Method of forming protective coatings by electrolysis

Claim 2

A process as set forth in claim 1 wherein the ruthenium layer is applied by electrodeposition.

Claim 3

A process as set forth in claim 1 wherein the ruthenium layer is applied by electrodeposition from an aqueous acidic plating bath solution containing the reddish brown ruthenium sulfamate complex resulting from heating an aqueous solution of ruthenium trichloride with an excess of sulfamic acid to hydrolyze the sulfamate.

Claim 4

A process as set forth in claim 1 wherein at least a major proportion of the electrically conductive article is titanium.

Claim 5

A process as set forth in claim 1 wherein the passage of electric current through the bath is continued until the exterior of the immersed ruthenium layer is anodically oxidized to an RuOx composition characterized by an x value greater than 2.0.

Claim 6

A process as set forth in claim 6 wherein the exterior of the ruthenium layer is anodically oxidized to an RuOx composition characterized by an x value of 2.5 to 3.7.

Claim 7

A process as set forth in claim 1 which additionally comprises heat treating the anodically oxidIzed coating for at least 5 minutes at about 350*C. to about 800*C.

Claim 8

A process for forming a protective electrically conductive ruthenium oxide coating over an electrically conductive substrate having an adherent exterior stratum of ruthenium comprising anodically oxidizing an outer surface of the ruthenium stratum on the substrate while said substrate having the ruthenium stratum is connected as an anode at least partially immersed in the bath of an electrolytic cell comprising a cathode and an aqueous electrolyte bath solution containing potassium permanganate in an amount of at least 0.01 mole per litre and up to the solubility limit of potassium permanganate in the bath, said bath being at a temperature sufficient to dissolve at least 0.01 mole per litre potassium permanganate and not greater than about 95*C., and passing between the anode and the cathode a unidirectional electric current at a current density sufficient to promote adherent oxidation of the immersed ruthenium surface to provide a continuous coherent, adherent, RuOx composition characterized by an x value of at least 1.0 and meanwhile controlling the current density to not exceed 15 milliamperes per square centimeter of immersed anode surface.

Claim 9

A process in accordance with claim 9 wherein the potassium permanganate solution is characterized by a potassium permanganate content of at least 0.05 mole per litre, a pH of at least 0.5 and a temperature of at least 40*C. and the anode current density is at least 8 milliamperes per square centimeter.

Claim 10

A process in accordance with claim 9 wherein the substrate is titanium and the ruthenium stratum is an electroplate on the titanium, which comprises heat treating the ruthenium on the titanium in an inert atmosphere at 1,000*C. to 800*C. for 5 minutes to 60 minutes before oxidizing the ruthenium in the potassium permanganate solution and thereafter heat treating the ruthenium oxide coating in air at 480*C. to 350*C. for 2 hours to 10 hours.

Claim 11

A protectively coated article having a ruthenium oxide coating produced by the process set forth in claim 9 and having manganese in the coating.