Two phase-diagrams of the thermal roughening transition on polycrystalline nickel surfaces dissolvedanodically under sulfuric acid solution concentrations and temperatures were prepared using a confocallaser scanning microscope (CLSM) and dissolution mass measurement (DMM). One phase diagramshows the transition between polycrystalline surfaces free of grooves formed by preferential grainboundary dissolution and those with grain boundary grooves. Solution concentrations and temperaturesat which no formation of grain boundary grooves occurred were demonstrated. The other phase diagramshows stable states among smooth surfaces, rough surfaces, and combined smooth and rough surfaces.CLSM and DMM analyses demonstrated that the transition from smooth surfaces to rough surfacescaused a drastic change in dissolution mass and was attributed to a change in dissolution modes fromthe motion of kink-antikink pairs to the random formation of adatom-vacancy pairs.
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