This paper presents a summary of the results obtained during 3 years of PhD studies on “AC Corrosion of Cathodically Protected Pipelines” at the Technical University of Denmark (DTU)1, which was finalized in October 2018 and defended in January 2019.1  Amongst the findings are: An improved understanding of AC corrosion as different corrosion phenomena under low and high levels of cathodic protection respectively. An enhanced understanding of the reactions in soil systems that lead to establishment of corrosive environments. Discovery of a close correlation between current density criteria and the Pourbaix diagram. An improved understanding of the influence of the CP level on the electrochemical double-layer characteristics. Presentation of a new model for AC corrosion that considers ionic dissolution and hydrogen evolution in the passive film destabilisation mechanism. The results are discussed in relation to literature and relevant cathodic protection and AC interference standards.

Subject
Cathodic protection, Passive films, Cathodic current, Pourbaix diagrams, Current densities, Cathodic current density, Steel, Alternating current corrosion, AC interference, Coating defects, Corrosion resistance, Polarized potential, Soil
Keywords:
AC corrosion, AC interference, cathodic protection, corrosion rate
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2021
Association for Materials Protection and Performance (AMPP)
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