Painted Reinforced Concrete as an Alternative to Galvanized Steel in Chloride-Rich Environments

Abstract Galvanization is one of the most common anticorrosive techniques for the protection of metallic structures in atmospheric applications. However, in extremely aggressive atmospheric environments, the material fails to deliver its usual performance, and replacement can be necessary, as in this case study. Painted reinforced concrete has emerged as a promising alternative for extending the service life and enhancing corrosion resistance. They combine the barrier and passivation mechanisms associated with steel reinforcement embedded in concrete with the anticorrosive protection provided by the high-performance coating systems. In this context, this work evaluated the performance of combinations of carbon steel and galvanized steel reinforcement concrete with three commercial coating systems (CS1, CS2, and CS3) under severe conditions expected at the installation site. The test specimens were manufactured using Brazilian CPII cement concrete, and the performance of galvanized steel was assessed in comparison to the expected behavior of carbon steel. Concrete characterization tests were conducted to verify its suitability for the intended application, including water absorption, void index, bulk density, and compressive strength tests, and salt spray exposure tests were performed to assess the anticorrosive performance of the different combinations. Each coating system was individually characterized using techniques to measure its physical and barrier properties, and the reinforcing steels were evaluated for their mechanical properties and chemical compositions. Electrochemical methods, including open-circuit potential monitoring, electrochemical impedance spectroscopy, and polarization resistance, were used to complement the other analyses. The results indicated that the traditional carbon-steel-and-concrete system exhibited a superior anticorrosive performance. Even after long-term exposure to salt spray, the specific influence of each coating system applied to the concrete could not be clearly distinguished, given its excellent anticorrosive performance. Despite this, CS3 consistently showed favorable results in the characterization tests and was therefore selected for the final application.