Comparative Analysis of the Corrosion Resistance Epoxy-Coated, Textured Epoxy-Coated, and uncoated Reinforcement Bars

The corrosion of steel reinforcement inside concrete remains a significant challenge for the construction industry. In the United States alone, an estimated annual cost of $240 billion is incurred from corrosion-related damage, with about 20% attributed to the corrosion of reinforced concrete [1]. Among various corrosion prevention techniques for reinforced concrete, epoxy coating of rebars (EC), has been widely adopted. However, due to the smooth surface of epoxy coating, its bond strength with concrete is reduced significantly, which has become a barrier for its large-scale adoption [2]. To tackle this, Sherwin Williams developed textured epoxy coated rebars (TEC) (figure 1a) with feature enhanced surface roughness and enhanced bond strength [3], [4]. The purpose of this study is to investigate how the texturizing coating (figure 1b) impacts their corrosion resistance. While the additional texturizing layer may increase overall coating thickness, potentially improving corrosion resistance, existing literature indicates that corrosion in EC rebars typically initiates and propagates through coating defects (holidays), rendering additional layers ineffective [5], [6]. Additionally, the hydrophobicity induced at the steel concrete interface by the increased roughness of the TEC might also affect the progression of cathodic and anodic areas at the coating boundary with the holidays. To answer these questions, this study investigates the corrosion resistance of undamaged and damaged (holiday induced) EC and TEC bars along with uncoated steel bars using ASTM G-109 macrocell tests. The comparison of damaged and undamaged rebars addresses longstanding questions related to the corrosion mechanisms of coated rebars as well.