On the mitigation of corrosion under insulation (CUI) of mild steel using local cathodic protection

A strategy based on cathodic protection (CP) could be a practically feasible means to protect steel piping from corrosion under insulation. However, experimental studies investigating CP of steel through moist insulation are scarce. Herein, CP was explored to protect insulated steel specimens using sacrificial zinc anodes. The conditions to effectively impart CP through the moist insulation have been discussed. The "throwing power" or protection achieved using sacrificial zinc anodes coupled with mild steel specimens in moist insulation was also estimated using copper electroplating. It was validated that the efficacy of CP depends upon the ionic resistivity of the moist insulation and the moisture content (by volume) must be >25% for efficient ionic conductivity through the insulation. The maximum throwing power of CP through the insulation was achieved when zinc was in direct physical contact with mild steel, with zinc to mild steel area ratio being 1:10.