Corrosion Rate Evaluation and Prediction for Piles Based on Long-Term Field Performance

A study to evaluate corrosion rates was conducted using pile foundations abandoned during the reconstruction of I-15 through Salt Lake Valley, Utah. Corrosion rates were measured for 20 piles extracted from five sites after service lives of 34–38 years. Measurements were made of soil index properties, resistivity, pH, cation/anion concentrations, and water table elevation. The critical zone for corrosion was typically located within the groundwater fluctuation zone; but correlations with soil properties were generally poor. Despite low resistivity, average corrosion rates for pile caps in native soil were typically between 2 and 9?μm/year with a maximum of 19?μm/year and did not pose any structural integrity problems. Nevertheless, for abutment piles where chloride concentration was very high, the average pile corrosion rate increased to 13?μm/year within the embankment and the maximum corrosion rate was 48?μm/year in the underlying native soil. Based on data from this and previous studies, equations were developed to predict maximum corrosion loss for piles in nonaggressive soil as a function of time.