Corrosion and High Temperature Oxidation Behavior of Structural Steels Coated with Aluminum Alloys

Abstract

Structural steels are among the most widely used materials in today s industry. Various surface coating processes are used to protect structural steels from corrosion in atmospheric or aggressive environments. The most commonly used method is the galvanizing process based on forming zinc coating on the steel surface by using the hot dip method. Zinc coatings are insufficient to protect against corrosion, especially in chlorinated environments. Aluminum and its alloys stand out as an alternative material group to zinc in chlorinated environments. In this study, aluminum and aluminum alloy coatings, which are thought to be an alternative to zinc coating, were coated on the structural steel surface using the hot dip method. To examine how different aluminum alloys affect the corrosion and high-temperature oxidation properties of steels, nearly pure AA1050, high Cu content AA2024, and high Mg content AA5083 alloys were coated on structural steels. The coating process was carried out by dipping the structural steels into molten aluminum baths kept at a constant temperature of 700°C for 1, 3, and 5 minutes. The optimum adhesion and surface properties were obtained from dipping time for 3 minutes. The properties of coatings and intermetallic structures formed at the coating-steel interface were examined using an optical microscope, X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM), and Energy Scattering Spectroscopy (EDS) systems. To examine the high-temperature oxidation properties of the coatings, the coated samples were oxidized for 24 hours at 750°C under open-air conditions, and the changes in weight were investigated. Immersion corrosion tests were performed in 3.5% NaCl solution, and corrosion losses and degradation patterns were investigated. As a result of the studies, it has been determined that the Al coatings produced by the hot dip process significantly increase the oxidation and corrosion resistance of the structural steels.