Visualization and simulation investigation of Copper-Nickel alloy and carbon steel galvanic corrosion in marine environment

Corrosion of Q235 carbon steel and the BFe30-1-1 copper-nickel alloy was studied in seawater with electrochemical methods and surface characterization. The open circuit potential (OCP) for the copper-nickel alloy and carbon steel were -225 mV and -700 mV, respectively. A Gel visualization test showed that Turnbull's blue was precipitated on the surface of Q235, which indicated accelerated corrosion of the Q235 anode after coupling. The increased Kelvin potential determined for the Q235 surface with a Scanning Kelvin Probe test indicated that the Q235 surface generated electrons and transferred them to the BFe30-1-1 surface, which resulted in the protection of BFe30-1-1. These tests showed that the Q235 anode underwent corrosion, and the BFe30-1-1 cathode was protected after coupling in seawater. Surface analyses showed that Q235 corroded faster over time due to electric coupling, while BFe30-1-1 corrosion was inhibited by a stable passivation film. Analysis of the physical phase showed that the corrosion products of Q235 were beta-FeOOH, alpha-FeOOH and Fe3O4, and the BFe30-1-1 corrosion products were Cu2O and Cu2Cl(OH)(3). The electrochemical and numerical results were consistent, indicating an accurate prediction of the galvanic corrosion process.