An engineer tasked with designing a building or piece of infrastructure will soon have access to a new tool that will estimate the corrosion rate for the site with an unprecedented degree of accuracy.
It will also assist in determining whether or not their plans comply with standards set out in the National Construction Code, potentially resulting in significant cost savings and shorter project schedules.
The Interactive Corrosion Map of Australia app has been developed by the Galvanizers Association of Australia (GAA) in conjunction with CSIRO and RMIT University. It follows pressure from the construction industry for more detailed and reliable data on corrosion rates, which are key factors in building design and choice of materials.
Currently, structural engineers have to rely on tools like the Durability of Galvanizing Estimator on GAA’s website to help them work out the appropriate type and thickness of coating they’ll need to apply. The Estimator’s more rudimentary estimates are based largely on the type of, and distance to, the nearest coast.
“It is a real game changer for engineers designing residential buildings, highways, bridges or industrial plants as it will provide real-location assessments of climate that include a 27-fold increase in data points from the current system’s salinity map,” GAA CEO Peter Golding said.
The app’s sophistication means there’ll be a greater likelihood that the readings will be a more accurate reflection of local conditions than those obtained via the estimator. It uses 10 years of weather data to calculate the surface time of wetness and surface salt concentration at three-hourly intervals over a typical year.
This then allows calculation of an annual corrosion rate that can be updated in the future as new climate data becomes available.
“Corrosion is affected by much more than just distance from the sea,” Golding said. “To make better informed judgements, you have to factor in the building’s orientation and any landscape or design features which may impact its exposure to rain, prevailing winds or sunlight.”
The user-friendly app, which will be accessible via GAA’s website later this year, will also consider the local generation, transport and deposition of salt aerosols, the effect of rain washing and the extent to which the site is shielded by nearby buildings, all of which affect corrosion levels.
“If it’s in the CBD of a capital city, there will generally be more protection from airborne salt from the ocean than there would be in a rural location so that has to be taken into account as well,” he said.
Enhanced accuracy
Another of the app’s key advantages will come into play over time as weather patterns become disrupted by climate change.
“When new data is available we’ll be able to reconfigure its analyses and predictions based on actual weather events,” Golding said. “So, if temperatures rise and there’s a resulting knock-on effect on rainfall and wind, that will be reflected in the reported corrosion rates. That’s simply not possible with the current static database.”
This will be crucial as rainfall, temperatures and the severity of storms change over time.
“If a region becomes more prone to flooding or rain dries up completely, those changes will inform the advice on corrosion rates,” Golding said. “If stronger winds carry more salt, it’ll generally cause an increase in the corrosion rate so a thicker galvanized coating may be appropriate.”
The amount of moisture in the air also affects the dew point, so if the relative humidity is low, surface salts will be dry and there will be less of an impact. Conversely, high humidity levels can also limit airborne salt aerosol transport inland. This highlights the fact that the effect of climate change on corrosion is complex, will vary across Australia and can’t be generalised.
“All of these considerations will combine to produce a highly localised estimate of corrosion rate that engineers can be more confident of using,” he said. “And it’s not just for the construction itself. It’ll also be invaluable in working out how regularly a structure needs to be washed to remove a build-up of salt, particularly those spaces not exposed to rainwater such as verandahs and balconies.”
New compliance rules
The launch of the interactive map is timely given the changes about to be introduced to the National Construction Code. New requirements for residential buildings are designed to make it easier for engineers to understand whether their plans are compliant.
“The advice will be clearer and more prescriptive, so it’ll be even more critical to know local corrosion rates,” Golding said. “The new app won’t just calculate the conditions more reliably; it’ll also come up with the optimal galvanized coating and the minimum thickness of steel required to achieve this.”
It will also estimate how many years the coating on the structure will last, and when any regalvanizing may need to be carried out. If more durability is needed, then adjustments can be made in the design phase to achieve the desired outcome.
“It’s a transformational innovation,” he said, “and we can’t wait to share it with engineers across Australia.”
The Interactive Corrosion Map of Australia app will be launched later in 2024.
Find out more about how GAA helps engineers assess corrosion rates and galvanizing solutions.