Application of membrane method to high speed iron electroplating from concentrated aqueous FeCl
2 baths of 105 210 g/l Fe
2+ at temperatures between 25100°C with cathode current densities up to 100 A/dm
2 was examined. The same electrolyte as catholyte and HCl solutions of different concentrations were used as anolyte.
When FeCl
2 solutions with pH 1.111.73 were used as anolyte, emission of Cl
2 gas from Pt anode was completely suppressed in contrast to HCl anolytes. Also with FeCl
2anolyte, the catholyte pH and iron deposition efficiency were kept almost constant during electrolysis. Thus, FeCl
2 solutions are preferable as anolyte. The potential drop within the fluorinated membrane became larger with the increase of FeCl
2 concentration and the electrolyte temperature. It also increased with the decrease in the water content of the membrane.
However, the potential drop was only about 2 V (14% of the total cell voltage), when plating was conducted in the 158 g/l Fe
2+ bath at 100°C with 100 A/dm
2. Therefore, it can be concluded that the membrane method using FeCl
2 solutions as anolyte is beneficial to iron plating at high current densities.
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