1. An anti-corrosion coating comprising an aluminum alloy comprising 0.03 wt.% to 0.5 wt.% tin.

2. The corrosion protection coating of claim 1, wherein the aluminum alloy comprises 0.045-0.35 wt.% tin, preferably 0.1-0.3 wt.% tin, preferably 0.13-0.19 wt.% tin, and particularly preferably 0.13-0.15 wt.% tin.

3. The corrosion protection coating of claim 1, wherein the aluminum alloy consists of 0.03-0.5 wt.% tin and the balance aluminum and unavoidable impurities.

4. The corrosion protection coating according to claim 1, wherein the aluminum alloy consists of 0.045-0.35 wt.% tin, preferably 0.1-0.3 wt.% tin, preferably 0.13-0.19 wt.% tin, and particularly preferably 0.13-0.15 wt.% tin, and the balance aluminum and unavoidable impurities.

5. Anti-corrosion coating according to one of claims 1 to 4, wherein the anti-corrosion coating has a thickness of 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 5 to 25 μm and particularly preferably 7 to 20 μm.

6. The corrosion protection coating according to any one of claims 1 to 5, wherein the corrosion protection coating is adapted to be applied to a substrate by means of a vacuum deposition process.

7. A coated object which is at least partially manufactured from a material and which is at least partially coated with an anti-corrosion coating according to one of claims 1 to 6.

8. The coated object of claim 7, wherein the material is ferrous.

9. A coated object according to claim 7 or 8, wherein the material is steel.

10. Coated object according to one of claims 7 to 9, wherein the substrate is completely coated with the corrosion protection coating.

11. Coated object according to one of claims 6 to 10, wherein the corrosion protection coating is applied by means of a sputtering technique or an IVD (ion vapour deposition) method.

12. A method for manufacturing a coated object according to one of claims 7 to 11, having the steps of:

providing an object, and

at least partially, preferably completely, coating the object with an anti-corrosion coating according to one of claims 1 to 6.

13. The method according to claim 12, wherein the substrate is coated with the corrosion protection coating by means of a sputtering technique, preferably by means of a co-sputtering technique.

14. Use of an aluminium alloy comprising 0.03-0.5% by weight of tin, preferably 0.045-0.35% by weight of tin, more preferably 0.1-0.3% by weight of tin, still more preferably 0.13-0.19% by weight of tin, and particularly preferably 0.13-0.15% by weight of tin, for the manufacture of an anti-corrosion coating for an iron-containing object.

15. Vehicle, preferably aircraft, comprising an anti-corrosion coating according to one of claims 1 to 6 or a coated object according to one of claims 7 to 11.

Background

Since decades ago, cadmium layers have been used in aerospace for various applications and in particular for components made of steel, since cadmium has good corrosion resistance and a sacrificial anodic protection for various substrates (in particular ferrous substrates, such as steel), and furthermore has galvanic compatibility with aircraft fuselages made of aluminum alloys, high electrical conductivity, good weldability and brazeability and also a certain lubricating effect. Generally, the connecting elements, structural components or electrical components (e.g. plugs or the like) may have a cadmium coating. Electrolytically deposited cadmium layers with subsequent passivation layers based on cr (vi) are particularly commonly used here. However, the use of cadmium may be limited by future legislation.

No coating is currently known to achieve the good technical properties of cadmium for all-aircraft use. In general, the sacrificial anodic protection of cadmium, particularly on ferrous substrates (e.g., steel), is a primary function that must also be fulfilled by alternative coatings. In the last few years, coatings have been studied in place of cadmium, these coatings comprising in particular zinc and aluminium based alloys or metal-filled organic or inorganic coatings, such as zinc flake coatings or aluminium-pigmented (aluminium-pixentiierte) coatings. Here, electrolytically deposited zinc-nickel (ZnNi) layers with a nickel content of about 10% to 15% have proved to be the most promising for the development. However, it is not possible to cover all applications in aeronautics with a ZnNi layer. Furthermore, it is advantageous to limit the use of nickel compounds as much as possible.

