How de-icing salt works for effective winter gritting
De-icing salt works by lowering the freezing point of water. This is known as freezing point “depression”. When pure salt is mixed with water, it dissolves into separate sodium and chloride ions. These ions interfere with the formation of ice crystals, making it more difficult for water to freeze and effectively lowering the freezing point of water.
When de-icing salt is applied to ice or snow, it dissolves in any moisture present, such as water from melting snow or ice. This process is endothermic, which means it absorbs heat energy from the surroundings.
As the salt dissolves, it lowers the freezing point of the liquid solution. For example, when sodium chloride is added to water, it forms a saltwater solution with a lower freezing point than pure water. This means that the temperature at which the water would freeze is lowered, making it more difficult for ice to form or to stay frozen.
The saltwater solution created on the road or footpath surface due to the presence of de-icing salt comes into contact with the ice and snow. Because the freezing point of the solution is lower than the air temperature, it begins to melt the existing ice and snow by drawing heat from the surroundings, further dissolving the salt in the process.
The dissolved salt helps prevent the melted ice and snow from refreezing as long as the temperature remains above the new freezing point of the saltwater solution. This allows for safer travel and easier removal of snow and ice.
The effectiveness of de-icing salt depends on a number of factors, including the type of salt used, the temperature, and the amount of water present. The most common type of de-icing salt is sodium chloride (NaCl), a white substance. Sodium chloride is effective at melting ice at temperatures above -10 degrees Celsius, and the purer the salt, the better the action.
Other types of de-icing salts include magnesium chloride (MgCl2) and calcium chloride (CaCl2). These salts are more effective at melting ice at lower temperatures, down to -30 degrees Celsius (-22 degrees Fahrenheit), but they are also significantly more expensive.
De-Icing Salt Facts & Figures
Over 2 million tonnes of salt are spread onto UK roads each year. The most grit ever used in the UK in a single winter was 2.7 million tonnes in 2010-11.
The use of de-icing salt in the UK has increased significantly in recent years. In the 1990s, around 1 million tonnes of salt was used each winter. Today, this figure has more than doubled. The increase in the use of de-icing salt has been attributed to a number of factors, including the increasing severity of winters, the increasing emphasis on health and safety the increasing demand for guaranteed distribution and transport networks.
De-icing salt and specialist de-icing products
We supply a broad range of specialist liquid and granular de-icing products and equipment to cater for all surfaces or ecologically sensitive areas.
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