METHOD FOR ESTIMATING THE RISK OF CORROSION

Abstract

A method for determining the corrosion risk caused by biofilm formation for installations in natural bodies of water includes a) providing a device for measuring electrode potentials, comprising at least one metal sample and at least one reference electrode at a location close to the installation within the natural body of water b) continuously or intermittently measuring potential differences between said at least one metal sample and said at least one reference electrode over a sufficiently long period of time to allow for identifying any changes of potential of the sample resulting from ennoblement caused by biofilm formation, c) comparing the measured potential difference to one or more reference values for the respective metal of the metal sample, and d) estimating if and when the potential difference resulting from biofilm formation attains or may attain a critical value which would result in the corrosion of the respective metal at the respective location of the natural body of water.

Claims

1. A method for assessing the risk of corrosion caused by biofilm formation for installations located or to be constructed in natural bodies of water, said method comprising: a) providing a device for measuring electrode potentials, comprising at least one metal sample and at least one reference electrode at a location close to the installation within the natural body of water; b) continuously or intermittently measuring potential differences between said at least one metal sample and said at least one reference electrode over a sufficiently long period of time to allow for identifying any changes of potential of the sample, which result from ennoblement caused by biofilm formation; c) comparing the measured potential difference to one or more reference values for the respective metal of the metal sample; and d) estimating if and when the potential difference resulting from biofilm formation attains or may attain a critical value which would result in the corrosion of the respective metal at the respective location of the natural body of water.

2. The method according to claim 1, wherein said location is situated in close proximity to the installation within the natural body of water.

3. The method according to claim 1, wherein the measurements of the potential differences are carried out over a period of at least one week, preferably of at least two weeks.

4. The method according to claim 1, wherein one or more additional environment parameters selected from temperature, light incidence, electrical conductivity and flow velocity of the water, pH, and the concentration of certain ions are measured using said device.

5. The method according to claim 1, wherein additionally galvanic currents are measured using said device.

6. The method according to claim 1, wherein the measurement values are stored in the device and/or wirelessly transmitted to a computer.

7. The method according to claim 1, wherein said installation is a hydropower plant.

8. A device for detecting biofilms with ennoblement effect on metal surfaces in natural bodies of water by measuring potential differences, said device comprising: a housing, the interior of which is divided by a separating wall into a watertight compartment and a compartment through which the water flows; one or more mounts arranged in said compartment through which the water flows and connected to the housing; one or more material samples and reference electrodes attached to each of said one or more mounts; at least one power supply arranged in said watertight compartment; and electronics arranged in said watertight compartment for measuring potential differences between said material samples and said reference electrodes and for storing and/or transmitting data.

9. The device according to claim 8, wherein said housing comprises an external wall which is watertight in the area of said watertight compartment and water-permeable in the area of said compartment through which the water flows.

10. The device according to claim 9, wherein said external wall consists of a water-permeable material and/or is provided with openings in the area of said compartment through which the water flows.

11. The device according to claim 8, wherein said housing is roughly streamline-shaped.

12. The device according to claim 8, wherein said housing comprises a cover plate which is provided with openings.

13. The device according to claim 8, wherein said mounts are perforated rails.

14. The device according to claim 8, wherein said electronics are connected to said material samples and said reference electrodes via cables running through an otherwise sealed opening in said separating wall from said watertight compartment into said compartment through which the water flows.

15. The device according to claim 8, wherein said electronics comprise at least one voltmeter.

16. The device according to claim 8, wherein said electronics additionally comprise at least one current meter.

17. The device according to claim 15, further comprising at least one potentiostat.

18. The device according to claim 8, wherein additional facilities for measuring one or more environment parameters selected from temperature, light incidence, electrical conductivity and flow velocity of the water, pH, and the concentration of certain ions are provided.

19. The device according to claim 8, wherein said electronics comprise a sender/receiver for data transmission.

20. The device according to claim 19, wherein said housing comprises two separable parts, comprising said watertight compartment and said compartment through which the water flows, respectively.

21. The device according to claim 8, wherein said two parts of said housing are connected by screws.

22. The device according to claim 8, further comprising an anchoring element for anchoring it to the bottom of the body of water.

23. The device according to claim 8, further comprising a ballast element counteracting buoyancy in the natural body of water.

