METHOD OF SEALING A SURFACE AND DEVICE THEREFOR

Abstract

A method of sealing a surface is provided, the method comprising the steps of providing a metallic composition; providing a propellant; heating the metallic composition to above the melting point of the metallic composition to provide at least partially liquid metallic composition; accelerating the at least partially liquid metallic composition towards the surface by means of the propellant; and applying the at least partially liquid metallic composition to the surface.

Claims

1. A method of sealing a surface comprising: providing a metallic composition; providing a propellant; heating the metallic composition to above the melting point of the metallic composition to provide at least partially liquid metallic composition; accelerating the at least partially liquid metallic composition towards the surface by means of the propellant; applying the at least partially liquid metallic composition to the surface.

2. The method according to claim 1, wherein the surface to be sealed comprises at least one surface defect to be sealed.

3. The method according to claim 2, wherein the surface at least partially defines a volume defining a container, wherein the container comprises an at least partially liquid or fluid substance.

4. The method according to claim 3, wherein the at least one surface defect is the source of a leak from which matter comprising the at least partially liquid or fluid substance may escape.

5. The method according to claim 1, wherein the surface to be sealed is at least partially submerged in an aqueous fluid, optionally wherein the surface is submerged under water.

6. The method according to claim 1, wherein the method further comprises the step of heating the propellant.

7. The method according to claim 6 wherein the metallic composition is heated by contacting the metallic composition with the heated propellant.

8. The method according to claim 1, wherein the metallic composition is heated otherwise than by contact with the heated propellant.

9. The method according to claim 1, wherein both the metallic composition and the propellant are heated.

10. The method according to claim 1, further comprising the steps of: (i) accelerating the propellant towards the surface; and (ii) contacting the propellant with the surface; prior to accelerating the at least partially liquid metallic composition towards the surface.

11. The method according to claim 1, further comprising the steps of: (i) providing a separate stream of heated propellant; and (ii) directing the separate stream of heated propellant towards the surface during application of the at least partially liquid metallic composition to the surface.

12. The method according to claim 1, wherein the at least partially liquid metallic composition cools on contact with the surface to form a solid metallic composition seal.

13. The method according to claim 12 wherein the at least partially liquid metallic composition is applied to the surface as a constant stream.

14. The method according to claim 13 wherein the at least partially liquid metallic composition at least partially melts previously applied solid metallic composition, coalesces with the previously applied solid metallic composition, and cools to form solid metallic composition.

15. The method according to claim 1, wherein the at least partially liquid metal composition is at a temperature no greater than 200° C., preferably no greater than 100° C. when it is accelerated towards the surface.

16. The method according to claim 1, wherein the at least partially liquid metal composition is accelerated towards the surface at a velocity no greater than around 100 m/s, preferably no greater than around 50 m/s and more preferably no greater than around 25 m/s.

17. The method according to claim 1, wherein the propellant provides sufficient propulsion to force the at least partially liquid metallic composition into deformations in the surface, optionally wherein the deformations comprise one or more of cracks, fissures, punctures, and holes.

18. The method according to claim 1, wherein the propellant cleans and/or heats the surface before the at least partially liquid metallic composition is applied.

19. The method according to claim 1, wherein the propellant is selected from the group consisting of steam or air.

20. The method according to claim 1, wherein the propellant is steam.

21. The method according to claim 1, wherein the metallic composition comprises a metal alloy, preferably wherein the metal alloy is selected from the group consisting of bismuth alloys, antimony alloys, indium alloys, tin alloys, lead alloys and gallium alloys; preferably wherein the metallic composition comprises a bismuth alloy.

22. The method according to claim 1, wherein the surface to be sealed is a hazardous waste, selected from the group consisting of radioactive waste, nuclear waste, and biohazardous waste.

23. The method according to claim 1, wherein the surface to be sealed is selected from the group consisting of oil and gas wellbores and pipelines; chemical refinery equipment; aircraft components such as aircraft fuselage and wings; military equipment; mining equipment; and marine vehicles such as submarines, ships and boats.

24. An apparatus for sealing a surface comprising a metallic composition source; a propellant source switchably in fluid connection with the metallic composition source; a heat source configured to provide heat to the propellant and/or to the metallic composition to provide an at least partially liquid metallic composition; a nozzle in fluid connection with the metallic composition source and/or the propellant source, the apparatus being configured to expel a stream of at least partially liquid metallic composition and/or propellant from the nozzle.

