Potential variation of a temporarily protective oil coating before its degradation

A wire-beam electrode using mild steel wires was developed and used to stud y the potential variation of temporarily preventive oil coating before its degradation It was found that the distribution of corrosion potential on th e surface of oil-coated wire-beam electrode was heterogeneous before the de gradation of temporarily protective oil coating. At the early stage of imme rsion, the distribution of corrosion potential gradually shifted to a highe r potential range with increasing of immersion time. When the distribution of corrosion potential reached to a highest potential range, it began to sh ift negatively to a lower potential range. It is suggested that this situat ion may be due to metal corrosion taking place at the metal/coating interfa ce. The distribution of corrosion potential on oil-painted wire-beam electr ode followed a normal probability distribution before the degradation of oi l coating. With increasing of immersion time, the distribution of corrosion potential on oil-painted wire-beam electrode may change from normal probab ility distribution before the degradation of oil coating to discontinuous b inomial distribution after the degradation of oil coating. (C) 2001 Elsevie r Science Ltd. All rights reserved.