Corrosion of Copper-bearing High Strength Mooring Chain Steel Affected by Microbes in Seawater

Corrosion behavior of copper-free (BR5) and copper-bearing (BR5Cu, 0.8% Cu) bainite type grade R5 mooring chain steels is investigated in sterile and bacteria-containing seawater. Electrochemical impedance spectroscopy and weight loss results demonstrate that both steels corrode steadily with similar rates in sterile seawater, which is closely related to stable dissolved oxygen (DO) concentration and loose corrosion product layers. While in bacteria-containing seawater, corrosion is inhibited at the initial stage due to DO consumption and biofilm formation, and the inhibition efficiency declines with time because of bacteria decay, leading to a slightly smaller total weight loss than that in sterile media. Although less adhesive bacteria are observed on BR5Cu steel owing to the antimicrobial activity of copper, it does not bring a visible difference in corrosion rate. The validity of copper introduction in mooring chain steel towards seawater corrosion and MIC inhibition is expected to be checked further in different systems.