Effect of Filming Biocides on the Performance of Zn Sacrificial Anodes Used in Seawater Ballast Tanks

Abstract Ballast tanks are an integral part of marine vessels such as oil tankers, cargo ships, cruise ships, and pressure vessels as well as offshore oil and gas production platforms. Constructed from carbon steel, these tanks ensure stability and buoyancy by filling or emptying with seawater. To protect against corrosion, ballast tanks are internally coated, and sacrificial zinc (Zn) anode cathodic protection (CP) systems are commonly employed to address any coating defects. Additionally, biocides are introduced to mitigate the potential proliferation of harmful aquatic organisms and bacteria. However, the effect of newly developed multifunctional filming-forming biocides on the performance of Zn sacrificial anodes within these CP systems remains uncertain. A study was undertaken to determine whether seawater biocide treatment could impact the performance of the CP Zn anodes used in offshore production platform Ballast Tank. Two commercially available filming biocides from two different manufacturers were chosen for the study. Tests were conducted using ASTM standards at the recommended dosage and at 1.5 times the recommended dosage level for each manufacturer. Additionally, a control seawater sample (without biocide) was included for comparison. Based on the results of the study, the presence of the selected biocides did not significantly affect the functionality of the sacrificial Zn anode. Further experiments with coated specimens, the results of which are not included here, also showed that the biocides did not have any adverse effect on the performance of the internal coating of the tank.