How Do Phosphate Coatings Reduce Wear on Moving Parts

The benefits provided by phosphate coatings in reducing wear are ascribed to the controlled etching of the surface subjected to wear. Through tests it appears that the manganese phosphate coating is the most effective application, the reason being the number of larger pits formed by manganese phosphate and the greater amount of phosphate retained in these pits.

Chemical reactions involved in the production of these coatings are reviewed together with a comparison of the reactions involved in some of the common phosphate coating baths. The effect of treatment of metal surface prior to coating and the type of coating bath used are compared by examining the coatings as produced and after burnishing.

These coatings have been reported to provide wear resistance by removing surface irregularities after machining and lapping, increasing lubricating efficiency, and preventing welding under loads.