25. The apparatus according to claim 24 wherein the heat source is provided by means of thermal conduction and/or by electrical means and/or by pyrotechnical means.

26. The apparatus according to claim 24 wherein nozzle further comprises a nozzle aperture, wherein preferably the shape of the nozzle is selected from the group consisting of cone shaped, cylindrical shaped, cuboid shaped, and arcuate shaped, optionally wherein the nozzle aperture is circular, rhombus or arcuate shaped, further optionally wherein the apparatus comprises two or more nozzles.

27. Use of a liquid bismuth alloy spray in sealing a surface.

28. The use according to claim 27, wherein the surface to be sealed comprises at least one surface defect to be sealed.

29. The use according to claim 28, wherein the surface at least partially defines a container, wherein the container comprises an at least partially liquid substance.

30. The use according to claim 29, wherein the at least one surface defect is the source of a leak from which matter comprising the at least partially liquid substance may escape.

31. The use according to claim 27, wherein the surface to be sealed is at least partially submerged in an aqueous fluid.

32. The use according to claim 31, wherein the surface is submerged under water.

33. The use of a bismuth alloy according to claim 27, wherein the surface is a hazardous waste selected from the group consisting of radioactive waste, nuclear waste, and biohazardous waste.

34. The use of a bismuth alloy according to claim 27, wherein the surface to be sealed is selected from the group consisting of oil and gas wellbores and pipelines; chemical refinery equipment; aircraft components such as aircraft fuselage and wings; military equipment; mining equipment; and marine vehicles such as submarines, ships and boats.

35. The use of a bismuth alloy according to claim 27, wherein the seal is applied to repair a surface damaged by one or more of bullets, missiles, shrapnel, explosives, and shaped charges, wherein optionally the surface is comprised in a fuel tank, a fuel line or a radiator.

36. The use of a bismuth alloy according to claim 27, wherein the seal is applied to repair a surface comprising one or more of cracks, fissures, punctures and holes.

Description

DESCRIPTION OF FIGURES

[0068] FIG. 1 is an illustration depicting an apparatus according to some embodiments of the present invention.

[0069] FIG. 2 is an illustration depicting an apparatus according to some embodiments of the present invention.

[0070] FIG. 3 is a schematic illustration of the method according to the fourth aspect of the present invention.

DETAILED DESCRIPTION

[0071] The present invention provides a method and an apparatus for sealing a surface, in particular for sealing a surface defect that the surface comprises. Surface defects may include holes, cracks, fissures, fractures, failings of a joint, pores and punctures which prohibit the surface from functioning correctly or leaks. For example, surfaces may develop defects, which require sealing to prevent leaks therefrom, or to stop a leak of matter emanating therefrom. Surfaces may also develop defects which require reinforcement or a protective seal. For example the surfaces of containers may become corroded or weakened during use, and require a protective seal and/or reinforcing to restore the integrity of the surface.

[0072] Surfaces that may be sealed by the present invention include, but are not limited to wooden surfaces, metallic surfaces, geological formation surfaces (e.g. stone or rock), composite surfaces (e.g. cement), and architectural surfaces. Surfaces and/or surface defects that may be sealed by the present invention also include hazardous surfaces. In particular, the present invention is relevant to sealing one or more of radioactive waste, nuclear waste and biohazardous waste. Surfaces that may be sealed by the present invention also includes oil and gas wellbores and pipelines; chemical refinery equipment; aircraft components such as aircraft fuselage and wings; military equipment; mining equipment; and marine vehicles such as submarines, ships and boats. The present invention also has particular application to the maritime industry and/or to the disposal of waste in aquatic environments, where surfaces may be at least partially submerged under water.

[0073] As used herein, the term sealing will be understood to mean one or more of filling, covering, coating, masking and/or providing a layer to a surface, and the like; and in particular may be understood to mean one or more of to a surface defect that the surface comprises. For example, a surface may comprise one or more surface defects such as a crack, fissure, hole, rupture which may require filling, covering, coating, masking and/or providing a layer thereto

[0074] The term sealing will also be understood to mean providing a seal to close off the surface and/or the surface defect, such that substances are prevented from coming into contact with surface and/or surface defect, to which the seal is applied. For example, following provision of a seal to a surface defect on a surface that is submerged under water, the access of water to the surface defect would be prevented.

