EXPLORING CORROSION RESISTANCE AND MICROSTRUCTURE OF MANGANESE PHOSPHATE CONVERSION COATING ON 65Mn SPRING STEEL

Manganese phosphate conversion coatings were prepared on 65Mn spring steel. The surface morphologies and compositions of the coatings were examined through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion resistance of the coatings was investigated using a copper sulfate titration experiment, salt spray test and electrochemical corrosion test. The results showed that a uniform and dense coating was obtained when the acid ratio was 10, the phosphating temperature was 85 °C, and the phosphating time was 5 min. There was no obvious rust on the manganese phosphate coating surface after 48 h of salt spray. Ultimately, the growth mechanism and corrosion behavior of the manganese phosphate conversion coating are explained.