Stray Current Corrosion Due to Utility Cathodic Protection

Abstract

The conditions in which stray currents contribute to the corrosion damage of highway structures, the tests to determine if these conditions exist, and the methods recommended to alleviate either the conditions or the damage caused by stray current corrosion are investigated. An extensive review of the literature concerning the fundamentals of stray current corrosion and the practices of utility cathodic protection is presented, including a comprehensive study of the history of stray current corrosion, from its conception with the direct current trolley systems of the late 1880's to its present day problems in the cathodic protection industry. Federal, state, and Kansas Department of Transportation rules and policy are reviewed as they pertain to utility cathodic protection and the damage it may cause to adjacent underground highway structures. Based on the research covered within this report, procedural changes for the prevention of stray current corrosion damage to highway structures and additions to the KDOT Utility Accommodation Policy (1994) are recommended. The research herein concludes that: (1) that all construction close to cathodically protected utilities should be reported to the utility owners so that stray current interference can be assessed, (2) any utility pipeline found uncovered should be reported to its owner so that it can be inspected for corrosion damage, and (3) no underground highway structure should be located within the area of influence of a cathodic protection groundbed. Additionally, its recommended that the KDOT Utility Accommodation Policy (1994) be modified to: (I) directly state the policy on stray current interference from utility cathodic protection systems, (2) require utilities installing cathodic protection systems to submit the design plans as part of the process necessary to obtain a permit agreement for operating in a highway right-of-way, and (3) state that KDOT may require additional inspections along pipelines where interference could jeopardize the structural integrity of an underground highway structure.