GB1604630A - Preventing microbiologically induced metal corrosion - Google Patents

Description

(54) PREVENTING MICROBIOLOGICALLY INDUCED METAL CORROSION (71) We, STANDARD TELE PHONES AND CABLES LIMITED, a British Company of 190 Strand, London W.C.2. 1 DO England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to composite materials and in particular to a material comprising a metal matrix having a solid particulate material dispersed therein.

A serious problem in the use of metals, particularly ferrous metals, in applications in which the metal surface is in contact with a liquid is microbiologically induced corrosion. For example, in the presence of sulphur compounds, the growth of sulphate reducing bacteria can cause severe corrosion to adjacent steel surfaces: this is a well known problem in marine-oil storage tanks. Treatment with conventional biocidal materials is effected over an extended period only by continuous application of the material.

Our co-pending application Number 45015/77 (Serial No. 1604629) describes a corrosion inhibiting composite material, comprising a metal matrix having dispersed therein a solid particulate material, the solid materials iff particulate form dispersed soluble substance which substance has a passivating effect on the metal.

That application also describes methods of making the composite material.

According to the present invention there is provided a composite material adapted to release a biocidal substance into an aqueous medium in contact with the material, the composite material comprising a metal matrix containing one or more glass materials in particular form dispersed therein, at least one of said glasses being water soluble and containing either the biocidal substance or a substance which, on dissolution in water, provides the biocidal substance.

The composite material may be formed as a thin coating on the metal surface to be treated, or as a monolithic body. The glass composition is selected so that, when the matrix metal surface is exposed to an aqueous or water containing medium, the contained glass particles resent at the interface between the liquid phase and the metal release a selected biocidal ion or ions at a predetermined rate. The dispersion of glass particles throughout the matrix ensures a steady release rate over an extended period since, as the metal is removed e.g. by corrosion or mechanical means, new glass particles cqntinue to be exposed.

The composite materials may be made in various ways, e.g. by powder compaction, electrophoretic deposition or by electro- deposition. In a preferred method the powdered glass is mixed with an electroplating solution of the matrix metal, the mixture being subjected to continuous agitation to maintain the solid particles in suspension. Electroplating from the solution on to a metal surface to be treated, or on to a substrate, produces a layer of the matrix metal in which the glass particles are codeposited and trapped. Such a process is described in our co-pending application No.

45015/77 (Serial No. 16046292. For example the matrix metal may be iron deposited from an iron plating solution on to a ferrous metal surface. Such a technique may be employed to provide corrosion protection e.g. to an oil storage tank. In other applications, e.g. the provision of coatings on a metallic surface, electroless plating techniques may be employed.

The composition of the glass is determined by the particular application.

Thus, for many bactericidal applications a glass containing silver may be employed.

Such a glass can provide a local Ag+ ion concentration of e.g. 10 weight parts per billion over an extended period. Such a concentration is sufficient to provide an effective bactericidal action. In further applications other cations or anions may be included in the glass to provide protection e.g. against the growth of algae or animal life, or corrosion inducing fungi.

Other suitable glasses for this purpose are to described in our published UK specification No. 1,511,381.

In further applications two glass compositions may be employed one of which.controls the dissolution rate of the other. Such glass systems are described in our published specification No. 1,542,064.

In such systems one glass so controls the pH of water in contact with the glass system as to enhance or inhibit dissolution of the other glass.

WHAT WE CLAIM IS: 1. A composite material adapted to release a biocidal substance into an aqueous medium in contact with the material, the composite material comprising a metal matrix containing one or more glass materials in particulate form dispersed therein, at least one of said glasses being water soluble and containing either the biocidal substance or a substance which, on dissolution in water, provides the biocidal substance.

2. A composite material as claimed in claim 1, in which the matrix metal comprises an electroplated layer of a metal substance, the glass or glasses being codeposited with the matrix metal.

3. A composite material as claimed in claim 1 or 2, and in which the matrix metal is iron.

4. A composition as claimed in claim 1, 2 or 3, and in which at least one said glass is adapted to release silver (Ag+) ions into aqueous solution.

5. A biocidal composite material substantially as described herein.

6. A ferrous metal storage tank provided with a coating of a material as claimed in any one of claims I to 5.

7. A method of making a biocidal composite material substantially as hereinbefore described.

8. A method of protecting a metal surface against microbiologically induced corrosion, which method is substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. concentration of e.g. 10 weight parts per billion over an extended period. Such a concentration is sufficient to provide an effective bactericidal action. In further applications other cations or anions may be included in the glass to provide protection e.g. against the growth of algae or animal life, or corrosion inducing fungi. Other suitable glasses for this purpose are to described in our published UK specification No. 1,511,381. In further applications two glass compositions may be employed one of which.controls the dissolution rate of the other. Such glass systems are described in our published specification No. 1,542,064. In such systems one glass so controls the pH of water in contact with the glass system as to enhance or inhibit dissolution of the other glass. WHAT WE CLAIM IS:

1. A composite material adapted to release a biocidal substance into an aqueous medium in contact with the material, the composite material comprising a metal matrix containing one or more glass materials in particulate form dispersed therein, at least one of said glasses being water soluble and containing either the biocidal substance or a substance which, on dissolution in water, provides the biocidal substance.

2. A composite material as claimed in claim 1, in which the matrix metal comprises an electroplated layer of a metal substance, the glass or glasses being codeposited with the matrix metal.

3. A composite material as claimed in claim 1 or 2, and in which the matrix metal is iron.

4. A composition as claimed in claim 1, 2 or 3, and in which at least one said glass is adapted to release silver (Ag+) ions into aqueous solution.

5. A biocidal composite material substantially as described herein.

6. A ferrous metal storage tank provided with a coating of a material as claimed in any one of claims I to 5.

7. A method of making a biocidal composite material substantially as hereinbefore described.

8. A method of protecting a metal surface against microbiologically induced corrosion, which method is substantially as hereinbefore described.