CORROSION OF METAL
Because corrosion is a very complex issue, there are few simple answers to corrosion questions across all real-world situations. One generalization that can be made is that common types of bare metal exposed to chloride typically experience increased corrosion. There is little difference in corrosion effect between the various chloride-based deicers, including rock salt (NaCl), calcium chloride, and magnesium chloride.
Some vendors may cite a particular lab test to support claims that one chloride-based product is "less corrosive" than another; however, lab tests often fail to accurately represent real-world performance. Good science doesn't support attempts to differentiate the corrosion performance of one chloride-based deicer versus another. Non-chloride deicers are less corrosive than chloride-based deicers; however, their deicing performance is generally weak, and there are certain situations where even these more expensive products can be associated with corrosion problems.
The impact of deicing materials on reinforcement steel embedded in pavement, metal infrastructure, vehicles, and application equipment should be managed by:
- Applying engineering best practices for material selection and installation of infrastructure components.
- Implementing strategies to limit the amount of deicing chemicals used. These strategies can include matching deicer application rates to temperature conditions, reducing accumulation of snow and ice on roadways through the use of snow fences or other measures, predicting when to apply deicers, improving the application of deicers with better distribution systems, maximizing the effectiveness of deicers through prewetting, and allowing deicers sufficient time to work before plowing and reapplication.1 Liquid calcium chloride ice melters from OxyChem are used as prewetting and anti-icing agents that help increase the effectiveness of solid deicers and abrasive materials and minimize total deicer requirements, which can reduce deicing expense and the amount of deicer introduced into the environment.
- Thoroughly washing vehicles and application equipment after direct exposure to deicers or to brine spray from wet winter pavement. The International Carwash Association provides tips for maintaining vehicles exposed to deicing chemicals as well as abrasive materials, mud, precipitation and other winter byproducts at http://www.ultimatewash.com/weather.htm.
1 The Deleterious Chemical Effects of Concentrated Deicing Solutions on Portland Cement Concrete, Report No. SD2002-01-G, Michigan Tech Transportation Institute (L. Sutter, K. Peterson, et al), 2008