Editing Sodium chloride (section)

===Road salt===
{{main|Road salt}}
The second major application of salt is for [[deicing]] and anti-icing of roads, both in [[grit bin]]s and spread by [[winter service vehicle]]s. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated [[solution (chemistry)|solution]] of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For deicing, mixtures of brine and salt are used, sometimes with additional agents such as [[calcium chloride]] and/or [[magnesium chloride]]. The use of salt or brine becomes ineffective below {{convert|−10|°C|0}}.

[[File:Winter road salt.jpg|thumbnail|left|upright=1.15|Mounds of road salt for use in winter]]
Salt for deicing in the United Kingdom predominantly comes from a single mine in [[Winsford]] in [[salt in Cheshire|Cheshire]]. Prior to distribution it is mixed with <100 ppm of [[sodium ferrocyanide]] as an [[anticaking agent]], which enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money.<ref name=usgs/>

In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is {{convert|−21.12|C|F}} for 23.31 wt% of salt. Freezing near this concentration is however so slow that the [[eutectic point]] of {{convert|−22.4|C|F}} can be reached with about 25 wt% of salt.<ref name="u1"/>

====Environmental effects====
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their [[osmoregulation]] ability.<ref>{{cite news |last=Rastogi |first=Nina Shen |date=2010-02-16 |title=Salting the Earth |language=en-US |work=Slate |url=https://slate.com/technology/2010/02/does-road-salt-harm-the-environment.html |access-date=2023-03-11 |issn=1091-2339 |archive-date=11 March 2023 |archive-url=https://web.archive.org/web/20230311162816/https://slate.com/technology/2010/02/does-road-salt-harm-the-environment.html |url-status=live }}</ref> The omnipresence of salt in coastal areas poses a problem in any [[coating]] application, because trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The [[International Maritime Organization|IMO]] regulation is mostly used and sets salt levels to a maximum of 50&nbsp;mg/m<sup>2</sup> soluble salts measured as sodium chloride. These measurements are done by means of a [[Bresle test]]. Salinization (increasing salinity, aka ''[[freshwater salinization]] syndrome'') and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways.<ref>{{cite web |url=https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |title=Saltier waterways are creating dangerous 'chemical cocktails' |website=phys.org |access-date=3 December 2018 |archive-date=3 December 2018 |archive-url=https://web.archive.org/web/20181203202733/https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |url-status=live }}</ref>

In highway de-icing, salt has been associated with [[corrosion]] of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. [[Surface runoff]], vehicle spraying, and windblown salt also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied.<ref name=usgs/> A 2009 study found that approximately 70% of the road salt being applied in the [[Minneapolis-St Paul]] metro area is retained in the local watershed.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2009/02/090210125424.htm |title=Most Road Salt Is Making It into Lakes And Rivers |date=20 February 2009 |website=www.sciencedaily.com |publisher=University of Minnesota |access-date=27 September 2015 |archive-date=14 February 2009 |archive-url=https://web.archive.org/web/20090214150117/https://www.sciencedaily.com/releases/2009/02/090210125424.htm |url-status=live }}</ref>

====Substitution====
Some agencies are substituting [[beer]], [[molasses]], and [[beet]] juice instead of road salt.<ref>{{cite web |url=https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html |author=Casey, Michael |title=Turning to beet juice and beer to address road salt danger |website=phys.org |access-date=3 December 2018 |archive-date=29 January 2018 |archive-url=https://web.archive.org/web/20180129122230/https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html |url-status=live }}</ref> Airlines utilize more [[glycol]] and [[sugar]] rather than salt-based solutions for deicing.<ref>{{cite web |url=https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |title=EASA Cautions on Organic Salt Deicing Fluid |date=9 December 2016 |website=MRO Network |access-date=3 December 2018 |archive-date=10 January 2018 |archive-url=https://web.archive.org/web/20180110171604/https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |url-status=live }}</ref>