Sodium chloride and alkaline earth salts such as magnesium chloride are used extensively and in large quantities on roads and other structures for melting snow and ice. These agents generally work extremely well in deicing applications, but have several drawbacks. Sodium chloride's effectiveness as a deicer, its wide availability, and its low cost has made it one of, if not the most, widely used deicer. Unfortunately, salt is also a leading cause of structural corrosion of the nation's bridges and highways, concrete spalling, and vehicle corrosion.
Various additives have been proposed for mixing with salts to aid in inhibiting corrosion caused by the salts. For example, British Patent 1,328,509 to Bishop et al. describes a composition suitable for use in the inhibition of corrosion caused by salt, which includes a water soluble polyphosphate and a surface active agent (e.g., various amine compounds). E. E. Steed, Road Research Laboratory, Ministry of Transport, Report LR268-1969, reports that polymetaphosphate inhibitors which require the presence of calcium ions are effective as a corrosion inhibitor for brine solutions. Other phosphate-based inhibitors and deicing compositions have been used to lessen the corrosive effects of sodium chloride. Generally, however, the required amount of such phosphate compounds or inhibitors is relatively large and present environmental concerns.
There remains a serious need to provide a low cost deicing composition which reduces corrosion caused by sodium chloride. Thus, it would be highly desirable to develop a corrosion inhibiting, low cost, salt-based deicer composition that has considerably less residual impact on corrosion of the nation's highways and bridges as well as vehicles using those highways and bridges. It would also be highly desirable if such alternative salt-based deicer compositions only required relatively low levels of corrosion inhibitors and possessed, therefore, limited environmental concerns. It would also be highly desirable if the inhibitor system used in such alternative salt-based deicer composition did not interfere with the deicing rate of the salt and did not accelerate concrete spalling. The compositions and methods of this invention generally provide such characteristics.
The present invention is directed to providing corrosion resistant, low cost, solid deicing compositions which are suitable for use on highways, bridges, sidewalks, and the like. Accordingly, one of the principle objects of the invention is to provide deicing compositions which deice rapidly. Another object of this invention is to provide deicing compositions which cause reduced levels of corrosion to vehicles. Yet another important object of this invention is to provide deicing compositions which primarily utilize sodium chloride as a cost effective deicer, but reduce the highly corrosive effect of sodium chloride on vehicles.
Another object of the present invention is to provide a deicing composition comprising about 94.0 to 99.8 weight percent of a deicing salt, about 0.1 to 3.0 weight percent of a water-soluble rare earth salt, and about 0.1 to 3.0 weight percent of a water-soluble organic acid salt selected from the group consisting of gluconate salts, ascorbate salts, tartrate salts, and saccharate salts.
Still another object of the present invention is to provide a deicing composition comprising at least about 90 weight percent of sodium chloride, an effective corrosion-inhibiting amount of a water-soluble rare earth salt, and an effective corrosion-inhibiting amount of a water-soluble organic acid salt, wherein the rare earth salt is a water-soluble lanthanum salt, a water-soluble cerium salt, a water-soluble praseodymium salt, a water-soluble neodymium salt, or a mixture thereof and wherein the water-soluble organic acid salt is a gluconate salt, an ascorbate salt, a tartrate salt, or a saccharate salts.
Still another object of the present invention is to provide a method for deicing ice- or snow-covered surfaces, said method comprising applying an effective amount of a deicing composition to the surface to be deiced and allowing the deicing composition to melt or partially melt the ice or snow covering the surface, wherein the deicing composition comprises about 94.0 to 99.8 weight percent of a deicing salt, about 0.1 to 3.0 weight percent of a water-soluble rare earth salt, and about 0.1 to 3.0 weight percent of a water-soluble organic acid salt selected from the group consisting of gluconate salts, ascorbate salts, tartrate salts, and saccharate salts.
Still another object of this invention is to provide a deicing composition comprising about 94.0 to 99.5 weight percent of a deicing salt and about 0.5 to 6.0 weight percent of a corrosion inhibitor, wherein the corrosion inhibitor is selected from the group consisting of water-soluble rare earth salts, water-soluble gluconate salts, water-soluble ascorbate salts, water-soluble tartrate salts, and water-soluble saccharate salts.
These and other objects and advantages of the of the present invention will become apparent from the following description.