It is known to apply aluminum coatings to components by means of Ion Vapor Deposition (IVD) to replace cadmium. However, such coatings are subject to a strong self-passivation of the aluminum, so that all relevant components cannot be coated with IVD aluminum. PVD processes and especially magnetron sputtering of aluminium alloys onto surfaces are known. However, columnar growth of the layer may lead to adverse effects, as this leads to high porosity and thus to increased losses. Electrodeposition methods are also known.

Disclosure of Invention

The object of the present invention is to provide an anti-corrosion coating for objects, in particular for metal objects, for example iron-containing objects or objects made of steel, which serves as a sacrificial anode for anti-corrosion protection, has particularly low losses, can be applied cost-effectively and in a small layer thickness, and furthermore contains no cadmium. The object of the invention is also to provide an object coated with the corrosion protection coating and a method for producing such an object coated with the corrosion protection coating.

This object is achieved by an anti-corrosion coating having the features of independent claim 1 and by a coated object having the features of independent claim 6 and by a method having the features of independent claim 12. Advantageous embodiments and developments emerge from the dependent claims and the following description.

Drawings

FIG. 1: for showing various uncoated and coated substrates after immersion in Harrison's solution (0.05% NaCl + 0.35% (NH)₄)₂SO₄) Graph of the current measured after the second three hours.

FIG. 2: for showing various uncoated and coated substrates after immersion in Harrison's solution (0.05% NaCl + 0.35% (NH)₄)₂SO₄) Mixed potential measured after medium three hours.

Detailed Description

An anticorrosion coating is provided, the anticorrosion coating comprising an aluminum alloy comprising 0.03 wt.% to 0.5 wt.% tin (Sn). In a preferred embodiment, the corrosion protection coating consists of an aluminum alloy as described herein and in the claims.

The use of aluminium alloys in the corrosion protection coating is advantageous because aluminium has a low electrode potential. For example, the electrode potential of aluminum is typically lower than that of iron-containing materials (e.g., steel), which are potential and preferred substrates that can be coated with corrosion-resistant coatings. The coating serves as a sacrificial anode and protects the substrate coated with the coating or the object coated with the coating as a cathode. As a result, the coating gradually dissolves and thereby protects the underlying substrate, e.g., iron-containing material (e.g., steel). The degree of dissolution of the aluminum alloy can be minimized by the appropriate composition of the aluminum alloy, so that the corrosion protection effect of the corrosion protection coating is maintained for a sufficiently long time.

However, pure aluminum coatings tend to passivate due to the formation of an aluminum oxide layer on the surface of the aluminum coating. The aluminum oxide layer protects the aluminum located thereunder, thereby protecting aluminum, which is not inert by itself due to the low electrode potential, from dissolution. In order to prevent excessive passivation of the aluminum or at least to inhibit passivation of the aluminum to the extent that it is made available for cathodic protection of objects coated with aluminum, the aluminum alloy in the corrosion protection coating according to the invention comprises tin (Sn) as another alloying component. At the same time, however, a certain degree of passivation of the aluminum alloy is also desirable, since this prevents the corrosion protection coating from being consumed too quickly and thus contributes to a longer durability of the corrosion protection coating.

The aluminium alloy in the corrosion protection coating according to the invention comprises 0.03 wt. -% to 0.5 wt. -% tin (Sn) relative to the total weight of the aluminium alloy. Preferably, the aluminium alloy in the corrosion protection coating according to the invention comprises 0.045-0.35 wt.% tin, for example 0.1-0.3 wt.% tin or 0.1-0.2 wt.% tin, respectively, relative to the total weight of the aluminium alloy. More preferably, the aluminium alloy in the corrosion protection coating according to the invention comprises 0.13-0.19 wt.% tin, such as 0.13-0.17 wt.% tin or 0.13-0.16 wt.% tin, respectively, relative to the total weight of the aluminium alloy. Particularly preferably, the aluminium alloy in the corrosion protection coating according to the invention comprises 0.13-0.15 wt.% tin relative to the total weight of the aluminium alloy.

