Parkerizing

From Freepedia

Parkerizing (also called phosphating) is a method of protecting a steel surface from corrosion and increasing its resistance to wear. It is commonly used on firearms as a more effective alternative to bluing. However, the process cannot be used on non-ferrous metals such as aluminum, brass, copper or stainless steel.

The method was developed by the Parker family in the United States in the late 1800s, and the term Parkerizing is a registered trademark of the Parker Company. The process was first used on a large scale in the manufacture of firearms for the United States military during World War II.

The process involves submerging the metal part into an acid solution whose active ingredient is zinc or manganese. The solution is heated to a temperature of 190-210°F for a period ranging between 5 and 45 minutes. A stream of small bubbles is emitted from the metal part as the process takes place; when the bubbling stops, the process is complete.

Zinc phosphating results in a non-reflective, light- to medium-gray finish. Manganese phosphating produces a medium- to dark-gray or black finish. The finish is not a coating, but is actually part of the metal surface. However, the Parkerized surface must be completely covered with a light coat of oil to maximize corrosion and wear resistance. A heavy oil coating is unnecessary and undesirable.

Alternatively, the Parkerized surface may be painted over with an epoxy or molybdenum finish for added wear resistance and self-lubricating properties.