Kinetics investigation of alumina ceramics corrosion in nitric acid

ABSTRACT The most widely used ceramic material is aluminium oxide, known as alumina. Due to its superior properties such as chemical stability, high wear resistance, refractoriness and so on, it is ideal for applications in aggressive environment. This type of environment often includes exposure to corrosive solids, liquids and gases. When ceramics come in contact with corrosive medium, several corrosion mechanisms can occur, depending on a number of parameters. Therefore, the corrosion behaviour of cold isostatically pressed (CIP) high purity alumina ceramics was observed under different conditions: 0.5, 1.25 and 2 mol dm−3 of nitric acid at 25°C, 40°C and 55°C through 10 days. Purity of used alumina ceramics was 99.8345 wt. % with 0.1655 wt. % of both sintering aid (MgO) and impurities (SiO2, CaO, Na2O and Fe2O3). The results show that Al2O3 ceramics exhibit good corrosion resistance in nitric acid. Al2O3 corrosion behaviour varies depending on the temperature, time and HNO3 concentration. In view of the reaction kinetics, it proceeds in the near-parabolic law in HNO3 aqueous solution and decreases with an increase of the HNO3 concentration.