Corrosion Behavior of Copper in Liquid Perfluorocarbon
Minamitani Rintaro; Hatsuda Toshio; Shimazu Hiromi; Kasai Ken'ichi
Abstract:Liquid perfluorocarbon coolant Fluorinert FC 72 for electronic devices has high thermal stability and low chemical reactivity. However, the presence of water in FC 72 at less than 10 wt ppm has been shown to appreciably increase copper corrosion. In the present study, the corrosion mechanism under low solubility of water in FC 72 was investigated by chemical analysis, water volume measurement, and corrosion testing. It was found that FC 72 liberates no decomposition products in temperatures below 100 deg. and copper corrosion depends on liquid temperature, dissolved water, and oxygen. In FC 72, copper specimens were corroded by wet oxidation at temperatures of 50, 70, and 85 deg. and by both wet and dry oxidation at 100 deg.. Copper corrosion was induced when dissolved water in FC 72 was increased to more than 8 wt ppm. However it was reduced when oxygen in FC 72 was decreased to less than 25 ml/L. Dissolved water in FC 72, as in air, equilibrates with adsorbed water on copper surface. Therefore, the mechanism of copper corrosion in FC 72 is the same as that in air. It is considered that the mechanism for FC 72 can be extended to explain corrosion behavior in almost all inert coolants. Key Words:perfluorocarbon, inert coolant, corrosion, atmospheric corrosion, water adsorption