Corrosion of Pure Cr and Ni-30Cr Alloy by Soda-Lime-Silicate Melts: Study of Simplified Systems
Résumé
The corrosion characteristics of model chromia-forming alloys (i.e. pure Cr and Ni-30 wt%Cr alloy) were studied in molten soda-lime-silicate (i.e. Na2O-CaO-xSiO(2), x = 3 or 6, molar composition) at 1100 and 1150 A degrees C using electrochemical techniques coupled with ex situ observations. High Cr activity of pure Cr led to high corrosion rates and also the inability of the material to develop a long term protective oxide scale after a preoxidation treatment. By contrast, the Cr2O3 scale built on preoxidized Ni-30Cr exhibited a protective behavior at 1100 A degrees C. The variation of basicity of the silicate melts showed a minor influence on the corrosion behavior of both materials. An increase in the temperature up to 1150 A degrees C led to higher solubility of Cr2O3, and thus did not allow the growth of a protective oxide scale on Ni-30Cr.