An investigation of the dependence of atmospheric corrosion rate on temperature using printed-circuit iron cells

Abstract

Chloride-mediated atmospheric corrosion was simulated on multilaminar, printed-circuit cells, in order to ascertain the effect of temperature on iron corrosion rate (early stages). Tests were carried out at 25, 35 and 45°C, under salt contaminations equivalent to chloride deposition rates of 0.25, 1.00 and 4.00 mg dm −2 day −1; relative humidity was kept at 85% throughout and surface wetness was allowed to result solely from moisture uptake. Electrochemical data generated by linear polarization and zero-resistance ammetry are discussed with reference to acceleration factors, energy barriers (Arrhenius model) and process control. Temperature has a direct, marked influence on the rate of corrosion and also seems to regulate the catalytic rate dependence on [Cl −] through Freundlich isotherms. The apparent activation energy goes up to 87.5 kJ mol −1, and gives almost perfect plots with [Cl −] (semi-log) and electrode overpotential (linear). All features concerning energy barriers suggest an overall corrosion process under mixed control, bearing a significant, if not predominant contribution from charge transfer.