Specimens immersed for 18 and 40 days were detected by X-ray
diffraction (XRD) to analyze the principal corrosion products.
Figs. 11 and 12 show the XRD graphs of the two steels. The compositions
of corrosion film measured by X-ray diffraction indicate
that corrosion products of the two steels are all principally composed
of the corrosion substance in seawater (containing plenty of Cl−).