FR3111145A1 - Antimicrobial alloy rich in copper, part made from this alloy, and method of manufacturing such a part, with stabilization of an active contact layer on the surface of said alloy - Google Patents

Abstract

TITLE. Copper-rich antimicrobial alloy, part made from this alloy, and method of making such a part, with stabilization of an active contact layer on the surface of said alloy. The invention relates to a copper-based alloy, characterized in that it comprises, on its surface, an active contact layer which makes it possible to maintain over time the capacity of copper to destroy numerous microorganisms, such as bacteria, or virus, said alloy consisting of: - zinc (Zn) in a proportion of between 2 and 10%, - an element chosen from iron (Fe) in a proportion of between 0.5 and 3%, cobalt (Co) in a proportion of between 0.5 and 3%, nickel (Ni) in a proportion of between 0.5 and 3%, manganese (Mn) in a proportion of between 0.2 and 2%, l tin (Sn) in a proportion of between 0.1 and 1%, or a combination of several elements chosen from iron (Fe) in a proportion of less than 3%, cobalt (Co) in a proportion of less than 3%, nickel (Ni) in a proportion less than 3%, manganese (Mn) in a proportion less than or equal to 2%, tin (Sn) in a proportion n less than or equal to 1%, the total proportion of the combination being between 0.5 and 3%, - of silicon (Si) in a proportion of between 0.2 and 4%, the rest of the alloy being copper (Cu) in a proportion greater than 85%, the percentages being by mass relative to the total mass of the alloy, said active contact layer having a thickness of between 5 and 50 nm and consisting of at least three elements chosen from carbon (C), oxygen (O), nitrogen (N), chlorine (Cl) and sulfur (S), the proportion of this combination being at least 25% by mass, the rest of the layer consisting of constituent elements of said alloy.

Description

Antimicrobial alloy rich in copper, part made from this alloy, and method of manufacturing such a part, with stabilization of an active contact layer on the surface of said alloy

The present invention relates to a particular copper alloy and to a part produced, at least at the level of its outer skin, from this copper alloy, as well as to a method of manufacturing a solid part made entirely from such an alloy. or a part of which only the outer skin is made of such an alloy.

The copper alloy according to the present invention is particular in that its very specific composition results in the formation, at the level of the surface of the outer skin, or of the part, made of this alloy, of a specific surface state. , in the form of an extremely thin layer, of the order of ten nanometers in thickness, having a composition different from that of the alloy.

Such a layer, referred to in the remainder of the description as “active contact layer” makes it possible to maintain, over time, resistance to microbial development at the surface of said part.

The present invention will find an application, in particular, in the manufacture of parts the surface of which is intended to be manipulated (door handles, window handles, handrails, support bars, push plates, handrails, etc.) having a power. antimicrobial lasting over time, and intended, for example but not limited to, to equip establishments traditionally associated with care (hospitals, accommodation establishments for dependent elderly people, etc.), such establishments being able to be qualified as sensitive in relation to the development and transmission of pathogenic microorganisms, such as in particular certain bacteria, certain viruses, or even certain fungi.

The parts made up, at least at the level of their external skin, of the alloy in accordance with the invention can however be, more generally, put in place and be of great interest in all places and establishments receiving or accommodating people. sensitive or likely to be carriers of pathogenic germs, in places and public buildings with high traffic (airports, stations, etc.), in bathrooms, and in all places where the activity promotes hand / mouth contact (rooms collective meals, bathrooms, etc.).

The antimicrobial properties of pure copper have been widely recognized and studied for many years.

However, pure copper can hardly be used for the manufacture of finished products. It is, in fact, relatively soft and not very resistant mechanically; therefore, it deforms and scratches very quickly.

Certain usual copper-based alloys make it possible to obtain a compromise by reducing the antimicrobial power associated with copper in order to obtain greater hardness and mechanical strength, as well as resistance to tarnishing, by applying in particular a physical surface protection. in the form of a varnish and / or chemical corrosion protection.

However, in the solutions known from the state of the art, this inevitably results in a loss of the antimicrobial power of the parts made from the usual alloys rich in copper over time, during the aging of the part.

