Phosphatizing Powdered Metal Parts
My company makes powdered metal parts that are pressed to shape from metal powders to a density of 6.0 to 6.5 g/cc. The parts are then manganese-phosphate coated, and the phosphate coating does not always have a dark, even appearance, but is mottled. This has been attributed to the high copper content of the powdered metal parts. What do you think?
Q. My company makes powdered metal parts that are pressed to shape from metal powders to a density of 6.0 to 6.5 g/cc. The composition of these parts is iron, copper and carbon. Following the pressing operation, the parts are sintered in a furnace with a protective atmosphere to reduce oxidation and to retain the carbon. On a particular series of parts, the requirements are such that we machine, hardened then finish-machine to size. The parts are then manganese-phosphate coated, and it is this last operation that causes us considerable problems. The phosphate coating does not always have a dark, even appearance, but is mottled. This has been attributed to the high copper content of the powdered metal parts, but some at the plant disagree. What do you think? S.J.
A. I agree with your assessment of the problem. The fact that manganese phosphate reacts differently with various metals accounts for the irregular appearance on the surface of your parts. Although powdered metal technology is outside my area of expertise, I believe the mottled appearance indicates a lack of homogeneity on the surface of your parts. The manganese phosphate coating should have an even, dark appearance all over the surface.
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.
-
Curing Oven Basics
Simply heating up the substrate does not cure the coating. There are many variables to consider when choosing the best cure oven for your application...
-
Coatings Plant Evolves with Market Trends
Expanding its focus from exclusively serving the RV industry, one of this company’s stand-alone coatings plant has successfully extended its services to additional markets.