Phosphates are salts of phosphoric acids. Phosphorus is derived from the Greek “phōsphoros,” meaning “morning star” or “bringer of light.” It is the 15th element in the periodic table and is essential to all life, with the average human body containing 25.6 ounces (751.3 g). It is found in products ranging from kitchen matches to conversion coatings for corrosion resistance (as phosphates).
Phosphate conversion coatings on metals are used to impart corrosion resistance and lubricity, or to serve as a base layer for subsequent coatings, such as paints, dyes and more. In simple terms, the process solution consists of a phosphate salt in a solution of phosphoric acid. The immersion process is commonly applied to steel parts, but is also applicable to other metallic substrates, including zinc, cadmium and tin, among others. The conversion coating consists of a phosphate of the substrate metal (for example, iron phosphate in the case of steel).
In addition to surface finishing applications, phosphate chemistry is widely used in commerce, including agriculture and other areas. Accordingly, phosphates in process wastewater can produce serious problems in the environment, the most harmful being eutrophication.
