The article presents the research results of analyzing the hardness of the balls formed during the skew rolling process, and then subjected to cooling in different media. The influence of the applied cooling medium (water, quenching oil and air) on the hardness of the obtained balls was analyzed. The effects of the applied methods of rolling (conventional and modified) were compared with respect to the changed hardness of the balls, and the obtained results were referred to the stock materials (bearing steel 100Cr6 and the steel from rail heads).
This study considers the role of chloride and sulphate anions in the cathodic reduction of zinc ions from gluconate solutions (chloride, sulphate, chloride-sulphate). Cyclic potentiodynamic and potentiostatic polarization measurements, as well as chronoamperometric experiments, were performed. Electrochemical results were correlated with the speciation of the baths. The experiments revealed the inhibiting effect of sulphate ions on the cathodic process caused by the formation of stable neutral ZnSO4 complex in the sulphate-gluconate bath. It resulted in zinc deposition under a limiting current, with the release of metal cation as a rate-determining step. The less stable ZnGlu+ complex dominated both chloride-containing baths, thus the metal deposition ran under activation control. Independent of the solution composition, the nucleation of zinc occurred according to the instantaneous model.
