Corrosion of ceramics in halogen-containing atmospheres

Most single component oxide ceramics undergo active corrosion in halogen-co ntaining gases such as HCl to form gaseous corrosion products only. At high temperatures, such corrosion reactions are controlled by gaseous diffusion Of the product gases away from the solid surface. As a result, the reactio n kinetics and the corrosion rate can be predicted if the thermodynamics of the reaction ape known. Similar behaviour is expected for nitride ceramics . However, several multicomponent oxides, typified by NiAl2O4, and carbides may, react to form a porous solid product layer through which diffusion ta kes place and controls the corrosion rate. Nevertheless, evert in these cas es, if gaseous diffusion still controls, the rate of corrosion can be model ed and predicted. (C) 1999 Elsevier Science Limited. All rights reserved.