Iron Phosphate High Temperature Performance
My company paints carbon steel parts with a baking enamel. After painting, these parts are cured in an oven at 300°F for 15–30 minutes. My question is will curing the parts at 300°F adversely affect the iron phosphate coating?
Share
Q. I read the question and answer in the Dec. 2005, Painting Clinic titled “Hot Dry-Off Oven Causing Problem”. My company paints carbon steel parts with a baking enamel. Before painting, these parts are processed through an immersion paint pretreatment consisting of alkaline cleaning, iron phosphate and seal, with rinses between each step. After painting, these parts are cured in an oven at 300°F for 15–30 minutes. My question is will curing the parts at 300°F adversely affect the iron phosphate coating? Thank you for your response. T. K.
A. In the referenced question, K. C. observed flash rusting of iron phosphated steel parts in a too hot (350ºF) dry-off oven. I answered that a dry-off oven whose temperature is greater than 250ºF can have a disastrous effect on iron phosphate treated steel parts. At these high dry-off oven temperatures and owing to the low phosphate film thickness, the steel substrate has been known to oxidize (flash rust) without affecting the iron phosphate itself. This is indicated by a shift in the color of the iron phosphated surface from blue to gold. Because of this oxide, the corrosion resistance of painted articles can be greatly reduced.
Atmospheric oxygen must contact the phosphated steel substrate for this oxidation process to occur. Since your parts are painted before heating above the critical temperature of 250ºF, the paint eliminates atmospheric oxygen contacting the substrate and it will not oxidize. Don’t worry, you are safe.
Related Content
-
Shedding Light on Surface Inspection
State-of-the-art reflector-based lighting system improves luminosity and ergonomics for surface inspection tasks while reducing energy usage.
-
Robots, AI and Superb BMW Surfaces
There isn’t an automotive paint shop in the world that doesn’t have post-paint inspection and defect processing. But BMW is doing this with levels of technology at a plant in Germany that exceed all other paint shops in the world.
-
Henry Ford Is Still Right When It Comes to Color
Who would have imagined that more than 100 years after his famous statement about any color as long as it’s black would still have relevance of a sort?
