CORROSION OF HIGHWAY STRUCTURES

A research study was undertaken with the objectives of evaluating existing corrosion design procedures for corrugated metal pipe and determining if the development of new corrosion test methods for service life designs was indicated and feasible. As a results of the research, a field test method for corrugated metal pipe installations was developed to measure corrosion reaction rates. By utilizing the new test method to measure corrosion rates, it was determined that metal pipes in high-resistivity soils (rho greater than 3000 ohm-cm) had low corrosion reaction rates. The rate of corrosion in medium-resistivity soils (rho above 2100 ohm-cm) was high initially but decreased grealty after a few years. However, in low-resistivity soils (rho less than 1000 ohm-cm) the corrosion reaction continued at a high rate. Also, a linear polarization test method was developed and compared with the conventional resistivity test method with satisfactory results. The study included corrosion protection of corroded steel pilings utilizing magnesium anodes. Research showed that corroded corrugated metal pipes could not be protected as easily because of the large surface area and soil resistance. The use of bituminous-coated corrugated metal pipe was found to be effective for inhibiting corrosion in most cases tested in Arizona.