Zinc Sleeve

Contaminated and wet insulators display a biased leakage current having DC component. This DC component causes electrolytic corrosion and reduction of pin diameter.

Pin Corrosion of suspension (disc) insulator

• Resultant reduction of mechanical strength
• Breakage of ceramic body due to expansion of pin

NGK developed Zinc Sleeve to prevent pin corrosion.

• Galvanically positive
• Large potential difference from iron
• Sacrificial electrode at cement boundary
• Bonded area of sleeve: Min. 80% of sleeve/pin interfacial area to prevent corona discharges
• Purity of zinc >- 99.8% to prevent granular corrosion