Black Oxide Finish

Flat Phillips Drive Machine Screw – Black Oxide Finish
Example of a Black Oxide Finished Screw

Black oxide finished screws commonly used in electronics.


Clients often ask us about the difference between black oxide and other available black coatings on fasteners. We thought a brief review on black oxide would be useful.

A conversions coating

Black oxide coating is a low cost conversion coating produced by chemically altering the surface of a metallic substrate. The result is a decorative matte black finish with many useful properties.

Black oxide offers dimensional stability

This treatment has virtually no effect on the dimensional aspects of the part, adding only 5 to 10 millionths of an inch to the fastener’s dimensions.

A lasting finish

Because it is a chemical modification of the metal substrate itself, it is very stable even at high temperatures and does not chip, peel or rub off and resists abrasions better than black phosphate or zinc coating.

Moderate corrosion resistance

Black oxide by itself provides virtually no protection against corrosive environments. Additional treatments like oil or wax are needed for corrosion resistance. But even with oil or wax, black oxide only offers moderate protection and as such is ideally suited for indoor applications.

No white rust

An important property of black oxide, unlike some electroplated finishes, is that white rust does not form over time on the finish. Since the formation of white rust is a risk factor for electrical shorts, black oxide fasteners are often preferred in the electronics industry.

Elliminates the risk of hydrogen embrittlement

The conversion coating process does not involve known risk factors contributing to hydrogen embrittlement and material failure in certain types of fasteners. Consequently, no additional treatments are necessary to address this concern.


Aspen Fasteners offers full lines of many different types and styles of black oxide finished fasteners suitable for a variety of applications. The lines include but are not limited to:

Available from stock

All parts are stock and available for same day shipping from our distribution centers across the USA and Canada. And remember, it’s always FREE shipping.

Read about black oxide and other finishes in greater detail here.

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