Applications of Scanning Kelvin Probe Studies in Adhesion Science

Applications of Scanning Kelvin Probe Studies in Adhesion Science 

Diffusion of Ions into Metal/Adhesive Interfaces 

If a polymer-covered metallic sample in contact with a halide-containing electrolyte is examined in a humid atmosphere free of oxygen, no corrosion reactions take place. Therefore, the electrode potential of the metal in contact with the electrolyte is almost equal to the thermodynamic Nernst potential. This value is significantly more negative than the electrode potential of the metal in contact with the polymer. 

In the case of a three-boundary layer between an electrolyte, the polymer, and the metal, water molecules, water clusters and hydrated ions can diffuse into the polymer/metal interface. 

As a scanning electrochemical technique, the SKP is able to detect an electrolytic conductance along the polymer/metal interface between the defect border (negative potential) and the polymer-coated area. When the ions diffuse into the polymer/metal interface, the interfacial resistance is lowered in the respective area and the corresponding potential is shifted to more negative values - ideally to the electrode potential of the defect. Based on this shift of the interfacial electrode potential, the transport of ions along the interface can be studied to a very high accuracy. 

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