PHYSICO-MECHANICAL AND CORROSIONCHARACTERISTICS OF STEEL BLACKENING COATINGSDEPOSITED AT ROOM TEMPERATURE

摘要

Steel blackening process in copper-selenic solution has been proposed for deposition ofrnconversion coatings at room temperature (20-40℃) . Kinetics and mechanism of reaction has also beenrninvestigated and discussed. Reaction rate depends on bath solution concentrations and pH value byrnequation V = k[H+][SeO3 2-][Cu2+]. The physico-mechanical characteristics, decorative appearancern(gloss and colour) and protective performance of the coatings have also been evaluated and comparedrnwith conventional coatings treated in hot alkali solution (140-148℃). The colour appearance expressedrnin L*C*h coordinates gives quite good lightness value (27.7). Corrosion characteristics of the coatingsrnhave been checked by different methods, including salt spray and EIS measurements. The coatingsrnshow good protective properties in accelerated and under shelter testing conditions.