Various surface treatments on rolled zinc have also appeared on the market, mainly for reasons of architectural aesthetics. One type of treatment is application of colour, another is pre- weathering, leading to a light grey appearance similar to the patina of natural rolled zinc, or to a dark grey appearance, compatible with slate products. The life cycle of rolled zinc products in building applications is very precisely assessed since use began at the beginning of the last century. Examples of zinc roofs renovated after some 100 years of continuous service are numerous in Europe. At the end of their life cycle, rolled zinc products have traditionally been recovered by roofers and plumbers.
Systematic collection is facilitated by ease of dismantling and by an advantageous purchase price.
The main users of old rolled zinc products are secondary zinc refiners, brass producers and zinc oxide producers. SO2 is very corrosive to zinc because it reacts with the patina on the surface of the zinc to form a sulphate, which is then dissolved in rainwater. As a consequence of lower SO2 emisssions, the rate of corrosion of rolled zinc has dramatically decreased over the last 25 years and in future, the life expectancy of rolled zinc in building applications will be well above one hundred years. Ecological problems caused by the use of zinc have not been observed, even in a city such as Paris where it has been the leading roofing product for over 150 years. The durability and recyclability of zinc mean that its cost effectiveness and ecological impact have to be measured on a timescale that is not even accessible to many other building materials.