High Temperature Corrosion Behavior of Si-Containing Alloys in the Liquid Phase of Na2SO4 25.7 Mass% NaCl

The high temperature corrosion behavior of Si-containing alloys consisting of Cr-Si-Ni and CoNiCrAlY-Si alloys fabricated by spark plasma sintering technique was investigated in the liquid phase of Na2SO4 + 25.7 mass% NaCl at temperatures ranging from 923-1273 K. The purpose of this study is to develop excellent corrosion resistant alloys for coating applications. Our experimental results show the CrSi2 alloy with 10 mass% Ni content and the CoNiCrAlY alloy with 30 mass% Si content are the most promising materials for applications in this atmosphere. This is due to the formation of a protective SiO2 and Al2O3/SiO2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO2 plays a significant role in hindering the inward diffusion of chlorine and sulfur to the alloys substrate. Particularly, the corrosion mechanism of Cr-Si-Ni alloys and the influence of Ni addition on the corrosion resistance of CrSi2 alloy are discussed in the present paper.