Surprisingly it has been demonstrated that: the use of a given amount of tin in the aluminum alloy has achieved a complete passivation of the aluminum which is thereby prevented or sufficiently strongly suppressed. At the same time, it has also surprisingly been demonstrated that: this amount of tin also ensures that the corrosion of the aluminum coating does not proceed too quickly and thus the corrosion protection of the aluminum alloy of the invention on a substrate, for example a ferrous substrate (e.g. steel), is maintained for a sufficiently long time. These properties and in particular the prevention of passivation can be ensured here under the conditions which occur in applications at aircraft, in particular under aeronautical conditions (i.e. in the absolute pressure range of about 0.25 bar to about 1 bar and in the temperature range of about-50 ℃ to about 60 ℃).

The aluminium alloy in the corrosion protection coating according to the invention may comprise further alloy components. These further alloy components are preferably selected from: manganese (Mn), silicon (Si), zinc (Zn), gallium (Ga), magnesium (Mg), chromium (Cr), iron (Fe), titanium (Ti), indium (In), bismuth (Bi), selenium (Se), copper (Cu), zirconium (Zr), antimony (Sb), cobalt (Co), and combinations thereof. These elements can be used to set the electrochemical potential of the obtained aluminium alloy, these elements being close to that of cadmium, since each of these elements is in principle suitable to shift the electrochemical potential of pure aluminium towards a more electronegative value. Furthermore, by adding these additional alloy components, a more uniform corrosion protection coating can also be formed, which can, for example, achieve a more uniform consumption of the sacrificial anode. For this purpose, manganese (Mn), zinc (Zn) and magnesium (Mg) are particularly advantageously used. Aluminium alloys with a certain manganese proportion are distinguished by particularly high corrosion resistance. Silicon can be used to lower the melting point of the aluminum alloy and thus can improve the process of coating a substrate with the aluminum alloy of the present invention. Zinc generally improves the corrosion protection characteristics of the aluminum alloy. Particularly advantageously and preferably, zinc (Zn) is used as an additional alloying component of the aluminum alloy.

The aluminium alloy of the anti-corrosion coating according to the invention may comprise the above-mentioned additional alloying constituents manganese (Mn), silicon (Si), gallium (Ga), magnesium (Mg), chromium (Cr), iron (Fe), titanium (Ti), indium (In), bismuth (Bi), selenium (Se), copper (Cu), zirconium (Zr), antimony (Sb), cobalt (Co), for example In an amount of up to 2 wt. -%, preferably 1 wt. -%, more preferably 0.5 wt. -%, for example In an amount of 0.01 wt. -% to 0.3 wt. -% or 0.05 wt. -% to 0.2 wt. -%, respectively, relative to the total weight of the aluminium alloy.

Instead of or In addition to the additional alloying constituents manganese (Mn), silicon (Si), gallium (Ga), magnesium (Mg), chromium (Cr), iron (Fe), titanium (Ti), indium (In), bismuth (Bi), selenium (Se), copper (Cu), zirconium (Zr), antimony (Sb), cobalt (Co) In the amount described herein, the aluminium alloy In the corrosion protection coating according to the invention may comprise the additional alloying constituent zinc (Zn) mentioned above In an amount of up to 10 wt.%, preferably up to 7 wt.%, for example 1 to 5 wt.%, preferably 2 to 4 wt.%, respectively, relative to the total weight of the aluminium alloy.

In a preferred embodiment, the aluminum alloy in the corrosion protection coating according to the invention comprises zinc (Zn) as an additional alloying component only in an amount of up to 10 wt. -%, preferably up to 7 wt. -%, for example 1 to 5 wt. -%, preferably 2 to 4 wt. -%, respectively relative to the total weight of the aluminum alloy.

