Under-Deposit Corrosion on Steel Pipeline Surfaces: Mechanism, Mitigation and Current Challenges

Under deposit corrosion (UDC) is a serious risk in the industry, threatening critical failures in oil and gas pipelines, boiler and heat exchanger tubes, cooling systems and wastewater treatment facilities. Generally speaking, there is no single defined mechanism for UDC as it follows any of many different routes depending on the local chemistry and the nature of the deposits involved. In addition, UDC is frequently combined with microbiologically influenced corrosion (MIC), which adds further complexity to the mechanism and enhances the resulting damage. At the moment, different mechanical and physical techniques are implemented in the industry to combat UDC with varying success. Mitigation of UDC is generally difficult and requires a detailed understanding of the species involved, the deposits present and, finally, the mechanism taking place. This paper aims to provide a brief review of the recent literature on UDC. First, the basic definition, corrosion mechanisms and types of deposits are discussed. Then, the relationship between deposit structure and corrosion mechanism and association with MIC are thoroughly explored. Finally, a general overview of the main mitigation approaches in the oil and gas industry is presented.