Corrosion of steel rebars in reinforced concrete constructions in marine environments is one of the major problems baffling the construction industry. To synthesis a suitable protective coating to rebars is necessary duty. In this study, two kinds of novel epoxy-based organobentonite nanocomposites with low-loading of ZnO-ZrO2/ZnO-Al2O3 nanoparticles were prepared for protective coating on the surface of reinforced concrete and protective coating on the rebars embedded in concrete in 8 series of sample for exposure test into artificial seawater (ASW). In the same conditions, three series of bare rebars embedded in concrete were tested for comparison. After 112 days exposure to ASW, those two kinds of nanocomposites have proved performance well as good and durable coatings.