A method of preparing a modified-metal surface. The method includes preparing a solution of a phosphorous-based acid in a solvent; immersing a strip of the metal work piece into the solution of the phosphorous-based acid; immersing a strip of a reference metal into the solution of the phosphorous-based acid; supplying a voltage for a duration of time to prepare a phosphorous acid-modified metal work piece; removing the phosphorous acid-modified metal work piece; cleaning and drying the phosphorous acid-modified metal work piece; applying a chitosan solution to the surface in order to attach chitosan/modified chitosan to the phosphorous acid based modified surface; prepare the modified-metal surface; and cleaning and drying the modified-metal surface.