METAL MOLD INCLUDING ANTI-CORROSION PROTECTION, METHOD FOR PROTECTING A METAL MOLD AGAINST CORROSION

Abstract

The invention relates to a metallic mold (1) for casting a fresh concrete mix, a method for protecting such a mold (1) against corrosion, and a method for producing a concrete product by casting fresh concrete into such a mold. The mold (1) comprises at least one wall (3) delimiting a receiving volume (4) for the mix (7) and is characterized in that the side wall (3) has an inner face (30) provided, in whole or in part, with a coating composed of a metallic film (5) having a lower electrochemical potential than the mold material (1) and a layer of an electrolytic material (6) ensuring the adhesion of the metallic film (5) to the mold (1) so as to protect from corrosion a surface exposed to the concrete mix cast into the receiving volume that is adjacent to the wall. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: METAL MOLD COMPRISING ANTI-PROTECTION CORROSION, METHOD FOR PROTECTING A METAL MOLD AGAINST CORROSION. TECHNICAL FIELD OF THE INVENTION.

[0001] The present invention relates to the field of manufacturing concrete products.

[0002] The invention relates more particularly to a metal mold for casting a fresh concrete composition and a method for protecting such a mold from corrosion.

[0003] The metal mold according to the invention is intended for the manufacture of all types of concrete products, including low-carbon concrete products. STATE OF THE ART

[0004] Until recently, building elements were produced using concrete composed primarily of cement with a high clinker content. However, in a context of strong ecological transition, constituents with a lower carbon footprint are increasingly favored in the manufacture of concrete products, and concrete compositions are emerging that include additions to replace cement clinker.

[0005] These new concretes with lower environmental impacts (low-carbon concretes) nevertheless exhibit different early-age reaction kinetics and lower pH levels than those of high-clinker concretes. However, in the case of high-clinker concretes, it is the kinetics of the hydration reactions and the pH of the concrete in its fresh state that contribute to maintaining conditions that promote the passivation of the steel molds receiving the concrete mix, and thus protect the molds receiving the concrete mix against corrosion.

[0006] Due to the use of decarbonized or reduced carbon impact binders instead of high clinker cements, "low carbon" concretes no longer contribute to sufficiently protecting metal molds against corrosion, and pitting corrosion on metal molds may appear during manufacturing operations.

[0007] The presence of corrosion pits has the problem of causing degradation of the metal mold (deformation, micro-cracking), leading to a reduction in its lifespan.

[0008] The presence of corrosion pits on the mold also has the problem of causing, by transfer from the mold onto the concrete facing, aesthetic surface defects on the manufactured products.

[0009] In an attempt to prevent the appearance of pitting corrosion on metal molds in contact with fresh concrete mixes, solutions have been proposed, such as applying a coating to the surface of the metal mold to form an insulating layer (release oil, paint, mill scale, etc.). Although these coatings delay the appearance of pitting corrosion, they nevertheless prove insufficient to effectively prevent the corrosion phenomenon.

[0010] Electrochemical solutions such as sacrificial anodes (or galvanic anodes) are also known to combat the corrosion of reinforcement in reinforced concrete structures located in environments that promote corrosion.

[0011] A galvanic anode is a metallic electrode that corrodes sacrificially when coupled to a nobler metal in a conductive medium, thus providing a protective electric current to the noble electrode. This galvanic anode protects the metallic material and corrodes instead of the metal to be protected. The operating principle of sacrificial anodes is as follows: the part of the metal to be protected—the cathode—is placed in contact with the sacrificial anode, which is generally made of a metal with a more electronegative potential than the metal to be protected so that corrosion occurs on the sacrificial anode rather than on the protected structure. In order to fulfill their corrosion protection function, sacrificial anodes are connected to the structure to be protected by conductive wires or cast iron straps. The conductive wires can be attached by welding or by mechanical connections.

[0012] In reinforced concrete structures, the reinforcements are thus protected from corrosion via sacrificial anodes connected to the reinforcement to be protected and the application of an electric current from an external current source.

[0013] While sacrificial anodes constitute a solution to prevent corrosion of reinforcement in hardened concrete, this solution is not applicable to the problem of corrosion of molds in contact with fresh (i.e. unhardened) concrete during casting / molding operations.

[0014] The invention aims to remedy the problems of prior art solutions by proposing a metal mold exhibiting improved resistance to corrosion regardless of the composition of fresh concrete received in the mold, as well as a method for making such a mold.

