where is it commonly used?
Trains, rail switches, aircraft, etc.
De-icing
Trains and rail switches in arctic regions have large problems with snow and ice build up. They need a constant heat source in cold days to assure functionality. 
na is the symbol for which of the following chemical elements Sodium what is the historical story of this? In medieval Europe, a compound of sodium with the Latin name of "sodanum" was used as a headache remedy. apart from food, where else is it used? Sodium chloride is extensively used for anti-icing and de-icing and as a preservative. what is the meaning of the second icing method you just mentioned? De-icing is the process of removing snow, ice or frost from a surface.
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De-icing [SEP] Trains and rail switches
Trains and rail switches in arctic regions have large problems with snow and ice build up. They need a constant heat source in cold days to assure functionality. On trains it is primarily the brakes, suspension and couplers that require heaters for de-icing. On rails it is primarily the switches that are sensitive to ice. These high-powered electrical heaters efficiently prevent ice formation and rapidly melt any ice that forms. The heaters are preferably made of PTC material, e.g. PTC rubber, to avoid overheating and potentially destroying the heaters. These heaters are self-limiting and require no regulating electronics; they cannot overheat and require no overheat protection.