Evaluation of the wettability of metal surfaces by micro-pure water by means of atomic force microscopy

The wetting characteristics of polished, air oxidized and pure water immersed pure chromium, nickel, iron and SUS304 steel surfaces were observed with a digital microscope and an atomic force microscope. The macro- and micro-wetting contact angles were measured and compared and the influence of the surface composition on wettabilities is discussed. The surfaces represent not only pure metals (chromium, nickel and iron) but also their oxides and hydroxides. The macro- and micro-wettabilities were different for pure chromium, nickel, iron and SUS304 steel. The micro-wettabilities were higher than the macro-wettabilities for all specimens and the scatter of values was large. The micro-water droplets were more stable than the macro-water. The wettabilities also changed with the change in surface composition resulting from different pretreatments such as wet polishing, air oxidation and pure water immersion