Exoskeletons of prawn, shrimp, and crab discarded as waste are rich sources of inorganic and organic materials. Currently, these discards are mainly utilized for the extraction of chitin and less attention is paid to the recovery of other organic constituents present in the exoskeletons. The present study aimed to synthesize nano carbon dot (CD) and chitin from prawn shell, and utilization of CD as an additive to epoxy polymers to obtain a corrosion resistant polymer coating. Nano CDs were synthesized through a hydrothermal carbonization process and the characteristics were evaluated using spectrophotometric, fluorescence, and Fourier transform infrared spectroscopy studies. The CD reinforced bisphenol epoxy polymer composite coated over boat building steel exhibited the least defect, which in turn imparted the highest polarization resistance with the lowest capacitance. Chemical and morphological data of epoxy polymer composite highlighted the interaction of NH2 present in CD with polymer matrix. The functional group NH2 from CD synergistically acted along with hardener to form a pore free epoxy coating. Hydrothermal process of prawn shell enabled to extract chitin as evidenced by their spectral signature peaks. This study gave two economically important products through a green synthesis protocol.