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This is a picture showing corrosionThe chemicals used for snow and ice control are typically some form of chloride.  This includes sodium chloride (rock salt), calcium chloride, and magnesium chloride.  Chlorides are the most cost-effective way to depress the freezing point of water, which is critical for snow and ice control.  Unfortunately, chlorides are also known to accelerate corrosion on most bare metals, which is why northern states have always had to contend with corrosion issues.

Recently, there have been some claims that the corrosion issue has become worse in the last couple years.  In addition, calcium chloride is often held up as the culprit for this perceived increase.  While we may not have all of the answers to what may be influencing these statements; we can offer the following facts and observations:

  1. Rock salt is, by far, MaineDOT’s primary snow and ice material. (Reference the “Snow and Ice Materials” section of this web site)
  2. Liquid calcium or magnesium chlorides are generally used to supplement rock salt during cold storms through pre-wetting. When these types of products have been purchased by MaineDOT, we have paid approximately $0.40 more per gallon to add corrosion inhibitors that bring the corrosion rate of these products on bare steel down to almost that of distilled water.

    When these products are used (which is not every storm or in all areas of the state), they are normally used at a rate of about 2 gallons per mile. Presently, MaineDOT uses a product known as Ice-B-Gone (Reference the “Snow and Ice Materials” section of this web site), which is an environmentally-friendly magnesium chloride blend. Due to performance and cost considerations, MaineDOT has not purchased liquid calcium chloride since May 2005.
  3. Motor vehicle inspection laws have become stricter in recent years and licensed mechanics have indicated that corrosion that would have previously passed inspection will not pass today’s standards.
  4. Automobile manufacturers have been eliminating the use of a chemical known as “hexavalent chromium”. Hexavalent chromium has been used as a corrosion resistant coating on many steel, zinc, aluminum, and magnesium motor vehicle parts, including thousands of fasteners, v-belt pulleys, brackets, levers, radiators, brake lines, body panels and wheel rims. From what MaineDOT has been able to find, the following list indicates the time frame in which various auto manufacturers eliminated the use of hexavalent chromium:

    Volvo, Opel
    Toyota, Hyyndai
    Nissan, Daimler Chrysler

    More information on hexavalent chromium is available on the web or directly from the automobile manufacturers.

  5. Reports of premature corrosion seem to be associated with certain years, makes and models of automobiles while other manufacturers seem to have very little or no issues with corrosion.
  6. The manner in which a person uses their vehicle also affects how corrosion may come into play. Vehicles that are washed and used regularly throughout the winter season generally seem to have fewer issues. Vehicles that are driven only during storms and are then parked until the next storm (typically 4WD vehicles) seem to fare the worst.


This page last updated on 11/12/13