Effects of Flow Velocity, pH, and Temperature on Galvanic Corrosion in Alkaline-Chloride Solutions

The aqueous corrosion characteristics of a carbon steel (CS) coupled to Type 304 (UNS S30400) stainless steel (SS) were studied in deaerated alkaline-chloride solutions with velocity (0, 0.2, 0.4, and 0.6 m/s), pH (8, 9, and 10), and temperature (25, 50, and 75°C). The electrochemical properties of specimens were investigated with a potentiodynamic test and galvanic corrosion test using a rotating cylinder electrode (RCE). The galvanic corrosion between CS and Type 304 SS was accelerated by the presence of an oxide layer formed on the CS. The galvanic current density increased with increasing flow velocity and temperature, but decreased with increasing pH. Flow velocity had a small effect on the galvanic current density at 25°C, whereas the flow velocity increased galvanic current density significantly at 50°C and 75°C. This effect can be explained by the increased solubility of magnetite at the higher temperature.