Indeed, over time, a number of reactions will occur at the surface of the part made from such copper-based alloys, and promote oxidation of this metallic copper (Cu), the degree of which oxidation rate is 0, copper (II). However, at this degree of oxidation, copper loses about 90% of its antimicrobial properties compared to metallic copper.

The reactions which are likely to occur on the surface of the alloy, and the main consequence of which is the decrease in the biocidal power of the metal copper, can be of different origins, and in particular be due to:

- in contact with the skin and sweat by manipulation of said surface;

- the application of cleaning or disinfection products;

- mechanical friction, due for example to the use of rags, fabrics or the like for cleaning the surface, or to contact between said surface and keys, jewelry, etc. ;

- the natural environment (temperature, humidity, etc.).

The parts obtained from the usual copper alloys therefore lose their antimicrobial effectiveness over time, and are no longer able to prevent the transmission of pathogens between different people in contact with these parts.

The present invention is intended to be able to remedy, at least in part, the drawbacks of the alloys known in the state of the art by proposing a solution making it possible to retain the power to reduce the number of pathogenic microorganisms or viruses, or that of avoid a multiplication of microorganisms, over a longer period than pure copper or the usual copper-based alloys.

The solution of the invention is thus particularly effective in destroying the main pathogenic viruses and bacteria, including certain bacteria resistant to antibiotics. Also, applied to a part having a support surface intended to be handled by different people, the solution of the invention makes it possible to substantially reduce, or even prevent, transmission of microbes between these people who are likely to be in contact with it. said support surface, and to retain this antimicrobial capacity over a relatively long period of time, which may range up to several decades.

In an inventive step, it was thus imagined, in particular, a particular composition of a copper alloy, as well as a process for obtaining a part manufactured at least in part from such an alloy, in order to 'obtain at the surface of such a part, an active contact layer, in order to maintain, over time, a resistance to microbial development or a capacity for destroying certain microorganisms or viruses.

Thus, the present invention relates in particular to a copper-based alloy, characterized in that it comprises, on its surface, an active contact layer which makes it possible to maintain over time the capacity of copper to destroy numerous microorganisms, such as bacteria or viruses, said alloy consisting of:

- zinc (Zn) in a proportion between 2 and 10%,

- an element chosen from iron (Fe) in a proportion of between 0.5 and 3%, cobalt (Co) in a proportion of between 0.5 and 3%, nickel (Ni) in a proportion of between 0.5 and 3%, manganese (Mn) in a proportion between 0.2 and 2%, tin (Sn) in a proportion between 0.1 and 1%, or a combination of several elements chosen from iron (Fe) in a proportion of less than 3%, cobalt (Co) in a proportion of less than 3%, nickel (Ni) in a proportion of less than 3%, manganese (Mn) in a proportion less than or equal to 2%, tin (Sn) in a proportion less than or equal to 1%, the total proportion of the combination being between 0.5 and 3%,

- silicon (Si) in a proportion between 0.2 and 4%,

the remainder of the alloy being copper (Cu) in a proportion greater than 85%, the percentages being by mass relative to the total mass of the alloy, said active contact layer having a thickness between 5 and 50 nm and consisting of at least three elements chosen from carbon (C), oxygen (O), nitrogen (N), chlorine (Cl) and sulfur (S), the proportion of this combination being d 'at least 25% by mass, the remainder of the layer consisting of constituent elements of said alloy.

The invention also relates to a process for manufacturing a part based on the aforementioned alloy, and for stabilizing an active contact layer on the surface of said alloy, said part consisting of a solid part made of alloy. copper or comprising an outer skin with a thickness greater than or equal to 0.1 mm made of copper alloy covering a support material, said process being characterized in that it comprises, at least, the following steps:

- The copper is melted and the alloying elements are added to the bath of molten metal,

- Solidification molding of the alloy material is carried out in the form of a blank or a part;

- Optionally, after the molding of said blank or said part, a hot deformation is carried out at more than 100 ° C and / or a cold deformation followed by at least a heat treatment at more than 100 ° C;

- A surface preparation treatment is carried out either by chemical treatment comprising a degreasing operation followed by stripping and rinsing, or by mechanical treatment by abrasion, preferably by fine brushing or polishing;

- A stabilization treatment is carried out on the active contact layer on the surface of said alloy for 20 to 200 hours in a ventilated atmosphere with a humidity level of between 40 and 60% and a temperature kept constant at a value of between 15 and 25 ° C, preserving said part from any contact.

