A recently-developed sequential electrochemical reduction analysis method permits nondestructive assessment of solderability loss associated with surface oxides on metals and can be applied to almost any part geometry, including printed wiring board through-holes and surface pads. Preliminary results indicate that metal sulphides can also be detected, at least in some cases. The type and amount of oxides detected for tin coatings are shown to correlate with solderability determined by the wetting balance method. The data indicate that formation of excessive amounts of SnO2 in the surface oxide is a primary cause of Sn solderability degradation.