Why is blackening treatment necessary for steel?

Steel rusting is a common phenomenon. While phosphating treatment is a widely used solution for rust prevention, there is actually a more convenient alternative: blackening treatment.

Blackening treatment is the process of forming a dense oxide film on the surface of steel, like putting a protective suit on the metal, isolating it from the air, and making it difficult for rust to form.

When WUMA reducer factory customize special products for customers or apply them to special industry conditions, we will blacken the worm shaft ,flange of worm reducer and oil plug screws.

So how do we perform the blackening process?
We immerse the worm shaft in a specialized blackening agent, allowing the surface to slowly transform into a very thin layer of bluish-black magnetite film. This film is typically only 0.5~1.0μm thick, but it has a uniform texture and strong adhesion, hence the name "blueing."

The pretreatment stage before blackening requires removing oil, rust, scale, etc., from the worm shaft surface to prepare it for oxidation into a high-quality oxide film. This mainly includes chemical degreasing and pickling.

The blackening stage involves immersing the cleaned worm shaft in a blackening bath for a period of time to allow the desired oxide film to form on the worm shaft surface. The auxiliary processing stage after blackening primarily involves immersion in rust-preventive oil, which aims to further improve the corrosion resistance of the oxide film, increase lubricity, and enhance surface gloss.