Part containing an aluminum substrate with a high copper content

Abstract

Title: Part comprising a high-copper aluminum substrate. The invention relates to a part comprising a high-copper aluminum substrate with a copper content strictly greater than 0.1%, in particular 0.3%, in particular 0.5%, with an inert barrier layer on the surface of this substrate configured to protect the substrate against corrosion, particularly in the presence of salt water. Figure for the abstract: Fig. 1

Description

Title of the invention: Part comprising a high-copper aluminum substrate

[0001] The present invention relates to parts comprising an aluminum substrate with a high copper content.

[0002] Nowadays, we seek to reduce the CO2 impact in manufactured products.

[0003] The use of high-copper aluminum reduces the CO2 footprint compared, for example, to aluminum alloys. However, the disadvantage of high-copper aluminum is its greater susceptibility to corrosion. This corrosion can lead to problems such as sealing issues.

[0004] When in contact with salt water, the high copper content in cast aluminum is exposed to salt penetration and is likely to cause corrosion of the aluminum. There is a very high potential difference between aluminum and copper, creating a galvanic cell effect between the aluminum and the copper aggregates. The more copper there is, the greater the galvanic corrosion risk, and the more necessary it is to prevent contact between aluminum with a high copper content and salt water.

[0005] In the case of a housing made by assembling several cast aluminum parts, including a sheet metal cover or a cast aluminum cover, corrosion can migrate inside the housing, compromising the product's sealing. This can result in the presence of salts inside the housing, which can be critical in electronic applications where sealing must be effective against, for example, salts that could affect electronic components and cause component failures.

[0006] To protect aluminum parts with a high copper content from corrosion, a metallic layer of nickel, also called Ni, or nickel phosphorus, also called NiP, is deposited on these aluminum plates. An interface zone between the aluminum and the Ni or NiP layer is then exposed to a liquid that leads to galvanic corrosion of the aluminum. A sacrificial layer of Ni or NiP is thus created on the surface of this interface zone. However, its formation, when very close to the sealing zone between two aluminum parts, can lead to a loss of sealing.

[0007] The deposition of Nickel layers which is electrolytic, and the deposition of NiP layers which is chemical, are two types of depositions carried out in complex polluting chemical baths which treat the whole of a housing.

[0008] Furthermore, to restrict the deposit area, it is necessary to carry out complex operations where areas are masked in order to spare them.

[0009] The same surface treatment problems are encountered in the anodizing of aluminum, where the aluminum surface is oxidized by electrolysis in a bath. Furthermore, anodizing is significantly disrupted by a high proportion of copper in the aluminum, as copper resists the anodizing process, contributing to the creation of inhomogeneous anodized layers.

[0010] The invention aims to reduce the CO2 footprint during the manufacture of aluminium parts with a high copper content while limiting corrosion and loss of sealing during their assembly.

[0011] The invention relates to a part comprising an aluminium substrate with a high copper content with a copper content strictly greater than 0.1%, in particular greater than or equal to 0.3%, in particular greater than or equal to 0.5%, with an inert barrier layer on the surface of this substrate configured to protect the substrate against corrosion, in particular in the presence of salt water.

[0012] The term “copper content” means a mass percentage of copper relative to the total mass of the aluminum substrate.

[0013] The term "corrosion" refers to galvanic corrosion caused by a potential difference between copper and aluminum in contact with salt water. This can be described as the formation of a galvanic cell. The corrosion can be, for example, pitting or crevice corrosion on the substrate.

[0014] The term "barrier layer" refers to a protective layer configured to act as a barrier against corrosion, thereby preventing a galvanic cell effect with aluminum containing a high amount of copper. This barrier layer is made of a relatively inert material. The barrier layer is not a sacrificial layer.

[0015] By adding, on the high copper aluminum substrate, a barrier layer configured to block the intrusion of corrosive agents such as salts, the anti-corrosion properties of the substrate are greatly improved.

[0016] According to one aspect of the invention, the high copper content aluminium substrate can be an aluminium of grade 47100, 46100, 46000.

[0017] According to one aspect of the invention, the substrate comprising an aluminum with a high copper content has a copper content between 0.7% and 2.6%, for example 0.9%.

[0018] According to one aspect of the invention, the barrier layer can be an organosilicon layer with SiOx chains where x is an integer between 1 and 4, and optionally polymer chains.

[0019] According to one aspect of the invention, the barrier layer has a layer thickness of between 0.5 pm and 2 pm, deposited on the substrate.

[0020] Thus, the barrier layer is deposited as a homogeneous and regular layer, free from cracks, to prevent the penetration of salt water which can cause corrosion of the substrate. In other words, the thickness of the barrier layer, between 0.5 µm and 2 µm, improves the anti-corrosion properties of said barrier layer deposited on the substrate.

