Thread: Black coatings..

Parkerizing:

The Parkerizing process is different from the bluing process (which is essentially a pre-rusting/ oxidising of the steel surface) in that Parkerizing is actually a manganese- phosphate coating that chemically bonds to the surface of the steel. The colour obtained is grey to dark grey/black depending largely on the hardness of the steel. Generally the softer the steel the darker the finished colour. For this reason you often get a different colour shade between the barrel and receiver or other 'hardened parts'. Parkerizing bonds best onto a bead blasted surface, the finish is a matt non-glare coating, that is microscopically porous. This helps to hold rust preventing oils on the surface. Parkerizing has long been used as a military coating, and while not being as attractive to some as bluing, it is an excellent choice for hunting guns being far more durable than all of the types of bluing.
The process is usually complete within a few hours. At the end the parts are soaked in oil or dried. If dried they can quickly be painted, the Parkerizing acting as an excellent 'primer'.

Note: Bluing and Parkerizing can only be applied to the carbon or chrome-moly type steels used in firearms, and sometimes castings. They will usually not work on stainless steels, although there are some exceptions.

Can do it yourself - google for "homemade parkerizing recipe"