Corrosion failures of concentric neutral conductors of buried power distribution cables have been recognized and investigated by some engineers and scientists.[1-10] Study of this problem was initiated in Bell Laboratories because at two locations in New Jersey the telephone cable - buried in joint trench with corroding power cable - picked up large (20-37 amperes) ac current causing service affecting failures. Presently there is little agreement among the different investigators about the nature of these corrosion failures. Marwick and McNamara[1] favors the idea of galvanic and stray dc current corrosion. Puschel[5,9] argues that differential aeration is the primary corrosion mechanism. McLellan and Schick[7,8] have seen evidence of corrosion caused by ac current leakage. It is likely that the failures are caused by several different superimposed corrosion mechanisms. However, one of these mechanisms may be more effective than the rest of them combined. The knowledge of this corrosion mechanism can serve as a basis to predict the probability of future failures and how to protect against them.
