Study on Galvanic Corrosion Behavior of Q345 Steel in Simulated Ocean Thermocline Environment

Abstract

In order to study the galvanic corrosion behavior of Q345 steel in an ocean thermocline environment, a self-made simulated ocean thermocline device and detachable array electrodes were used.The detachable electrodes were connected via a salt bridge.The corrosion morphology and corrosion products of Q345 material in the ocean thermocline environment were analyzed using immersion and electrochemical methods.Results showed that at the initial stage of the experiment, the galvanic current of the chain electrode measured by electrochemical noise technology was positive at both ends and negative in the middle, indicating that a macro corrosion cell with anodes at both ends and a cathode in the middle had formed between the chain electrodes.With the increase in immersion time, the galvanic current density between the chain electrodes varied significantly, with the maximum difference reaching 1.71 μA/cm2, and the electrode polarity was reversed.From the corrosion rate of the metal, it was concluded that the average corrosion rate of the top and bottom electrodes of the chain electrode was significantly higher than that of the middle electrode, which was consistent with the variation in galvanic current density.Through the analysis of corrosion product morphology and XRD, it was found that the corrosion products on the top and bottom surfaces of the chain electrode were covered with thick layers, exhibiting a loose structure and delamination, with relatively high contents of Fe3 O4 and γ-FeOOH in corrosion products, whereas the corrosion products on the middle electrode were less covered and denser, with relatively high contents of α-FeOOH and lower contents of γ-FeOOH in the rust layer.

Keywords

• ocean thermocline； galvanic corrosion； temperature； q345 steel； electrochemical noise