An Investigation on Effect of Heat Treatment on Corrosion Resistance of Zinc Phosphate Coating Applied on Plain Carbon Steel - Determination of the Optimum Temperature

Phosphate coatings are in the hydrated state because of they are formed in aquatic environment and therefore when these coatings are exposed to high temperatures such as paint oven، the chemical stability of such coatings especially dehydration behavior is of great concern. Thus، phosphate layer applied on the surface should be dried، by application of non – aquase organic or powder organic coatings until thermal stability of phosphate coatings، and removal of their structural water during exposing the samples in the furnace not result in the loss of paint quality. In this article، the effect of heat treatment at different temperatures of 120، 180، 250، 280، 350 °C on the weight loss and corrosion behavior of zinc phosphate coating formed on the surface of plain carbon steel was investigated. The results showed that heat treatment of phosphate coating at 120 °C improved protective behavior because of the loss of structural water. But increasing temperature to 180 °C and higher، decreased the corrosion resistance.