Composite magnesium phosphate coatings for improved corrosion resistance of magnesium AZ31 alloy
Abstract Corrosion performance of magnesium phosphate composite coatings consisted of struvite (MgNH4PO4*6H2O) and newberyite (MgHPO4*3H2O) on magnesium AZ31 alloy obtained in a high concentrated NH4H2PO4 phosphating bath at different pH ranges in 1 wt. NaCl aqueous solution were analyzed using potentiodynamic polarization test, EIS analysis and immersion test. The test results revealed that the corrosion performance increased with increase in the coating bath pH which could be attributed to the uniform and dense magnesium phosphate coating with fewer defects and increase in the content of insoluble struvite phase.