The properties of chromium electrodeposited with programmed currents. Part I. Direct current

The electrodeposition of chromium in programmed direct current (DC) was investigated in the regime of high current density (77 A dm-2). Chromium was deposited in a system of plane-parallel electrodes in chromic-sulphuric acid solution, on specimens of steell, during one hour. The basic properties of deposits, the appearance, thickness, morphology, microhardness and brightness were investigated. Thicknesses of the coatings (between 28 and 82 μm) were measured at 36 points on the surface of the specimens by the non-destructive ferromagnetic method. Based on these results, graphic models of the surface distribution of the deposits were made. Three ranges of thickness could be seen on the model (range 1 - average thickness 29.87 μm, range 2 - average thickness 42.0 μm and range 3 - thickness 67.87 μm). For the whole speciments, the average thickness was 50.8 μm with a coefficient of variation of 0.3281. The basic properties of the coating, morphology and brightness changed depending on the deposit thickness being very different at different points of one and the same specimen. For this reason these chromium deposits should not be considered reliable protection against aggressive gases at high pressures and temperature of systems from corrosion, wear and erosion.