This research presents Phase 1 of a study for climate change impacts on the atmospheric corrosion of structural steel components of infrastructure such as bridges. ISO standards that provide quantitative models to calculate corrosion rate as function of key exposure parameters, namely, temperature, relative humility, chlorides, and sulfur dioxides are used in the evaluation, where the first-year corrosion rate is used to quantify and classify the severity of a corrosive environment. The corrosivity environment of six Canadian cities/locations for carbon steel bridges was modelled for the 1954-2020 period and the next 80 years using projected climatic data up to year 2100. The model was calibrated by the 10-year corrosion field data for these six locations for the 1954-1964 period, where good agreement was observed especially for locations in low and medium environmental corrosivity categories per ISO classification. The results also demonstrated that the methodology can be adopted in Canadian infrastructure standards/codes such as the Canadian Highway Bridge Design Code to enhance the current descriptive environmental exposure with quantitative corrosion rates. This study represented an initial effort and in order to fully implement into a more reliable and quantitative corrosion protection design more research is required.


There are more than 47,000 publicly-owned roadway bridges in Canada.1 Over 25% of these bridges have main structural load bearing components made of structural steel (i.e., truss and steel girder bridges) based on data from the Ministry of Transportation, Ontario – MTO.2 According to Statistics Canada, the condition of approximately 40% of these bridges is rated as either very poor (unfit for sustained service), poor (increasing potential of affecting service), or fair (requires attention).3

It was reported by Koch et al.4 that corrosion is one of the main reasons that lead to structural deficiency of steel components of highway bridges. Especially in marine environments, steel bridges are at risk of high rates of corrosion, particularly beyond 15-20 years in service.5 This observation can be expanded to locations where the use of de-icing salt is common practice such as urban areas in North America. In addition, future climatic changes that are evident (i.e., change in temperature and relative humidity) may potentially affect the rate of corrosion-induced deterioration and affect the resistance of bridges against various load types throughout their life-cycle.

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