Electrochemical investigations of carbon‐based conductive coatings for application as anodes in ICCP systems of reinforced concrete structures

Abstract

Carbon‐based conductive coatings are complex composites, consisting of an organic or inorganic binder and conductive carbon components, for application as anodes in impressed current cathodic protection systems of reinforced concrete structures. The electrochemical properties of three coatings at different humidity and in saturated calcium hydroxide solution were studied by electrochemical methods, such as electrochemical impedance measurement, measuring of open circuit potential over time and galvanostatic polarization. The dissolved organic and inorganic carbons in electrolyte solution were quantified by using a photometric method. The structures of the coatings were investigated before and after the electrochemical tests by microscopy and scanning electron microscope/EDX analysis. The results of the electrochemical impedance measurements show that the tested coatings all have a relatively low resistance, which is between 100 and 200 Ω. The binder and the surface porosity influence the degradation behavior of those coatings. Especially the organic binder reacts with the strong alkaline medium under dissolving of organic carbon.

Durability behavior of polymer impregnated carbon textiles in alkaline solution as CP anode

“…In the Pourbaix diagrams, the pH value at the contact surface between solution and carbon is considered as influencing factor of the carbon's stability. However, it does not take the process of acidification at the anode's surface into account, which is a general and commonly reported issue leading to locally strongly acidic conditions.…”

Carbon enhanced cementitious coatings: Alternative anode materials for impressed current cathodic protection systems intended for reinforced concrete

“…[15] Instead of installation of a metal mesh as the anode in an ICCP system (see Figure 1) also conductive coatings can be used. From such studies [16][17][18] it is clear that the main challenge is to create a conductive coating material that not only maintains its functionality in the alkaline concrete environment, but also withstands external environmental conditions, such as rain or splashes, and exhibits resistance towards consequences of ICCP chemical reactions. Especially the effect on the anode is of importance for the service life and performance.…”

“…Delamination is thus the most critical parameter to consider when accounting for the service life and durability of the coating material. In the literature there are several studies investigating conductive coating materials, see for example, Refs, [16][17][18]21] but very few evaluate the long-term performance. In fact, not even a patented conductive coating material for the anode of an ICCP system [22] is assessed for long-term performance.…”

Performance assessment of specialist conductive paint for cathodic protection of steel in reinforced concrete structures

“…For ICCP of reinforced concrete, research has been centred on the development of anode materials, e.g. thermal sprayed zinc [16][17][18][19][20][21][22][23][24], titanium anodes [25,26], conductive coating [27][28][29][30][31], and conductive cementitious overlay anodes [9,[32][33][34][35]. However, the researchers are still trying to find new anode materials with improved performance characteristics, such as higher bond strength, lower acidification, low cost and improved installation convenience [11].…”