The present invention has many advantages.

First of all, in a particularly advantageous manner, the particular composition of the alloy of the invention makes it possible to delay the loss of the antimicrobial power of copper during the aging of a part obtained from said alloy, compared to parts manufactured at from pure copper or from usual alloys rich in copper. The constituents of the alloy indeed promote the formation of a thin active contact layer on the surface of the alloy, and this layer slows down the transformation of the surface copper metallic Cu (0), active against microbes, in a Cu (II) state where it is no longer effective in destroying the microbes in question or slowing their multiplication.

The solution of the invention is thus particularly effective in destroying the main pathogenic viruses and bacteria, including bacteria which have developed resistance to certain antibiotics.

Also, it could be demonstrated that the alloys, as well as the active contact layer, of the invention resist well to most cleaning and disinfection products which are inevitably and commonly used in healthcare establishments. It is indeed essential to maintain, in such establishments, the principles of cleaning, despite the antimicrobial capacities of the alloy parts according to the invention, in particular to remove therefrom organic residues from various contacts.

It should also be noted that the solution proposed by the invention has the advantage of being inert towards humans and their environment. Indeed, the present solution does not use any surface coating, and no nanoparticles, which would require application processes at risk for human health, as well as for the environment, and would entail risks of release during cleaning operations. or during the recycling of components, after their dismantling.

Finally, the alloy of the invention is easily malleable for easy shaping of the final part, the aesthetic appearance of which is perfectly acceptable.

Other objects and advantages of the present invention will become apparent from the description which follows relating to embodiments which are given only by way of indicative and non-limiting examples.

The invention relates to a copper-based alloy intended to enter into the composition, at least in part, of a part, which may for example consist of a door handle, a ramp, a handrail, a push plate. , or any other element that can constitute a contact surface, more or less often handled, in an establishment intended for care, in an establishment open to the public, in a company, or even in a single-family home.

The alloy of the invention is an alloy rich in copper (Cu), and as such comprises more than 85% by mass of Cu, relative to the total mass of the alloy, due to the antimicrobial power present this element.

By way of remark, it will be noted that all the proportions of the constituent elements of the alloy are expressed, in the remainder of the description, as a percentage by mass of the element in question relative to the total mass of the alloy.

In addition to copper, the alloy of the invention consists of zinc (Zn) in a proportion of between 2 and 10%.

The presence of Zn in the proportions indicated above (between 2 and 10% by mass) is particularly interesting because this element has the ability to oxidize preferentially to copper, and to produce zinc oxide ZnO. Therefore, this Zn element is synergistic with copper for the latter's antimicrobial properties.

Also, the base alloy of the present invention incorporates an element chosen from iron (Fe) in a proportion of between 0.5 and 3%, cobalt (Co) in a proportion of between 0.5 and 3%, nickel (Ni) in a proportion between 0.5 and 3%, manganese (Mn) in a proportion between 0.5 and 2%, tin (Sn) in a proportion between 0.2 and 1% .

Instead of one of its elements, the alloy can contain a combination of several elements chosen from Fe, Co, Ni, Mn and Sn.

In the event that the alloy incorporates a combination of two or more of these aforementioned elements, the total proportion of the combination should be between 0.5 and 3%. In addition, the proportion of each of the elements present in the combination respects the recommendations indicated in the case where one of these elements (Fe, Co, Ni, Mn, Sn) is present alone, the elements Fe, Co and Ni being then necessarily incorporated in a proportion strictly less than 3% by mass.

Thus, more precisely, in the case of a combination of several elements chosen from Fe, Co, Ni, Mn, Sn, the proportion of Fe is less than 3%, the proportion of Co is less than 3%, the proportion in Ni is less than 3%, while the proportion of Mn is less than or equal to 2%, the proportion of Sn is less than or equal to 1%.

The alloy also incorporates a proportion of silicon (Si) between 0.2 and 4%.

