ABSTRACT
In the oil and gas industry, supermartensitic stainless steel (Super 13Cr) has been used in the manufacture of steel tubes for use in oil drilling. Super 13Cr is a more financially viable option than super duplex steel in the oil and gas market. The objective of this work is to evaluate the influence of pH variations and the presence of H2S dissolved in the medium in the corrosion resistance of super martensitic steel in saline solution saturated with H2S, thus simulating the operating conditions in the industry's pre-salt of oil. The electrochemical tests used were anodic potentiodynamic and cyclic polarization. For the subsequent characterization of the surface, the techniques used were optical microscopy and scanning electron microscopy (SEM). The effect of the presence of H2S in the medium increased the susceptibility to corrosion of the steel due to a greater destabilization of the naturally formed passive layer, reduction of the pitting potential and of the repassivation potential. Super 13Cr steel was also less resistant when the pH was varied to lower values, causing a reduction in pitting potential. With the tests carried out and the analysis of the micrographs, the super 13Cr steel was less resistant to corrosion in more acidic media and in the presence of hydrogen sulfide in the medium. The main consequences of this increase in severity were the presence of larger and deeper pits, which can develop into cracks if there are mechanical stresses, less noble pitting potentials and great resistance to repassivation.
Keywords
localized corrosion; super martensitic steel; sulfide corrosion; anodic polarization
