Paint Over Chrome
Q1. We currently use an aqueous cleaning system for our chrome plated parts before wet coat mask painting. The system is designed for exterior automotive adhesion specs. Can a modern vapor degreasing system provide the same adhesion? R.M.
A1. If the only pretreatment given is an aqueous cleaning, vapor degreasing should provide the same adhesion characteristics. The paint doesn’t care how the part is cleaned—only that it is clean. You can prove this to yourself by asking the vapor degreaser vendor to clean some parts for you.
Q2. Thank you for your reply. I should have given you more detail on our aqueous cleaning steps. They are: mild detergent spray, cathodic electro- clean, rinse, chromic acid, rinse, DI rinse, oven dry-off. We have always tried to follow the rule of painting within 8 hr of plating to get the best adhesion, but due to product variations and quantities, most of the parts will sit 48 hr to a week after plating, before cleaning and coating.
Again, would a vapor degreasing system be a viable alternative? We are looking to do the same cleaning/activation in a smaller foot print. R. M.
A2. In a word, the answer is NO! I am glad you clarified your question by telling me the extent of the process. The only thing the vapor degreasing process will do is clean (by degreasing) the parts. It will not, I repeat, WILL NOT replace your present pretreatment process and will therefore probably not provide the same adhesion characteristics. Again, you can prove this to yourself by asking the vapor degrease vendor to clean some parts for you.
As this question shows, there is a lesson to be learned: When asking for outside help and advice, to get the right answer, it is important to ask the right question!
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Masking is employed in most any metal finishing operation where only a specifically defined area of the surface of a part must be exposed to a process. Conversely, masking may be employed on a surface where treatment is either not required or must be avoided. This article covers the many aspects of masking for metal finishing, including applications, methods and the various types of masking employed.