Alloy Steel Black Oxide Coating & Blackening Services

Black oxide coating for alloy steel is a MIL-C-13924 alkaline oxidizing process that converts the surface of low alloy steel into black iron oxide (magnetite). It creates a uniform black finish, offers mild corrosion protection, reduces light reflection, and adds no measurable dimensional change, making it ideal for precision alloy steel components.

Black oxide coating provides mild corrosion protection for alloy steel, but it should be sealed with a protective oil or supplemental coating to meaningfully resist rust. On its own, black oxide offers less corrosion resistance than platings like zinc or cadmium.

Both alloy steel and carbon steel use the same MIL-C-13924 Class 1 alkaline oxidizing black oxide process, producing a similar black finish and corrosion resistance. Alloy steel typically applies to higher-strength, low-alloy components like fasteners and shafts, while carbon steel covers standard steel grades used across general industrial parts.

Black oxide coated alloy steel parts are commonly used in aerospace, military & defense, and oil & gas industries. These sectors rely on alloy steel's strength combined with black oxide's mild corrosion resistance and dimensional stability for fasteners, shafts, and structural components.

Black oxide coating for alloy steel is performed to MIL-C-13924, along with MIL-DTL-13924 and AMS 2485. Class 1 of this specification covers wrought iron, cast and malleable irons, common carbon, and low alloy steels using an alkaline oxidizing process for a uniform black finish.