The Phosphating Treatment for Industrial Fasteners

Surface phosphating treatment is a common fastener surface treatment. Phosphating for the fastener (like flat head nut, blind rivet nuts), commonly refers to zinc phosphating and manganese phosphating. Zinc phosphating lubricating performance is better than manganese phosphating, but its corrosion resistance is inferior to manganese phosphating, wear resistance performed not as good as galvanizing. It costs less than galvanizing, and its corrosion resistance is not as good as that of galvanizing. Its use temperature can reach 225 degrees Fahrenheit to 400 degrees (107~204 C).

After phosphating, it should be oiled, and fastener’s corrosion resistance is greatly affected by the performance of the oil. For example, the general anti-rust oil lasts only 10 to 20 hours in the neutral salt spray test, while the high grade anti-rust oil can reach 72~96 hours. But its price is 2 to 3 times higher than ordinary phosphating oil.

Industrial fasteners are often treated with phosphating and oiling. Because those fasteners have a good torque-preloading consistency and can meet the tightening requirements expected in the design during assembly. Especially the connection of some important parts. For example, the connection of steel structures, engine connecting rod bolts and nuts, cylinder heads, main bearings, flywheel bolts, wheel bolts and blind rivet nuts.

High-strength bolts through phosphating can also avoid the problem of hydrogen embrittlement, so the industrial bolts above grade 10.9 generally adopt phosphating surface treatment.