[0075] As used herein, the phrase sealing a surface will be understood to mean that the surface may be sealed entirely or partially. In some circumstances, it may be desirable to encapsulate the surface entirely such that the entirety of the surface is covered by a layer of metallic composition. Such surfaces may be defect free, but it is simply desired to contain the surface. Providing an encapsulating layer to a surface may be desirable, for example, when providing a containment layer to nuclear waste.

[0076] As used herein, the phrase sealing a surface defect may include sealing a surface defect which is the source of a leak. As used herein, the phrase sealing a surface defect may include sealing a surface defect which is the source of a leak from which matter comprising the leaking substance is actively escaping (an ‘active’ leak).

[0077] As used herein, the term fragile will be understood to mean susceptible to damage on impact with matter that is travelling at a high velocity. High velocities typically include velocities greater than 150 m/s, preferably greater than 75 m/s and more preferably greater than 50 m/s. Fragile surfaces may include, but are not limited to, metal sheets including pipes, containers and the like; geological formations such as sandstone, and composite formations such as cement, concrete, polymers, plastics, and the like. It will be appreciated that the present invention is not limited to these particular surfaces and may be applied to any surface which requires sealing.

[0078] Referring to FIG. 1, the present invention provides an apparatus (2) for applying a seal to a surface (S). The apparatus comprises a metallic composition source (4), a propellant source (6), a heat source (8) and a nozzle (10). The metallic composition source (4) and propellant source (6) are in fluid connection. As shown in FIG. 1, the metallic composition source (4) may provide a metallic composition stream (12), wherein the metallic composition stream (12) comprises metallic composition. The propellant source (6) may provide a propellant stream (14) wherein the propellant stream (12) comprises propellant. The apparatus may, in some embodiments, be provided with housing (28) which houses the aforementioned components of the apparatus, with the exception of the nozzle which preferably protrudes from the housing (28). In some embodiments, the housing (28) and the aforementioned components housed therein may be portable. For example, the housing (28) may be provided as a portable pack that can be carried by the user, and the nozzle (10) protrudes therefrom such that the user can direct the nozzle towards the surface. The apparatus may be configured for operation under water or in air.

[0079] The metallic composition stream (12) and propellant stream (14) may be configured to be in fluid connection to form a first stream (16). The first stream (16) may comprise at least partially liquid metallic composition, propellant, or a mixture thereof. A valve (18) may be provided to control the metallic composition entering the first stream (16). A valve (20) may be provided to control the propellant entering the first stream (16). The composition of the first stream (16) may be controlled by isolating the metallic composition stream (12) and/or the propellant stream (14) from the first stream (16), by means of valves (18) and (20) respectively.

[0080] The heat source (8) may be configured to provide heat to the propellant that is provided by the propellant source (6). The heat source (8) may be configured to provide heat to the metallic composition that is provided by the metallic composition source (4). The metallic composition may thus melt to provide at least partially liquid metallic composition. The heat source (8) may provide heat to one or more of the metallic composition stream (12), the propellant stream (14) and the first stream (16). The heat source may provide heat by means of thermal contact conductance, by electrical means, by pyrotechnical means, or by any other suitable method. In some embodiments, the heat source is a pyrotechnical charge.

[0081] The nozzle (10) may be configured to be of variable position, such that different areas of the surface (S) may be sealed. For example, as depicted in FIG. 2, a hose (22), or any other suitable means, connecting the nozzle (10) to the rest of the apparatus (2) via first stream (16) may be provided, such that the nozzle (10) can be easily moved relative to the surface (S) and the rest of the apparatus (2).

[0082] The nozzle (10) is in fluid connection with the metallic composition source and/or the propellant source. Referring to FIG. 1, the nozzle (10) is shown to be in fluid connection with the metallic composition source (4) and propellant source (6) by means of the first stream (16). Referring to FIG. 2, the nozzle (10) is shown to be in fluid connection with the metallic composition source (4) and propellant source (6) by means of the first stream (16) via hose (22).

[0083] The apparatus (2) is configured to expel a stream of at least partially liquid metallic composition and/or propellant from the nozzle (10). The first stream (16) may comprise at least partially liquid metallic composition and/or propellant. The nozzle (10) may comprise a nozzle aperture (not shown) through which the first stream (16) is expelled.

