Abstract:

The presence of alternating current (AC) may cause serious damage on metal structures even when cathodic protection (CP) is applied and off-potential matches -850 mV_CSE criterion. When pipelines are in the vicinity of a high AC electrical field, such as a power line or an electrical railway, this corrosion may occur at the location of coating holidays. Although AC corrosion of metal was only a fraction of an equivalent amount of direct current, but the corrosion damage cannot be ignored. For direct current (DC) corrosion on metal structures there is large agreement on criteria to be used for corrosion mitigation. AC corrosion mechanism is not yet understood and reliable techniques for the determination of the corrosion risk are not yet available. Therefore, the basic problems on AC corrosion should be investigated in detail. An overview of the AC induced metal corrosion is presented. Increasing number of cases and laboratory test results confirmed that AC corrosion risk really exists and it is a serious factor in corrosion of pipelines. Many studies indicate that a number of variables affect the severity of AC corrosion activity, e.g. AC frequency is one of the factors affecting corrosion rate. Investigations show that corrosion rate decreases with increasing frequency firstly, but with further increase of frequency up to a threshold corrosion rate increases. Several mechanism hypotheses of AC corrosion are presented, but without consensus regarding the mechanisms. There are several criteria to evaluate the probability of AC corrosion, which are based on the AC density or the ratio between AC density and DC density, or the AC voltages or the instantaneous off-potential, furthermore, the charges needed to oxidize corrosion produces on the corroded steel surface. However, criteria based solely on one indicator are inefficient. The comprehensive evaluation indicators system considers the balance between such induction effects as electrolyte environment and cathodic protection level, may be more reasonable.

摘要：

交流电能够诱导金属发生腐蚀，为有效控制与利用交流腐蚀，必须加强对金属交流腐蚀问题的基础性研究。本文回顾了金属交流腐蚀的研究历程，总结尚已认识的交流腐蚀行为，指出有待探索和发现的规律。对近年来国内外开展的有关交流腐蚀电化学行为及影响因素的研究进行综述，讨论了交流腐蚀机理的典型假说，重点评述了目前具有代表性的交流腐蚀风险评估标准，并对这一领域的研究前景及发展方向进行了展望。