supplier could do solvent cleaning. If he solvent wipes, it is very important to use clean rags for this to work effectively. Otherwise, after the first few wipes, he will actually be spreading the soil around on the part. Therefore, wiping rags must be changed often. It is also important to change solvent often.

Another approach is to use an aqueous cleaner to remove the oily soils. I don’t know what kind of pretreatment equipment your supplier uses, but aqueous cleaners are applied by spraying or dipping into the chemical solution. The cleaning step is followed by a clear water rinse and then a dry-off before painting. Have him ask his pretreatment chemical supplier for product recommendations.