A method for studying the curing of 100 mu m-thick epoxy-based layers coated on steel substrates is described. A simple waterborne epoxy reactive system based on a diglycidylether of bisphenol-A prepolymer and with a polyether triamine was set up by emulsifying the epoxy resin with the use of an ethoxylated-nonylphenol emulsifier. The particular phenomena involved during the isothermal curing of such an epoxy emulsion were decomposed by considering the same formulation without water and without water + emulsifier. The chemical kinetics were determined by DSC and by size exclusion chromatography. As previously proposed for numerous epoxy-amine reactive systems, for the three types of coatings, a second-order autocatalytic law was able to interpret the data. The presence of water delays the gelation characterized by rheological measurements. As a consequence, the epoxy conversion at the gel point increases. This phenomenon can be related to the inhomogeneous polymerization process during which the epoxy groups can be trapped into the initial epoxy particles. In addition, the microdielectrometry technique was used to follow the curing degree of the epoxy reactive system of thin layers during the drying and curing processes under radiant heatings such as infrared curing.