Principle of ER Corrosion Rate Monitoring for Paint Degradation

High-frequency testing cannot measure solution resistance. The reciprocal of the impedance reflects the formation status of the water film. This mechanism is easy to understand: as the solution dries up, its solution resistance approaches infinity, and its reciprocal becomes nearly zero. For low-frequency measurement, the resistive component of impedance corresponds to the resistance of the alumina film, whose reciprocal represents the relevant parameter. Moreover, this method can quantify the film’s ability to block dissolved oxygen, a substance that governs the corrosion rate. By characterizing the high-frequency and low-frequency impedance evolutions as a dynamic changing process, we can achieve corrosion rate evaluation.

When metal corrodes and thins, its cross-sectional area shrinks, which in turn raises its electrical resistance. Since the resistance of metal varies with temperature, we arrange metal electrodes and coat them with corrosion-resistant materials to fabricate base plates, followed by measuring reference resistance values. The influence of temperature fluctuation can be eliminated by calculating the resistance ratio between two electrodes.