Abstract: The electrochemical corrosion behavior of TiN coatings prepared by reactive plasma spraying was studied in seawater by SEM technology and electrochemical methods such as electrochemical impedance spectroscopy.The results showed that the corrosion potential of TiN coatings was higher than that of the substrate and the coatings had a good corrosion shielding effect on the substrate.The coatings resistance declined and capacitance increased because the corrosion medium permeated into the coating/metal interface through pinholes and microcracks immediately. Due to the products of corrosion the corrosion was restrained, but the products can not stop the local corrosion of the substrate. The electrochemical corrosion of the coatings were mainly as the result of holes in the coatings.