Evaluation of grounding electrode materials for corrosion resistance in high-salinity coastal environments

How long will your grounding system last when the soil itself becomes the enemy? This question confronts electrical engineers designing installations along Sweden's extensive coastline, where saline conditions accelerate material degradation at rates that can surprise even experienced practitioners. The present investigation examined five commonly specified grounding electrode materials pure copper, galvanized steel, stainless steel type 316, carbon steel, and copper-clad steel under controlled laboratory conditions simulating high-salinity coastal soil environments characteristic of the Gothenburg archipelago region. Experimental work was conducted at the Gothenburg Technical University Corrosion Testing Laboratory from April through November 2024. Electrode specimens measuring 500mm in length were buried in soil chambers maintained at salinity concentrations ranging from 5 to 45 g/L sodium chloride equivalent, replicating conditions measured at seventeen coastal monitoring sites throughout western Sweden. Temperature was held constant at 15 °C to isolate salinity effects from seasonal thermal variations. Gravimetric analysis after 180 days revealed substantial differences in corrosion performance across materials. Pure copper demonstrated superior resistance with mass loss rates of 0.012 mm/year at extreme salinity levels, followed by stainless steel 316 at 0.022 mm/year. Carbon steel exhibited the poorest performance with degradation rates reaching 0.71 mm/year under identical conditions nearly sixty times greater than copper. Galvanized steel showed intermediate behavior with initial protection from the zinc coating followed by accelerated base metal corrosion once the sacrificial layer depleted. Electrochemical impedance spectroscopy confirmed that copper maintained stable passive film characteristics throughout testing, while carbon steel polarization resistance decreased progressively with exposure duration. Economic analysis incorporating material costs, installation expenses, and projected replacement intervals identified copper-clad steel as offering optimal lifecycle value for installations with moderate salinity exposure, while pure copper proved most cost-effective where extreme conditions warrant maximum longevity despite higher initial investment. These findings provide quantitative guidance for material selection decisions affecting grounding system reliability in coastal infrastructure applications throughout Scandinavian coastal regions and similar environments globally.