| 摘要 |
PURPOSE:To prevent the generation of non-uniform corrosion such as pitting or interstitial corrosion, in a cathodic corrosion-proof method utilizing an Al material used in water as a cathode, by applying cathode pulse voltage to the Al material intermittently. CONSTITUTION:An anodic oxidation film is formed on the surface of a member made of Al or an Al alloy according to a usual method and fine pores in the film are subjected to sealing in boiled water. In using this Al member used in sea water, voltage is applied between the Al member as a cathode and an opposed electrode to apply cathodic corrosion-proofness. In this case, when the potential of the Al material in sea water is negative potential of 0.4-0.8V and the pH of sea water is within a range of 4-9, the Al member is stable and is no corroded. When the potential of the Al member is approaches a point A in the vicinity of 0.4V during cathodic corrosion-proofness, pulse voltage is applied to once reduce the potential of the Al member to a point B and, if the application of pulse voltage is stopped, potential is rapidly returned to a point C to enter an immobilized region generating no corrosion while is gradually moved to the point A. By repeating this process, the Al member is prevented from pitting generation. |
