Black Oxide

Black oxide coating is an ideal choice for enhancing the corrosion resistance, appearance, and durability of metal parts. This process creates a thin, black finish that provides a mild level of corrosion protection and reduces light reflection, making it suitable for applications in firearms, automotive parts, and industrial tools. Additionally, black oxide coating improves lubricity and minimizes galling, ensuring smoother operation and longer lifespan of the treated components.

Black oxide, also known as blackening or “bluing”, is a conversion coating applied to ferrous materials (such as steel or iron). Here are the key points.

Black oxide serves several purposes:

• Corrosion Resistance: It adds mild corrosion resistance to the material.
• Appearance: It provides an aesthetically appealing matte black finish.
• Reduced Light Reflection: Black oxide minimizes light reflection.

Process for Hot Black Oxide:

The material is dipped in hot baths containing sodium hydroxide (NaOH) and nitrates/nitrites. This converts the surface into magnetite (Fe ₃O ₄), which offers better corrosion protection than red oxide (rust).

Post-Treatment: Fresh black oxide is porous, so oil is often applied afterward to seal it and prevent corrosion when specified.

               Advantages:

                               Can be done in larger batches.

                               Minimal dimensional impact.

               Cost-effective compared to paint or electroplating.

Black oxide specifications:

The most widely used specification for black oxide is MIL-DTL-13924. Other specifications include AMS 2485, ASTM D769, and ISO 11408.