Conventional coating films are typically solvent based and contain a high percentage of volatile organic compounds (VOCs) which are environmentally damaging and pose health risks to humans. Our developments have been made to the introduction of water based low VOC coating systems. Research into the bulk material properties of these low VOC coatings is necessary to understand the degradation process of the coatings. Water sorption behavior of the bulk was focused in this research. So we attempt to determine the kinetic of water sorption properties of two water based urethane/epoxy coating as well as two solvent based urethane/epoxy coating film systems.Water sorption properties of a material can be characterized by two primary properties its diffusion coefficient and its equilibrium saturated water content. These two properties are measured for individual layers of each coating film system multi layer samples of each coating film and samples of each coating bonded to a steel substrate.To characterize the effects that water absorption have on the bulk material properties of the coating films two tests are performed on dry and saturated samples of each coating. Stress relaxation measures the rate of decay of stress incurred in a coating after being deformed by some applied strain. This data is correlated with the fractional water content of each coating at the time of testing. Finally adhesion testing determines a coatings ability under tensile stress to remain bonded to a steel substrate in both dry and saturated conditions.