Effect of Composition on Glass‐Metal Interface Reactions and Adherence

Reduction‐oxidation reactions and enhanced wetting or spreading of Na 2 Fe x Si 2 O 5+x , and Na 2 Ni x Si 2 O 5+x glasses on substrates of Fe, Co, Ni, Ni‐Fe, and Ni‐Co were observed at 1000°C at low partial pressures of O 2 and Na as the O/Si ratio of the glass increased. When the substrate had a higher oxidation potential than the metal of one of the cations in the glass, e.g. CoO‐containing glass on Fe, metallic precipitates formed by redox reactions under all conditions. A redox reaction based on reduction of the valence of a cation in the glass, e.g. Fe 3+ to Fe 2+ , also occurred. Adherence developed between substrates and glasses containing amounts of substrate oxide, either in the starting composition or formed by redox reactions, approaching saturation.