Coated metal electrode with improved barrier layer

Claim 1

An electrode for use in electrolytic processes comprising: a film forming metal substrate having a porous electrocatalytic coating comprising at least one of a platinum-group metal and a platinum-group metal oxide in an amount of at least about 2 g/m 2 over the projected surface area of the substrate, and the substrate having below the coating a preformed barrier layer of a surface oxide film grown up from the substrate and at least one of rhodium and iridium oxides incorporated in the surface oxide film during formation thereof in an amount of up to 1 g/m 2 on a metal weight basis per projected surface area of the substrate.

Claim 12

A method of manufacturing an electrode for use in electrolytic processes, comprising forming a barrier layer on a film-forming metal substrate and applying over the barrier layer a porous outer electrocatalytic coating comprising at least one of a platinum-group metal and a platinum group metal oxide, in an amount of at least about 2 g/m 2 over the projected surface area of the substrate, the barrier layer being formed by applying to the substrate at least one coating of a very dilute acid solution containing thermodecomposable compounds of at least one of rhodium and iridium, separately drying and heating each applied barrier coating to form on the substrate a mixed crystal metal oxide barrier layer of substrate metal oxide and oxide decomposition products of the thermodecomposable compounds contained in the very dilute solution, the number of applied coats being such that the barrier layer so formed contains up to 1.0 g/m 2 of oxides of the thermodecomposable compounds on a metal weight basis over the projected surface area of the substrate.

Claim 13

A method of manufacturing an electrode for use in electrolytic processes, comprising forming a barrier layer on a film-forming metal substrate and applying over the barrier layer a porous outer electrocatalytic coating comprising at least one of a platinum-group metal and a platinum group metal oxide, in an amount of at least about 2 g/m 2 over the projected surface area of the substrate, the barrier layer being formed by applying to the substrate at least one coating of a very dilute acid solution containing thermodecomposable compounds of at least one of rhodium and iridium, separately drying and heating each applied barrier coating to form on the substrate a mixed crystal metal oxide barrier layer of substrate metal oxide and oxide decomposition products of the thermodecomposable compounds contained in the very dilute solution, the number of applied coats being such that the barrier layer so formed contains up to 1.0 g/m 2 of oxides of the thermodecomposable compounds on a metal weight basis over the projected surface area of the substrate.

Claim 15

A method of manufacturing an electrode for use in electrolytic processes, comprising forming a barrier layer on a film-forming metal substrate and applying over the barrier layer a porous outer electrocatalytic coating comprising at least one of a platinum group metal and platinum metal oxide, in an amount of at least about 2 g/m 2 on a metal weight basis over the projected surface area of the substrate, the barrier layer being formed by applying to the substrate several coatings each containing up to 0.2 g/m 2 on a metal weight basis over the projected surface area of the substrate of thermodecomposable compounds of at least one of rhodium and iridium in a film-forming metal attacking solution, and drying and heating each coating after application to produce a mixed crystal barrier layer of oxides of the film-forming metal grown up from the substrate up to a total of 1.0 g/m 2 of iridium and rhodium oxides on a metal weight basis.

Claim 16

A method of manufacturing an electrode for use in electrolytic processes, comprising forming a barrier layer on a film-forming metal substrate and applying over the barrier layer a porous outer electrocatalytic coating comprising at least one of a platinum group metal and platinum metal oxide, in an amount of at least about 2 g/m 2 on a metal weight basis over the projected surface area of the substrate, the barrier layer being formed by applying to the substrate several coatings each containing up to 0.2 g/m 2 on a metal weight basis over the projected surface area of the substrate of thermodecomposable compounds of at least one of rhodium and iridium in a film-forming metal attacking solution, and drying and heating each coating after application to produce a mixed crystal barrier layer of oxides of the film-forming metal grown up from the substrate up to a total of 1.0 g/m 2 of iridium and rhodium oxides on a metal weight basis.

Claim 38

A method for manufacture of an electrode for use in an electrolytic process comprising the steps of: (1) selecting an electrode having a film-forming metal substrate surface; (2) selecting a relatively dilute coating solution comprising at least one thermodecomposable compound of at least one of rhodium and iridium metals, the coating solution being of a type at least mildly chemically aggressive to the film forming metal and forming a barrier layer grown up from the substrate; (3) applying the coating solution to the electrode; (4) drying the applied coating solution and heating the electrode and the applied coating solution to at least partially thermally decompose the solution metals and to at least partially oxidize the film-forming metal at the surface of the substrate, thereby incorporating a substantial portion of the solution metals into the substrate surface constituting an electrode barrier coating; (5) repeating steps (3) and (4) until a desired quantity of the barrier solution metals have been incorporated into the substrate surface; (6) selecting an electrocatalytic coating compound comprising at least one of a platinum-group metal and a platinum-group metal oxide of the type forming a electrocatalytic coating; (7) making at least one application of the electrocatalytic coating compound to the electrode, thereby establishing an outer electrocatalytic coating on the electrode; and (8) controlling the application of the electrocatalytic coating compound whereby platinum-group metal and platinum-group metal oxide accumulating over the projected surface area of the substrate is greater than about 2 g/m 2 .

Claim 39

A method for manufacture of an electrode for use in an electrolytic process comprising the steps of: (1) selecting an electrode having a film-forming metal substrate surface; (2) selecting a relatively dilute coating solution comprising at least one thermodecomposable compound of at least one of rhodium and iridium metals, the coating solution being of a type at least mildly chemically aggressive to the film forming metal and forming a barrier layer grown up from the substrate; (3) applying the coating solution to the electrode; (4) drying the applied coating solution and heating the electrode and the applied coating solution to at least partially thermally decompose the solution metals and to at least partially oxidize the film-forming metal at the surface of the substrate, thereby incorporating a substantial portion of the solution metals into the substrate surface constituting an electrode barrier coating; (5) repeating steps (3) and (4) until a desired quantity of the barrier solution metals have been incorporated into the substrate surface; (6) selecting an electrocatalytic coating compound comprising at least one of a platinum-group metal and a platinum-group metal oxide of the type forming a electrocatalytic coating; (7) making at least one application of the electrocatalytic coating compound to the electrode, thereby establishing an outer electrocatalytic coating on the electrode; and (8) controlling the application of the electrocatalytic coating compound whereby platinum-group metal and platinum-group metal oxide accumulating over the projected surface area of the substrate is greater than about 2 g/m 2 .