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 NaZn 4 Cl(OH) 6 SO 4 ·6H 2 O which occurs mainly in marine and traffic environments and Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O which occurs in industrial, rural and urban environments were analysed using infrared and Raman spectroscopic methods and the vibrational modes of SO 4 2− ion, OH radical and H 2 O molecules have been identified and discussed. The symmetric stretching vibrations of the SO 4 2− ion of the compounds give an indication of the distorted structure for the SO 4 anion in the compounds, the distortion being more in Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O. Due to the presence of strong hydrogen bond network, an unusual lowering of the symmetric stretching mode of SO 4 is observed in both the compounds. In NaZn 4 Cl(OH) 6 SO 4 ·6H 2 O, medium to weak hydrogen bonding network is present while strong to weak hydrogen bonding is present in Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O.