[0084] The shape of the nozzle (10) and the shape of the nozzle aperture may vary depending on viscosity of the propellant used and/or the viscosity of the metallic composition to be applied to the surface. The nozzle may be any suitable shape including, but not limited to, cone-shaped, cylindrical-shaped, cuboid shaped, and arcuate shaped. The internal profile of the nozzle may also be adjusted according to the viscosity of the propellant used and/or viscosity of the metallic composition. For example, the internal angle may be more obtuse, or acute, relative to the plane defined by the nozzle aperture. The nozzle aperture may be circular, a rhombus, arcuate, or any other suitable shape. As such, it will be understood that the shape of the nozzle and aperture can be modified according to the desired application of the present invention. For example, where more viscous metallic compositions and/or more viscous propellants are employed, a wider nozzle aperture may be required. The nozzle may be made of any suitable material, including, but not limited to 3D printed polycarbonate polymer. Preferably the nozzle is cone-shaped and the nozzle aperture is located at the apex of the cone.

[0085] In some embodiments, a means for accelerating one or more of the metallic composition stream (12), the propellant stream (14) and the first stream (16), is provided. As shown in FIG. 2, in some embodiments the apparatus may further comprise one or more pumps (24) configured to accelerate the first stream (16), such that the first stream (16) is expelled from the apparatus via nozzle (10) at a desired velocity. Pump (24) may also be configured to accelerate the propellant stream (14) and/or the metallic composition stream (10). The pump (24) may be an electric pump, or any other suitable means. In some embodiments, the propellant provides sufficient propulsion to accelerate one or more of the metallic composition stream (12), the propellant stream (14) and the first stream (16) independently. The propellant may be under pressure, such that when a valve is opened, the pressurised propellant is able to pass through the valve and exit the apparatus.

[0086] In some embodiments, the apparatus expels metallic composition such that the metallic composition is applied to the surface at low velocity. Surfaces may be fragile and susceptible to damage if metallic compositions are applied at high velocities. The velocity at which the first stream (16), comprising the at least partially liquid metallic composition and/or propellant, is expelled from the nozzle may depend on the configuration of the apparatus. For example, the exit velocity of the first stream (16) from the apparatus may depend on one or more of the flow rate of the first stream (16), the propulsion provided by the propellant, the diameter of the fluid connections within the apparatus (e.g. the diameter of first stream (16), hose (22), propellant stream (14)), the shape of the nozzle (10), the shape of the nozzle aperture, and in embodiments, the strength of accelerating means (e.g. pump (24)).

[0087] On application of the at least partially liquid metal composition to the surface, the metal composition may begin to cool and solidify. The at least partially liquid metallic composition may also heat the surface. Preferably, the at least partially liquid metallic composition is applied to the surface with sufficiently low velocity that the metal and/or metal alloy cools on contact with the surface. The partially liquid metallic composition exiting the apparatus may thus be in contact with the cooler metal already deposited on the surface, and as such a constant stream of metallic composition may be administered.

[0088] The metallic composition may be selected such that the at least partially liquid metallic composition rapidly solidifies and cools on the surface to which it is applied, and thus thermal damage to the surface is reduced. Advantageously, rapid cooling and solidification of the liquid metal composition which is applied to the surface means that the liquid metal composition does not drip from the surface to which it is applied under the force of gravity. As such, the metallic composition sealant may be applied directly to a surface that is vertical, horizontal, curved, round, or at any other angle, relative to the plane of the ground.

[0089] Preferably, the metallic composition expands when it reaches the solidification isotherm i.e. when the metallic composition cools from a liquid to a solid following application to a surface. The expansion of metallic compositions on solidification is contrary to most typical metals which contract on solidification and further cooling. The expansion of the metallic composition on cooling or solidifying results in the metallic composition exerting pressure on the crack, fissure, hole, or other suitable surface, such that the metallic composition is trapped therein. In some embodiments, the metallic composition does not expand or contract on cooling or solidifying. In other embodiments, the metallic composition may contract on cooling or solidifying.

[0090] Preferably, the solidification isotherm of the metallic composition is such that the liquid metallic composition rapidly cools on contact with the surface, and as such does not drip or flow through a crack, fissure or hole on a surface as a liquid. Metallic compositions with suitable solidification isotherms may comprise and/or be bismuth and/or bismuth alloys.

