Application of magnesium anode for cathodic protection of buried thermally insulated metallic pipeline - CANCELLED (C2026-00165)

Dezhi Tang, 昌堃 龙, Weizhi Zhang, Xiaolong Zhao, Yuxiao Yuan, Dacheng Guo, Liang Dong

Buried thermally insulated metallic pipelines are usually protected by an outer jacket (electrically insulated) , a thermal insulation layer, and an anti-corrosion coating. Due to the cathodic protection(CP) shielding of the outer jacket and the confined space within the thermal insulation layer, CP current from traditional remote groundbeds struggles to reach coating defects on thermally insulated pipelines. Consequently, effective protection of the pipeline substrate is compromised. As a result, corrosion under insulation (CUI) becomes the primary factor in external corrosion failure. In this work, application of magnesium alloy sacrificial anode for CP of buried thermally insulated metallic pipeline is investigated by field experiments, potentiodynamic polarization measurements, and numerical simulation. Results show that magnesium ribbon anodes installed inside the thermal insulation layer can provide enough CP to thermally insulated metallic pipeline when thermal insulation layer flooding occurs. The protected length correlates with coating performance. For 3PE-coated pipelines, a 1-meter magnesium ribbon anode can provide 4-5 m of effective unidirectional protected length. Considering standard pipe lengths of 12 m, installing built-in magnesium ribbon anodes within the thermal insulation layer at low-lying sections (prone to water accumulation) presents an effective solution for mitigating CUI risks of buried thermally insulated metallic pipelines.