The synergistic mechanism of inhibitor including molybdate, organic phosphate,PESA and Zn²⁺on the metal surface was explored with methods of EDS,XPS and SEM. EDS analysis showed that Fe content was increased from 62 . 68 % to 96 . 80 % and the calcium content was decreased from 34 . 56 % to 0 . 10 % by comparing to the blank seawater specimens with adding inhibitors specimen. So the crevice corrosion under the scale was slowed. XPS analysis showed that compound inhibitor was added so that coverage rate on the metal surface of the iron oxide film was higher and denser and calcium was not found, which was consistent with the test results of the EDS. SEM analysis showed that there was no corrosion trace and no mechanical scratch in solution adding composite formulations; Crystals of calcium carbonate became from the most stable structure of calcite scale layer to unstable dispersion vaterite.