Comparative Study of API 5L X60 and ASTM 572 Gr50 Steel Exposed to Crude Oil and Seawater

In the petroleum industry, the biphasic conditions in storage and separation tanks allow that the material to remain exposed to two different environments, causing its deterioration. In this article, an evaluation is made of the corrosive behavior and Vickers microhardness (HV) of two high strength low alloy (HSLA) steels and how their surfaces are characterized. The ASTM 572 Gr50 steel showed a lower corrosion rate in all systems after being immersed for 720 and 1440 hours. Characterizing the surface by means of Scanning Electron Microscopy (SEM) showed uniform and localized corrosion for the both steels, and revealed that the ASTM 572 Gr50 steel shows pitting corrosion in crude oil systems. The electrochemical results revealed that the corrosion potential of API X60 steel was more negative; however the ASTM 572 Gr50 steel had a higher current density and a lower polarization resistance when immersed in an oil/seawater mixture. It also observed that, after being immersed in the corrosive fluids, the microstructures of the steels were not modified and variations in their microhardness (HV) were minute