document: The related Volta potential (Ψ) is the potential difference between a position infinitely far away from the surface and a position just outside the surface, and is the measureable quantity characterising electrochemical behaviour of a metal [12,17]. The scanning Kelvin probe force microscopy (SKPFM) technique allows detection of local EWF (if the EWF of the tip is known), or Volta potential differences (ΔΨ) between an atomic force microscopy tip (usually Pt coated) and the metal surface [14,15,19]. The lateral resolution of SKPFM can be as high as 10’s of nm in ambient air, with a sensitivity up to 10–20meV [19]. Volta potential is a characteristic property of a metal surface and can be used to understand electrochemical processes [16] . It is sensitive to any kind of surface defects, chemical variations, and residual stress [13,17]. Volta potential differences in microstructure have been used to predict corrosion behaviour [10,15,18,20–22]. Regions with larger (ΔΨ) indicate increased surface reactivity [11,15,18], and even a correlation between Volta potential differences measured in nominally dry air and their free corrosion potential (Ecorr) pre-determined under immersed conditions has been reported [18].
extractive_keyphrases: ambient air atomic force microscopy tip detection of local ewf dry air ecorr electrochemical behaviour of a metal electrochemical processes free corrosion potential measureable quantity metal potential difference predict corrosion behaviour pt coated scanning kelvin probe force microscopy skpfm volta potential δψ ψ
abstractive_keyphrases: larger (δψ) indicate increased surface reactivity metal surface property of a metal surface understand electrochemical processes volta potential differences volta potential differences in microstructure