EXAMPLE 1
A composition suitable for coating on to an electrode support was prepared by boiling under a reflux condenser for 12 hours a mixture of 15 g. of stannic chloride, 0.4 g. of water and 55 g. of n-amyl alcohol and then stirring into 5.8 g. of the resultant mixture 0.125 g. of antimony trichloride. Twelve coats of this composition were painted on to a strip of titanium which had been immersed overnight in hot oxalic acid solution to etch the surface, then washed and dried. Each coating was dried in an oven at 200.degree. C. before the next coat was applied and after each third coat the structure was heated in air in a furnace at 450.degree. C. to convert the coating substantially to the oxides of antimony and tin. The total weight of the finished coating was 11.0 g./m squared of the titanium surface. The theoretical composition of the finished coating was SnO2 90 percent, oxides of antimony (calculated as Sb2O3) 10 percent by weight.
The coated titanium was operated successfully as an anode in chlorinated brine containing 21.5 percent w/w NaCl at pH 3 and 65.degree. C. with a current density of 8 kA/m squared. The chlorine overpotential was initially 470 mv. and had risen to 480 mv. after 5 days.
EXAMPLE 2
The procedure of Example 1 was repeated but with the amount of Antimony Trichloride in the coating composition reduced to provide a finished coating on the electrode of theoretical composition SnO2 99 percent, oxides of Antimony (calculated as Sb2O3) 1 percent by weight. Under the same conditions of test as an anode as in Example 1 the initial Chlorine overpotential was greater than 1,000 mV.
EXAMPLE 3
The procedure of Example 1 was repeated but with the amount of Antimony Trichloride in the coating composition increased to provide a finished coating on the electrode of theoretical composition SnO2 85.5 percent, oxides of antimony (calculated as Sb2O3) 14.5 percent by weight. The Chlorine overpotential recorded in the test was the same as with the electrode of Example 1, both initially and after 5 days.
The full patent is here and gives some background reading and refs. for DTO coatings in regard to Anodes.
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