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The producers of components require that cuts of steel sheets for superficial parts of cars would have guaranteed surface microgeometry, minimum defects, homogenous surface over the full width and length of the belt, mat appearance, good adhesion of the Zn layer. Microgeometry of the surface of galvanized sheets for superficial parts of cars is one of the decisive factors affecting the appearance of the surface after painting and stampability of steel sheets. Requirements for microgeometry are mainly focused on the roughness parameters Ra [μm] (roughness), Pc [cm-1] (number of peaks) or Wa [μm] (undulation roughness). This paper presents the study results of the influence of selected parameters of electric discharge texturing of rolls of the rolling mill on the Ra roughness parameter and number of peaks. Reliability of the process of electric discharge texturing of work rolls was assessed according to Cpm and Cp reliability indices. Dependencies on electric discharge texturing were depicted to predict Raand Pc qualitative indices of roughness.

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The paper investigates the influence of the chemical composition and temperature of electrolyte, the oxidation time, voltage, and the current density on Vickers microhardness of aluminium oxide layers, at the same time. The layers were generated in the electrolytes with different concentrations of sulphuric and oxalic acids and surface current densities 1 A·dm−2, 3 A·dm−2, and 5 A·dm−2. The electrolyte temperature varied from −1.78°C to 45.78°C. The results have showed that while increasing the electrolyte temperature at the current density of 1 A·dm−2, the increase in the layer microhardness values is approximately by 66%. While simultaneously increasing the molar concentration of H2SO4in the electrolyte, the growth rate of the microhardness value decreases. At the current density of 3 A·dm−2, by increasing the electrolyte temperature, a reduction in the microhardness of the generated layer occurs with the anodic oxidation time less than 25 min. The electrolyte temperature is not significant with the changing values of the layer microhardness at voltages less than 10.5 V.