Current oscillation of strained low carbon steel electrode in concentrated phosphoric acid solution

The impacts of tensile stress on the non-linear electrodissolution behaviour of carbon steel were investigated in an aqueous solution of 5M phosphoric acid. The frequency of the current oscillations within the transpassive potential region increases slightly when the elastic deformation was introduced to the electrode by applying tensile stress, but the oscillatory mode is essentially unchanged. The elastic deformation could induce the current oscillations in the passive potential region that was not observed on stress free state. This fact suggests that the tensile stress can reduce the stability of passive film. Immediately after the tensile stress exceeds the yield strength, the oscillatory mode changes into a chaotic one with high frequency and recovers the original state gradually. This phenomenon resembles the consequence due to the injection chloride to the electrode/electrolyte interface and implies that the plastic deformation may result in the formation of more defective passive films.