SEDL / STP / STP1137-EB / STP19752S

Synergistic Effects of Acid Deposition and Road Salts on Corrosion

Baboian, R
Principal Fellow and Head, Electrochemical and Corrosion Laboratory at Texas Instruments Inc., Attleboro, MA

Pages: 13    Published: Jan 1992

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Abstract

The interaction of our natural environment (rain, snow, humidity) with chemicals introduced to the environment (road salts, emissions) provides a complex chemistry. During the past three decades, this chemistry throughout the world has changed drastically. Use of sodium chloride and calcium chloride for ice and snow removal has increased to an extremely high level. Emissions of SO² and NO^x have also risen to such levels. These emissions convert to sulfuric and nitric acids and are deposited over large areas by precipitation. The combination of protective film disruption on metals by chlorides and the deposition of reducible hydrogen ions by acid precipitation provides a synergistic effect on corrosion of infrastructure metals. Results of laboratory and field tests show that steel is much more susceptible to corrosion in this type of environment.