Before the opening of the Storebælt bridge connection in 1998, Storebælt has investigated the market for de-icer agents to find alternatives for sodium chloride. This was justified by wish to avoid corrosive effects of sodium chloride on the constructions.
From the first winter season there were used deicers in the form of:
- Calcium magnesium acetate (a salt of acetic acid used in a 25% solution)
- Potassium formate (a salt of formic acid was used in a 30% solution). In periods with very low temperatures, a 50% solution was used.
The results and conclusions of using Calcium Magnesium Acetate (CMA) and Potassium Formate
The overall experience with calcium magnesium acetate and potassium formate was good with few exceptions:
- In case of heavy snowfall, it was difficult to keep the roadway completely clean from snow and ice.
- There were areas where the snow was driven info very firm substance, and it was difficult to remove it with the above-mentioned deicer agents.
To help to overcome this difficulty, Storebælt has used two large self-driving sweepers that were mounted in the snowmobile column between the snow plows and the salt spreaders. The sweepers’ task was to remove the remaining snow left by snow plows, and thus they reduced the consumption of the de-icer agent.
The test of the long-term corrosion
The test of the long-term corrosion effect of de-icers is usually performed by an accelerated 7 days trials.
Assuming, that the actual corrosion course could differ from the results of this test, simple experiments were initiated in December 2001, where the long-term impact of calcium magnesium acetate, potassium formate and sodium chloride were examined on galvanized items.
The tested subjects were located outdoors at Storebælts outside area, where on weekdays throughout the winter season, they were sprayed with respectively: 22% sodium chloride solution, calcium magnesium acetate in a 25% solution and potassium formate in a 30% solution. At the end of the winter the tested subjects were cleaned with clean water under high pressure.
After 30 months the tested subjects were visually evaluated to determine the effect of corrosion.
The results and conclusions of short term trials
It was stated, that the items sprayed with a 22% sodium chloride solution or calcium magnesium acetate solution showed signs of white rust on surfaces, and rust on some point shaped areas.
The subject sprayed with a 30% potassium formate solution showed clear signs on rust along edges as well as around the bolts.
When the tested items were disconnected into two halves, the corrosion degree between the panels was almost identical.
It was assessed, that this occurred since the environment in that area of the tested items was moist and there was still residue of the deicer agent between the two halves.
The results and conclusions after long term trials
Storebælt’s own long-term trials show in 2017, 16 years after they were initiated, that the subjects treated with CMA showed no sign of corrosion.
The subjects that have been treated with a 30% potassium formate solution have clear signs of corrosion in larger and smaller areas throughout the subject.
The subject that has been treated with a 22% sodium chloride solution has corrosion around the edges, while surfaces are not significantly corroded.
Source: Guidelines on use of Deicers, National Road Committee, 2017