Improving the Long-Term Protection of Buried Steel Tanks: Considering the Impact of Temperature and Extended Sacrificial Anodes

Abstract

Corrosion prevention techniques such as cathodic protection (CP) are commonly applied to extend the useful lifetime of buried steel tanks in corrosive environments. Sacrificial anodes effectively supplement CP systems through controlled galvanic corrosion. For buried steel tanks, magnesium-based anodes are regularly used due to suitable current output over extended deployment periods. However, field conditions such as temperature fluctuations and proximity effects between adjacent tanks can influence CP performance. This study numerically simulates the CP of a 3.8 m diameter, 12 m long steel tank which the upper section of the tank is located at a depth of 1 m, protected by uniformly distributed magnesium anodes. To understand the importance of the current output of extended anodes, conventional anodes (i.e., 7.7 kg, 38.7 mA) and extended anodes (i.e., 9 kg, 62.7 mA) were studied. Proximity effects on anodes placed between adjacent buried tanks were also examined. In addition, the influence of temperature and concentration parameters was investigated along with a time-dependent analysis of the protected structure. Under the hottest and coldest conditions, the bottom temperature of the computational domain (in height of 6.8 m) reached 8.7°C and 11.3°C, respectively, with noticeable concentration gradients. The temperature rise necessitated increased protective current, leading to the need for additional sacrificial anodes to meet the demand. The simulation results indicated that the anodes positioned between the two tanks experienced the highest corrosion rate. After 21.5 y, approximately 85% of the mass of these anodes will be lost, with full depletion occurring shortly thereafter. This modeling approach offers valuable insights for selecting the optimal type and placement of anodes, ensuring the long-term integrity of underground infrastructure under varying thermal conditions.