Evaluation of Corrosivity of Antifreeze for Automobiles Containing Non-amine Type Corrosion Inhibitors for Copper

The development of new antifreeze mixtures containing non-amine-type corrosion inhibitors, which considers environmental protection, has become a major issue. In this study, four non-amine-type corrosion inhibitors were synthesized and used to produce five kinds of new antifreeze for automobiles to evaluate the rate of copper corrosion. The effects were evaluated by the weight change, surface observation, roughness measurement, and measurement of copper elution in the solution. The amount of copper eluted measured by ICP from Sample 4 was small, and the elution rate was prolonged. Sample 4 showed the best anti-corrosion performance owing to a corrosion suppression effect by passivating copper because the metal surface was smooth after the test, and the corrosion product layer was formed evenly on the surface as small local corrosion was observed. The major corrosion inhibitor added to Sample 4 was 1-aminomethyl(N',N'-di(2-hydroxyethyl)benzotrazole, which contained a certain amount in Sample 5 to show relatively high local corrosion but passivation in progress. Therefore, among the four corrosion inhibitors, 1-aminomethyl(N',N'-di(2-hydroxyethyl)benzotrazole had the highest corrosion inhibitory effect. This corrosion inhibitor prevents corrosion by promoting the passivation of copper on the antifreeze.