The Influence of Noble Metal Additions on the Sulfide Corrosion Performance of AISI 4130 Steel

Additions of copper, silver, palladium, platinum, and nickel were made to a 690 MPa yield strength AISI Type 4130 steel to evaluate their influence on the absorption of hydrogen into the steel and the subsequent cracking behavior. The results showed that copper, silver, and nickel additions at the concentration levels of 0, 0.05, 0.1, 0.5, and 1 weight percent had no effect on the sulfide cracking performance. Palladium and platinum, however, at concentrations in excess of 0.5 percent, rendered the steels immune to both sulfide stress cracking and hydrogen induced blister cracking. The results were analyzed in terms of the influence of the solutes on the proton discharge mechanism at the steel/corrodent interface, and also in terms of the decoration of second-phase nonmetallic inclusion interfaces with noble component where retardation of hydrogen-gas precipitation occurs.