Breviary Technical Ceramics



 Defect Site Corrosion

Defect site corrosion can occur in practically any ceramic. If the defects are small, they are not relevant to deterioration.

Aluminium oxides (99.5 %) typically contain small proportions of Na2O3CaO, Fe2O3 and often of MgO as additives. Na2O and MgO combine with Al2O3 to form a small number of isolated crystallites distributed through the material, with the chemical composition of MgO . Al2O3 (spinel) or Na2O . 11Al2O3 (?-Al2O3). Corrosive attack is not critical, because the reactions only take place on the surface itself.
If larger inhomogeneities are dissolved away, significant damage to the surface occurs. In the final stage this can lead to deeper damage (in particular if intergranular corrosion is also taking place), which can in the end result in component failure.

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