Enhancement of Corrosion Resistance in Carbon Steels Using Fe-Based Amorphous Metallic Coatings Under High-Temperature Flowing Water

Abstract

Carbon steels are the backbone material of modern industry applications owing to excellent forming, machining, and welding properties. However high-temperature flowing water condition induces complex corrosion phenomena involving destructive electrochemical reactions and mechanical wear for carbon steels thus a cost-effective countermeasure for the corrosion of carbon steels is highly required. In this study, to enhance the corrosion resistance in carbon steels under high-temperature flowing water, Fe-based amorphous metallic coatings (AMC) are deposited on carbon steels using high-velocity oxygen fuel (HVOF) technique. The Fe-based AMC gathers tremendous interests as they exhibit excellent corrosion and wear resistance thus it is expected that it provides effective corrosion protection ability for carbon steels even in severe environments including nuclear power plants. To examine the corrosion resistance of the Fe-based AMC, rotating cage corrosion (RCC) test was designed with a magnedrive-installed autoclave and recirculation loop system. The temperature for each test was 125, 150, 175, and 200 oC, respectively. To simulate power plant water chemistry, pH 9.3 ETA solution was continuously supplied. The weight loss of each specimen was measured after 2 weeks of elapsed time and the result shows that the Fe-based AMC exhibits excellent RCC resistance at all temperature and most effective at 150 oC as shown in Fig. 1. Further, while microstructure evolution of carbon steels displays the formation of porous Fe3O4 at the surface, the Fe-based AMC displays the formation of thin Cr2O3 layers meaning passivity as shown in Fig. 2.. At 200 oC, the formation of FeCr2O4 was also observable (Fig. 3) The early conjecture is that the Fe-based AMC is able to protect carbon steels by forming passive oxide layer at its surface. Previous research argued that Cr and its passive layer is the most effective RCC barrier in high-temperature. Thus, further investigation using transmission electron microscopy and X-ray photoelectron spectroscopy will be carried out to figure out their stoichiometry and detailed microstructure evolution. Figure 1