Zinc in the environment
Zinc is a light, grey metal, which is relatively easy to extract. The density of zinc is 4,7 g/cm3. Zinc is naturally present in the environment and is the 24th most abundant element in the earth’s crust. The average concentration of zinc is calculated to be 70 mg/kg. At the mine, zinc is found in form of zinc blende (a sulphide of zinc).
When zinc is exposed to moist air, a thin film of hydroxide and carbonate is formed on the surface. The film has a low solubility in water and protects the zinc from further corrosion. If high amounts of sulphur dioxide are present in the atmosphere, zinc sulphates form on the surface. Zinc sulphate has higher solubility in water and is more easily washed away, so a fresh zinc surface is exposed to corrosion. However, the level of atmospheric sulphur dioxide has decreased considerably in both Europe and the Nordic countries during the last 20 years and today very low concentrations are measured.