This standard establishes the general principles to be adopted to minimize the effects of stray current corrosion caused by direct-current (d.c.) on buried or immersed metal structures. The standard is intended to offer guidance for: . the design of direct current systems which may produce stray currents; . the design of metal structures, which are to be buried or immersed and . which may be subject to stray current corrosion; . the selection of appropriate protection measures. The standard mainly deals with external stray current corrosion on buried or immersed structures. However, stray current corrosion may also occur internally in systems containing an