Corrosion Characteristics of Rolling Oil on the Rolled Copper Foil

Static corrosion experiments were carried out to investigate the corrosion of each kind of component in the rolling oil on the rolled copper foil. The surface morphology and chemical composition of corrosion products were detected by a digital camera, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that the maximum corrosion rate of rolled copper foil in the base stock and friction modifiers (butyl stearate and dodecanol) was close to zero, while that of rolled copper foil in the N-containing borate, phosphate and the fully formulated rolling oil were 0.17, 1.12 and 0.78 mm/a, respectively. The color of rolled copper foil changing from pink into purple-black when corroded in the N-containing borate. The composition of it was mainly CuO and Cu₂O with some N-containing borate adsorbed on it. However, the color and composition of the corroded copper foil in the phosphate were similar to that of the original copper foil. It was complicated for the corroded copper foil in the fully formulated rolling oil, which showed characteristics both in the N-containing borate and in the phosphate according to different positions. It indicated that there might be little corrosion for the base stock and friction modifiers on the rolled copper foil. It might mainly be extreme pressure additives (N-containing borate and phosphate) that caused the corrosion of rolled copper foil. There might be competition between N-containing borate and phosphate for the corrosion of rolled copper foil in the fully formulated rolling oil, resulting in a lower corrosion rate compared with that in the phosphate.