Electrochemical study of two microalloyed pipeline steels in H2S environments

The electrochemical behavior of microalloyed steel under H2S environment at room temperature and at 55 °C suggests that the superficial degradation in this steel is due to the combination of several mechanisms in which uniform corrosion plays a less relevant role, while localized corrosion and diffusion control (where diffusion of species such as H2S, HS - is possible) are key mechanisms for the corrosion process of this steel. It also was found that the limiting current ( i l ) increases proportionally with increase in temperature, leaving clear evidence for the existence of diffusion control. The estimation of corrosion rates by means of the R p technique, taking into account the diffusion control shows that, at room temperature, steel 2 presents the lowest corrosion rate with respect to steel 1. This behavior is reversed at 55 °C, steel 2 being more susceptible to corrosion.