Potential variation of a temporarily protective oil coating before its degradation

Abstract A wire-beam electrode using mild steel wires was developed and used to study the potential variation of temporarily preventive oil coating before its degradation. It was found that the distribution of corrosion potential on the surface of oil-coated wire-beam electrode was heterogeneous before the degradation of temporarily protective oil coating. At the early stage of immersion, the distribution of corrosion potential gradually shifted to a higher potential range with increasing of immersion time. When the distribution of corrosion potential reached to a highest potential range, it began to shift negatively to a lower potential range. It is suggested that this situation may be due to metal corrosion taking place at the metal/coating interface. The distribution of corrosion potential on oil-painted wire-beam electrode followed a normal probability distribution before the degradation of oil coating. With increasing of immersion time, the distribution of corrosion potential on oil-painted wire-beam electrode may change from normal probability distribution before the degradation of oil coating to discontinuous binomial distribution after the degradation of oil coating.