The total amount of additional alloying constituents in the aluminium alloy in the corrosion protection coating according to the invention may be up to 20 wt. -%, preferably up to 10 wt. -%, more preferably up to 7 wt. -%, e.g. 1 to 5 wt. -%, preferably 2 to 4 wt. -%, respectively relative to the total weight of the aluminium alloy.

The aluminum alloy in the corrosion prevention coating according to the present invention includes aluminum and inevitable impurities as a main component or a balance. Unavoidable impurities may for example be included in the aluminum alloy in a total amount of up to 0.5 wt.%, such as up to 0.1 wt.% or up to 0.05 wt.% or up to 0.01 wt.%, or preferably up to 0.001 wt.%, respectively, relative to the total weight of the aluminum alloy.

The aluminium alloy in the corrosion protection coating according to the invention preferably does not comprise cadmium and particularly preferably does not comprise cadmium at all, i.e. does not comprise cadmium as an unavoidable impurity either.

In one embodiment, the aluminium alloy in the corrosion protection coating according to the invention consists of: tin (Sn) in an amount described herein; optionally an additional alloying component selected from the group consisting of manganese (Mn), silicon (Si), zinc (Zn), gallium (Ga), magnesium (Mg), chromium (Cr), iron (Fe), titanium (Ti), indium (In), bismuth (Bi), selenium (Se), copper (Cu), zirconium (Zr), antimony (Sb), cobalt (Co), and combinations thereof, In amounts described herein; and aluminum and inevitable impurities as a main component or the balance in the amounts described herein.

In one embodiment, the aluminium alloy in the corrosion protection coating according to the invention consists of: tin (Sn) in an amount described herein; optionally an additional alloying component selected from the group consisting of manganese (Mn), silicon (Si), zinc (Zn), magnesium (Mg), and combinations thereof, in an amount described herein; and aluminum and inevitable impurities as a main component or the balance in the amounts described herein.

In one embodiment, the aluminium alloy in the corrosion protection coating according to the invention consists of: tin (Sn) and zinc (Zn), respectively, in the amounts described herein; optionally an additional alloy component selected from manganese (Mn), silicon (Si), magnesium (Mg), and combinations thereof, in an amount described herein; and aluminum and inevitable impurities as a main component or the balance in the amounts described herein.

In one embodiment, the aluminium alloy in the corrosion protection coating according to the invention consists of: tin (Sn) in an amount described herein; zinc (Zn) as an additional alloying component, optionally in amounts described herein; and aluminum and inevitable impurities as a main component or the balance in the amounts described herein.

In another preferred embodiment, the aluminum alloy consists of: 0.03-0.5% by weight of tin, preferably 0.045-0.35% by weight of tin, for example 0.1-0.3% by weight of tin or 0.1-0.2% by weight of tin, respectively, relative to the total weight of the aluminum alloy; and the balance aluminum (Al) and inevitable impurities. Unavoidable impurities may be included in the aluminum alloy in the amounts described herein.

In a particularly preferred embodiment, the aluminum alloy consists of: 0.13-0.19 wt% tin, such as 0.13-0.15 wt% tin, respectively, relative to the total weight of the aluminum alloy; and the balance aluminum (Al) and inevitable impurities. Unavoidable impurities may be included in the aluminum alloy in the amounts described herein.

The aluminium alloy in the corrosion protection coating according to the invention has the following advantages: the aluminum alloys do not exhibit excessive passivation that is detrimental to use as sacrificial anodes and, in addition, have electrochemical properties similar to those of currently common cadmium-containing protective layers.

