Review of Recent Developments in Induced AC Current Corrosion Mitigation Design, Materials, Installation and Monitoring Technologies

ABSTRACT

The issue of induced AC current corrosion and its mitigation for buried pipelines has seen increased interest and rapid development of new technologies for mitigation and monitoring over the last 10 years. These include work on development of a NACE International Standard Practice for AC current corrosion on cathodically protected pipelines, updates to the AC corrosion mitigation design criteria, new materials and installation methods, and AC corrosion current density remote monitoring technologies.

This paper presents a review of the design methods and mitigation technologies that were used in the past, and those that have been recently developed and continue to evolve, to meet the AC mitigation challenges faced by buried pipeline operators.

Background

The science and technology for induced AC current corrosion detection, mitigation design, mitigation systems, and monitoring has evolved rapidly over the last 10 years. Various factors have contributed to the increased efforts to update industry standards based on a growing body of knowledge in the area of corrosion protection on buried pipelines, and the associated development of new and updated design methodologies, mitigation systems and induced AC current monitoring.

Industry Standards

The two mostly commonly referenced industry documents referred to for defining the AC corrosion current mitigation criteria are the NACE International state-of-the-art report on AC Corrosion¹ issued in 2010, and the European Standard EN152802, which was last revised in 2013. Following up on the 2010 NACE report, NACE Committee TG430 started work in 2015 on a proposed “NACE Standard Practice on AC Corrosion”.

Design Criteria

In North America, the most commonly accepted AC current density criterion below which AC corrosion is not expected to occur is 20 A/m², as noted in the 2010 NACE report. However, the European Standard EN15280 raises this value to 30 A/m².

The proposed “NACE Standard Practice on AC Corrosion”, being developed by NACE Committee TG430, also recommends 30 A/m² as the upper limit for the AC current density, with the caveat that this value must be used in conjunction with the DC current density (the I_ac/I_dc ratio). This caveat is also noted in other recent industry reports by The Interstate Natural Gas Association of America (INGAA) Foundation³ and the Canadian Energy Pipeline Association (CEPA)⁴, and is also emphasized in the 2013 revision of European Standard EN15280.