Some studies on stress corrosion cracking of AISI 326 stainless steel in polythionic acid

Polythionic acid, having the general formula of H2SXO6, has been known to cause stress corrosion cracking in stainless steels at ambient temperatures. In the present study, Saman's solution, prepared by passing H2S in a H2SO3 solution, has been used as test solution. The effects of sensitization temperature and time, applied stress, applied potential and addition of sodium chloride, triethanolamin and sodium hydrogen phosphate on the stress corrosion behaviour of AISI 316 stainless steel have been studied. The cracking has been encountered only in the sensitized steel which has been supported by EPR studies. A general decrease in time to failure has been noticed with an increase in applied stress up to the yield stress, beyond which the time increases. The addition of sodium chloride shows an accelerating effect whereas the other two additives have shown to have inhibitive effect on cracking which has been explained on the basis of their adsorption and corresponding polarisation behaviour.