Corrosion rate of copper rotating-disk-electrode in simulated acid rain

Abstract

The dependence of corrosion rate of a copper rotating disk electrode in (i) simulated acid rain solution (pH 3.5), (ii) a mixture solution of 5 × 10 −3 mol dm −3 H 2SO 4 and simulated acid rain (pH 2.1) (iii) a mixture solution of 10 −2 mol dm −3 HNO 3 and simulated acid rain (pH 2.1) has been investigated. In these experiments, the amount of copper dissolved into a test solution was analyzed by ICP-AES, and electrochemical impedance was measured. In the range of rotation speeds from 0 to 2500 r.p.m., the corrosion rate in simulated acid rain solution was found to decrease with increasing rotation speed. This decrease was more pronounced in 5 × 10 −3 mol dm −3 H 2SO 4 + simulated acid rain (pH = 2.1), and in 10 −2 mol dm −3 HNO 3 + simulated acid rain (pH = 2.1) at the rotation speeds above 100 r.p.m. Magnitude of the electrochemical impedance was correlated with corrosion rate, and relationship between corrosion potential and the reciprocal of the absolute impedance revealed a local anodic-polarization curve when the solution pH was 2.1. Decrease in corrosion rate with increasing rotation speed was found to result from anion-adsorption which is diffusion-controlled.