Field measurements of galvanic anode cathodic protection of reinforced concrete systems in marine environment: Influence of water level and biofilm

Abstract

Corrosion of steel in concrete is one of the major deterioration mechanisms for reinforced concrete (RC) structures such as floaters of floating offshore wind turbines (FOWTs). As these are vital components of FOWTs, addressing corrosion is critical to ensure their durability with minimal maintenance. The existing literature indicates that RC in the tidal zone can experience premature corrosion. To mitigate this, galvanic cathodic protection (CP) is a well-known approach for protecting RC structures. Therefore, a field experiment in the tidal zone was conducted to study the behaviour of aluminum anode CP for RC with CEM I and CEM V cement types across two concrete surface textures, smooth and rough. The half-cell potentials (HCP) (for specimens without CP), mixed potentials and protection current (for specimens with CP) were monitored continuously. Furthermore, the effect of water levels and biofilm on corrosion characteristics of steel in concrete and the efficiency of CP was assessed. The findings highlighted that the biofilm on the concrete surface acts as a physical barrier, limiting the diffusion of oxygen – affecting the corrosion characteristics of steel embedded in concrete. This influence was distinctly observed in both protected and non-protected categories. In the protected category, the average protection current was found to increase upon biofilm removal for CEM I concrete - indicating that the CP is efficient/or working with or without biofilm on the concrete surface. Finally, this paper highlights the importance of understanding how the presence of biofilm on concrete surfaces can affect the corrosion characteristics of steel embedded in concrete.