Abstract
Hopeite and Phosphophyllite as zinc phosphate crystals were formed on galvannealed steel (GA) with alloy phase of FeZn7 and cold rolled steel (CR). The distribution of crystal components were analysed by Auger electron spectroscopy for the surface region and depth profile.
No Mn or Ni was detected on the Hopeite crystal surface and it was therefore concluded that the crystal surface was made up of Zn3(PO4)2⋅4H2O. Mn was, however detected on the Phosphophyllite crystal surface. These results correlated with those from X-ray photoelectron spectroscopy described in a previous paper.
In the depth profile analysis, Ar+sputtering was applied between 0-64.5min, and the intensity ratios were calculated for O/P, Zn/P, Fe/P, Mn/P and Ni/P from the Auger spectra and were plotted. For both Hopeite and Phosphophyllite crystal, the O/P ratio was constant in the bulk of the crystal layer, indicating that the structure of-PO4 was maintained uniformely. The ratios of Mn/P and Ni/P were also constant in the bulk of crystal layer.
The ratios for Zn/P and Fe/P of the crystal on GA steel and for Fe/P of the crystal on CR steel, however, showed a radical increase in accordance with the sputtering time. It was thought that this phenomenon was in response to the steel itself through the porosity of zinc phosphate crystal.
