Observation of an unusual case of triple-line instability

Bi vapors penetrate along the triple lines in electrodeposited Ni specimens to form open channels at 800 and 900 °C. This triple-line instability can be interpreted as a case of triple-line wetting by a gas phase. Further controlled experiments using high-purity Ni specimens suggest that the presence of S impurities is essential. This unusual wetting phenomenon is related to the formation of a bilayer complexion in Ni–Bi and its occurrence can significantly affect microstructural stability and corrosion resistance.