Hydrogen charging in low alloy steels exposed to H 2 S: impact of CO 2 or N 2 in the gas mixture
Résumé
This paper examines the influence of CO 2 / H 2 S ratio on hydrogen charging in low alloy steels. Hydrogen flux through the steel surface is the driving force for sulfide stress cracking (SSC). The impact of H 2 S and pH on SSC severity is extremely well documented, and these two parameters are used in the SSC severity diagram of ISO 15156-2 [1]. However, the CO 2 / H 2 S ratio is not considered in standard SSC testing procedures, even though it has a strong impact on corrosion. Indeed, according to several authors, competitive adsorption between HS-and HCO 3-on the steel surface could modify the charging flux, thus the SSC risks. The goal of the present study was to check if hydrogen charging is influenced by other parameters than the sole pH and P H2S. Experiments consisted in hydrogen permeation measurements through HSLA steel thin membranes. They were performed under cathodic charging in order to avoid corrosion products precipitation. Charging solutions with different H 2 S concentrations with or without CO 2 were used, in order to examine the individual contributions to the charging flux, and hence to evaluate a possible impact on SSC risks.
Domaines
Matériaux
Origine : Fichiers produits par l'(les) auteur(s)
Loading...