Electrochemical Testing for Soil Corrosivity Determination - The Impact of Test Methods on Corrosion Modelling

ABSTRACT: Soil resistivity measurements are an important parameter when designing earth installations such as steel-driven piles, soil nails, power supply facilities, electrical conduits, or instrumentation systems. Corrosion modelling considers many factors such as soil stratification and mineralogy, soils resistivity, moisture, chemical content and concentration of the soil, and potential for contamination. Selection of an accurate resistivity model for the soil is critical when designing the system that is expected to meet safety and reliability criteria. A wide range of soil resistivity test methods include in situ testing and testing of soils samples removed from the ground for use in the assessment and control of corrosion of buried structures. Other parameters to determine soil corrosivity include testing for sulphate and chloride concentrations, pH, and organic content determination. Evaluation of soil corrosion potential relies on specific standardized methods and on the limits for electrochemical parameters. When non-standardized analysis is conducted but the same limits for the electrochemical parameters are applied, the classification of soil corrosivity maybe skewed, and the risk of inadequate or conservative corrosion protection methods is increased. This paper is focused on evaluating test methods for resistivity and electrochemical parameters and the validity of the results. The sensitivity analysis test results and the potential impact on design of corrosion protection systems is discussed.