Long-Term Performance of Epoxy Coated Clay Bricks in Sulfuric Acid

Epoxy-based coatings are used in the rehabilitation and protection against acid attack in industrial and wastewater facilities made of concrete and clay bricks. In this study, the performance of two epoxy-based coatings on sewer grade clay bricks was evaluated using a combination of bonding strength and acid resistant tests over a period of three years. The test results showed that the bonding strength of the epoxy coatings depended on the dry and wet surface conditions of the clay brick at the time of coating. The bonding strength varied from 0.2 MPa to 3 MPa. The coating films effectively reduced the liquid uptake of the coated clay bricks and pinholes influenced the weight gain of the coated clay bricks. There was no direct relationship between bonding strength and acid resistant (weight gain) of the tested coatings. A film model was developed to predict the weight change in coated clay bricks. The mass transfer coefficients of the coatings varied from $0.8\times {10}^{-12}$ to $7.8\times {10}^{-12} m^2/s$ and $1.7\times {10}^{-12}$ to $6.6\times {10}^{-12} m^2/s$ in deionized water and 3% sulfuric acid, respectively.