腐蚀是一种众所周知的电化学过程，它可能是由地下金属结构产生的杂散直流电（DC）的拾取和随后向地面放电引起的。当地面与轨道平行时，地下金属结构可能成为直流轨道交通系统的地球回路的一部分；然后金属结构会受到腐蚀。美国第一条电气化铁路于19世纪后半叶投入运营。在这些系统开发的早期，运行轨道被用作将牵引电流返回电源的导体。 由于这些系统大多是街道铁路或手推车，因此修建铁路的区域也是最有可能有地下金属结构的区域，尤其是管道。据报道，地下金属结构的腐蚀早在1891年就归因于有轨电车回流。1900年左右，各种原因引起的地下金属结构腐蚀是许多研究的主题。所有使用牵引电流轨道回流的直流牵引系统都有一定程度的泄漏，这取决于影响轨道回流路径效率的设计和运行因素。 这种电流泄漏称为杂散电流。杂散电流会造成安全隐患，并对公用设施结构和整个社区造成严重影响。本报告的目的是提供有关轨道交通杂散电流的信息，因为它涉及交通和公用工程工程师。该报告不是一份详细的文本或“食谱”，而是一份为缓解公交系统杂散电流提供指导的报告。

Corrosion is a well-known electrochemical process that may be caused by the pickup and subsequent discharge into the earth of stray direct current (DC) from an underground metallic structure. Underground metallic structures can become part of the earth return for a DC rail transit system when the earth acts as a parallel path to the rails; the metallic structures are then subject to corrosion. The first electric railways in the U.S. were placed into operation during the latter half of the nineteenth century. Very early in the development of these systems, the running rails were used as conductors for returning traction current to the power source. Because most of these systems were street railways or trolleys, the areas in which the railways were built were also the areas most likely to have underground metallic structures, especially piping. It is reported that corrosion of underground metallic structures was attributed to streetcar return currents as early as 1891. Around 1900, corrosion of underground metallic structures from all causes was the topic of much research.All DC traction systems using rail return of traction current have a level of leakage that is dependent on both design and operating factors affecting the efficiency of the rail return path. This current leakage is known as stray current. Stray current can create safety hazards and have serious effects on utility structures and the community at large.The purpose of this report is to present information on rail transit stray current as it concerns transit and utility engineers. The report is not a detailed text or "cookbook," but rather a report that gives guidance on the mitigation of transit system stray current.