Paper 1: Corrosion Inhibitors as Additives to Highway De-Icing Salts-Laboratory Tests

Abstract

Up to a million tons of rock salt are spread on the roads of England and Wales during a severe winter. It has frequently been suggested that this salt causes increased corrosion damage to motor vehicles. In North America and Scandinavia considerable interest has been shown in the use of corrosion inhibitors as additives to highway de-icing salts and at least two inhibited salts are marketed in the United States.

Use of an intermittent salt spray test in the Road Research Laboratory (R.R.L.) has shown that a 3 per cent rock salt solution is about 13 times more corrosive than urban rainwater to bare steel. Polyphosphate and chromate type inhibitors were examined under these test conditions and were found largely ineffective in reducing the corrosion rate of bare steel. However, the polyphosphate inhibitor showed a large reduction in corrosion rate of damaged painted panels finished in current motor primers and full paint systems. The work is continuing.