IMPROVEMENT IN HARDNESS AND CORROSION RESISTANCE OF STEEL THROUGH RED MUD COATING

Abstract

Red mud is a waste product produced during alumina extraction from bauxite by the Bayer’s process and has become a major issue in connection with its disposal. As the aluminum demand in the world is increasing, the disposal of red mud waste into the environment also increases, bringing with its environmental issues coupled, however, a potential for the waste to generate a huge amount of unutilized resources still contained in the red mud, such as Fe2O3, Al2O3, SiO2, and others. As a possible useful utilization of the disposable waste, red mud can be used as a fine ceramic coating material onto metal substrates. For a fine ceramic coating, fine red mud powder was mixed with other substances to form a non-aqueous coating slurry with toluene as the solvent, PEG 6000 as the binder and plasticizer, and sesame oil as the dispersant. The coating process was performed by a dip-coating method onto ST-37 steel with a withdrawal speed of 0.23 mm/sec. The densification of coating material took place after calcinations at 900 °C, 1100 °C, and 1300 °C for 2 hours in nitrogen atmosphere. This treatment evinced an improvement of the surface hardness from 146.2 HV to 1738.8 HV for the sample calcined at 1100°C and the corrosion resistance by 4.14 times, for the sample calcined at 1300°C.