The report describes laboratory experiments to evaluate three proprietary corrosion inhibitors as additives to road de-icing salt. Test panels of both bare and painted mild steel were used; tests were carried out employing first an intermittent salt spray method and then an intermittent immersion method; and tests were carried out at temperatures of 25 C and 5 C. The inhibitors tested were sodium polymetaphosphate; emulsifier STH; and a commercial product called 'Carguard' containing sodium chromate. Under spray conditions, which are considered the more realistic, no inhibitor gave a useful degree of protection to bare steel, but polymetaphosphate markedly reduced rust creep from damaged areas of painted panels. In the immersion test the inhibitors gave a high degree of protection to bare steel. It was concluded that the laboratory tests are useful as screening tests for preliminary evaluation, but tests of potential inhibitors using actual vehicles under realistic conditions are now required. (Author)
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