[0091] To control the solidification isotherm, the metallic composition may be administered to the surface at a sufficiently high temperature, and with sufficient heat capacity, to melt the surface of the already deposited metallic composition. Advantageously, the metallic composition that has been administered to the surface may coalesce with previously deposited metallic composition on the surface, and solidify. By melting only the surface of deposited metallic composition, a series of layers may be built up to form a layer of increased thickness. Therefore, advantageously, the metallic composition sealant provided to a surface according to the present invention is not a sinter i.e. it is not provided by the process of compacting and forming a material through pressure, but is in fact provided as a constant stream of metallic composition dictated by constant cooling and heating. Thus a seal to a leaking hole in a container containing a fluid may also be provided, wherein the metallic composition solidifies first on the periphery of the hole, and subsequent layers build up through melting, coalescing and solidifying of the deposited metallic composition. As such, the diameter of the hole is narrowed until it is entirely sealed. Advantageously, the metallic composition may penetrate through the leaking hole into the container, thus providing a seal to the hole from the inside of the container. Thus, advantageously, the pressure of the fluid within the container may be exerted against the solidified metallic composition seal to further strengthen the seal formed.

[0092] As depicted in FIG. 2, in some embodiments, a further stream (26) of heated propellant may be directed towards the surface and the deposited metallic composition, during application of at least partially liquid metallic composition. Advantageously, in this way, the cooling or solidifying of the liquid metallic composition can be highly controlled during application to the surface.

[0093] In some embodiments, the metallic composition seal once cooled and/or solidified on the surface is heat treated. Heat treating the metallic composition seal may provide a smooth coating surface. Advantageously, the smooth coating provided can be wiped clean. This is particularly advantageous in industries where cleanliness of the coated surface is important.

[0094] Preferably, the propellant applies sufficient pressure (for example, hydraulic pressure) to advantageously force the metallic composition deep into cracks, fissures or holes on the surface to be sealed, for example, where the surface to be sealed is in a subterranean formation or fractured cement block. Preferably, the propellant applies sufficient pressure to the metallic composition whilst it is still liquid, thus the metallic composition solidifies only in locations sufficiently cool. Other sealants, for example cement, cannot penetrate deeply into such cracks, fissures or holes because fine particles therein form a filtration surface. Advantageously, metallic compositions according to the present invention can provide good tenacity deep within cracks, fissures or holes, affording greater integrity to the overall seal provided.

[0095] The propellant may be steam and may be super-heated. In some preferred embodiments, the propellant is steam and the at least partially liquid metallic composition is delivered underwater. Advantageously, the steam propels the at least partially liquid composition rapidly and directly to the surface. Advantageously the steam may clean cracks by removing particulates prior to application of the metal and/or metal alloy. Advantageously, the penetrating metallic composition may remove particulates from the surface as it is applied thereto.

[0096] Advantageously, a steam propellant forms no bubbles during application of the at least partially liquid metallic composition where the surface to be sealed is underwater. Bubbles may undesirably cause the metallic composition to separate into its constituent metals. Furthermore a lack of bubbles prevents the metallic composition from forming an aerosol, which may disrupt the water between the nozzle and the surface. The lack of bubbles therefore also allows the user to clearly see the surface to which the metallic composition is to be applied. In addition, bubbles may cause particulates to be carried to the surface of the water, which is particularly undesirable if said particulates are hazardous (e.g. radioactive particles). Advantageously, the steam simply condenses when it comes into contact with the water surrounding the surface, without the formation of any by-products, or possibly environmentally hazardous compounds. Furthermore, advantageously, the use of steam in underwater applications results in an area of localised heat about the nozzle of the apparatus, thereby ensuring that the at least partially liquid metallic composition does not solidify too rapidly.

[0097] By providing heated propellant, the location on the surface where the at least partially liquid metallic composition begins to solidify can be controlled. As such, the morphology and casting of the metallic composition seal can be manipulated according to the surface to be sealed.

[0098] In preferred embodiments, the heated propellant is steam and the surface to be sealed is underwater, wherein the solidification isotherm of the at least partially liquid composition is controlled such that the initially deposited metallic composition (i.e. the leading sealant) cannot extend into regions of the surface with a local temperature less that the melting point of the metallic composition. As such, molten metal can advantageously be deposited to underwater surfaces, without the molten metal dripping away from the surface to which it is deposited under the influence of gravity. In some embodiments, the at least partially liquid metallic composition is directed into a mould to control the morphology of the seal provided on the surface. For example, the metallic composition may be denser than water, and sink to the bottom of a mould to control the morphology of the seal. A mould may be provided around a leaking surface, for example, a crack in a concrete pond through which water is leaking. The at least partially liquid metallic composition directed into the mould may be in the form of prill and may be heated by means of steam or electrical means or pyrotechnical means. The at least partially liquid metallic composition may heat the concrete and may cross the solidification isotherm to provide a seal on cooling or solidifying.

