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:
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 hydroxycarbonate (2ZnCO3.3Zn(OH)2) which is the main component of the patina.
The patina forms a layer which is compact, adherent, 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.
With an average corrosion rate of 1 µm/year and typical initial thickness of 0.7 mm it is clear that rolled zinc has a life expectancy of over 100 years. However, zinc's longevity is directly linked to its environment. Thus the average life span of a zinc roof in a rural area is between 90 and 100 years, in a marine environment near the coast, 60 to 80 years. Nevertheless, legislation in many countries to reduce pollution, particularly sulphur dioxide (SO2) emissions, has resulted in a considerable reduction in the present gap between rural and industrialised environments which will continue to narrow.
By comparing the life span of zinc to other building materials, you easily see why zinc is a sound choice for both the environment and the longevity of your building.
In addition to its long life span, zinc is a very low maintenance material. It does not have a coating or varnish that wears out over time and needs to be reapplied. In fact, zinc continues to build a protective layer (patina) over time and will self repair imperfections or scratches. Unlike other materials, such as coated or painted building products, VM ZINC® materials do not have to be repainted, brushed or cleaned once installed.
