Raman and infrared spectral analysis of corrosion products on zinc NaZn4Cl(OH)6SO4·6H2O and Zn4Cl2(OH)4SO4·5H2O

Two corrosion products of zinc namely NaZn4Cl(OH)6SO4·6H2O which occurs mainly in marine and traffic environments and Zn4Cl2(OH)4SO4·5H2O which occurs in industrial, rural and urban environments were analysed using infrared and Raman spectroscopic methods and the vibrational modes of SO42− ion, OH radical and H2O molecules have been identified and discussed. The symmetric stretching vibrations of the SO42− ion of the compounds give an indication of the distorted structure for the SO4 anion in the compounds, the distortion being more in Zn4Cl2(OH)4SO4·5H2O. Due to the presence of strong hydrogen bond network, an unusual lowering of the symmetric stretching mode of SO4 is observed in both the compounds. In NaZn4Cl(OH)6SO4·6H2O, medium to weak hydrogen bonding network is present while strong to weak hydrogen bonding is present in Zn4Cl2(OH)4SO4·5H2O.