Hydrophobic Polyurethane Coating against Corrosion of Reinforced Concrete Structures Exposed to Marine Environment

The environment, in which structures are exposed influences durability performance and deterioration. The durability degradation of structural concrete located in aggressive marine environments due to corrosion is a major problem in the construction industry. Deterioration due to corrosion is associated with quantifiable losses, which is a financial burden for any developed country. The initiation of corrosion can be obviated to some extent by different methods. Hydrophobic coatings are waterproofing coatings on the external surfaces of concrete structures, which are used to combat the problem of deterioration due to corrosion and to extend the serviceability of reinforced concrete structures. Polyurethane coatings can be used to protect structural materials, particularly those exposed to corrosion, abrasion, weathering, and other processes that would help to degrade base materials over time. From the experimental study conducted, a total of 58 specimens of different descriptions were cast and subjected to several tests, including chloride permeability, chemical resistance, chloride diffusion, water absorption, and corrosion-accelerated procedures using the galvanostatic method. The results indicate that the effectiveness of polyurethane in resisting the diffusion of chloride is eight times greater than that of the base concrete specimen. It has a lower percentage weight reduction, considering acid penetration. The chloride permeability of the coated specimens was negligible, and the water absorption was low. The crack frequency was reduced in the specimens with hydrophobic coatings. The group of specimens with hydrophobic coatings had lower corrosion rates and narrower crack openings and had less reduction in diameter. Furthermore, it takes longer for cracks to develop on the surface of the specimen with polyurethane coatings. It has a lower amount of corrosion, and it takes a longer period to accumulate a critical amount of corrosion. Thus, hydrophobic polyurethane coatings are highly effective in reducing the chloride permeability and water penetration values, which helps to eliminate corrosion and lengthen the service life of structures located in an aggressive marine environment.