Corrosion Rates of API 5L X-52 and X-65 Steels in Synthetic Brines and Brines with H₂S as a Function of Rate in a Rotating Cylinder Electrode

摘要

This paper investigates the importance of the hydrodynamic conditions in the corrosion rates in steeltype API 5L grade X-52 and X-65 in synthetic brine with and without H2S at 30 and 60C, tested in arotating cylindrical electrode (RCE) under hydrodynamic flow conditions within a rotation range of 0to 7500 rpm (4.319 m/s). It was found that the rotation rate influences the electrochemical processwhich takes place in the steel surface because it increases the corrosion rate with increasing rotationalrate. As expected, it was observed that at a temperature of 60C, corrosion rates higher than thetemperature of 30C were obtained, this effect being more evident in media with H2S. And the effectof H2S in the steel, was the one of increasing the corrosion rate drastically as a function of therotational rate. In the absence of H2S, the corrosion products formed on the steel surfaces werecomposed mainly of iron oxides, and in brine containing H2S the corrosion products were composedmainly of iron oxides and some sulfur (mackinawite) which was nonadherent and cracks easily. Thesteel has the best behavior under absence of H2S at 30C is the API 5L X-52 as it has the lowest valuesof corrosion rates not so when the temperature is increased to 60C where the steel has the bestbehavior is the API 5L X-65. Under presence of H2S at 30 and 60C the steel has the best performancewith respect to the corrosion rate by exhibiting lower values is the API 5L X-52.