[0021] According to one aspect of the invention, the substrate has a surface with a maximum arithmetic mean roughness of 0.6 pm and a maximum depth mean roughness of 5.5 pm so as to have a homogeneous surface state for the deposition of the barrier layer.

[0022] In other words, the surface condition, particularly the roughness of the substrate surface containing aluminum with a high copper content, is important for achieving corrosion protection after the barrier layer is deposited. The smoother and freer the substrate surface, the more homogeneous the barrier layer, free of cracks or weaknesses. This barrier layer is more effective and optimal when its thickness is uniform and it has no weaknesses or defects that could be points of corrosion.

[0023] According to one aspect of the invention, the thickness of the high copper aluminum substrate can be between 5 mm and 15 cm.

[0024] The invention also relates to an assembly comprising at least two parts, at least one of which is a part described above being assembled with another part of the assembly by forming a junction interface between these two parts.

[0025] According to one aspect of the invention, only one of the two parts of the assembly is a part comprising a high copper aluminium substrate with a copper content strictly greater than 0.1% with, on the surface of this substrate, an inert barrier layer configured to protect the substrate against corrosion, particularly in the presence of salt water.

[0026] According to another aspect of the invention, the two parts of the assembly are parts comprising an aluminum substrate with a high copper content and on the surface of this substrate an inert barrier layer configured to protect the substrate against corrosion, particularly in the presence of salt water.

[0027] According to one aspect of the invention, the joining interface between the two parts of the assembly comprises an adhesive or a sealing gasket.

[0028] The present invention applies, for example, to vehicle on-board chargers or to electronic devices, such as inverters. More generally, the invention applies to electronic applications that use a housing made from aluminum, particularly by the die-casting process.

[0029] According to one aspect of the invention, the assembly is an electronic device, in particular an electric charger or an inverter, comprising a housing provided with a receptacle formed by the part comprising an aluminum substrate with a high copper content and on the surface of this substrate an inert barrier layer configured to protect the substrate against corrosion, in particular in the presence of salt water.

[0030] According to one aspect of the invention, the housing includes a cover to close the receptacle, this cover may or may not be made by a part comprising an aluminum substrate with a high copper content and on the surface of this substrate an inert barrier layer configured to protect the substrate against corrosion, particularly in the presence of salt water.

[0031] According to one aspect of the invention, the glue can be a polymer, for example a silicone glue.

[0032] According to one aspect of the invention, the barrier layer is deposited on at least the junction interface.

[0033] According to one aspect of the invention, the barrier layer is deposited on the junction interface and at least on an area adjacent to this junction interface.

[0034] According to one aspect of the invention, the barrier layer makes it possible to protect the interface of the junction of the two parts against corrosion and to promote their sealing.

[0035] By the term "sealing" it is understood that the fluid responsible for corrosion, for example salt water, does not seep in and does not diffuse through the interface of the junction between the two parts.

[0036] The invention also relates to a method for manufacturing a part comprising an aluminum substrate with a high copper content, with a copper content strictly greater than 0.1%, the method comprising the following steps: - surface treatment of the substrate to obtain a homogeneous surface finish, - deposition of the barrier layer on the substrate over at least one region of the substrate.

[0037] According to one aspect of the invention, the deposition of the barrier layer on the substrate is done by plasma.

[0038] According to one aspect of the invention, the substrate has a copper content of between 0.7% and 2.6%, preferably 0.9%.

[0039] According to one aspect of the invention, the barrier layer can be an organosilicon layer with SiOx chains where x is an integer between 1 and 4, and optionally polymer chains.

[0040] Advantageously, the CO2 emission rate associated with the deposition of the barrier layer is low compared to the relative gain of using the substrate containing aluminum with a high copper content.

[0041] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0042] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0043] [Fig-1] The [Fig.1] is a schematic representation of a housing according to the invention;

[0044] [Fig.2] [Fig.2] is a scanning electron microscope image capture of the surface of a housing receptacle with a barrier layer according to the invention, after treatment with severe salt spray, with a magnification X23;

[0045] [Fig.3] Fig.3 includes two scanning electron microscope image captures of the surface of a housing receptacle without a barrier layer, after treatment with severe salt spray, with a magnification of X23 for Figure 3A and a magnification of X450 for Figure 3B.

[0046] We will now give an example according to the invention. [Fig. 1] shows an aluminum inverter housing 100, formed of a receptacle 10 which is closed by a cover 50. The cover 50 is formed of an aluminum plate with a copper content between 0.05% and 0.2%. The receptacle 10 is formed of an aluminum substrate with a copper content strictly greater than 0.1%. The receptacle 10 has a smooth surface finish with an arithmetic mean roughness Ra = 0.6 pm and an arithmetic mean roughness Rz = 5.5 pm.

