Phosphate conversion coating
technique of protection of steel surfaces against corrosion
Phosphate conversion coating is a chemical treatment applied to steel parts that creates a thin adhering layer of iron, zinc, or manganese phosphates to improve corrosion resistance or lubrication or as a foundation for subsequent coatings or painting. It is one of the most common types of conversion coating. The process is also called phosphate coating, phosphatization, phosphatizing, or phosphating. It is also known by the trade term Parkerizing, especially when applied to firearms and other military equipment.
A phosphate coating is usually obtained by applying to the steel part a dilute solution of phosphoric acid, possibly with soluble iron, zinc, and/or manganese salts. The solution may be applied by sponging, spraying, or immersion. Phosphate conversion coatings can also be used on aluminium, zinc, cadmium, silver and tin.
History
The phosphatizing of firearms was discovered around 1910, when it was found that the surface of steel, if changed to a phosphate, acquires significant corrosion resistance. Until the 1940s it was very popular in the USA until more modern but similar methods of metal finishes were introduced.
Types
The main types of phosphate coatings are manganese, iron, and zinc.
“Phosphate conversion coating” enters the record as technique of protection of steel surfaces against corrosion. Crown Archives preserves that source wording while asking what Phosphate, conversion and coating can confirm, complicate or overturn.
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This entry incorporates text from “Phosphate conversion coating” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.