This specific combination of the constituent elements of the alloy, in the precise proportions which were indicated previously in the description, promote the formation of an active contact layer on the surface of the alloy, and in particular on the surface of a part of which at least the outer skin, with a thickness of between 0.1 and 10 mm, consists of the present alloy.

This insoluble active contact layer, which is different in nature from that of the alloy, has a thickness of the order of ten nanometers, this thickness being more generally between 5 and 50 nm.

This extremely reduced thickness is particularly advantageous because it does not prevent contact between the pathogens to be eliminated (bacteria, viruses, etc.) and the copper, while allowing, under the active contact layer, the copper to be kept in the same state. metallic (Cu (0)).

Analysis of this active contact layer by XPS spectrometry (X photoelectronic spectrometry) has shown that said active contact layer is composed of more than 25% of carbon (C), nitrogen (N) and oxygen. (O), chlorine (Cl) and sulfur (S) and that the other elements present in said active contact layer are the constituent metallic elements of said alloy. Analysis of this same layer after prolonged use of the alloy surface or the outer skin of the part shows that the oxygen and nitrogen composition increases, as well as the presence of sulfur (S) and chlorine ( Cl).

More particularly, the active contact layer comprises at least three elements chosen from carbon (C), oxygen (O), nitrogen (N), chlorine (Cl) and sulfur (S), and the proportion of this combination is at least 25% by mass, the remainder of the layer consisting of constituent elements of said alloy.

This active contact layer is characteristic of a "dry" oxidation which allows the formation of Cu (I) to be stabilized for a longer time, while in a humid environment the formation of Cu (II) is favored.

In order for copper ions to be active on the contact surface, no barrier preventing ionization of the copper, nor any surface protection (varnish), nor any chemical corrosion protection used to prevent surface tarnishing, should be applied. .

The constituent elements of this active contact layer, in accordance with the Pourbaix diagram of copper, indicating the domains of existence or predominance of the different forms of copper depending on the pH and the corrosion potential of the solution considered, allow copper to be maintained. Cu (I) as insoluble compounds, and therefore the presence of copper Cu (0) below this protective active contact layer.

It has also been demonstrated by the inventors that said active contact layer forming on the extreme surface of the alloy develops during the immersion of the surface of the alloy or of the skin of the part in a solution having a pH of between 5 and 10, being weakly cathodic compared to copper while exhibiting a free corrosion potential (Open Circuit Potential or OCP) which is slightly positive compared to copper.

Indeed, the element or the combination of elements chosen from among Fe, Co, Ni, Mn, Sn, compensates for the very slightly anodic effect of zinc.

This insoluble active contact layer does not directly participate in the attack of microbes, bacteria or viruses mainly, to be eliminated.

However, said active contact layer probably allows, by its very small thickness, during contact, the oxidation reaction of the copper atoms in their Cu (0) form, protected by the layer where the copper would then be present in the form Cu (I) thus allowing an attack of said microbes, by the establishment of mechanisms of action studied in the scientific literature. These mechanisms leading to the destruction of certain pathogens consist in particular, for bacteria in particular, in the rupture of the integrity of the outer membrane, in the influx of copper inside the cell and the oxidation damage which result, in particular the degradation of genetic material. A degradation of the microbial genome has also been demonstrated upon contact with copper surfaces (deterioration of viral RNA for certain viruses or of the DNA of bacteria).

To achieve such a result, and maintain an action of copper over a longer period than that permitted by existing alloys, the active contact layer forming on the surface of the alloy of the invention must be weakly cathodic and have a Slightly positive OCP relative to copper, as previously noted.

However, the combination and the proportions of certain constituent elements of the alloy of the invention promote the formation of this contact layer by compensating for the slightly anodic effect of the zinc.

The selection of at least one element among Fe, Co, Ni, Mn, Sn, in the proportions and limits indicated for each element, and if the total concentration is between 0.5 and 3% in case of combination, have for effect of promoting the formation of this film.

Indeed, alloyed alone with copper, for example, they exhibit a corrosion-free potential value in seawater, relative to copper, between 0 mV and +100 mV.

