AC corrosion on cathodically protected pipelines is commonly experienced due to interference from high voltage transmission lines at a frequency of 50 or 60 Hz. In some cases, the source of interference may be low frequency AC transit systems (1/3 of the fundamental frequency) and in other cases higher harmonics of the fundamental frequency can be detected on pipelines. In part A of this paper a field investigation of a 120 Hz rectifier ripple, suspected to lead to AC corrosion, is investigated. In this part B of the present investigation, AC corrosion of cathodically protected steel is investigated using electrical resistance (ER) probes at various frequencies and different CP levels in an artificial soil solution. The effect of frequency on basic aspects and understanding of AC corrosion, specifically in terms of alkalization mechanisms and related time constants for involved processes, is discussed.

Subject
Voltage, Cathodic protection, Corrosion rate, Probes, Inspection, Experimental data, Current densities, Steel, Corrosion data, Alternating current corrosion, AC interference, Corrosion coupons, Electrical resistance probes
Keywords:
Alternating current, AC interference, Cathodic protection, Electrical Resistance Probes, AC corrosion, AC frequency
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2021
Association for Materials Protection and Performance (AMPP)
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