Chemical blacking on steel provides a uniform black finish. The film is a particular state of iron oxide which is black in appearance and on its own it has very little protective value so requires a protective coating of oil to prevent corrosion. A dry coating will quickly revert to the more typical brown/rusty coloured oxidation state of iron and corrode very quickly. The film is of negligible thickness and makes no discernible changes to the dimensions of the parts treated.
With the hot caustic blacking process, parts must be able to resist processing temperatures of up 1500 C.
It is not feasible to process mixed materials, for instance components that include copper such as bronze bushes, or brazed assemblies, as the copper will not blacken and will contaminate the blacking solution.
It is known as Blackodising, Chemical blacking and Chemi-black.
Blacking on stainless steel is also available (we have capacity for small machined components only).
There are a number of black oxide specifications available including;