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Need alternative black coating that doesn't plug phillips head
I have a samll screw with a phillips head on it. Current callout is for a black phosphate and paint per GM4435M Code B, 72 hour salt spray. This coating tends to fill the phillips head at times. Is there an affordable alternative coating for this that would still meet the salt spray? It would need to be a GM approved coating.Dale Fedewa
Project Engineer - Grand Rapids, Michigan
The paint is what fills the recess, so eliminating that should fix the problem. I would just use phosphate + oil according to GM4435M Code A (I believe that's the designation, I don't have the standard in front of me). A high-quality phosphate + oil can easily meet 72 hours of salt spray testing without any red rust.Toby Padfield
Automotive module supplier - Michigan