Reaction of Silicate Glasses and Mullite with Hydrogen Gas

The increasing order of corrosion resistance to H 2 gas flowing fast enough to ensure that the reaction is the slow step is fused silica, aluminosilicate glass, and mullite at T =1300° to 1500° C; the activation energies are 347.3, 358.6, and 389.1 kj/mol (83.0, 85.7, and 93.0 kcal/mol), respectively. No detectable reaction with a‐Al 2 O 3 was observed. Addition of a small amount of CaO to the glass reduced its activation energy (283.7 kj/mol (67.8 kcal/mol)) and made its reactivity with H 2 similar to that of mullite at high temperatures. The reaction product for the glasses consisted of a porous zone composed of an intermediate layer close to mullite in composition and an outer layer of a‐AI 2 O 3 . The reaction product for mullite consisted of a porous a‐Al 2 O 3 residue layer.