24. The device according to claim 22, further comprising a floating body serving as a buoy on the water surface.

25. A device for detecting biofilms with ennoblement effect on metal surfaces in natural bodies of water by measuring potential differences, said device comprising: a housing, the interior of which is divided by a separating wall into a watertight compartment and a compartment through which the water flows; one or more mounts arranged in said compartment through which the water flows and connected to the housing; one or more material samples and reference electrodes attached to each of said one or more mounts; at least one power supply arranged in said watertight compartment; and electronics arranged in said watertight compartment for measuring potential differences between said material samples and said reference electrodes and for storing and/or transmitting data, the device being used to perform a method for assessing the risk of corrosion caused by biofilm formation for installations located or to be constructed in natural bodies of water, said method comprising: a) providing a device for measuring electrode potentials, comprising at least one metal sample and at least one reference electrode at a location close to the installation within the natural body of water; b) continuously or intermittently measuring potential differences between said at least one metal sample and said at least one reference electrode over a sufficiently long period of time to allow for identifying any changes of potential of the sample, which result from ennoblement caused by biofilm formation; c) comparing the measured potential difference to one or more reference values for the respective metal of the metal sample; and d) estimating if and when the potential difference resulting from biofilm formation attains or may attain a critical value which would result in the corrosion of the respective metal at the respective location of the natural body of water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Referring to the appended drawings illustrating non-limiting embodiments of the invention, the invention will be examplarily described below.

[0047] FIGS. 1a to 1c show a device according to the second aspect of the invention for carrying out a method of the invention, and

[0048] FIG. 2 shows a preferred embodiment of the method of the invention, specifically the design and positioning of the device for its implementation.

DETAILED DESCRIPTION

[0049] FIG. 1 shows a preferred embodiment of the device according to the second aspect of the invention to examine biofilm formation on metal surfaces in natural bodies of water by measuring potential differences.

[0050] FIG. 1a shows a housing (numeral 1) consisting of the parts 1a to 1c, whose interior 3 is divided by a separating wall 2 into a watertight compartment 3a and a compartment 3b through which the water flows. The housing is preferably entirely manufactured of a watertight material, such as a watertight plastic foil (e.g. of PVC) or a stainless steel cylinder, part 1b being provided with slits, holes, or perforations to enable water to enter the interior of compartment 3b.

[0051] The cover plate 1c of the housing, which in this case is essentially planar and serves as a bottom plate, is also provided with openings to let water pass, i.e. depending on the device's orientation, let it enter and escape from the interior of the invention during operation.

[0052] Mounts 4 arranged in the compartment 3b through which the water flows and firmly connected to the separating wall 2 and the cover plate, e.g. by screws, rivets, and/or adhesive, each of them being intended to receive or fixing one or more material samples 5 and reference electrodes 6. In the embodiment shown in FIG. 1, several samples 5, each preferably comprising another metal to be examined, or two or three samples 5 of the same metal (to allow for averaging), are connected, e.g. by screws or clamps, to each of the mounts 4, which in this case are perforated rails, as is preferred according to the invention.

[0053] Additionally, one of the mounts 4 holds a reference electrode 6, which is not subject to specific limitations, but in view on the conditions of use in a natural body of water preferably is a silver/silver chloride electrode, as mercury/mercury salt (e.g. -chloride, -sulfate or -oxide) electrodes are not preferred due to potential mercury contamination resulting from a potential damage or loss of the device.

[0054] As mentioned above the mounts 4 may also hold further detectors or measurement probes, e.g. for measuring temperature, light incidence, electrical conductivity and flow velocity of the water, pH and the concentrations of certain ions.

[0055] As can be seen in FIG. 1b, the watertight compartment 3a is provided with a power supply 7, which preferably consists of several batteries or rechargeable batteries, which for reasons of environmental friendliness in cases of failure should be free of problematic heavy metals, such as mercury, cadmium, and lead, and electronics 8 for measuring potential differences between the material samples 5 and the reference electrode 6 and for storing and/or transmitting data are provided in the watertight compartment 3a, as indicated by three blocks 8 in FIG. 1.

[0056] The electronics are connected to the material samples 5, the reference electrodes 6 and any further measurement facilities via cables 9 which run through an opening in the separating wall 2 and are sealed with respect to this opening to prevent water from entering the compartment 3a.

[0057] FIG. 1c shows a plan view of the above device of the invention standing on the cover plate 1c.

[0058] FIG. 2 shows a preferred embodiment of the method of the invention and the design and positioning of the device of the invention for implementing said method. The device, referred to by numeral 1 for the housing as pars pro toto, is connected to an anchoring element 11 via a rope or a cable 13, said anchoring element 11 keeping the device on the bottom 10 of the natural body of water. The anchoring element 11 may either be an actual anchor or simply a sufficiently heavy weight, e.g. a concrete block.

[0059] The device 1 is also connected with a floating body 12, e.g. a buoy, via the cable 13, said buoy indicating the device's position under water; numeral 14 refers to a plurality of holes in the housing wall, which let the water enter the compartment through which the water flows.