4 ms·
> Deicing salt works by absorbing moisture as it lands, before it can form a sheet of ice. That's...false? Salt gets spread on existing ice to melt it all th
by ink_13 6y ago
> Deicing salt works by absorbing moisture as it lands, before it can form a sheet of ice.
That's...false? Salt gets spread on existing ice to melt it all the time. Where does the absorbed water go in this model? This assertion is so confusing.
As someone who grew up in a cold climate, the way I recall it is that the salt lowers the freezing point of water by forming a brine, allowing it to run off the road and/or be evaporated by the sun.
- pc86 6y agoIt's not quite as straightforward as "yes it does" / "no it doesn't." There's a temperature at which it's too cold for salt to work, and a great deal of the benefit of salt comes from friction as cars drive over it, crushing pieces of ice and forming that slush we all know and love, even at temperatures where it won't actually melt the ice.
- ink_13 6y ago> There's a temperature at which it's too cold for salt to work Sure, brine has a freezing point. > a great deal of the benefit of salt comes from friction as cars drive over it, crushing pieces of ice and forming that slush we all know and love, even at temperatures where it won't actually melt the ice. What do you think slush is? It has liquid in it, and that's not molten salt.
- skynet-9000 6y ago> a great deal of the benefit of salt comes from friction as cars drive over it You may have never tossed a handful of rock salt on steps that have a quarter-inch of ice on them and watch holes actually form in the ice within a half hour or so.
- Green_man 6y agoOn thin ice, you can watch it form in real time!
- jjk166 6y agoAgain, it's temperature dependent. Salt lowers the freezing point of water about 4 degrees (either units). Typically when it snows, it is close to freezing (if warmer it would rain, if much colder there wouldn't be enough moisture in the air for precipitation) so adding salt will melt the ice, but there's plenty of time when it's not in that narrow temperature range.
- busyant 6y ago> before it can form a sheet of ice. I think the person is just saying that pre-emptively salting the road (before snow/freezing rain actually lands) provides some additional level of safety because the road might spend less time with a frozen coating (as opposed to salting only after the surface is frozen over).