If you live in Canada, you’re probably familiar with city trucks roaming the streets after a snowfall, spreading de-icer in their wake. You might even use salt based de-icer on your own sidewalks and driveway. But have you ever wondered how salt causes ice to melt?
Salt lowers the freezing and melting temperature of water. Water freezes when heat is removed and the molecules stop moving and get so tightly packed together they form a solid mass. That usually happens at 0 degrees Celsius. Add salt to the mix, and it keeps those water molecules excited and water liquid until the temperature drops even lower.
Normal water freezes at 0 degrees Celsius. A solution of 10% salt and 90% water freezes at -6 degrees C. A solution of 20% salt doesn’t freeze until the temperature drops to -16 degrees C.
In order for salt to melt ice, there has to be water present. A sheet of ice usually has a thin layer of water on its surface. When a grain of salt lands on it, it starts to dissolve, mixes with the water, and lowers the temperature at which it freezes.
De-icers are available under a lot of different names but almost all are made from five common ice melting products.
Calcium Chloride is the old standby and it’s very effective. It can melt ice at temperatures as low as -31 C. It’s also exothermic which means as it dissolves, it gives off heat, melting ice faster. However, it destroys metal and can be very harmful to the environment if overused.
Sodium Chloride, or good old rock salt is inexpensive and effective to between -6 and -7 C. It’s less damaging to concrete than Calcium Chloride but will cause metal to corrode and can damage plants.
Potassium Chloride is expensive but is very effective when mixed with rock salt. It prevents water from freezing to -11 C.
Urea is commonly used as a fertilizer but it’s also used as a de-icer. It continues to melt ice until the temperature drops to -6 C. It’s non-toxic and is used in many pet safe de-icers.
Calcium Magnesium Acetate is made from limestone and acetic acid which is what gives vinegar its zing. It’s only effective to around -6 C. It’s not a great ice melter but it prevents snow and ice from sticking to pavement, and creates dry, powdery snow which gives cars better traction.
If you need help keeping your sidewalk, driveway, or parking lot snow and ice free this winter, contact 5 Star Landscaping in Calgary.