January 13, 2014

Hot Report: Use of Magnesium Chloride During Snow Storms

OLR Report 2014-R-0001 answers the questions: Does magnesium chloride, which the state uses in combination with salt to remove snow from the roads, cause more corrosion than other deicers? Is it possible to add a rust inhibitor to this chemical to reduce the amount of corrosion? How much would that cost?

The state Department of Transportation (DOT) uses liquid magnesium chloride to pre-wet salt it applies to roads during snowstorms. Magnesium chloride, like other such chemicals, is corrosive. DOT is aware of the chemical’s effect on vehicles, but says chloride salts are currently the most effective and economical material for maintaining safe winter roads, and that the benefits of a chloride-based snow and ice program for motorists’ safety and the efficient flow of traffic far outweigh the increased risk of corrosion.

DOT began using liquid chemicals to pre-wet salt in 2006. It first used calcium chloride for this purpose, but switched to magnesium chloride because magnesium chloride was more readily available, less costly, and generally more effective.

It is possible to add a rust inhibitor to the liquid chemicals DOT uses for snow removal, and DOT has done so in the past. DOT estimates it would cost between 10 cents and 20 cents per gallon to add a rust inhibitor, or between $100,000 and $200,000 per million gallons (the amount DOT uses in a winter). However, cost is not the primary reason DOT does not currently use an inhibitor. DOT initially used an inhibitor to the calcium chloride solution, but discontinued its use in 2007 for a number of reasons, including the Department of Energy and Environmental Protection’s (DEEP) concern that the rust inhibitor was depleting oxygen levels in state streams, posing a threat to aquatic life.

DOT says it is constantly evaluating new products, and would probably add an inhibitor if DEEP approved it and its benefits outweigh its cost.

For more information, read the full report.