What is the AccuBlack Chemical Blacking Process?

Accu takes us through the technology and process behind its AccuBlack coating…

Chemical blacking also known as ‘black oxide coating’ refers to a chemical reaction which alters the pigment of stainless steel. Accu is one of the UK’s leading precision engineering component suppliers which offers a wide range of coatings including AccuBlack. AccuBlack utilises a specialist hot PX-3 chemical blacking process to create a long lasting matte black finish, while maintaining all the precision, tensile strength and corrosion resistant properties of stainless steel components.

What Happens to Stainless Steel Components During the Chemical Blacking Process?

Accu’s PX-3 chemical blacking process involves the use of a heated bath of sodium hydroxide with an oxidising agent, which results in the partial conversion of the top layer.

The black oxide coating of steel is composed of magnetite - ferrous-ferric oxide Fe304 (FeO*Fe203).

The final outcome is a conversion coating which maintains the original dimensions, strength and integrity of the steel component. In order to prolong the aesthetics of the components over time, it is recommended that oil is added during maintenance.

Why use AccuBlack Chemical Matte Black Finish?

In comparison to conventional oxidising methods, AccuBlack coatings have an increased abrasion resistance and an improved appearance. AccuBlack coatings are also more durable and more black than cold blacking finishes. Cold blacking is carried out at room temperature using a copper selenium compound that leaves a sooty residue on the component.

Unlike similar finishes such as paint coatings and plating, AccuBlack maintains the accuracy of the component because the chemical pigment is embedded into the outermost layer of the stainless steel rather than adding a solid layer to the fixing and negatively affect the precise dimensions. The AccuBlack conversion coating provides a smooth, even finish with no significant dimensional changes. The coating thickness is less than a micron which is ideal for precision engineering where components are manufactured to a tight tolerance.

Accu’s PX-3 coatings are used in a wide range of industries, including automotive, aerospace and military stealth projects because the coatings are fully compliant with the military specification MIL-DTL-13924D Class 4 for controlling reflective glare.

Accu prides itself on making high-quality products available to everyone via a lightning-fast website and its custom component manufacturing service that caters for engineers who require a bespoke high-precision solution for specialist applications.

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