Parkerizing is a technique used to add a phosphate coating to steel to provide it with protection against wear and corrosion. This coating is typically composed of a zinc phosphate, though it can also use iron or manganese instead. It cannot be applied to nonferrous metals such as copper and aluminum, and even steel that has a high content of nickel can be unsuitable.

The technique of parkerizing is based on iron phosphating processes that were first carried out in the late 19th century. Similar manganese phosphating was also experimented with in the early 20th century, which ledto the development of parkerizing around 1915.