How cold is too cold for deicers?
Deicers are used to prevent accidents and they do this, reducing falls and accidents by around 80%.
As the temperatures dip far below freezing, someone asked me if there was a point at which ice-melt won't work anymore. The answer is yes but don't panic.
Deicers work by disrupting the bonds between the ice molecules --making it harder for them join together and make a solid--but there is a limit to which they can depress a freezing point. The first study I could find on this topic was published in 1918 by Worth H. Rodebush. He measured the eutectic points of various salt solutions, essentially the lowest temperature they can reach before being solid. His figures match those found today so here is a partial list:
Salt, sodium chloride, NaCl -21 C or 1-6 F (works efficiently to melt ice at temperatures above 15 F). This is what is used on Iowa roads.
Calcium chloride -51 C or -60F ( for practical purposes it works above -20 F)
Potassium acetate -30C or -76F (safest for grass and concrete and most effective above -22 F)
Magnesium chloride -15 C or -5 F (best above 5 F)
The list above is for salts, inorganic compounds with ionic bonds.
Glycols such as propylene glycol are carbon-based compounds that can be used as deicers. These have a eutectic point of around -55 C which is -67 F. These are most often used on airplanes. So don’t panic about your airplane.
As you can see, these substances do have their limits but thankfully we rarely face these extreme temperatures--although we do on occasion reach -22 F in Iowa and on roads, we are using the absolute cheapest product.
A temperature of -93 C or -136F has been recorded in Antarctica by a satellite device with -128.6F (-89 C) being the coldest official temperature measured by a thermometer. Here's a spot where deicers wouldn't be effective.
What's the coldest a substance can get? Helium freezes at -458 F or -272 C. You'll probably never see any of these temperatures so enjoy your deicers in moderation, using caution below -22 F.
Why in moderation? Deicers can "aggravate" flaws in concrete and of course when wet, they make part the perfect combination to corrode your car—corrosion caused by the combination of electrolyte, water, and air. Salts are the electrolyte. Besides eating up a fifth or more of local and state road budgets, they also contribute quite a lot of sodium and chloride to the local waters. Locally, Big Rock Park Creek had elevated salt levels in the spring after an icy winter. Not only is this dangerous to wildlife, it can cause corrosion issues such as seen in Flint, Michigan, when pipes were chewed up by salty water and released lead into the drinking water. The alternatives such as acetates, used in Minnesota, are much more environmentally friendly but also more expensive. Beet juice waste can be used, but it tends to add a lot of organic matter to water, deoxygenating it. Sand provides traction but won’t keep water from freezing. Better snowplows are a possible solution.
Don't forget, the lower temperature of deiced pavements can make pet paws get so cold that they can get frostbite. Rock salt can cause pain and be unhealthy. So protect your pets this winter and travel safely
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