Abstract
Behavior of stressed Type 304 steel in H2SO4 solutions with addition of cyanide or thiocyanate has been studied in view of the reported strong adsorption characteristics of these spiecies. Annealed Type 304 wire was examined at 353 K in 1 to 4 kmol/m3 H2SO4 solutions with additions of different quantities of KCN, NH4SCN, or NaN3 (pseudohalides) mainly under open circuit conditions at a stress of 275 MPa.
With increased additions of KCN or NH4SCN the attack morphology changed from heavy general corrosion to cracking or localized attack and the time or fracture was prolonged. KCN was a cathodic and anodic inhibitor and NH4SCN was a cathodic inhibitor. The latter was also an anodic inhibitor at and near the open circuit potential. In the solutions containing NaN3 Type 304 did not fail due to passivation resulting from the cathodic reaction stimulated by NaN3 or fractured by general corrosion at the small addition of NaN3.
