Effect of Dissolved Oxygen on Aluminum Corrosion in Simulated Cooling Water for HVDC Systems at 50 °C

Abstract

The corrosion behavior of aluminum in 50 °C deionized water with varying dissolved oxygen contents was studied. Compared with deionized water, an aqueous solution with dissolved oxygen promoted aluminum corrosion. With increasing dissolved oxygen content, the corrosion of the aluminum surface became more serious, and the corrosion resistance of the aluminum gradually decreased. When the oxygen content in the water was increased from 0 mg L-1 to 4.0 mg L-1, the aluminum corrosion potential decreased from -1.282 V to -1.503 V, the corrosion current density increased from 1.987 × 10-7 A cm-2 to 4.904 × 10-7 A cm-2, and the charge transfer impedance decreased from 8.057 × 104 Ω cm-2 to 2.427 × 104 Ω cm-2. The corrosion products for aluminum in water containing oxygen are Al(OH)3 and Al2O3, and the corrosion type is mainly pitting corrosion. The number of the pitting holes gradually increase with increasing oxygen content in the aqueous solution. Removing the dissolved oxygen from the cooling water of a valve cooling system with nitrogen is an effective method to limit corrosion of aluminum radiators and the scaling of grading electrodes in high-voltage direct current transmission systems.