Study on the repair behavior of passive film of iron-based amorphous coatings by eco-friendly phosphate inhibitors

The passivation ability of the coating can be improved by adjusting the elements proportion in the Iron-based Amorphous Coating and the spraying process, but the process is complicated and costly. In this study, it was found for the first time that Iron-based Amorphous Coatings can quickly form passive films in phosphate atmosphere, which simplifies the coating strengthening process. Electrochemical measurements, XPS, AFM, FTIR, and SEM-EDS were used to investigate the inhibition mechanism of eco-friendly phosphates on the dynamic dissolution of passive film of Fe-based amorphous coating. When the coating was soaked in 3.5 wt% NaCl + 0.1 M solution, the iron phosphate compound on the coating surface promoted the repair and growth of the passive film, and the film thickness increased by more than 32.9 %. The increase of Fe2+/Fe3+ and (O2-+H2O)/ OH- in the passive film means that more insoluble Fe-Cr compound growth significantly reduces the donor density (Nd) in the passive film and inhibits the degradation rate of the passive film in the corrosive environment.