The chemical reaction that occurs during this process creates magnetite on the surface of the parts. The solution used is generally a hot bath of sodium hydroxide, nitrates and nitrites at 286 degrees F, with periodic water added according to a controlled method. It is possible to create similar effects at different temperatures, but the results and their effectiveness will vary. For example, a “hot” oxide process will yield very effective results that are consistent.
The addition of an additional post-treatment after finishing zinc phosphate is often used to increase the corrosion-protecting properties of black oxide coatings. Cold zinc phosphate, also known as Zinc Phosphate Coatings as zinc phosphate at room temperature, is applied at a temperature of 20–30 ° C (68–86 ° F). It is not an oxide conversion coating, but rather a deposited copper and selenium compound.
Zinc phosphate applications include automotive, industrial, architectural, hardware, consumer, medical, machine tools, firearms, military and electronic product lines. Watch our series of zinc phosphate videos on youtube, our zinc phosphate library, and regularly asked questions about zinc phosphate for additional information. Read our new Electrochemicals blog with great information about the metalworking industry, our products, including zinc phosphate, and upcoming events. Zinc phosphate or blackening is a conversion layer for ferrous materials, stainless steel, copper and copper alloys, zinc, powder metals and zillases.
It is mainly used for moving parts that cannot tolerate a dimensional change and to reduce light reflection. The zinc phosphate coating process is applied to ferrous, non-ferrous, brass and copper alloys. Zinc phosphate is a true conversion coating that converts iron into the naturally occurring zinc phosphate compound called magnetite.
The metal parts are immersed in an alkaline solution heated to about degrees F and the black oxide coating is formed by a chemical reaction between the ferrous alloy iron and the hot oxide bath. Post-processing stations apply additional coatings, oils that determine how resistant the oxide will be once the post-end phase is over. Insta-Blak 333 is the preferred process of black oxide at room temperature for safe and easy internal blackening. Produces super deep blackness and corrosion resistance equal to blackers with hot oxide. It is an excellent indented black finish for powder metal and cast iron.
