Fundamentals of Glass‐to‐Metal Bonding: VII, Wettability of Iron by Molten Sodium Silicate Containing Iron Oxide

Contact angles, and adherence of sodium disilicate glasses with varying iron oxide additions on platinum and iron were studied at 1000°C. in vacuum. In the glass‐platinum systems the iron concentration in the glass did not affect either the contact angle or the adherence. No devitrification occurred in the glass‐platinum systems. The glass‐iron systems showed a lowering of the contact angle with increasing iron content in the glass, ranging exponentially from 55° to approximately 22°. Adherence was poor with no iron in the glass, and it increased as the iron content and reaction at the interface increased. Crystals, identified as fayalite (Fe 2 SiO 4 ), were observed in some of the glass drops from the glass‐iron systems. Polished cross sections of the glass‐iron assemblies showed a greater attack of the metal surface as the iron content in the glass increased. The configuration suggests greater attack along the grain boundaries.