A previously polished titanium plate 200 mm by 50 mm and 1 mm thick was defatted in a boiling 10 percent NaOH solution, and was dipped into a 5 percent hydrofluoric acid solution at room temperature for 1 min, and then washed with water. Electro-deposition was carried out for 19 min in an electrolyte at 25C consisting of 130 g/l of ferrous sulfate heptahydrate (or 88g/l Dihydrate, or 79.5g/l Monohydrate, or 71 g/l Anhydrous), 100 g/l of ammonium sulfate and 6 g/l of formalin by using said titanium plate as a cathode (a cathodic current density = 25 mA/cm squared) and a low carbon steel as an anode. After the electrodeposion was completed, said iron deposited titanium plate was washed well with water, and then dipped into a solution of 20 g/l of ammonium ferric oxalate at 13C, and was allowed to stand for 20 min under a reduced pressure of 15 mm Hg abs. produced by a vacuum pump and dried under the reduced pressure and was then subjected to heat treatment at 650C for 2.5 hrs. in an atmosphere of a hydrogen/steam gaseous mixture consisting of 20 percent by volume of hydrogen and 80 percent by volume of steam prepared by passing hydrogen into hot water at 94C. On the surface of the product the formation of a magnetite-coated layer was clearly recognized. The thickness of said layer was confirmed to be 20 micron by weighing said product. The appearance of said product was uniformly black and fine-grained and no crack was observed therein.
An electrolyte consisting of 250 g/l sodium chloride, 70 g/l of sodium chlorate, and 2 g/l of sodium bichromate was electrolyzed at 60C for 11 months with an anodic current density of 10 A/dm square (100mA per cm squared) by using an anode coated with magnetite prepared as described in Example 1 as an anode with the use of a mild steel plate as a cathode. The current efficiency was 85 percent and the average cell voltage was 3.38 V. The required energy per ton sodium chlorate was 6,000 kwh. During this period almost no change was observed on the surface of the anode.
Some good results have been obtained from a solution
of the double salt of ammonio-sulphate of iron. Mr.
Walenn has obtained good results from a solution of
sulphate of iron and sulphate of ammonia, one part of
iron sulphate to five parts of water. Meidenger found
that a solution of iron sulphate gave good results when
sal-ammoniac was added to the bath. It is advisable to
cover the surface of the bath with glycerine whilst at
work, and to keep it under cover when not in use, to
prevent decomposition by action of the air.
See also US 003103484
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