Dose-response functions
The results of ICP Materials not only confirm the corrosive effect of SO2 and other pollutants in the multi-pollutant situation but also enable quantification for a wide range of materials in the form of dose-response functions. A dose-response function links the dose of pollution, measured in ambient concentration and/or deposition, to the rate of material corrosion. For unsheltered positions the materials damage is usually discussed in terms of dry and wet deposition. Wet deposition includes transport by means of precipitation and dry deposition transport by any other process.
Dose-response functions for the SO2 dominating situation are available for many materials in unsheltered and sheltered position after 8 years of exposure (1987-1995) as described in Report 30 Statistical analysis of 8 year materials exposure and acceptable deterioration and pollution levels.
Dose-response functions for the multi-pollutant situation are available for some materials and are given in the draft mapping manual chapter 4, which is currently under revision (see below for a description of the mapping manual).
The dose/response functions constitute the main results of the programme and are of outmost importance for development of systems for classification of corrosivity of environments, for mapping of areas with increased risk of corrosion, and for calculation of cost of damage caused by deterioration of materials.
Trends in corrosion and pollution
In the period 1987–1997 the decreasing trend in the concentrations of acidifying air pollutants resulted in a decreasing trend in corrosion of all trend materials (carbon steel, zinc and limestone). During 1997–2003 the corrosion rate of carbon steel continued to decrease, but the corrosion rate of zinc and limestone increased slightly. More details can be found in the report Trends in corrosion and air pollution in 1987-2003. The data obtained from the most recent exposure in 2005-2006 shows that even for carbon steel the average trend is no longer decreasing.
Mapping, tolerable levels and calculation of corrosion costs
Maps on corrosion attack and also acceptable/tolerable levels can be produced on different scales and in different regions. It is therefore necessary to develop and establish clear procedures for mapping areas with elevated risk of corrosion in order to facilitate comparisons of maps produced by different institutes or organisations and for different countries. It is also important to define methodologies to obtain data on stock of materials at risk, which is one of the most important pieces of information that is required for a cost calculation. The mapping manual is provided by ICP Modelling and Mapping and the 2004 version is available in English and Russian. Chapter 4 of the mapping manual describes mapping of effects on materials, acceptable/tolerable levels and calculation of corrosion costs and is currently under revision (se above).
For assessment of direct costs of corrosion damage caused by air pollutants a model has been developed and used first in three cities in Europe, Stockholm, Sarpsborg and Prague. The model has subsequently been applied also for a rough estimation for whole Europe. The estimated total cost savings were 9.5 x 109 US$/year for SO2 induced corrosion in Europe resulting from the implementation of the second Sulphur Protocol within UN ECE.
Climate change
Climate and pollution are acting together in a complex way as demonstrated by the obtained dose-response functions, resulting in corrosion and degradation of materials. Further reducing air pollutants are one of the more effective ways of compensating for increased risk of corrosion due to climate change. More details can be found in the report Combined effects of climate change and air pollution on materials including cultural heritage.