Effect of Anode-to-Cathode Distance on Corrosion Rate and Cathodic Protection of Submerged Low Carbon Steel in Riverine and Marine Environments

Abstract

Corrosion of submerged steel structures, such as port piers, poses a significant threat to infrastructure durability, especially in aggressive aquatic environments. This study investigates the influence of anode-to-cathode distance on the corrosion rate and cathodic protection performance of low carbon steel using zinc as a sacrificial anode. Experiments were conducted using a Potentiostat MLab 200 system in two simulated environments, representing the riverine Abu Flos Port and the marine Khor Al-Zubair Port at anode distances of 5, 10, 15, 20, and 25 cm. Key electrochemical parameters including corrosion potential (Ecorr), corrosion current density (Icorr), and corrosion rate were obtained using Tafel extrapolation. Results indicated that the shortest distance (5 cm) provided the most effective cathodic protection in both environments, with Ecorr values reaching (–904 mV) and (–1044 mV), respectively. Correspondingly, the corrosion rate was minimized, demonstrating a strong inverse relationship between protection efficiency and anode distance. The zinc anode alloy used was also confirmed to meet ASTM B-418 standards for sacrificial anodes. These findings highlight the importance of optimal anode placement in cathodic protection design and confirm that zinc is an effective anode material in both riverine and marine environments. The study also validates the rapid assessment capability of the linear polarization resistance (LPR) technique for evaluating corrosion protection performance in submerged steel structures.