In-Service Corrosion of Galvanized Culvert Pipe

The Wyoming Highway Department changed the criteria it was using to select corrosion protection levels for culvert pipe in 1981. A study was undertaken to compare the effect of these changes in selection criteria to corrosion developed on pipe in service. Twelve 35 to 40-year-old culvert pipes from four highway reconstruction sites were sampled to determine the maximum weight loss from the most corroded area of each pipe. In-situ and laboratory soil resistivities were determined in or adjacent to each pipe trench, along with soil pH and soluble salts including sulfates. Corrosive weight loss was shown to be related to the field resistivity but not to the other factors. This indicates that minimum resistivity and soil pH, the two most commonly used soil parameters for culvert pipe selection, may not be reliable corrosion predictors in practice.