[0015] The invention also relates to a metal mold enabling the manufacture of a concrete product free from traces of corrosion after its casting in a metal mold.

[0016] The invention also relates to a method for protecting a metal mold against corrosion in a simple, fast, repeatable way and without altering the mold. SUBJECT OF THE INVENTION

[0017] To this end, and according to a first aspect, the invention proposes a metallic mold for casting a fresh concrete composition, comprising at least one wall delimiting a receiving volume for the composition, the mold being remarkable in that the side wall has an internal face provided in whole or in part with a coating composed of a metallic film having a lower electrochemical potential than the material of the mold and a layer of an electrolytic material ensuring the adhesion of the metallic film to the mold so as to protect from corrosion a surface exposed to the concrete composition cast in the receiving volume which is adjacent to the wall.

[0018] The expression "exposed to the concrete composition" means a surface in contact with the concrete composition. The surface may be a surface of the mold itself or a surface of a support separate from the mold and on which the mold is placed.

[0019] Thus, thanks to the adhesion of a metallic film to all or part of the inner wall of the mold via an electrolytic material ensuring optimal contact and electrical continuity between the metallic film and the adjacent metallic surface to be protected from corrosion, the appearance of pitting corrosion on the surface in question, due to its contact with the fresh concrete, is prevented. The metallic film acts as a sacrificial anode, with the electrolytic material acting as the cathode.

[0020] The effectiveness of the coating against corrosion depends on the ratio between the surface area of ​​the metallic film and the total surface area of ​​the steel to be protected. To this end, according to a preferred embodiment, the coating is dimensioned to have a coverage ratio of at least 1 / 8 of the total surface area of ​​the surface to be protected from corrosion.

[0021] Advantageously, the electrolytic material is a hydrogel.

[0022] The invention also relates to a method for protecting against corrosion a metal mold for casting a fresh concrete mix, said mold comprising at least one wall delimiting a volume for receiving the mix, the method being remarkable in that it comprises a step of applying to all or part of the inner face of the lateral wall a layer of an electrolytic material, advantageously a hydrogel, and a metallic film having a lower electrochemical potential than the mold material, the layer of electrolytic material ensuring the adhesion of the metallic film to the inner face, the application being carried out in such a way as to coat the inner face concerned with a view to protecting against corrosion of the surface exposed to the composition of concrete poured in the receiving volume which is adjacent to the wall.

[0023] Advantageously, the metallic film and the layer of electrolytic material are applied to define a face coverage ratio of at least 1 / 8 of the total surface area to be protected from corrosion.

[0024] Advantageously, the metallic film and the layer of electrolytic material are in the form of a pre-assembled two-component film.

[0025] Advantageously, the layer of electrolytic material is applied to the inner face so as to border the surface to be protected from corrosion, in contact with the latter.

[0026] The invention also relates to a method for producing a concrete product, advantageously low carbon, by pouring and molding fresh concrete in a metal mold as described above. BRIEF DESCRIPTION OF THE FIGURES

[0027] Other features and advantages of the invention will become apparent from the detailed description of the invention that follows, given by way of example and with reference to the single attached [Fig. 1] in which:

[0028] [Fig.1] Fig.1 represents a schematic cross-sectional view of a metal mold according to an example of an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] In relation to [Fig.1], a metallic mold 1 is described, in the example of parallelepiped shape, comprising a mold bottom 2, side walls 3 and a receiving volume 4 of a concrete composition to be molded 7 delimited by the mold bottom 2 and the internal faces 30 of the side walls 3. In the case of this mold configuration, the surface to be protected against corrosion is the mold bottom 2.

[0030] According to the invention, the mold 1 is provided with a coating composed of a metallic film 5 covering in whole or in part the internal faces 30 of the side walls 3 of the mold 1 and a layer of electrolytic material 6 interposed between the metallic film 5 and the side walls 3.

[0031] The metallic film 5 associated with the electrolytic material 6 has the function of ensuring cathodic protection of the mold 1 receiving a concrete composition in the fresh state, protecting said mold 1 from corrosion pitting.

[0032] The metallic film 5 is formed of a material having a lower electrochemical potential than the mold material 1. The film is based on polyvinyl acetate (PVA).

[0033] The electrolytic material is chosen to ensure both the adhesion of the metal film 5 to the side walls of the mold 1 and the electrical contact between the mold and the metal film. In a preferred embodiment, the electrolytic material 6 is a hydrogel.

