Contribution of solution pH and buffer capacity to suppress intergranular stress corrosion cracking of sensitized type 304 stainless steel at 95 degrees C

The effects of solution pH and buffer capacity on intergranular stress corr osion cracking (IGSCC) of sensitized type 304 stainless steel ([SS] UNS S30 400) was examined at 95 degrees C by slow strain rate technique (SSRT) with an in-situ cracking observation system, It was found that an increase in s olution pH or buffer capacity increased crack initiation time and decreased mean crack initiation frequency, but exerted almost no effect on crack pro pagation. This inhibition effect on IGSCC initiation was explained as resul ting from a retarding effect of solution pH and buffer capacity on the decr ease in pH at crack nuclei caused by the hydrolysis of metal ions dissolved when the passive film was ruptured by strain in SSRT.