Abstract
Stray current corrosion in buried pipelines can cause serious material damage in a short period of time. However, the available methods for mitigating stray current corrosion are still insufficient. In this study, as a countermeasure against stray current corrosion, calcareous depositions were applied to reduce the total amount of current flowing into pipelines and to prevent corrosion. This study examined the reduction of stray current corrosion via the formation of calcareous deposit layers, composed of Ca, Mg, and mixed Ca and Mg, at the current inflow area. To verify the deposited layers, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed. The electrochemical tests revealed that all three types of calcareous deposits were able to effectively act as current barriers, and that they decreased the inflow current at the cathodic site. Among the deposits, the CaCO3 layer mitigated the stray current most effectively, as it was not affected by Mg(OH)2, which interferes with the growth of CaCO3. The calcium-based layer was very thick and dense, and it effectively blocked the inflowing stray current, compared with the other layers.
Highlights
The potentiostatic tests were performed at −1.0 VSCE for 30 h to form three kinds of calcareous deposits on the carbon steel
When the specimens were negatively charged in the solution containing both Ca and Mg, the dissolved oxygens were converted into OH− ions, leading to an increase in the pH on the surface
This study evaluated the stray current corrosion mitigation of calcareous deposits on carbon steel in a synthetic soil solution using the electrochemical tests, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the UK, GBP 500 million is spent annually on infrastructure restoration and repair due to stray current corrosion [14] To solve this issue, drainage systems and electrical shields have been applied to buried pipelines to prevent corrosion [1,15,16,17]. Since it is hard to predict where stray current corrosion will occur, it is difficult to ensure that all pipelines are protected To overcome these issues, we applied calcareous deposits for protection against stray current corrosion. Potentiostatic polarization tests were performed to form calcareous deposits with different compositions [23]. Potentiostatic acceleration tests were undertaken to verify the effects of the calcareous deposits on the stray current corrosion, and to determine the most effective composition for protection against it
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