抄録
Iron-Chromium alloys of a wide range of composition have been electrodeposited from a 40% (v/v) dimethylformamide bath containing FeCl2 and CrCl3 with a total concentration of 0.8M. The deposition potential of chromium in the dimethylformamide bath was found to be less noble than those of hydrogen and iron, and the maximum current efficiency of chromium deposition was obtained at higher current densities than that of iron deposition. Chromium content in the Fe-Cr deposit increased with increasing molar ratio of Cr/Fe in the alloy bath and a smooth, white-gray and bright deposit was obtained under these conditions. When the electrolysis was carried out at the current densities larger than the diffusion controlled current of iron deposition, chromium content in the Fe-Cr alloy deposit was found to be more than 15%. Both the current efficiency of chromium deposition and the chromium content in the alloy deposits decreased with increasing temperature up to 60°C, but the composition of Fe-Cr alloy was found to be insensitive to the change in pH 1 to 2.5. Fe-Cr alloys having higher Cr content were obtained at temperature below 20°C, but the alloy deposit was found to be matt, rough and brittle. The microscopic examination of the Fe-Cr alloy deposits revealed that a spherical nodular growth was observed on the initial smooth layer and the roughening of the surface was pronounced with an increase in the deposition time. Fe-Cr alloy deposits (10-60% Cr) up to about 20μm can be obtained from a 40% dimethylformamide bath (pH 1-2.5) with the Cr/Fe molar ratio of 0.5/0.3-0.6/0.2 using the current densities of 50-500mA·cm-2 at 20-40°C.
