A Case Study on Severe Corrosion and Degradation of Galvanized C-Pile Supports in a PV Solar Plant

Abstract This case study examines the severe corrosion and degradation of galvanized C-pile supports in a photovoltaic (PV) solar plant, with a focus on root cause analysis (RCA) following BS EN 62740 mainly. The RCA methodology encompassed data collection, laboratory testing of extracted samples, failure analysis, validation and the recommendation of corrective measures. Multiple contributing factors were identified, including soil chemistry, oxygen differential cells, galvanic coupling, AC/DC stray currents, construction practices and environmental influences. The geographical condition of this area is characterized by a desert environment, which presents challenges such as high temperatures and frequent sandstorms. The region has a hot desert climate with scorching summers and mild winters. The cooler months extend from November to March, while summers are extremely hot, with air temperatures often exceeding 50°C and water temperatures reaching 38–39°C. General guidance for steel selection recommends levels of carbon less than 0.25 percent; phosphorus less than 0.04 percent, manganese less than 1.35 percent and silicon levels less than 0.04 percent or between 0.15 and 0.22 percent. The steel samples complied with the above-mentioned limits. A key finding is that galvanized steel piles, though widely used, exhibit significant corrosion in buried sections due to aggressive soil conditions, moisture content and electrochemical interactions. Soil analysis revealed elevated chloride and sulfate concentrations, accelerating zinc depletion and subsequent steel corrosion. Furthermore, the presence of grounding copper mats and stray electrical currents likely intensified galvanic corrosion. Oxygen differential cells and seasonal variations in soil conditions further exacerbated the degradation process. To mitigate corrosion, the study explores alternative protection strategies, such as fusion-bonded epoxy (FBE) coatings, cathodic protection (CP), reinforced concrete supports or protective wraps at critical air-soil interfaces. These findings underscore the importance of optimized material selection and a comprehensive corrosion protection strategy to enhance the long-term durability of PV solar plant structures.