[0034] The coating is dimensioned to advantageously present a coverage ratio of the faces on which it is affixed of at least 1 / 8 of the total surface of the bottom of the mold 2.

[0035] In the illustrated embodiment, the coating extends over the entire height of the internal faces 30, from the bottom of the mold 2 to the top of the mold. Similarly, in the illustrated example, the coating is provided on each of the mold's side walls. This is, of course, just one embodiment; other arrangements of the coating on the mold may be provided without departing from the scope of the invention, provided that it covers a minimum surface area of ​​the side walls relative to the total surface area of ​​the mold bottom, thus ensuring cathodic protection of the mold bottom 2. For example, an arrangement may be provided in which one or more side walls are provided with a cathodic protection coating, the coating covering all or only part of the side wall in question.

[0036] The mold 1 according to the invention is advantageously made as follows.

[0037] First, a layer of electrolytic material 6 is applied to each of the inner faces 30 of the lateral walls 3 of the mold 2. This layer must be applied continuously to a thickness of a few millimeters (approximately 1 to 3 mm). A metallic film 5, with a lower electrochemical potential than that of the mold material 1, is then applied to the layer of electrolytic material 6, which ensures the adhesion of the metallic film 5 to the inner faces 30.

[0038] In the illustrated embodiment, the layer of electrolytic material 6 and the metallic film 5 are affixed to each of the internal faces 30 so as to border the surface to be protected from corrosion, namely the bottom of the mold 2, a contact line being created between the protective coating and the part of the mold to be protected (bottom of the mold 2).

[0039] The advantage of providing a mold thus coated is to allow the molding of a concrete product advantageously with low carbon (pH less than 13), without the development of corrosion pits on the bottom of the mold and therefore without the formation of stains on the concrete products obtained.

[0040] The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention. In this case, the mold according to the invention is not limited to the shape described in the embodiment illustrated in [Fig. 1], the mold being able to have any other shape, such as a circular cross-section, or any other more complex geometry. Depending on the shape of the mold, the surface to be protected from corrosion may then be a surface other than the mold bottom.

Claims

Demands

1. Metallic mold (1) for casting a fresh concrete composition, comprising at least one wall (3) delimiting a receiving volume (4) for the composition (7) characterized in that the side wall (3) has an internal face (30) provided in whole or in part with a coating composed of a metallic film (5) having a lower electrochemical potential than the material of the mold (1) and a layer of an electrolytic material (6) ensuring the adhesion of the metallic film (5) to the mold (1) so as to protect from corrosion a surface exposed to the concrete composition cast in the receiving volume which is adjacent to the wall.

2. Metallic mold (1) according to claim 1, characterized in that the coating is dimensioned to have a coverage ratio of the face (30) on which it is applied of at least 1 / 8 of the total surface area of ​​the surface to be protected from corrosion.

3. Metal mold (1) according to any one of the preceding claims, characterized in that the electrolytic material is a hydrogel.

4. A method for the corrosion protection of a metallic mold (1) for casting a fresh concrete composition, said mold (1) comprising at least one wall (3) delimiting a receiving volume (4) for the composition (7), characterized in that it comprises a step of applying to all or part of the inner face of the wall (3) a layer of an electrolytic material (6) and a metallic film (5) having a lower electrochemical potential than the mold material, the layer of electrolytic material (6) ensuring the adhesion of the metallic film (5) to the inner face (30), the application being carried out so as to coat the relevant inner face (30) for the purpose of corrosion protection of a surface exposed to the concrete composition cast in the receiving volume which is adjacent to the wall.

5. A method for the corrosion protection of a metallic mold (1) according to the preceding claim, characterized in that the metallic film (5) and the layer of electrolytic material (6) are applied to define a face coverage ratio of at least 1 / 8 of the total surface area to be protected from corrosion.

6. A method for corrosion protection of a metal mold (1) according to claim 4 or claim 5, characterized in that the metal film (5) and the layer of electrolytic material (6) are in the form of a pre-assembled two-component film.

7. A method for protecting a metal mold (1) against corrosion according to any one of claims 4 to 6, characterized in that the layer of electrolytic material (6) is applied to the inner face (30) so as to border the surface to be protected from corrosion, in contact with the latter.

8. A method for corrosion protection of a metallic mold (1) according to any one of claims 4 to 7, characterized in that the electrolytic material is a hydrogel.

9. Method for producing a concrete product by pouring a fresh concrete composition into a metal mold (1) according to any one of claims 1 to 3.