Abstract

The corrosion of steel structures in soils has been a topic of industrial research for many decades. Research has shown that the corrosivity of a soil is highly variable and a function of numerous interconnected parameters including soil resistivity, moisture content and pH. Despite the complexity of the soil environment, methods have been developed to evaluate soil corrosivity and guidelines for corrosion control during the design phase and lifetime of a steel structure. An opportunity exists to apply this understanding to optimize the corrosion protection and capital expenses for new projects. For example, the identification of regions of low corrosivity where coatings are not required could lead to cost savings without compromising the long-term integrity of the structure.

This paper presents work conducted to assess the applicability of three soil-corrosivity standards, AASHTO R27-01 [1], DIN 50929-3:2018 [2], ANSI/AWWA C105/A21.5 [3] for this purpose. A field study was conducted which involved collecting buried structural steel samples and soil samples from eight pipeline meter stations and one light industrial facility located across Alberta. The corrosion damage of the buried structural steel samples was assessed through visual examination and pit depth measurements. The soil corrosivity was determined with the three soil-corrosivity standards using soil properties (e.g., pH, resistivity, sulphide and chloride concentration) collected in the field and measured in the laboratory. The corrosion damage was compared to the soil corrosivity predictions to evaluate the standards.

The results demonstrate that these standards provide a conservative assessment of soil corrosivity, with a tendency to overpredict corrosivity at the locations studied. Practical and economic considerations for the application of these standards to decisions on the need to coat buried structures are discussed.

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