Predicting Metal Corrosion Could Extend The Life Of Buildings

Metal corrosion remains a major challenge for architecture and infrastructure. Although modern metal components last much longer than they did several decades ago, corrosion still destroys several tonnes of steel worldwide every second. Replacing this material consumes valuable resources, while damage to bridges, roofs and railways costs industrialised countries an estimated three to four per cent of their gross domestic product.

Researchers at Swiss materials science institute Empa are studying how environmental conditions affect corrosion. Their work could support more durable buildings, improve material selection and reduce the need for resource-intensive replacement.

Tracking Corrosion Across Europe

Empa researcher Ulrik Hans contributes to ICP Materials, an international network that monitors the effects of air pollution and climate on materials and cultural monuments at more than 60 locations. Standardised samples of metals such as weathering steel and titanium-zinc are exposed at each site.

Titanium-zinc is widely used for roofs and gutters and is fully recyclable. Understanding its corrosion behaviour can help designers extend a component’s service life from perhaps 40 to 80 years, significantly reducing material use and maintenance.

At the Swiss monitoring site on Chaumont, near Neuchâtel, steel loses around 30 grams per square metre annually. By comparison, industrial locations lost much larger amounts when measurements began. At Kopisty in the Czech Republic, researchers recorded around 500 grams of rust per square metre in 1987. Today, steel losses at industrial sites have fallen to between 100 and 150 grams per square metre per year.

Changing Environmental Threats

The reduction closely follows a sharp decline in sulphur dioxide pollution. In the 1980s, this pollutant contributed to acid rain and accelerated corrosion. Industrial areas once recorded concentrations of up to 460 micrograms per cubic metre of air. Today, levels generally remain below 10 micrograms.

However, corrosion involves many interacting factors. Researchers are now investigating how ozone affects modern polymers and how particulate matter, nitrogen oxides, volatile hydrocarbons and climate change influence metallic infrastructure.

Predicting Material Performance

Empa analyses new materials during development to predict their corrosion behaviour. Advanced techniques, including Kelvin probe force microscopy and hard X-ray photoelectron spectroscopy, reveal changes within surfaces and deeper material layers.

These insights can guide the development of suitable alloys, protective coatings and nanometre-thin passive layers. They are also relevant to emerging production methods such as additive manufacturing and laser structuring. More accurate predictions could help architects and engineers use less material while creating components that remain functional for longer.

Protecting Cultural Heritage

Since 2010, ICP Materials has also monitored 26 UNESCO World Heritage sites, including Bern’s Old Town and the Abbey District of St Gallen. Case studies suggest that air pollution, particularly from road traffic, can account for up to 80 per cent of building maintenance costs.

By combining data on material composition, corrosion, limestone weathering and pollution, researchers aim to distinguish natural ageing from damaging deterioration. At St Gallen Cathedral, corrosion threatens copper roofs and has already affected nails in the 100-metre roof structure. Restoring the tiled roof is expected to cost almost eight million Swiss francs.

Source & photos: Empa