Inhibition of Stress Corrosion Cracking of Type 403 Stainless Steel in Sodium Sulfate Solutions

The effect of various organic and inorganic compounds in inhibiting the stress corrosion cracking (SCC) of Type 403 stainless steel in 0.01 M Na2SO4 solution at 100 C has been investigated. Polarization measurements were conducted in the absence and in the presence of various potential inhibitors, such as sodium silicate, sodium phosphate, sodium nitrite, sodium sulfite, sodium cyanide, sodium chromate, hexylamine, cyclohexylamine, morpholine, and octadecylamine. Times to failure of round tensile specimens, as determined using the slow strain rate technique, were measured in 0.01 M Na2SO4 solutions with and without the inhibitors at an applied potential of + 540 mVH. Sodium silicate was found to be the only effective inorganic inhibitor, and a failure time equivalent to that in air was found with the addition of 0.28M Na2SiO3. Hexylamine, cyclohexylamine, morpholine, and octadecylamine were also effective in inhibiting the SCC of Type 403. Their inhibiting efficiencies on a molar concentration basis were as follows: octadecylamine > cyclohexylamine ≈ hexylamine > morpholineThe critical concentration of octadecylamine necessary to retard the SCC of Type 403 stainless steel was found to be much less than those for hexylamine, cyclohexylamine, and morpholine.