The effects of mechanical stress, environment and cathodic protection on the degradation and failure of coatings: An overview

Organic coatings have been used in conjunction with cathodic protection as the most economical method of corrosion protection by the oil and gas pipeline industry. In a bid to prolong the life of the pipelines, the degradation and failure of pipeline coatings under the effects of major influencing factors including mechanical stress, the environmental corrosivity and cathodic protection have been extensively investigated over the past decades. This paper provides an overview of recent research for understanding coating degradation under the effect of these factors, either individually or in combination. Electrochemical impedance spectroscopy remains the primary and the most commonly used technique of studying the degradation of organic coatings, although there have been attempts to use other techniques such as electrochemical polarization (both dynamic and static), electrochemical noise, Scanning Kelvin Probe, Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Dynamic Mechanical Analyser. Major knowledge and technological gaps in the investigation of the combined effects of mechanical stress, environmental corrosivity and cathodic protection on coating degradation have been identified.