This paper analyses the observed spreading kinetics of drops of a Ni-11P braze and of copper on metal substrates. The observed spreading rates were initially fast but decreased progressively in accord with the de Gennes model in which a surface energy driving force is balanced by a viscous impedance. However, the observed spreading rates depended on the chemistries of the substrates and were usually far slower than those predicted by the de Gennes model. It is suggested that these discrepancies are due to the reactivity of the systems and a concentration of the viscous damping in narrow regions adjacent to the braze/substrate interfaces.
