Corrosion of steel structures in soils has been a topic of industrial research for many decades. The 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 to evaluate soil corrosivity and guidelines for corrosion control during the design phase and lifetime of a structure have been developed. An opportunity exists to apply this understanding to optimize the corrosion protection and capital expenses for new projects, e.g., identifying regions of low corrosivity where coatings are not required could lead to cost savings without compromising the integrity of the structure. However, within the industry, there is no universally accepted method to guide such decisions. This work helps address this issue by presenting a literature review and a case study on the topic. The literature review identifies the factors that influence the corrosion of buried steel structures, the range of corrosion rates observed on buried steel structures and quantitative and qualitative methods for assessing soil corrosivity. In the case study, industry standards identified during the literature review (AASHTO R27-01, DIN50929-3:2018, ANSI/AWWA C105/A21.5 and Eurocode 3-5) are applied to evaluate the soil corrosivity of three meter station project sites in Alberta. The structures for which the standards are intended, the information required to apply each standard, and the nature of the results are compared in the case study.  Eurocode 3-5 provides corrosion rate estimates for broadly defined soils and was found to not always be conservative relative to the other standards. AASHTO R27-01 and ANSI/AWWA C105/A21.5 provide qualitative soil corrosivity results and prescriptive mitigation strategies whereas DIN50929-3:2018 provides both qualitative and quantitative soil corrosivity results without providing mitigative strategies. A data collection protocol for geotechnical site investigation is recommended to support and improve the assessment of soil corrosivity.


Assessing Soil Corrosivity for Buried Structural Steel

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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