Corrosion of Co-Cr-W alloy in liquid zinc

Abstract

The corrosion of Co-Cr-W alloy in the presence of both static and dynamic liquid zinc has been investigated at 465 °C. It was shown that the Co-Cr-W alloy is severely attacked by liquid zinc especially under dynamic condition. The corrosion rate of this alloy in the moving liquid zinc was about 1.5 times higher than in static liquid. Corrosion of the Co-Cr-W cast alloy in liquid zinc can be characterized as alloying (of Co-Zn and Fe-Zn) and dissolution (of Cr and W atoms from Co-base γ phase into liquid zinc). The static corrosion of Co-Cr-W alloy is characterized as preferential corrosion in eutectic groups and uniform corrosion of Co-base γ phase. The dynamic corrosion of this alloy is characterized as frequent break of the corroded surface layer and preferential corrosion in grain boundaries besides uniform corrosion. The Fe content of this alloy is another important factor affecting its corrosion rate in liquid zinc. Based on these results, it is suggested that the amount of eutectic groups and the elemental Fe content in the Co-Cr-W alloy should be limited in order to improve its corrosion resistance in liquid zinc. Moreover, the refinement of its grain structure will also be useful for the improvement of its corrosion resistance.