Corrosion of Structural Ceramics Under Sub‐Critical Conditions in Aqueous Sodium Chloride Solution and in Deionized Water. Part II: Dissolution of Al2O3‐Based Ceramics

Abstract

Two types of alumina‐based ceramics, pure solid‐state sintered (SSS) alumina ceramics, and a liquid phase sintered (LPS) alumina were corrosion tested under both static and quasi—dynamic conditions in 0.5M NaCl solution and in deionized water reference medium at the temperature of 290°C. Static tests were also performed at 150° and 200°C in order to obtain the data for determination of kinetic parameters, and for calculation of the activation energies. The apparent activation energies of dissolution of the LPS alumina in deionized water and in 0.5M NaCl solution were identical and ranged around 49 kJ/mol. The SSS alumina ceramics corroded by grain‐boundary attack and slow dissolution of alumina matrix grains, and the corrosion rates were negligible in both corrosion media. The LPS alumina, corroded by preferential attack and dissolution of calcium aluminosilicate grain‐boundary glass. The alumina matrix remained relatively intact. The dissolution was markedly faster than in the SSS alumina. The rates of dissolution were found to be temperature dependent, but no influence of the corrosion medium was observed.