Steel piles at the tidal zone can be seriously corroded. Common protective methods such as painting or coating with rubber or other protective materials

etc. cannot provide full protection when used as supplementary protection because these traditional methods require strict pretreatment and sealing of the metallic surface from the corrosive mediums

and time for the protective coatings to solidify. This is very difficult under the severe action of waves and surges on the sea. With our oil-soluble DZ-2 tape

protection efficiency for hanging steel plates at the tidal and splash zones reaches to 82–99%. The protection efficiency of water soluble DZ tape at the tidal zone reaches to 92.9%. The DZ and DZ-2 tapes can rapidly reduce the original corrosion velocity to ten percent and one percent respectively as fully proved by the 500 hour rapid corrosion testing with indoor salt fog and by the relevant electrochemical parameters of instantaneous corrosion velocity

etc. DZ tape absorbs much OH− to cause a pH rise. A synergistic protective effect is gained when DZ tape is used together with cathodic protection of steel piles at the tidal zone. The working principle of DZ tape is different from that of DZ-2 tape even though they are composed of the same chemical materials. The latter provides protection because of the close affinity between metal and its carboxyl group shields the active centre at the metal surface to reduce the activation energy of metal. The carbon chain forms a covering oil film of netted structure.