Facundo Varela

An overview of major methods for inspecting and monitoring external corrosion of on-shore transportation pipelines

Abstract Corrosion can occur on underground pipelines especially at coating defects, where metal can be considered directly exposed to the soil, or under disbonded coatings, where the occluded geometry significantly affects the efficiency of cathodic protection (CP). In order to ensure the effectiveness of corrosion mitigation measures such as CP and protective coatings, inspection and monitoring of pipeline corrosion are required. This paper provides an overview of major methods that are used for inspecting and monitoring external corrosion of on-shore pipelines subjected to CP. Particular focus is on discussing the advantages and limitations of major inspection tools that are used to ensure pipeline integrity, and electrochemical corrosion sensors that are designed to monitor pipeline corrosion processes and rates. It is shown that there is a need for expanding the capabilities of corrosion monitoring methods suitable for the pipeline industry.

A Novel Approach for Monitoring Pipeline Corrosion Under Disbonded Coatings

Underground pipeline corrosion monitoring is a complex technical challenge. Currently there is no corrosion monitoring probe that is able to provide in situ information on corrosion under disbonded coatings. This paper presents a proof of concept of a novel corrosion monitoring probe intended to simulate corrosion under disbonded pipeline coatings and monitor its rate under Cathodic Protection (CP). The probe’s capabilities to measure corrosion rates and simulate disbonded coating conditions are illustrated by a typical experiment that involved testing of the probe in 0.1M NaCl at −850mVCSE. Estimated metal thickness losses based on results measured by the probe were compared against corrosion patterns and profilometry measurements of control specimens exposed to the same conditions.Copyright

Monitoring Cathodic Shielding and Corrosion under Disbonded Coatings

This work presents a novel corrosion monitoring probe designed for simulating the conditions developed under disbonded coatings and for measuring current densities and their distribution over a simulated pipeline surface. The probe’s concept was experimentally evaluated via immersion tests under Cathodic Protection (CP) in high resistivity aqueous solution. Under the disbonded area, anodic currents as well as cathodic currents were both measured. Anodic current densities were used to calculate metal losses by means of Faraday’s law. Calculated corrosion patterns were compared with corrosion damage observed at the probe’s surface after a period of test. The probe’s working principles are explained in terms of simple electrochemistry.