Electrochemical impedance study on brass corrosion in NaCl and (NH4)2SO4 solutions during cyclic wet?dry conditions

Abstract

Atmospheric corrosion of brass in sodium chloride (NaCl) and ammonium sulfate (NH4)2SO4 solution during wet/dry cyclic conditions was investigated. The effects of various parameters on the corrosion rate were studied including temperature, pH and surface inclination. The polarization resistance of brass samples, subjected to 1 h immersion and 7 h drying at 60% RH was monitored using an AC impedance. The corrosion rate measured at low temperature was found to be significantly lower than that observed at high temperature. The average reciprocal polarization resistance (VARPR) was also calculated during exposure. It decreased with the number of exposure cycles during the initial stages and attained a steady state value during the last stage of exposure. An atmospheric corrosion mechanism for brass, describing the successive stages during exposure, is subsequently proposed.