The permeability of various graphite foils with respect to porosity (Φ) and types was measured to verify the relation to the electro-chemical corrosion. Five pyrolytic graphite foils (PGS, Panasonic, Japan) with different porosities and an expanded flake-type graphite (BD-100, Samjung CNG, Republic of Korea) were tested. The properties of the graphite are listed in Table 1. The water vapor transmission rate (WVTR) was measured at 40 °C and 90% relative humidity based on the ASTM standard. To normalize the result, permeability coefficient was calculated as follows [12