Polarization Current and AC Impedance Characteristics of Electric Power Equipment Metal Materials with Different Corrosion Condition Under High Temperature and High Humidity Industrial Pollution Environment

Abstract

Metal structure materials of power equipment will be seriously corroded in the polluted atmosphere. Impedance spectrum and polarization current are effective means to monitor metal corrosion status, early warning and take protective measures. The corrosion characteristics and mechanism of metal materials in power equipment in high temperature, high humidity, high Cl- and industrial pollution atmospheres were investigated by scanning electron microscopy and electrochemical measurement. Results indicate that with the increase of corrosion time, the surface morphology and products of Q 235B low carbon steel are transformed from cracks in the precorrosion stage and flaky γ-FeOOH to the products of cotton-like α-FeOOH and constitute a dense rust layer gradually. The surface rust layer of galvanized steel also gradually changes to thicker and denser. The corrosion current I corr of carbon steel increases rapidly and then decreases slowly. The corrosion current I corr of galvanized steel rises slowly and then decreases rapidly. During the corrosion process, the corrosion current of carbon steel is larger than that of galvanized steel. The lowfrequency capacitive reactance arc radius of carbon steel and galvanized steel and the charge-transfer resistance R t after fitting are first reduced, then increased˗the charge transfer resistance R t of the galvanized steel after corrosion is greater than carbon steel. The rust layer of carbon steel will accelerate corrosion in the early stage, and the dense rust layer will resist corrosion in the later stage, but the effect is small. The rust layer of galvanized steel has better resistance to corrosion.