In addition, combined with copper, these elements exhibit a slow evolution of their corrosion free potential, compared to the reference electrode, this evolution stabilizing after an immersion time of between 50 and 110 hours.

It should also be noted that during the immersion of the copper alloy and of the elements claimed in an electrolyte consisting of a solution of cleaning or disinfecting product, the formation of the active contact layer can be associated with the development of the OPC value which must 1) remain permanently higher than the OPC value of copper, 2) must not be greater than +150 mV of the value of the free corrosion potential of copper taken under the same conditions and 3) after a time d 'immersion between 50 and 110 hours get closer to the OPC value of copper at the same immersion time (the OPC value of copper decreasing slowly over time to reach a value between -50 and -100 mV with respect to an electrode of reference after 50 hours of immersion).

In comparison, in the most generic copper alloys of the state of the art, in particular the CuZn, CuNi, CuSn, CuAl, CuMn alloys and their combinations, the OPC value leaves this “band”, the lower limit of which is the OPC value of copper and the upper limit complies with conditions 1, 2 and 3 above. The OPC value exhibits a greater difference with the value of copper, leading to corrosion or significant passivation which will accelerate the loss of the biocidal power of such alloys, compared to pure copper.

Thus, it emerges from the above that the active contact layer is more resistant to cleaning and disinfecting products than pure copper or traditional copper alloys.

On the other hand, it could be demonstrated by the inventors that, within the present alloy, it is necessary that the presence of elements such as aluminum (Al), arsenic (As), phosphorus (P), antimony (Sb) and selenium (Se) is either limited, or even completely avoided, either because of their too marked anodic effect, with regard to aluminum, for example, or of their action on the zinc, as regards arsenic, phosphorus, antimony or selenium, as a chelator of metal cations.

In addition, it should also be noted that the presence of aluminum in the alloy at a concentration greater than 1% would be liable to have the effect of modifying the nature of the active contact layer in favor of a layer of alumina of formula Al ₂ O ₃ .

Also, aluminum Al, in particular, should not be integrated within the alloy of the present invention.

As regards now the element Si, the latter is integrated within the composition of the alloy of the invention in a proportion of between 0.2 and 4%, in order to reduce the lack of resistance. mechanics of copper, in particular by promoting the formation of hard Ni / Si, Fe / Si, Co / Si precipitates, without harming the activity of the active contact layer as presented above. On the contrary, when combined with iron, silicon will reduce the preferential oxidation of iron in copper which would be liable to impair the formation of the active contact layer.

Thus, preferably, the alloy in accordance with the present invention comprises both nickel (Ni) and silicon (Si) or iron (Fe) and silicon (Si) or cobalt (Co) and silicon (Si ).

Therefore, in the selection of at least one element among Fe, Co, Ni, Mn, Sn, special preference will be given to Fe, Ni, Co in combination with possibly one or more other element (s) from this list.

The present invention also relates to a part manufactured, at least in part, from the rich copper alloy according to the invention.

The part in question can, in an exemplary embodiment, be formed entirely from the present alloy. In this case, the entire solid part of the part is formed from the alloy of the invention.

In another exemplary embodiment, the part has an outer skin with a thickness greater than 0.1 mm, preferably between 0.1 and 10 mm and even more preferably between 0.5 and 5 mm, said outer skin being made from the present alloy and covering the entirety of a material or support element of a different nature.

Such a thickness is sufficient for satisfactory maintenance of the mechanical and antimicrobial properties on the surface of the part for a relatively long period, in particular in comparison with the usual alloys or with a part made of pure copper.

The present invention also relates to a method of manufacturing such a part, said part consisting either of a solid part made of copper alloy in accordance with the invention and described above, or of an outer skin made of such an alloy. copper covering a support material, the manufacturing process being particularly favorable to the establishment and maintenance of the active contact layer on the surface of the part thus obtained.

Thus, the method of the invention can advantageously comprise at least one hot transformation step.

Indeed, a hot transformation allows thermal homogenization and fine recrystallization.

Thus, a hot-transformed structure exhibits, when counting the number of persistent bacteria, more results below the threshold for the significant presence of bacteria (89%), compared with a molded structure (78%).