The corrosion protection coating of the invention preferably has a thickness of 0.1 μm to 100 μm, more preferably 1 μm to 50 μm, still more preferably 5 μm to 25 μm and particularly preferably 7 μm to 20 μm. For example, the corrosion protection coating of the present invention may have a thickness of 10 μm to 20 μm or 7 μm to 10 μm. Such a thickness of the corrosion protection coating has proven to be advantageous, since on the one hand the total requirement of the corrosion protection coating can be kept small, and on the other hand a good and sufficiently long-lasting corrosion protection can be achieved, and furthermore the corrosion protection coating does not have an adverse effect on the total weight of the coated object.

Furthermore, the corrosion protection coating of the invention is preferably suitable for being applied to a substrate, for example an iron-containing object (e.g. steel), by means of a vacuum deposition process. For example, the corrosion protection coating according to the invention is suitable for being applied by means of sputtering techniques or IVD (ion vapour deposition) methods. The advantage of these application techniques is that a particularly uniform and homogeneous and, in addition, very thin coating application is thereby possible. Both sputtering techniques and IVD methods are well known to those skilled in the art.

Furthermore, a coated object is proposed, wherein the coated object is at least partially manufactured from a material and is at least partially coated with an anti-corrosion coating as described herein and in the claims. The object is also synonymously referred to herein as a substrate. Preferably, the object is manufactured from only one material and/or is completely coated with the corrosion protection coating according to the invention. It is particularly preferred that the object is manufactured from only one material and is completely coated with the corrosion protection coating according to the invention.

The materials that can be coated with the corrosion protection coating according to the present invention are not limited and can include all possible metals or alloys, including, for example, iron and iron alloys, steel, titanium and titanium alloys, copper and copper alloys, nickel and nickel alloys, aluminum and aluminum alloys, and the like.

In a preferred embodiment according to the invention, the object which is at least partially, preferably completely, coated with the corrosion protection coating according to the invention is manufactured from an iron-containing material. For example, the material may be: iron, such as cast iron or wrought iron; or any known ferrous alloy, such as a ferrous alloy qualified for aerospace use.

In a particularly preferred embodiment according to the invention, the iron-containing material of which the object is manufactured that is at least partially, preferably completely, coated with the corrosion protection coating according to the invention is steel. For example, all commercially available steels can be considered. Preferably steels qualified for use in aerospace, such as steels from the group of materials for "aerospace specialty steels" or alloys known to those skilled in the art under the names 1.7734, 1.6604, 1.6944, 1.7214, 1.1174, 35NCD16, 15-5PH, 17-4PH, 17-7PH, 13-8PH, 1.4544, 1.4944, 1.4044, 1.4304, 1.4541, 1.4544.

1.7734 steel is particularly preferred here. 1.7734 steel contains 0.12-0.18 wt.% carbon (C), 0.8-1.1 wt.% manganese (Mn), 0.20 wt.% or less silicon (Si), 0.02 wt.% phosphorus (P), 0.015 wt.% sulfur (S), 1.25-1.5 wt.% chromium (Cr), 0.8-1.0 wt.% molybdenum (Mo), and 0.20-0.30 wt.% vanadium (V).

The corrosion protection coating according to the invention on the coated object according to the invention can have a thickness of 0.1 μm to 100 μm, preferably 1 μm to 50 μm, more preferably 5 μm to 25 μm, and particularly preferably 7 μm to 20 μm, for example 10 μm to 20 μm or 7 μm to 10 μm.

In a preferred embodiment, the corrosion protection coating according to the invention is applied to the coated object according to the invention by means of a sputtering technique or an IVD (ion vapour deposition) method.

Another subject of the invention is a method for manufacturing a coated object as described herein and in the claims. The method according to the invention comprises the following steps: providing an object; and at least partially, preferably completely, coating the substrate with an anti-corrosion coating as described herein and in the claims, and preferably with an aluminium alloy as described herein and in the claims.

