The effect of Si addition on the stress corrosion cracking behavior of austenitic stainless steel was studied by measuring the time to failure using constant load method and by testing the polarization curve in the boiling aqueous solution containing 42% $MgCl_2$. The Si content of austenitic stainless steel was 0.43, 1.00, 1.42, 2.21 and 3.96 wt.%. All the specimens were annealed for 30 minutes at 1050℃ and then water quenched. Specimen containing 0.43, 1.00 and 1.42 wt.% Si showed austenitic single phase but specimen containing 2.21 and 3.96 wt.% showed austenitic-rerritic duplex phase.
The results of this study were as follows :
1) Specimen containing 2.21 and 3.96 wt.% Si was more resistant to stress corrosion cracking than specimen containing 0.43, 1.00 and 1.42 wt.% Si because of the retardation of stress corrosion crack growth by ferrite phase and the formation of more stable passive film.
2) For stressed specimen, the total anodic and the total cathodic current density showed greater value than the same specimen unstressed at the constant electrode potential.
3) For unstressed specimen, pitting breakdown potential was not varied with Si content and the critical anodic partial current density decreased with increasing Si addition. It means that Si addition to austenitic stainless steel increases electrochemical corrosion resistance.