| The effect of Si addition on the stress corrosion cracking (SCC) of austenitic stainless steel was studied in the boiling aqueous solution of 42% MgCl₂. Failutre time, under constant load, remained nearly constant for the specimen with Si content up to 1.42 wt.%, however, it increased drastically as Si content increased from 1.42 to 2.21 wt.%, and further increase in Si content did not affect the failure time. Metallographic examination showed that the specimen with Si <1.42 wt.% and Si> 2.21 wt.% had austenitic single phase and austenitic-ferritic duplex phase respectively. The increased failure time caused by Si addition was explained in terms of retardation of SCC growth due to ferrite phase and formation of stable passive film. No change in pitting potential(breakdown) was observed for both unstressed and stressed specimen regardless of its Si content respectively. The stressed specimen showed lower (more anodic) pitting potential than the unstressed. Critical passivation current density (critical anodic partial current density), in pass estimated from electrochemical polarization curve and weight loss measurement decreased with Si addition and higher passivation current density was observed with the stressed specimen compared with the unstressed. |
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