Corrosion resistance of borophosphate enamels in molten zinc

Abstract

A study has been conducted of the resistance to corrosion in molten zinc of borophosphate enamels. The melting temperature of the enamels was adjusted by adding the carbonates of alkali metals and alkaline earth metals. Scanning electron microscopy was used to examine solidified interfaces between the enamels and the molten zinc. At low magnification (× 30) no evidence of components from the B₂O₃-P₂O₅ enamels was detected by electron probe in the industrially pure zinc near the interface with the enamel, but elemental Zn was found in the initially zinc free B₂O₃-P₂O₅ enamels. When the interface was examined at a magnification of 1000 times, it was confirmed by electron probe that no phosphorus from the borophosphate enamel was present in the zinc matrix at a position 60 μm from the interface. The results show that the borophosphate enamels are extremely resistant to corrosion in molten zinc.