Corrosion-inhibited rock salt as an alternative deicing material has been extensively researched through laboratory and field tests of exposed structural steels, aluminium, and galvanised steel. Because ASTM corrosion test methods G4, G31, and B117 do not address this area of corrosion, a series of specifically designed corrosion tests in the laboratory and at bridge and highway sites was undertaken. Realistically sized metal coupons were used in tests undertaken to explore the role of chloride ion concentration in the deicing solution, the ratio of wet/dry time, and the difference between immersion tests and spray tests to achieve wetting with solutions of inhibited and normal rock salt. Test results indicate that a particular inhibited rock salt can cause reductions in weight loss from 25 to 98 percent, with average corrosion reductions of 55 to 70 percent in the laboratory tests. Results from field tests on the Dan Ryan Expressway and the Chicago Skyway during the 1990-1991 winter suggest a similar corrosion reduction of about 65 percent based on the wire resistance change per weight of chloride collected at six highway and bridge sites. Results of the test series during a 2-year period point toward realistic accelerated corrosion test methods to ensure that alternative deicing materials that show good laboratory performance also provide good performance on highways and bridges. (Author/publisher)
Abstract