Fig. 6: Analysis of large-scale immersion test in 5.0 wt% NaCl solution.

Digital images of a WPU, b WPU–GORM, and c WPU–GOLM coatings immersed in 5.0 wt% NaCl solution at different times. OM of the d WPU coating and g WPU–GOLM coating surface soaked for 246 h and e, h the corresponding carbon steel with the coating removed. AFM images of the f WPU coating and i WPU–GOLM coating surface morphology and digital photos of the corresponding carbon steel with the coating removed (inset in the lower right corner).