Pitting Corrosion Resistance of CrMn Austenitic Stainless Steel in Simulated Drilling Conditions—Role of pH, Temperature, and Chloride Concentration

Abstract

Austenitic stainless steels have been used for many years in components for drilling equipment. These stainless steels are predestinated to meet the demanding requirements in terms of mechanical, magnetic, and chemical properties necessary for the latest drilling technologies. Drilling conditions might become severe in terms of corrosion because of the combination of temperature and high salinity of drilling fluids. In this research work the pitting corrosion susceptibility of 19%Cr-21%Mn-Mo-N austenitic stainless steel has been investigated using electrochemical methods. Service conditions commonly observed during drilling operations have been simulated. Tests were performed in buffer solutions of pH 8, 10, and 12 containing chloride concentrations of 0.5 M, 2.25 M, and 4 M, at room temperature, 88°C, and 150°C. A detrimental effect of increasing temperature and chloride concentration on the pitting corrosion resistance of the material has been determined. On the other hand, an increase of the pH above 8 reduced the susceptibility of the CrMn stainless steel to pitting corrosion, especially at 150°C.