Main function of coating is providing barrier protection between substrate and environment. And its commonly used to protect pipeline. In this research, to evaluate a function of barrier, a different the thickness coating (50, 100, 150, 200, and 250 micron) were used. In addition, to make easier during application process, solvent 0, 10, and 20% were added to paint. Epoxy is used as premier paint to cover substrate material ASTM A36 Grade B in NaCl 3, 5% Environment. Conventional spray was used in paint application. Morphology of coating was investigated by SEM. To evaluate the function of the coating, adhesion strength, blistering, and water vapor transmission rate tests were applied. The result indicate that the blister size increase with the increasing thickness coating while the adhesion strength decrease with the increase thickness coating. Additional solvent in paint increase the water vapor transmission rate, consequently, the function of coating decrease.