The SEM micrograph at critical immersion time and the AFM images.

<p>(a) The SEM micrograph for VX9 alloy at 0.1M NaOH solution. (b) The SEM micrograph for VX9 alloy at 0.25M NaOH solution. (c) The SEM micrograph for VX9 alloy at 0.5M NaOH solution. (d) The SEM micrograph for VX50 alloy at 0.1M NaOH solution. (e) The SEM micrograph for VX50 alloy at 0.25M NaOH solution. (f) The SEM micrograph for VX50 alloy at 0.5M NaOH solution. (g)The AFM images for VX9 alloy at 0.1M NaOH solution. (h)The AFM images for VX9 alloy at 0.25M NaOH solution. (i) The AFM images for VX9 alloy at 0.5M NaOH solution. (j) The AFM images for VX50 alloy at 0.1M NaOH solution. (k)The AFM images for VX50 alloy at 0.25M NaOH solution. (l) The AFM images for VX50 alloy at 0.5M NaOH solution.