Phosphatation of Iron Powder Metallurgical Samples for Corrosion Protection

Recently, powder metallurgy methods have been used widely for industrial purposes. In this work, powder-metallurgically produced samples were selected for zinc phosphate coating. Zinc phosphate coating was performed at 50 and 70 °C for 20 min in a bath containing 10 g l-1 ZnO, 25.5 g l-1 H3PO4, 5.88 g l-1 HNO3, and 2 g l-1 NaNO3. The effect of temperature on the phosphating process has been studied. The structure and corrosion resistance of coats have been investigated using scanning electron microscopy (SEM) and electrochemical methods (polarization and EIS). Results show that an increase in temperature affects the crystalline structure of the coats. The formation of the zinc phosphate coat on the powder metallurgical samples significantly decreases the corrosion rate of the samples