Comparative study on rate of flow accelerated corrosion (FAC) of API 5L X-52-65-70 steels in a brine added with H₂S at 60°C by using a rotating cylinder electrode (RCE)

This work focuses on how important the hydrodynamic conditions are on the corrosion rates occurring in steel type API 5L grades such as X52, X65 and X70 when are exposed to synthetic brines with and without H₂S at 60°C. Experiments were conducted using a rotating cylindrical electrode (RCE) under hydrodynamic flow conditions over a rotation range from 0 to 6500 rpm (3.744 m/s). It was found out that the rotation rate affects the electrochemical process that takes place on the steel surface since it increases the corrosion rate when the rotational rate is increased. The effect of H₂S presence on the steel caused substantial corrosion rates as a function of flow rate. Under the presence of H₂S, the corrosion products were composed mainly of iron oxides, one sulphate (mikasaite) and some sulfur as the mackinawite, which was non-adherent and breaks out easily. The steel API 5L X-70 exhibited the best performance under the presence of H₂S at 60°C with respect to the corrosion rate by yielding the lower corrosion values.