Improving the wettability of aluminum foil with oxygen plasma treatments

The wettability of aluminum foil is an important concern in many industrial converting processes. X-ray photoelectron spectroscopy (XPS or ESCA) and water contact angle results indicated that relatively mild (i.e. 250 W, 15 s) oxygen plasma treatments efficiently removed residual carbon contamination from cold-rolled foil surfaces. This resulted in a significant improvement in the foil wettability. It was also found that the wettability of plasma-treated foils degraded with time, apparently due to the adsorption of hydrophobic, airborne carbon species and other contaminants. Furthermore, oxygen plasma treatments caused additional aluminum oxide to grow on the metal surface. The composition of this additional oxide was found to be similar to that of the native passivation oxide. The thickness of the aluminum oxide layer increased with both the plasma RF power and the plasma exposure time.