Influence of Al contents on the long-term corrosion behaviors of cold-sprayed Zn-xAl coatings

Abstract

ZnAl coating is considered one of the most economic candidates for marine static immersive corrosion protecting technology, in which the Al/Zn ratio is quite crucial to achieve a certain aggressive ions concentration corrosion. In this study, different Al contents Zn-xAl composite coatings were prepared using low-pressure dynamic cold spraying, potentiodynamic polarization and electrochemical impedance spectroscopy techniques were implied to reveal the long-term corrosion behaviors in 3.5 wt% NaCl solution and experimentally optimize the Al and Zn composition of the composite coating for marine static immersion corrosive resistance. The results showed that the weight loss kinetics curve of Zn-xAl composite coatings conforms well to a linear equation over time after logarithms, an increase in Al content leads to enhanced corrosion resistance of Zn-xAl composite coatings. After 1440 h immersion, the optimum Zn95Al composite coating, with high ECorr (−1.522 V) and low ICorr ((4.881 ± 0.98) × 10−5 A/cm2), presented the best corrosion resistance, due to the compact network passive film composing of Al(OH)3 and Al2(OH)5Cl∙2H2O, which slowed down mass-transfer step of Zn/Al elements.