What is Black Oxide Coating?

20 April 2016

Chemically Treated to Stay Rust-Free

On the flip side of this phenomenon, oxidation can be regulated so as to add a protective coating to a metal. A black oxide coating, for example, is a potent corrosion defeating mechanism because the addition of a surface-oxidized layer prevents further interactions between the underlying metal and the oxygen in the atmosphere. And, since the air is predominantly full of oxygen, this is a vital procedure if a chemically reactive metal is to be protected from rust (a less fanciful term for oxidation). In addition, the controlled application of the coating lends an attractive finish to the surface of the metal, an aesthetically pleasing look that’s dark, meaning harsh light reflectance is attenuated while good looks are maximized.

The Application of Black Oxide Coating

There are a handful of easily controllable methods used in the industry. Electrochemical methods use a dry technique where an anodizing reaction takes place as passive electrolytic films are produced. Just like the anode of a battery, a generated potential difference causes a substrate to form, and the surface that interacts with the air then discolours and oxidizes. More popular techniques abound in industry, with chemical acid baths and pools of alkaline compounds acting as hot liquid baths. Both methods can, of course, be combined to optimize the process.

Enhanced Surface Features

A black oxide coating adds something special to a product in terms of visual appeal. Like burnished steel, the low reflectance factor adds a lustrous finish to weaponry. Surgical instruments benefit from reduced glare, allowing a sharp pair of eyes to focus on the job at hand. And the coating isn’t separate from the metal, which means it can never crack or peel like a standard finish would when the going gets tough.

Suitable for hard-working tools and industrial locales, the chemically strengthened coating is as decorative as it is tough, and the underlying metal is now quite immune to rust, even when the component experiences shock, vibration, or exposure to the elements.

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