Effect of manganese on the formation of hybrid zirconium-based conversion coating on low carbon steel surface

This study revealed the effect of Mn on the formation of hybrid zirconium-based conversion coatings (HZCC) on low carbon steel. The XPS results indicated that the Mn compounds on the surface of low carbon steel were mainly MnO and Mn₂SiO₄. Combined with the electrochemical measurements, the corrosion resistance of HZCC showed an increase followed by a decrease with increasing Mn concentration, which was related to the Mn₂SiO₄ and SiO₂ on the surface of low carbon steel. The excessive Mn concentration resulted in the loss of SiO₂ and aggregation of Mn₂SiO₄ on the low carbon steel surface, which caused the aggregation of Zr compounds on the surface and reduced the uniformity of the coating. Meanwhile, a moderate amount of Mn addition would be beneficial to increase the adhesion of organic coatings.