Fabrication and chain corrosion blocking mechanism of hydrophobic coating on electrolytic manganese surface

Abstract Due to its unique polyvalence characteristics, electrolytic manganese without passivation treatment will produce obvious chain corrosion reaction, so blocking the chain corrosion reaction is particularly important for electrolytic manganese industry. The SS (sodium stearate) coating used in this work improves the stability of Mn2+ by combining with Mn2+ on the surface of electrolytic manganese, thus inhibiting the transition of Mn2+ to a higher valence state, and realizing the effective blocking of manganese chain corrosion reaction. In addition, the coating has good hydrophobicity and can be used as an effective barrier against corrosive media on the surface of electrolytic manganese. The corrosion resistance of the coating is optimized by studying the influence factors such as SS concentration, immersion time, immersion temperature and drying temperature. The structure, properties and passivation liquid properties of the coating are analyzed by various characterization methods and electrochemical tests. The results show that the SS coating not only has good corrosion resistance and hydrophobicity, but also exhibits good stability, corrosion resistance strength and durability. The corrosion current density is reduced from 3.782 × 10−4 A/cm2 of bare manganese to 1.592 × 10−7 A/cm2. Even compared with chromium salt, SS coating shows better corrosion resistance. In this paper, single component SS passivating agent is used to prepare hydrophobic coating on the surface of electrolytic manganese, without using organic solvent or adding promoting solvent, and the passivation method is simple and easy to operate, which has important practical application value. It is also of great significance to prepare hydrophobic coating on the surface of electrolytic manganese or other metals or alloys.