Anodically polarized surface for biofouling and scale control

• US 4,345,981 A
• Filed: 02/23/1981
• Issued: 08/24/1982
• Est. Priority Date: 11/24/1978
• Status: Expired due to Fees

• Current Assignee: Electrode Corporation
• Original Assignee: Diamond Shamrock Refining and Marketing Company (Valero Energy Corporation)
• Inventors: Bennett, John E., Elliott, Joseph E.
• Primary Examiner(s): Andrews, R. L.
• Application Number:
  US06/237,470
• Time in Patent Office: 547 Days
• Field of Search: 204/147, 204/149, 204/DIG. 9, 204/129
• US Class Current: 205/701
• CPC Class Codes: B08B 17/00 Methods preventing fouling preventing accumulation of deposits in pneumatic conveyors B65G53/521
• CPC Class Codes: B63B 59/04 Preventing hull fouling anti-fouling paints C09D5/16
• CPC Class Codes: C02F 1/4602 for prevention or elimination of deposits
• CPC Class Codes: C02F 1/467 by electrochemical disinfection; by electrooxydation or by electroreduction
• CPC Class Codes: C02F 2001/46133 characterised by the material
• CPC Class Codes: C02F 2103/003 Wastewater from hospitals, laboratories and the like, heavily contaminated by pathogenic microorganisms
• CPC Class Codes: C02F 2303/04 Disinfection
• CPC Class Codes: C02F 2303/22 Eliminating or preventing deposits, scale removal, scale prevention C02F1/042, C02F1/4602, C02F5/00 take precedence
• CPC Class Codes: C23F 15/005 Inhibiting incrustation
• CPC Class Codes: Y10S 204/09 Wave forms

Abstract

Biofouling and scale control in conductive aqueous systems is effected on metal, preferably valve metal such as titanium, surfaces on which such fouling normally occurs by applying thereto a stable electrocatalytic coating, anodically polarizing said valve metal coating such that essentially only oxygen is evolved at the surface thereof, preferably at a rate of at least about 4.66 millimoles per square meter per hour without evolution of any chlorine. Periodic current reversal is effected to forestall biofouling upon any cathode utilized in implementing the instant invention.

Claims

1. A method of maintaining an electrocatalytic electroconductive surface free of at least one of biological and hardness deposits in an aqueous environment containing chloride ions, said electrocatalytic, electroconductive surface being for generating an effective amount of oxygen to maintain said surface free of biological and hardness deposits with substantially no evolution of chlorine gas when made anodic, comprising:

making said electrocatalytic surface anodic to a second electroconductive surface whereby water in contact with the electrocatalytic surface is electrolyzed to produce sufficient oxygen and hydrogen ions at said anodic electrocatalytic surface to prevent formation of biological or hardness deposits without the evolution of chlorine, and periodically making the second electroconductive surface anodic to the electrocatalytic surface to effect a removal of at least hardness deposits on the second electroconductive surface.

7. The method of any of claims 1, 2, 3, 4 and 5 wherein the second electroconductive surface is an electrocatalytic surface, the electrocatalytic surfaces being made alternately anodic one to the other.

8. The method of any of claims 1, 2, 3, 4 and 5 wherein the electrical current flowing between anodic and cathodic surfaces is periodically interrupted.

2. A method of maintaining an electrocatalytic electroconductive surface free of at least one of biological and hardness deposits in sodium chloride containing aqueous environment, said electrocatalytic, electroconductive surface being one generating an effective amount of oxygen to maintain said surface free of biological and hardness deposits with substantially no evolution of chlorine gas when made anodic, comprising:

making said electrocatalytic surface anodic to a second electroconductive surface whereby water in contact with the electrocatalytic surface is electrolyzed to produce oxygen and hydrogen ions at said anodic electrocatalytic surface to in a quantity effectively preventing formation of biological or hardness deposits thereon, the electrolysis taking place at an applied voltage below a threshold voltage at which chlorine is evolved, and periodically making the second electroconductive surface anodic to the electrocatalytic surface to effect a removal of at least hardness deposits on the second electroconductive surface.

3. A method of maintaining a valve metal surface free of at least one of biological and hardness deposits in an aqueous environment containing chloride ions comprising:

applying to the surface of said valve metal a stable electrocatalytic coating for generating an effective amount of oxygen for maintaining the electrocatalytic surface free of biological and hardness deposits with substantially no evolution of chlorine gas when the surface is made anodic; and

thereafter, with the coated valve metal surface in the aqueous chloride ion containing environment, rendering the coated valve metal surface anodic to a second electroconductive surface and passing current between the surfaces thereby generating oxygen at a rate per square meter of coated valve metal surface area per hour to effectively prevent formation of hardness and biological deposits with substantially no chlorine gas being generated; and

periodically making the second electroconductive surface anodic to the coated surface to effect a removal of at least hardness deposits on the second electroconductive surface.

6. The method of any of claims 3, 4 and 5 wherein the coating on the valve metal is selected from a group consisting of iridium, ruthenium, rhenium, rhodium, delta manganese dioxide, platinum group metal alloys containing iridium, rhenium, ruthenium or rhodium, and mixtures containing at least one platinum group metal oxide and at least one valve metal oxide.

4. A method of maintaining a valve metal heat exchange surface free of heat exchange interfering deposits in an aqueous environment containing chloride ions comprising:

applying to the valve metal heat exchange surface a surface stable electrocatalytic coating, said coating being of a type generating a quantity of oxygen per square meter of coating surface area per hour through the electrolysis of water with evolution of substantially no chlorine gas to effectively maintain the surface free of biological and hardness deposits; and

thereafter, when the coated heat exchange surface is in the aqueous environment, rendering said coated heat exchange surface anodic to a second electroconductive surface and passing a current between the surface generating an amount of oxygen per square meter of coated heat exchange surface area per hour effective to prevent accumulation of hardness and biological deposits while generating substantially no chlorine gas, and periodically making the second electroconductive surface anodic to the coated surface to effect a removal of at least hardness deposits upon the second electroconductive surface.

5. A method of maintaining a valve metal heat exchange surface free of heat exchange interfering deposits of biological origin and hardness scale when in contact with saltwater containing chloride ions comprising:

applying to the valve metal heat exchange surface a stable electrocatalytic coating, the coating anodically generating a quantity of oxygen per square meter of coating surface area per hour through the electrolysis of water with evolution of substantially no chlorine gas effective to maintain the surface substantially free from biological and hardness deposits; and

thereafter, when the coated valve metal heat exchange surface is in contact with saltwater, rendering the coated valve metal heat exchange surface anodic to a second electroconductive surface and passing a current between the surfaces to generate an oxygen per square meter of coated valve metal heat exchange surface area per hour effective to prevent accumulation of hardness and biological deposits thereof while generating substantially no chlorine gas, and periodically making the second electroconductive surface anodic to the coated surface to effect a removal of at least hardness deposits upon the second electroconductive surface.