Blackening techniques for metal - Blackening metal, also known as black oxide finishing or metal patination, is a technique used to create a dark, protective, and decorative finish on metal surfaces. There are several methods to achieve blackening depending on the type of metal and the desired result. Here are common blackening techniques: 1. Parkerizing (Phosphate Coating) - Process: Metal is immersed in a phosphoric acid solution that contains either zinc or manganese, resulting in a dark, matte finish. - Metals: Typically used for steel and iron. - Finish: Provides good corrosion resistance and a durable, dark-grey to black appearance. - Applications: Military-grade firearms, automotive parts, and heavy equipment. - Example: Firearm parts like barrels or receivers.