Fig. 1. Reaction mechanism of FAS and WO₃ film

Fig. 2. Hydrophobic mechanism of WO₃ film modified by FAS

Fig. 3. Reaction mechanism of KH-570 and WO₃ film

Fig. 4. Preparation process of salt spray-resistant hydrogen sensitive film

Fig. 5. Fiber hydrogen sensing system

Fig. 6. Adsorption of water molecules on WO₃ surface

Fig. 7. Film contact angles in orthogonal experiments

Fig. 8. Hydrogen sensitivity performance of FAS-WO₃ films

Fig. 9. Thin film characterization. (a) SEM image of FAS-WO₃ film; (b) SEM image of WO₃ film; (c) EDS image of white particles; (d) FTIR images of FAS-WO₃ and WO₃ films

Fig. 10. Hydrogen sensitivity performance of KH-570 modified films with different R in salt spray environment. (a) Sensitivity;

Fig. 11. Dissolution of KH-570 in mixed solvent of water and ethanol

Fig. 12. FTIR spectra of FAS-WO₃ film before and after KH-570 modification

Fig. 13. Contact angles of films

Fig. 14. Experimental environment. (a) 85% humidity environment; (b) 90% salt spray environment;

Fig. 15. Hydrogen sensitivity performance of films in different environments. (a) Sensitivity; (b) response time

Fig. 16. Repeatability response curve of modified film

Fig. 17. Effect of placement time on hydrogen sensitivity of film in air. (a) Sensitivity; (b) response time

Fig. 18. Effect of placement time on hydrogen sensitivity of film in 90% salt spray environment. (a) Sensitivity; (b) response time