Guruprasad Sundararajan

The effect of absorbed hydrogen on the dissolution of steel

Atomic hydrogen (H) was introduced into steel (AISI 1018 mild steel) by controlled cathodic pre-charging. The resultant steel sample, comprising about 1 ppmw diffusible H, and a reference uncharged sample, were studied using atomic emission spectroelectrochemistry (AESEC). AESEC involved potentiodynamic polarisation in a flowing non-passivating electrolyte (0.6 M NaCl, pH 1.95) with real time reconciliation of metal dissolution using on-line inductively coupled plasma-atomic emission spectroscopy (ICP-OES). The presence of absorbed H was shown to significantly increase anodic Fe dissolution, as evidenced by the enhanced detection of Fe2+ ions by ICP-OES. We discuss this important finding in the context of previously proposed mechanisms for H-effects on the corrosion of steels.

The Effect of Absorbed Hydrogen on the Corrosion of Steels: Review, Discussion, and Implications

The presence of absorbed hydrogen (H) within pure iron and most steels (including carbon and stainless steels) has been found to increase their corrosion. Historically, the enhanced corrosion of H-charged steels has been attributed to the ability of H to destabilize the passive film formed upon the metal. However, recent works have revealed that absorbed H can promote Fe dissolution even in non-passivating solutions. This indicates that the effect of H on metal corrosion could be “intrinsic,” rather than through “extrinsic” mechanisms involving solely the destabilization of the passive film. In this review, the impact of absorbed H on the corrosion of different types of steels has been collated, summarized, and discussed. The influence of H on the pitting and environmentally assisted cracking mechanisms of steels has been elaborated. Some implications of H-assisted corrosion from an engineering perspective have also been discussed.