Abstract
Because of their versatility CrMn-stainless steels have become the most commonly used grades of steel in directional and logging drilling technology. In addition to their non-magnetic properties, these materials are also designed to reach high strength in combination with high toughness and galling resistance. Additionally, corrosion and wear resistance are also required to operate in corrosive drilling environments and resist contact with the formation and with rock cuttings, respectively. This paper presents the role of their chemical composition on pitting corrosion susceptibility in chloride-containing solutions at different temperatures. Pitting and repassivation behavior of several grades were investigated using open-circuit potential and cyclic potentiodynamic polarization measurements. Experimental results show that chromium, manganese, nickel and molybdenum play a decisive role on the pitting corrosion resistance of CrMn-stainless steels. The influence of alloying elements on pitting corrosion resistance of these materials was observed being strongly affected by temperature. The present study demonstrates the complexity of localized corrosion and challenge in defining a simple relationship between chemical composition and localized corrosion resistance which will operate at different temperatures.