The molded structure is considered to be coarser, in terms of grain size, less homogeneous in composition and structure, with a rougher surface, in comparison with a hot processed structure. However, this difference remains small enough to be able to use the molding process without preventing the formation of the active contact layer.

In addition, the active contact layer takes longer to form on a cold-cured surface (eg, cold-rolled), which exhibits greater hardness than a hot-processed and cold-cured surface.

However, for the production of a part having an outer skin with a thickness of less than 2 mm, cold transformation processes will be widely used which will lead to hardening of the skin without this preventing, thanks to the subsequent steps of the process. invention, the formation of the active contact layer.

It is also preferable, at the time of the final shaping, to avoid the repetition of the heat treatments at 100 ° C, which are likely to densify the protective Cu (II) layer and consequently to reduce the antimicrobial power of the product. 'alloy, especially in the presence of alloying elements other than precious metals (Ag, Au, Pt). Indeed, these elements, other than the aforementioned precious metals, in the event of repeated heat treatments, would be liable to oxidize more quickly than copper and to hamper, or even prevent, the formation of the active contact layer ( for example the presence of aluminum with formation of a layer of alumina Al ₂ O ₃ ). It is preferable also to avoid the use of lubricants which, alone or in combination with the heat treatment, will prevent the formation of the active contact layer.

However, in most cases to achieve the final shaping of the part, it will be necessary to heat the part to more than 100 ° C, in order to be able to transform it while hot or to reduce the hardening due to cold deformation, it It will also be necessary to use lubricants so as not to damage the surface. For these reasons, it will be advisable to give preference, subsequently, to a mechanical surface preparation treatment. Such a treatment will have the effect of allowing removal of the protective Cu (II) layer formed which may reduce the biocidal activity of copper.

Such a mechanical surface preparation treatment may consist of an abrasion treatment, preferably fine brushing, or even polishing. A mechanical-chemical tribofinishing must not combine media which deposits ceramic or plastic particles on the surface of the part, nor chemicals which protect the surface from corrosion. A more severe abrasion treatment by trovalisation or sandblasting, if it leads to a high surface roughness, will be unfavorable for the stability of the active contact layer and should be followed by a mechanical finishing treatment.

Surface preparation can also consist of a chemical treatment comprising a first degreasing operation, followed by stripping and then careful rinsing of the surface, considering that no neutralizing agent or protection against oxidation must be added. in the rinsing bath.

Such a surface preparation makes it possible to obtain a part whose surface has an optimum roughness in order, on the one hand, to avoid a dimension of anfractuosity similar to that of the bacteria or virus which will promote adhesion and make it difficult. cleaning action and, on the other hand, avoiding excessively high roughness which will not allow the active contact layer to be maintained for a long time when it is in contact with cleaning or disinfecting products.

Under these surface preparation conditions, the active contact layer will naturally occur after a residence time of 20 to 200 hours in a ventilated ambient atmosphere with a humidity level between 40 and 60% and a constant temperature between 15 and 25 ° C. It is essential that during this period no contact is possible (for example human, damp wood, closed box, etc.)

The production process will always begin with the melting of the copper and the addition of the alloying elements to the molten metal bath, will continue with the solidification molding of the material of the alloy in the form of a blank or a blank. a part and will always end with a surface preparation by mechanical or chemical means followed by a stabilization treatment of the active contact layer.

After molding the blank to make parts with an outer wall that can be reduced to a thickness of 0.1 mm, it will be useful to perform hot deformation followed by cold deformation and heat treatments. These manufacturing steps will prevent the formation of the active contact layer and should be followed by mechanical or chemical surface preparation.

The surface preparation step should never end with protection with a chemical corrosion inhibitor but with a stabilization treatment of the active contact layer.

After the stabilization treatment of the active contact layer, the product must be packaged in a watertight manner, protected from moisture and in a room maintained at a temperature of more than 10 ° C.

In the natural environment in which the part is intended for usual use, incorporating the contact of said part with human skin, sweat, cleaning products or disinfectants, and in association with conditions of friction, the layer of active contact remains particularly stable, both in terms of thickness and composition.

