Influence of Mg ion on corrosion resistance of phosphate coating on Zn-Mg alloy coated steel.

摘要

A phosphate conversion coating was formed on the surface of Zn-Mg alloy coatedsteel by immersing the specimen in a phosphating solution. The characteristicchanges and corrosion resistance of coating were investigated with varyingconcentrations of Mg in phosphating solution. Surface morphology were observed bySEM and the chemical copomsition was invetigated with EDS. Salt spray test,potentiodynamic polarization and EIS were used to evaluated the corrosionresistance of coatings. The results show that Mg ions have participated in formationof the phosphate layer. The addition of Mg ions in the phospating solution made thecrystal structure of phosphate coating fine and dense and the phosphated coatingcontaing Mg increases the corrosion resistance of the phosphated coating of Zn-Mgalloy coated steel sheets .