[0099] In some embodiments, the propellant is air. Preferably the air is heated. Preferably the air is compressed. It has been surprisingly found that, advantageously, compressed air may be used as a propellant to deliver at least partially liquid metallic compositions to a surface under dry conditions. Without wishing to be bound by theory, under dry conditions, it is thought that the solidification isotherm is much more localized, compared to submerged conditions. As such, more localized control of the surface of deposited metallic composition on a surface, melting and coalescing with at least partially liquid metallic composition being applied, can be achieved.

[0100] The propellant may alternatively be a noble gas, preferably argon.

[0101] The metallic composition comprises a metal, a metal alloy or a combination thereof. In some embodiments the metal composition is a metal. In some embodiments the metal composition is a metal alloy. The metal alloy may be selected from the group consisting of bismuth alloys, antimony alloys, tin alloys, lead alloys, gallium alloys, indium alloys, thallium alloys, zinc alloys, cadmium alloys, mercury alloys, copper alloys, silver alloys, gold alloys, nickel alloys, palladium alloys, platinum alloys, cobalt alloys, rhodium alloys, iridium alloys, iron alloys, ruthenium alloys, osmium alloys, or mixtures thereof.

[0102] Preferably the metal alloy is a bismuth alloy. Suitable bismuth alloys include, but are not limited to Field's Metal and Wood's Metal.

[0103] The metal may be selected from the group consisting of bismuth, antimony, tin, lead, gallium, indium, thallium, zinc, cadmium, mercury, copper, silver, gold, nickel, palladium, platinum, cobalt, rhodium, iridium, iron, ruthenium and osmium. Preferably the metal is bismuth.

[0104] Excipients such as, but not limited to, silica, may be added to the metallic composition.

[0105] The metal composition may be selected based on the desired application. Preferably a metallic composition is selected which does not chemically react with the propellant. Preferably the metallic composition is resistant to oxidation. More preferably, the metallic composition selected is resistant oxidation in water and/or resistant to oxidation in air. Advantageously, as the metallic composition is delivered to the surface, no oxidation film forms, and thus a constant stream of un-oxidised metal alloy is delivered to the surface. Preferably the metallic composition is resistant to reaction with the surface material to which it is applied.

[0106] The metallic composition can be optimised for specific applications. For example, specific metallic compositions may be used to provide a seal which affords one or more of good corrosion resistance, protection against radiation, good tensile strength, specific deformation properties (creep), malleability, and such like. Metallic compositions may also be optimised to control the viscosity of the at least partially liquid metal composition during application to a surface, wherein said viscosity may be temperature and/or pressure dependent. In some embodiments, it may be desired to provide a metallic composition seal which at a determined temperature range and/or determined pressure range, the metallic composition which forms the seal on the surface becomes liquid, and thus the seal is removed. In some embodiments, it may be desired to provide a metallic composition seal that is soft, such that the metallic composition seal can be easily removed. The metallic composition may be modified to increase or reduce the affinity of the metal composition for itself, or alternatively to increase or reduce the mechanical tenacity of metallic composition sealant once solidified.

[0107] Advantageously the metallic compositions of the present invention may be recycled. As the metallic compositions are preferably resistant to oxidation and/or reaction with the surface to which they are applied, the metallic composition may be re-used if desired. The metallic composition seal may be removed from a surface by, for example, heating the composition to re-form at least partially liquid metallic composition, or forcibly breaking the seal away from the surface.

[0108] In some embodiments, the apparatus and methods according to the present invention may be useful for entrainment of flux. The entrainment of flux may facilitate soldering onto suitable engineered surfaces, such as, but not limited to aluminium, steel, stainless steel and copper. Any suitable flux may be used.

[0109] In some embodiments, the apparatus and methods according to the present invention may be useful for coating reinforced concrete. An electric current may be applied to the coating and to the concrete interior through metal rebar to drive out impurities (or water-electro-osmosis) or to provide cathodic protection of the rebar (impressed current).