[0047] For one of the housings 100 (called +SiOx), prior to the assembly of the receptacle 10 with the lid 50, a barrier layer 1 is deposited on the receptacle 10. This barrier layer 1 is composed of an AntiCorr® coating comprising polymer chains and organosilicon compounds, supplied with the PlasmaPlus® system from Plasmatreat. This deposition is carried out by plasma. The average thickness of the barrier layer 1 is 400 nm.

[0048] No barrier layer 1 deposition is made on the receptacle 10 of the other case 100 (called -SiOx).

[0049] A severe salt spray attenuation test (SWAAT) is performed according to ASTM G85 Appendix 3. This test comprises a 2-hour cycle. Initially, the 100 closed cases are sprayed for 30 minutes with a NaCl solution (42 g / l) at a pH of 2.9. Then the 100 cases are exposed for 1.5 hours to a humidity of 98%RH, a temperature of 49°C and a pH between 2.8 and 3.

[0050] The SWAAT test is carried out for 500 cycles on the housing 100 (+SiOx) whose receptacle 10 is covered by barrier layer 1 and on the housing 100 (-SiOx) whose receptacle 10 is not covered by barrier layer 1.

[0051] Salt infiltration is analyzed after the SWAAT test has been carried out and the housings 100 have been opened, using surface images of the receptacles 10. These images are captured with a Hitachi SU510 scanning electron microscope (SEM) with magnifications of X23 and X450.

[0052] [Tables 1] Housing Material, Lid Material, Receptacle Material, Barrier Layer + SiOx Aluminum 0.05% <Cu< 0,2% Aluminium Cu > 0.1% yes -SiOx Aluminum 0.05% <Cu< 0,2% Aluminium Cu > 0.1% no

[0053] Figure 2 shows the surface of the receptacle 10 covered with barrier layer 1 of the housing 100 (+SiOx). The aluminum surface has a barrier layer 1 that is smooth and uniform. The aluminum surface is free from corrosion.

[0054] Figure 3A shows the surface of the receptacle 10 without the barrier layer 1 of the housing (-SiOx). The surface of the receptacle 10 has a corroded aluminum layer 2. Figure 3B shows a magnification of an area X of this surface where a corrosion path 3 caused by salt water can be seen.

[0055] Thus, it is observed that the presence of the barrier layer 1 on the receptacle 10 of the housing 100 (+SiOx) prevents the corrosion of the aluminum with a high copper content, whereas the absence of this barrier layer 1 on the receptacle 10 of the housing 100 (-SiOx) promotes the corrosion of the aluminum with a high copper content.

Claims

Demands

1. Part comprising a high copper aluminium substrate with a copper content strictly greater than 0.1%, in particular greater than or equal to 0.3%, in particular greater than or equal to 0.5%, with an inert barrier layer on the surface of this substrate configured to protect the substrate against corrosion, in particular in the presence of salt water.

2. Part according to claim 1, wherein the barrier layer is an organosilicon layer with SiOx chains where x is between 1 and 4 and optionally polymer chains.

3. Part according to any one of the preceding claims, wherein the barrier layer has a layer thickness of between 0.5 pm and 2 pm deposited on the substrate.

4. Part according to any one of the preceding claims, wherein the substrate has a surface with a maximum arithmetic mean roughness of 0.6 pm and a maximum depth mean roughness of 5.5 pm so as to have a homogeneous surface state for the deposition of the barrier layer.

5. Assembly comprising at least two parts, at least one of the two parts being according to one of the preceding claims, this part being assembled with another part of the assembly by forming a joining interface between these two parts.

6. Assembly according to claim 5, wherein only one of the two pieces of the assembly is a piece comprising a high copper aluminium substrate with a copper content strictly greater than 0.1% with on the surface of this substrate an inert barrier layer configured to protect the substrate against corrosion, particularly in the presence of salt water.

7. Assembly according to any one of claims 5 or 6, wherein the barrier layer is deposited on at least the junction interface.

8. Assembly according to any one of claims 5 or 6, wherein the barrier layer is deposited on the junction interface and at least on an area adjacent to this junction interface.

9. A method for manufacturing a part comprising a high-copper aluminum substrate with a copper content strictly greater than 0.1%, the method comprising the following steps: 8 - surface treatment of the substrate to obtain a homogeneous surface state, - deposition of the barrier layer on the substrate on at least one region of the substrate.

10. A manufacturing method according to claim 9, wherein the step of depositing the barrier layer on the substrate is done by plasma.

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