Rolled zinc is a durable material Rolled zinc products in
building applications have a very long life due to the self-
protecting property of zinc. In Europe, there are numerous
examples of zinc roofs renovated after about 100 years of
continuous service. The reasons for such a long service time are
now well understood : |Stage 1||Stage 2| The metallic zinc
surface reacts with atmospheric oxygen (O2) in the presence of
water (H2O) to form zinc hydroxide (Zn(OH)2). The zinc hydroxide
reacts with atmospheric carbon dioxide (CO2) to form zinc
hydroxicarbonate (2ZnCO3.3Zn(OH)2) which is the main component
of the patina. The patina forms a layer which is compact,
adhesive, insoluble in rainwater, and which will hinder any
further exchanges between oxygen and zinc, thereby controlling
the corrosion rate of rolled zinc and maintaining it at a low
level. Nevertheless, the durability of zinc can be reduced by
some acid pollutants, which increase the corrosion rate. The
main pollutant is sulphur dioxide (SO2). Sulphur d