[0110] FIG. 3 depicts a crack 34 in a surface being repaired in accordance with the fourth aspect of the present invention. A frame 30, which may be a gasket, is provided and surrounds the crack 34. A plate (not shown) is also provided which engages with the frame 30 to define a cavity between the plate and the surface. Metallic composition in the form of pellets is provided in the cavity. A heating element 32 which passes through the cavity is also provided. The heating element 32 provides heat to the metallic composition within the cavity and causes it to melt. The cavity fills within molten metallic composition until the level of the molten metallic composition 36 is higher than the damaged portion of the surface. In this way, the damaged portion of the surface is covered with molten metallic composition. The molten metallic composition enters any cracks or cavities in the damaged portion and is allowed to solidify, thereby providing a ‘patch’ to the damaged portion. It will be appreciated that the metallic composition could be added to the cavity defined between the retaining means and the surface according to the method or apparatus of the first and second aspects of the present invention.

EXPERIMENTS

[0111] The following examples are intended to exemplify embodiments of the invention. In no way are the following examples to be construed as limitations to the claims or scope of the invention.

[0112] Materials and Methods

[0113] Field's metal=eutectic alloy 32.5% Bi/51% In, 16.5% Sn; m.p. 62° C.

[0114] Wood's metal=eutectic alloy 50% Bi/26.7% Pb, 13.3% Sn; 10% Cd m.p. 70° C.

Example 1—Sealing of a Fragile Surface

[0115] An egg was selected as an exemplary fragile surface. An egg was clamped in an upright position on a rotating base, at room temperature. White Tack® (UHU) was used at the positions on which the egg was clamped. The egg was allowed to equilibrate to ambient temperature (approximately 20° C.). Field's metal was selected as the metallic composition sealant. Air was selected as the propellant. The air propellant was heated and contacted with Field's metal to form a stream of liquid Field's metal and heated air. The resulting liquid Field's metal stream was accelerated towards the egg at a velocity of less than 50 m/s, and directed towards the egg surface via a nozzle. As the Field's metal contacted the surface of the egg, the rotating base to which the clamp was secured was rotated such that all sides of the egg were covered with liquid Field's metal. The sealed egg was then allowed to cool. It was noted that dipping an egg into a pool of liquid Field's metal did not result in the metal adhering to the surface, but the application of the metal in a liquid spray form allowed a coating of the metal to be applied to the surface of the egg. As such, the present invention allows the application of metallic compositions to surfaces which would not be possible by simple immersion in liquid metallic composition.

Example 2—Deposition of a Seal without Thermal Damage

[0116] To demonstrate the lack of heat-induced damage to the surface, and also the rapid cooling of the deposition of the metallic composition, a sealed egg according to Example 1 was impacted with a sharp edge. It was noted that contacting the Field's Metal sealant with the sharp edge resulted in burnishing of the sealant. The sealant was found to have excellent tensile strength, and could not be removed from the egg surface by force.

[0117] The White Tack® (UHU) was removed to reveal a portion of the underlying egg shell. The egg shell was broken at this position. The inside of the egg was found to be liquid, and thus had not been subject to thermally induced precipitation i.e. had not cooked. It was therefore determined that the Field's metal sealant rapidly cools on contact with the egg surface, and thus thermal damage to the surface is avoided.

Example 3—Deposition of a Seal with High Pressure Resistance

[0118] The egg was removed from the clamp, the White Tack® removed, and the remaining exposed portions of egg shell sealed with Field's metal as described in Example 1.

[0119] To demonstrate that the seals according to the present invention are resistant to elevated pressures (i.e. do not break under increased pressure), an egg according to Example 1 was treated under high pressure. A pressure fitting that had been fitted to the egg before coating was used to pressurise the egg up to a pressure of 70 psi (twice the pressure of a standard car tyre). The sealant was found to be robust and did not shatter.

Example 4—Deposition of a Seal to a Crack in a Concrete Surface

[0120] A cracked concrete paving slab was selected as an exemplary cracked surface. Field's metal was selected as the metallic composition sealant. Air was selected as the propellant. The air propellant was heated, and contacted with Field's metal to form a stream of liquid Field's metal and heated air. The resulting liquid Field's metal stream was accelerated towards the concrete surface and directed towards the concrete surface via a nozzle. The liquid Field's metal was observed to solidify on contact with the concrete surface. The resulting sealed crack was allowed to cool to ambient temperature. The resulting seal was found to be highly tenacious with the crack and the surrounding surface. A seal of approximately 3.5 mm was provided.

