Adhesion Failure as Time Goes By

What failure mechanism could likely trigger this? What are the material conditions that might be contributing to this?


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Q. I read your Q&A, “Poor Surface Preparation vs. Paint Adhesion,” from October 2005. We have a roller coating process that applies a primer and paint after the brass roller coat is “cleaned” by a chemical. And we notice that after the paint is applied over that roller coat and cured, it begins to peel off after a month of observations. Meaning that after the first three weeks it was painted, no peel-off was observed, but on the fourth week, there were portions that began to show such conditions. We would like to ask your help regarding this event. Our questions are:

1) What failure mechanism could likely trigger this? and
2) What are the material conditions that might be contributing to this?
Please help us. We need your advice. R.R.

 

A. As I sit here scratching my head, I’m not sure I understand your process. I don’t like to answer questions with questions but I need to know the answers to help you. If you will straighten me out, I will straighten you out.
I could help you if I knew the following:

1) Are you cleaning and painting brass?
2) Do you paint immediately after pretreatment?
3) What is the pretreatment?
4) What kind of primer?
5) What kind of paint?
6) Does the paint peel from the primer?
7) Do the primer and paint peel from the substrate?

I couldn’t help but notice that the words you used in your question title, “As time goes by,” are the name of the song that Sam played at Rick’s Place in the movie Casablanca. But that’s another story. Meanwhile, as Rick Blaine (Humphrey Bogart) said, “Play it, Sam.”


 

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