Claims (5)

Copper-based alloy, characterized in that it comprises, on its surface, an active contact layer which makes it possible to maintain over time the capacity of copper to destroy numerous microorganisms, such as bacteria or viruses, said alloy being constituted:
- zinc (Zn) in a proportion between 2 and 10%,
- an element chosen from iron (Fe) in a proportion of between 0.5 and 3%, cobalt (Co) in a proportion of between 0.5 and 3%, nickel (Ni) in a proportion of between 0.5 and 3%, manganese (Mn) in a proportion between 0.2 and 2%, tin (Sn) in a proportion between 0.1 and 1%, or a combination of several elements chosen from iron (Fe) in a proportion of less than 3%, cobalt (Co) in a proportion of less than 3%, nickel (Ni) in a proportion of less than 3%, manganese (Mn) in a proportion less than or equal to 2%, tin (Sn) in a proportion less than or equal to 1%, the total proportion of the combination being between 0.5 and 3%,
- silicon (Si) in a proportion of between 0.2 and 4%,
the remainder of the alloy being copper (Cu) in a proportion greater than 85%, the percentages being by mass relative to the total mass of the alloy, said active contact layer having a thickness between 5 and 50 nm and consisting of at least three elements chosen from carbon (C), oxygen (O), nitrogen (N), chlorine (Cl) and sulfur (S), the proportion of this combination being d 'at least 25% by mass, the remainder of the layer consisting of constituent elements of said alloy. Copper-based alloy according to Claim 1, characterized in that the alloy comprises nickel (Ni) and silicon (Si) or iron (Fe) and silicon (Si) or cobalt (Co) and silicon ( Yes). Solid part made entirely of an alloy according to claim 1 or claim 2. Part with an outer skin having a thickness greater than or equal to 0.1 mm, preferably between 0.1 and 10 mm, said outer skin being made of an alloy according to claim 1 or claim 2 and covering a support material. A method of manufacturing a copper alloy part according to claim 3 or claim 4 and stabilizing an active contact layer forming on the surface of said alloy to a thickness between 5 and 50 nm, said layer being formed of at least three elements chosen from carbon (C), oxygen (O), nitrogen (N), chlorine (Cl) and sulfur (S), the proportion of this combination being at least 25% by mass, the remainder of the layer consisting of constituent elements of said alloy, said part consisting of a solid part in copper alloy or comprising an outer skin with a thickness greater than or equal to 0.1 mm in alloy copper covering a support material, the composition of said alloy consisting of a proportion of zinc (Zn) of between 2 and 10%, of an element chosen from iron (Fe) in a proportion of between 0.5 and 3%, cobalt (Co) in a proportion between 0.5 and 3%, nickel (Ni) in a p roportion between 0.5 and 3%, manganese (Mn) in a proportion between 0.5 and 2%, tin (Sn) in a proportion between 0.2 and 1%, or a combination of several elements chosen from among iron (Fe) in a proportion of less than 3%, cobalt (Co) in a proportion of less than 3%, nickel (Ni) in a proportion of less than 3%, manganese (Mn) in a proportion of less than or equal to 2%, tin (Sn) in a proportion less than or equal to 1%, the total proportion of said combination being between 0.5 and 3%, said alloy also consisting of silicon (Si) in a proportion between 0 , 2 and 4%, the remainder of the alloy being copper (Cu) in a proportion greater than 85%, the percentages being by mass relative to the total mass of the alloy, said process being characterized in that it comprises, at least, the following steps:

• The copper is smelted and the alloying elements are added to the bath of molten metal;
• Solidification molding of the alloy material is carried out in the form of a blank or a part;
• Optionally, after the molding of said blank or of said part, a hot deformation is carried out at more than 100 ° C and / or a cold deformation followed by at least one heat treatment at more than 100 ° C;
• A surface preparation treatment is carried out either by chemical treatment comprising a degreasing operation followed by pickling and rinsing, or by mechanical treatment by abrasion, preferably by fine brushing or polishing;
• A stabilization treatment is carried out on the active contact layer on the surface of said alloy for 20 to 200 hours in a ventilated atmosphere with a humidity level of between 40 and 60% and a temperature kept constant at a value of between 15 and 25. ° C, preserving said part from any contact.