Abstract
In harsh environments, the corrosion damage of steel structures and equipment is a serious threat to the operational safety of service. In this paper, a Zn-Al diffusion layer was fabricated on 45 steel by the Mechanical Energy Aided Diffusion Method (MEADM) at 450 °C. The microstructure and composition, the surface topography, and the electrochemical performance of the Zn-Al diffusion layer were analyzed before and after corrosion. The results show that the Zn-Al diffusion layer are composed of Al2O3 and Γ1 phase (Fe11Zn40) and δ1 phase (FeZn6.67, FeZn8.87, and FeZn10.98) Zn-Fe alloy. There is a transition zone with the thickness of about 5 μm at the interface between the Zn-Al diffusion layer and the substrate, and a carbon-rich layer exists in this zone. The full immersion test and electrochemical test show that the compact corrosion products produced by the initial corrosion of the Zn-Al diffusion layer will firmly bond to the Zn-Al diffusion layer surface and fill the crack, which plays a role in preventing corrosion of the corrosive medium and reducing the corrosion rate of the Zn-Al diffusion layer. The salt spray test reveals that the initial corrosion products of the Zn-Al diffusion layer are mainly ZnO and Zn5(OH)8Cl2H2O. New corrosion products such as ZnAl2O4, FeOCl appear at the middle corrosion stage. The corrosion product ZnAl2O4 disappears, and the corrosion products Zn(OH)2 and Al(OH)3 appear at the later corrosion stage.
Highlights
Metal materials have long been exposed to environments with high temperatures, high humidity, high salt spray, and intense sunlight, making their corrosion levels several times or even dozens of times higher than that in other environments at the same time [1,2,3,4,5,6,7,8,9,10]
The Mechanical Energy Aided Diffusion Method (MEADM) that emerged in surface recent years has become an attractive metal materials anti-corrosion technology in the field of strengthening
We investigated the microstructures and element distribution of the Zn-Al diffusion layer
Summary
Metal materials have long been exposed to environments with high temperatures, high humidity, high salt spray, and intense sunlight, making their corrosion levels several times or even dozens of times higher than that in other environments at the same time [1,2,3,4,5,6,7,8,9,10]. In the process of metal corrosion, the mechanical properties and internal microstructure of the metal have changed. Corrosion protection of metal materials is essential in many industrial applications [11,12,13,14]. The corrosion protection of steel structures and equipment have flourished over recent decades [15,16,17,18,19,20]. Chemical heat treatment is usually used to improve the corrosion resistance, high-temperature oxidation resistance and hardness of metal parts [21,22,23,24]. Due to the high temperature and Materials 2019, 12, x FOR PEER REVIEW long production time, it consumes a lot of energy, and affects the mechanical properties of parts. Due to the high temperature and Materials 2019, 12, x FOR PEER REVIEW long production time, it consumes a lot of energy, and affects the mechanical properties of parts. long
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