Abstract
The formation of protective layers on Cu‐9.4Ni‐1.7Fe alloy in air‐saturated, aqueous 3.4 weight percent 
solution, both under natural corrosion and under potentiostatic conditions, has been studied by ESCA (XPS), SEM, and x‐ray diffraction. It was concluded that the protective film formed under open‐circuit corrosion conditions has the following features: (i) is comprised of a relatively thick outer layer, mainly 
, and an inner thin layer containing appreciable chloride, oxygen, and copper, and some nickel, (ii) is rich in chloride throughout the film with a maximum concentration along a plane located within the inner layer near the inner layer/outer layer interface, (iii) is relatively poor in Ni and Fe in the inner layer compared to levels in the outer layer, and (iv) has, in early stages of growth, an outer surface consisting of a cuprous (probably 
) compound which with time gives way to a carbonate and finally to a cupric 
compound. The transition in Cl, Fe, Cu, and Ni concentrations is sharply confined to the interface region between the thin inner and thick porous outer layers. The thin inner layer is mainly responsible for the good corrosion resistance of the alloy according to electrochemical results reported in Part I of this series.