THE FORMATION OF ZN4CL2(OH)4SO4.5H2O IN AN URBAN AND AN INDUSTRIAL ATMOSPHERE

Phase identifications of a large number of field exposed sheltered zin c panels have revealed the presence of a number of different corrosion products on zinc. A few of these phases, Zn4SO4(OH)6.nH2O, Zn5(OH)8Cl 2.H2O, NaZn4Cl(OH)6SO4.6H2O and Zn4Cl2(OH)4SO4.5H2O, seems to exist as final corrosion products. In order to study the formation of these ph ases, a field exposure program was implemented in atmospheres yielding different end products. A multi-analytical approach was used for deta iled studies from the initial stages to fully developed corrosion film s. The present study aims at describing the formation of zinc chlorohy droxysulfate (Zn4Cl2(OH)4SO4.5H2O) appearing in urban and industrial a tmospheres. It involves the consecutive formation of three phases, nam ely zinc hydroxycarbonate as the initial phase, zinc hydroxysulfate as the intermediate phase and zinc chlorohydroxysulfate as the final pha se.