It is a method of protecting a steel surface from corrosion and increasing its resistance to wear through the application of a chemical phosphate conversion coating.
Parkerizing is commonly used on firearms as a more effective alternative to bluing, which is an earlier-developed chemical conversion coating. It is also used extensively on automobiles to protect unfinished metal parts from corrosion. As for all chemical conversion coatings, the Parkerized surface must be completely covered with a light coating of oil to maximize corrosion and wear resistance, primarily through reducing wetting action and galvanic action. Parkerizing, bonderizing, phosphating, or phosphatizing is a method of protecting a steel surface from corrosion and increasing its resistance to wear through the application of a chemical phosphate conversion coating. As for all chemical conversion coatings, the Parkerized surface must be completely covered with a light coating of oil to maximize corrosion and wear resistance, primarily through reducing wetting action and galvanic action. Parkerizing. This tutorial will take you through all the steps to do a parkerized finish on your guns. If you follow the instructions you will achieve professional, consistent results.This is a 4 step process and each step will be explained in detail, along with the necessary supplies and equipment.1. De greasing2. Parkerizing is an electrochemical process that creates a protective iron-phosphate layer on the outer surface of steel. It protects the steel from corrosion and also increases its resistance to wear. The resulting surface is irregular on a microscopic scale. It does not mean that electrodes and wires are involved at all! Parkerizing is the creation of an iron-phosphate layer on the outer surface of the steel, producing a grey matte finish that helps to protect from corrosion and increases wear resistance. The protection is in two parts. First, the iron-phosphate layer itself is protectiv Parkerizing is usually considered to be an improved zinc or manganese phosphating process, and not to be an improved iron phosphating process, although some use the term parkerizing as a generic term for applying phosphating (or phosphatizing) coatings that does include the iron phosphating process. As for all chemical conversion coatings, the Parkerized surface must be completely covered with a light coating of oil to maximize corrosion and wear resistance, primarily through reducing wetting action and galvanic action. It is a phosphate finish that is much more durable than a blued finish. It is very suitable for a service or duty type weapon. It is not as protective as the new coatings they put on Glocks and such but it holds up better than blue. Military weapons have used Parkerizing for a long time.  == Answer == Parkerized finish is a non reflective matte type finish (black). It is used on military weapons to prevent reflecting sunlight and giving away a soldiers position. It is also called a phosphate finish. It is produced by a chemical reaction with the metal itself rather than being painted on. To finish is a verb meaning that you have done something and you have completed it. The noun finish is the completion of a project, or the end line of a race. We do not recommend this finish as a primary finish due to its poor corrosion resistance and wear. We do not cover this finish in our lifetime warrantys Phosphating, better known as “Parkerizing”, is a process involving the transformation of the surface of the steel to a rust resistant manganese or zinc phosphate. 
https://en.wikipedia.org/wiki/Parkerizing https://en.wikipedia.org/wiki/Parkerizing http://projectguns.com/parkerizing.html http://m1-garand-rifle.com/parkerizing/ https://en.wikipedia.org/wiki/Parkerizing http://gunnerforum.com/gun-care/5680-parkerized-finish.html http://www.answers.com/Q/What_is_a_parkerized_finish_on_a_gun https://robarguns.com/custom-firearm-finishes/phosphating-parkerizing/
what is parkerized finish