Corrosion is one of the most common forms of steel materials, and corrosion protection of steel has been the focus worldwide. In recent years, the service life of steel materials has been effectively extended by preparing anti-corrosion coatings on the surface of steel substrates, reducing serious accidents and casualties caused by corrosion. The work aims to introduce the preparation of Zn-Al pseudo alloy coatings by arc spray and related applications, and review the research progress on the corrosion resistance of arc sprayed Zn-Al pseudo alloy coatings. Firstly, starting from the classification of thermal spray, the advantages and disadvantages of each spray technology were briefly expounded, and the main use of arc spray to prepare Zn-Al pseudo alloy coatings was clarified. Among several thermal spray techniques, flame spray and arc spray were suitable for preparing pseudo alloy coatings due to their lower temperature and slower particle velocity, which were beneficial for coating deposition. Compared to flame spray, electric energy and compressed air were used by arc spray instead of flammable gases such as oxygen and acetylene, resulting in significantly higher safety than flame spray. In addition, the coating structure prepared by arc spray was more uniform, and the bonding strength with the substrate was higher than that by flame spray. Therefore, arc spray was regarded as an ideal choice for the preparation of Zn-Al pseudo alloy coatings. Secondly, the long-term corrosion protection mechanism of Zn-Al pseudo alloy coating was elaborated, providing a theoretical basis for further improving the corrosion resistance of Zn-Al pseudo alloy coating anti-corrosion system. The microstructure of the arc sprayed Zn-Al pseudo alloy coating exhibited alternating overlap between Zn rich and Al rich regions, which was a mechanical mixture of Zn and Al phases. During the corrosion process, when the Al2O3 passivation film on the surface of the Zn-Al pseudo alloy coating was destroyed, the Zn phase corroded preferentially and generated a dense layer of corrosion products. The Zn corrosion products covered the surface of the Zn-Al pseudo alloy coating and the pores were blocked, thereby reducing the corrosion rate. As the corrosion time increased, the Zn phase was continuously consumed, and at this time, the Al phase served as a sacrificial anode to provide cathodic protection for the substrate. Besides, the current research status of improving corrosion resistance of Zn-Al pseudo alloy coatings was discussed from the aspects of zinc aluminum component, arc spray process parameters optimization, element addition, and post treatment. The Al content essentially made a significant effect on the corrosion resistance of Zn-Al pseudo alloy coatings. As the Al content increased, the corrosion potential of Zn-Al pseudo alloy coatings increased, making them less susceptible to corrosion. In addition, adjusting the spray distance, spray current, and spray voltage could change the size, temperature, and impact velocity of metal droplets, thereby changing the microstructure morphology and coating/substrate bonding strength of Zn-Al pseudo alloy coatings, which further affected the corrosion resistance of Zn-Al pseudo alloy coatings. Furthermore, due to the deformation of molten or semi molten metal droplets under impact during the arc spray process, and the formation of loosely packed spatters caused by pores and microcracks in the Zn-Al pseudo alloy coatings, the service life of Zn-Al pseudo alloy coatings was restricted. The addition of Mg, Si and RE to the Zn-Al pseudo alloy coating could reduce the porosity of the coating, and the corrosion products accumulated more quickly and formed a thick corrosion product layer, thus improving the corrosion resistance of the Zn-Al pseudo alloy coating. Moreover, as for the post treatment process, the sealing agent could fill the pores and microcracks in the coating, while laser remelting transformed the coating/substrate bonding mode into metallurgical bonding and eliminated the pores and cracks on the arc sprayed coating through the diffusion of elements near the coating and substrate interface. Subsequently, the application of Zn Al pseudo alloy coating anti-corrosion system in bridges, marine steel structural components, chemical equipment, and underground pipelines for power transmission and transformation was discussed. Finally, the challenges in current research work were summarized, and key issues for further research on arc sprayed Zn-Al pseudo alloy coatings were put forward. At present, significant progress has been made in the study of the corrosion resistance of arc sprayed Zn-Al pseudo alloy coatings, but there are still many scientific issues to be further studied, such as the corrosion behavior of Zn-Al pseudo alloy coatings in sulfur containing or other corrosive environments, the corrosion resistance of high aluminum content Zn-Al pseudo alloy coatings, and the mechanism of changing the coating/substrate bonding mode. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.
