Corrosion rate prediction of low carbon steel in brines containing CO₂ and H₂S

In this work, corrosion rate prediction models of type INC-516-G70 carbon steel in media that simulate the environment of water-oil separating tanks, the corrosion rate was determined by the electrochemical technique of linear polarization, as a function of temperature, pH and CO₂ and H₂S contents in NACE-ID-182 and NACE-ID-196 brines, with and without, O₂. In preliminary tests, the separated effect of temperature and pH on the corrosion rate was determined, as well as the effect of a layer of corrosion products on the metallic surface and the content of O₂ in the brine were evaluated and a model was obtained for the prediction of the corrosion rate as a function of temperature and pH simultaneously, in brines with and without, O₂ and surfaces without corrosion products. Furthermore, two corrosion rate prediction models were obtained one as a function of temperature and CO₂ pressure simultaneously, in brines without O₂ and surfaces with corrosion products, finally other as a function of temperature and CO₂ pressure and H₂S concentration simultaneously, in brines without O₂ and surfaces with corrosion products. The validation of models was done by comparison with models reported in the literature, commercial corrosion predicting software and data of corrosion rate measurements obtained from direct inspection of in-service separator tanks.