The Impact of Oxygen on the Galvanic Corrosion of Dissimilar Metals in Oil and Gas Drilling Environments

Abstract Located at the lowest segment of a drill string, the bottom hole assembly (BHA) comprises a variety of components and connectors. They are typically manufactured from diverse metallic alloy families and physically connected at various junctions and joints within BHAs. During drilling operations, concerns arise regarding potential galvanic corrosion between dissimilar metals at these connections. This study investigated the role of oxygen in the galvanic corrosion of an Cr-Mo low-alloy steel coupled with a Cr-Mn-N austenitic stainless steel (SS) and a Be-Cu alloy in simulated drilling environments. The investigation methods include immersion tests and electrochemical measurements, such as Potentiodynamic Polarization and Zero Resistance Ammeter (ZRA). Results indicate the galvanic corrosion of the low-alloy steel when coupled with the Be-Cu alloy or Cr-Mn-N austenitic SS is negligible under oxygen-free condition. However, this effect become significant in the presence of oxygen due to the enhanced cathodic reactions of Be-Cu alloy or Cr-Mn-N austenitic SS. Flow can also intensify galvanic corrosion by accelerating the mass transfer process, however, this effect is limited in the absence of oxygen.