Example 5—Deposition of a Seal to a Crack in a Concrete Surface and Maintaining the Temperature of the Sealant in the Crack Before Cooling

[0121] A cracked concrete paving slab was selected as an exemplary cracked surface. Field's metal was selected as the metallic composition sealant. Air was selected as the propellant. The air propellant was heated and contacted with Field's metal to form a stream of liquid Field's metal and heated air. The resulting liquid Field's metal stream was accelerated towards the concrete surface and directed towards the concrete surface via a nozzle. The temperature of the liquid Field's metal was maintained once applied to the surface, by means of a heated propellant stream directed directly towards the application area, to ensure a smooth application of the liquid Field's metal to the cracked surface. Without wishing to be bound by theory, it is thought that maintaining the temperature of the Field's metal within the crack on cooling provides a more favourable solidification isotherm. The resulting sealed crack was allowed to cool to ambient temperature. The resulting seal was found to be highly tenacious with the crack and the surrounding surface. A seal of approximately 3.5 mm was provided.

Example 6—Deposition of a Seal to a Crack with High Pressure Resistance

[0122] To demonstrate that the seals applied to cracks according to the present invention are resistant to elevated pressures (i.e. do not break under increased pressure), the sealed cracked concrete surfaced according to Example 5 was treated under high pressure. The sealed cracked concrete surface was placed in a pressurised chamber and exposed to pressures of up to 70 psi (approximately 5 bar). The sealant was found to be robust and did not break away from the concrete surface up to these pressures.

Example 7—Deposition of a Seal to a Cracked Surface in Submerged Conditions

[0123] A cracked concrete paving slab was selected as an exemplary cracked surface, and submerged under water. Field's metal was selected as the metallic composition sealant. Steam was selected as the propellant. The steam propellant was heated and contacted with Field's metal to form a stream of liquid Field's metal and steam. The resulting liquid Field's metal stream was accelerated towards the concrete surface, and directed towards the concrete surface via an underwater nozzle. The nozzle was held in a fixed position, and the crack moved relative to the nozzle. The high specific heat capacity (SHC) of water resulted in heat being quickly dissipated from the liquid Field's metal underwater. It was found that the liquid Field's metal solidified as soon as it was deposited in the crack via the steam propellant. The resulting sealed crack was allowed to cool underwater, and the sealed concrete surface removed from the water. The resulting seal was found to be highly tenacious with the crack and the surrounding surface.

Example 8—Deposition of a Seal to a Cracked Surface in Submerged Conditions and Preheating the Surface to be Sealed

[0124] A cracked concrete paving slab was sealed with Field's metal according to Example 7. Prior to deposition of the seal to the crack, the crack was pre-heated with the steam propellant. The preheated crack, and the resulting increase in the temperature of the ambient water temperature surrounding the crack, resulted in a more uniform, more tenacious and improved quality seal. Without wishing to be bound by theory, it is thought that applying steam to the surface before applying the liquid Field's metal to the surface, results in a more favourable solidification isotherm for cooling of the Field's metal.

Example 9—Deposition of a Seal to a Hole in a Leaking Container

[0125] In view of the results observed in Example 4, namely that the sealant solidified on contact with the cracked concrete surface, it was hypothesized that the present invention could be used to seal a leaking hole, wherein flow of a fluid is exiting the hole at the time of applying the sealant thereto.

[0126] A metallic cylinder filled with water was shot with a .22 rifle to create a dynamic leak. Field's metal was selected as the metallic composition sealant. Air was selected as the propellant. The air propellant was heated and contacted with Field's metal to form a stream of liquid Field's metal and heated air. The resulting liquid Field's metal stream was accelerated towards the hole in the container and directed towards the hole via a nozzle. The liquid Field's metal was observed to preferentially solidify at the periphery of the leaking hole, and with further application, continued to narrow the hole until the hole was entirely sealed. The liquid Field's metal was further observed to penetrate through the hole into the container at the site of damage, and to extend slightly beyond the periphery of the original hole size. Thus the penetration of the liquid Field's metal into the hole provided a “plug” like effect, wherein the pressure of the fluid therein pressed against the “plug”-like portion of the seal to secure it in place and provide additional sealing effects through pressure. The resulting seal was found to be highly tenacious with the surrounding surface and to completely seal the hole.

[0127] In summary, the method and apparatus of the present invention provides the ability to quickly and effectively seal a surface under a number of conditions. The surface to be sealed may be located in air or under water. The application of a spray of liquid metallic composition allows the metallic composition to adhere to surfaces which the metallic composition would not otherwise adhere.