P35.003: Structure and Sub-Grade Corrosion

Engineered Backfills and Conductive Concrete: Findings to date are that conductivity and compressive strength are inversely related when the water-to-cement ratio is varied. This new learning allows both the grounding engineer and the structural engineer to find a compromise for cost and performance in the design. In 2025, the project intends to initiate aging of concrete cylinders that contain a steel test coupon, which represents the rebar, and then measure the corrosion rate at specific time intervals. The corrosion rate measurements are intended to be validated by removing the coupons and determining mass loss through gravimetry.

Corrosion Due to Stray Direct and Circulating Alternating Currents: This task explores the methods to screen and quantify the effects of stray direct currents and circulating alternating currents. Once the source and magnitude of the currents are known, a mitigation strategy may be identified that is compatible with the environment. In 2025, this task aims to develop new methods to measure corrosion currents and evaluate them for accuracy and ease of use, which may provide utilities with a simple and effective method to understand the impact.

Corrosion Management Guidebook: This reference book contains asset management information for inspection, assessment, mitigation, and remediation of corrosion on transmission lines. The guidebook contains the fundamentals of corrosion, guidance for inspection and assessment, and information on mitigation methods that align with the environment. A new chapter focused on concrete management guidelines was added in 2023, and a section on engineered and wood pole management was added in 2024. In 2025, this task aims to add content on the development and operation of the corrosion monitoring system to provide an understanding of how dynamic stray current events may be understood and quantified.

Corrosion Due to the Operation of HVDC Transmission Systems: Severe corrosion may result from the operation of high-voltage direct current (HVDC) transmission systems. This task intends to evaluate the interaction between HVDC lines and other utilities or commercial activities within the same right of way. The findings may allow determination of the best practices and procedures for reducing and mitigating the risk of corrosion. Areas of future growth and gaps for corrosion inspection and corrective actions have been identified in renewables such as offshore wind and offshore drilling. The project plans to review how renewable generation may affect corrosion rates at the transmission line interconnect in 2025.

Corrosion and Corrosion Control Workshop: This workshop is held every two years; it provides both theory and practical experience in understanding corrosion and how to assess and implement various types of corrosion control technologies. A workshop is planned for 2025 at the EPRI Charlotte campus to support asset managers, engineers, maintenance managers, and field crews in gaining practical knowledge for extending the service life of their assets.

Modeling Asset Degradation Through an Understanding of Soil Corrosivity: Environmental models and maps are being developed by harvesting soils at utility service territories and cross-referenced to the U.S. Department of Agriculture (USDA) soil series. This allows a corrosion rate for steel, zinc, and copper to be understood and applied to engineering design and operation and maintenance (O&M) operations at each structure location within a service territory.

Ongoing research is focused on bringing soil chemistry, texture, and corrosion rates into a general model for the USDA soil series. This research is intended to support guidelines for screening a service territory for “at-risk” structures and allow asset managers to make life-cycle decisions. The goal for 2025 is to increase map coverage and data resolution, with a focus on additional factors such as topography and the impact of surface and ground water.

New and Emerging Coating Systems for Atmospheric, Subgrade, and Marine Service: Each year, EPRI evaluates new and emerging coating systems for addition to the coating library. Many of these coating systems are designed for application in a manufacturing facility, but many are also designed for repairs in the field. The value that utilities receive from this task is the ability to select a coating system for optimal performance in their service territory.

New coating formulations are intended to be added to the coating system library in 2025, with a focus on intumescent fire protection coatings. This research supports the development of a coating selection and web application, allowing utilities to understand coating system performance in their service territory and identify a coating system that is compatible with their service territory based on the environment. It will reside on the subscriber website for access by project funders.

Understanding the Degradation of Anchors and Recommended Inspection Methods: This task explores the mode of failure for various anchor designs and how to determine if that anchor is at risk because of stray or circulating current corrosion. This task is based on new learning that will allow utilities to understand why anchor systems degrade and how to mitigate that corrosion.

The project plans to focus on understanding circulating and stray currents in high soil resistivity and high ground water levels in 2025. This research is intended to support the development of inspection, assessment, and mitigation guidelines for transmission line structures.

Determining Key Locations for Lattice Structure Corrosion: Crevice corrosion requires specific environmental conditions to occur in bolt details in soil exposure. Grillage connections to towers are a primary location, and this task is focused on quantifying the environmental factors and resulting corrosion rates. Understanding these conditions will allow application of the appropriate corrosion control measures in line design guidelines. The project plans on using the results from the first set of experiments to continue literature reviews and formulate new methodologies for testing in 2025.

Cathodic Protection Design, Installation, and Maintenance: This application is designed to assist utilities in designing cathodic protection systems for their requirements and provide guidance on installation and maintenance operations. The goal is to migrate the information into a cathodic protection design web app in 2025.