Corrosion Behavior of EN18 Steel and Copper in the Sulfuric Acid Medium for As-Bought and Annealed Materials

Abstract EN18 steel and copper are used as materials for oil and gas industries for chemical storage, which come in contact with the sulfuric acid medium during the pickling process. In such instances cleaning of impurities and oxide layer removal, leads to excessive corrosion. Thus, the improvement in the microstructure through annealing treatment and its effect on the corrosion behavior of EN18 steel and copper are studied by immersing in 0.5 M H 2 SO 4 for as-bought and 0.5, 0.25, 0.1 M H 2 SO 4 medium solutions after annealing treatment. The metal specimens were heated to 900 °C for EN18 steel and 600 °C for copper and then both were furnace cooled and the change in the microstructure of annealed and as-received metal specimens was analyzed using Scanning Electron microscopy (SEM). The Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic polarization (PDP) measurement showed that there is a decrease in the corrosion rate for both metals after annealing treatment. The effect of corrosion rate at the temperature range of 30-50 °C was analyzed and activation parameters were described using Arrhenius and transition state theories. Suitable corrosion mechanisms for both steel and copper in the H 2 SO 4 medium have been discussed.