Kelvin probe study on the perfluoropolyether film on metals

The effect of mineral oil on surface potentials of copper and aluminum coat ed with a perfluoropolyether (PFPE) film is studied with a non-vibrating Ke lvin probe. The probe measures the contact potential difference (CPD) betwe en the probe surface and the coated copper and aluminum surfaces. The PFPE him was applied to the Cu and Al surfaces by a dip-coating technique. The K elvin probe signals are especially sensitive to the interface between the c oated and uncoated regions of the metal surfaces. It is found that the PFPE film causes the surface potentials of Cu and Al to drop by 150 and 98 mV, respectively. Immersion of the PFPE-coated surfaces in mineral oil causes t he surface potential difference of the PFPE/Cu and PFPE/Al to increase, and removing the mineral oil re-establishes the surface potential.