Decoding the Corrosion Risks of Galvanized Steel Coatings in T&D Structures Based on Knowledge-Based Inspection, Sensors, and GIS-Based Corrosion Forecasting

Abstract Coating degradation in galvanized steel transmission and distribution (T&D) structures is a gradual but critical process that affects the long-term reliability and integrity of utility assets. Unlike bare steel, galvanized steel benefits from a sacrificial zinc coating that deteriorates over time through electrochemical and environmental interactions. Understanding these mechanisms is essential for accurate condition assessment, proactive maintenance, and effective life-cycle management. This paper outlines the multi-stage degradation of zinc coatings, emphasizing the electrochemical corrosion of galvanizing intermetallic layers (gamma, delta, zeta, and eta) and the formation of oxides, hydroxides, and carbonates of zinc. Under chloride-rich or low-pH conditions, these layers weaken, exposing the steel substrate to corrosion. A high-confidence inspection approach is presented, integrating visual assessment, coating thickness, and electrochemical potential measurements to quantify corrosion risk more accurately. A case study demonstrates the use of real-time corrosion monitoring sensors for early detection and predictive modeling of coating lifespan. Integration with Geographic Information System (GIS)–based environmental mapping enables utilities to prioritize maintenance, extend asset life, and minimize unplanned outages.