In a preferred embodiment of the method according to the invention, the coating of the substrate, preferably an object made of an iron-containing alloy (e.g. steel), with the corrosion protection coating can be carried out by means of a sputtering technique, for example using a magnetron, preferably by means of a co-sputtering technique. Such application techniques are well known to those skilled in the art and need not be described in detail. It is also known to the person skilled in the art that in the so-called co-sputtering technique, the substrate is sputtered simultaneously in a specific mass ratio using two sputtering targets formed from two different alloys or pure substances or pure metals. This enables the application of a defined composition or alloy with the use of two different sputter targets. The advantage of this technique is that it is thereby possible to use, for example, easily commercially available sputtering targets.

Another subject matter of the invention is the use of an aluminum alloy comprising from 0.03 to 0.5% by weight of tin, preferably from 0.1 to 0.35% by weight of tin, more preferably from 0.13 to 0.19% by weight of tin, and particularly preferably from 0.13 to 0.15% by weight of tin, for producing an anticorrosion coating for iron-containing objects. Preferred here in the use according to the invention are the aluminium alloys as described herein and in the claims. It is furthermore preferred that the ferrous object is steel. The ferrous object may be a ferrous object as described herein.

Another subject of the invention is a vehicle, preferably an aircraft, comprising an anti-corrosion coating as described herein and in the claims or a coated object as described herein or in the claims.

For aeronautical applications in particular, for example, the galvanic compatibility of the coated connecting elements with respect to the material of the components to be connected is a very important prerequisite. The coated object can be, for example, a connecting element for fastening to a component comprising an aluminum alloy. This component may be, for example, a part of an aircraft fuselage made of an aluminum alloy.

Preferably, the object or substrate coated with the corrosion protection coating is an iron-containing material, such as steel. By means of the cadmium-free corrosion protection coating according to the invention, corrosion protection can be provided in particular at different components of an aircraft. These components include fastening elements, prongs, bushings, spacers and spacers, as well as a host of other elements.

It is additionally pointed out that characteristics or steps which have been described with reference to one of the above embodiments can also be used in combination with other characteristics or steps of other above embodiments.

Examples

Further features, advantages and possibilities of application of the invention emerge from the following exemplary embodiments. However, these examples should not limit the scope of the present invention, but are merely intended to better illustrate various subject matters and advantages of the present invention.

Example 1:

silicon wafers were coated with various aluminum alloys by magnetron sputtering. Here, the co-sputtering technique may be used in the case of using pure aluminum and Al1Sn as the sputtering target. This means that the substrate is sputtered simultaneously with two targets formed of pure aluminum and Al1Sn at different mass ratios.

The aluminum alloys were applied as pure Al1Sn and at the effective ratio (or sputtering ratio) of the sputtering target, Al1 Sn-aluminum (100:100), Al1 Sn-aluminum (50:100), Al1 Sn-aluminum (Al) (25:100), Al1 Sn-aluminum (16:100), Al1 Sn-aluminum (9:100), and Al1 Sn-aluminum (5: 100). For example, Al1Sn-Al (16:100) means that the Al1Sn alloy and aluminum (Al) are applied by co-sputtering at a sputtering ratio of 16 to 100. This corresponds to the amount of tin (Sn) theoretically contained in the layer (in weight%): 0.5 wt% Sn for Al1Sn-Al (100: 100); 0.33 wt% Sn for Al1Sn-Al (50: 100); 0.20 wt% Sn for Al1Sn-Al (25: 100); 0.138 wt% Sn for Al1Sn-Al (16: 100); 0.083 wt% Sn for Al1Sn-Al (9: 100); and 0.048 wt.% Sn for Al1Sn-Al (5: 100).

After immersion in Harrison's solution (0.05% NaCl + 0.35% (NH)₄)₂SO₄) The current was measured after three hours between the steel (1.7734.5) and various coatings formed of aluminum alloys on silicon wafers. The Harrison solution is a typical solution used in corrosion protection testing. The surface area of the steel was 0.01cm²And the surface area of the coating layer formed of the aluminum alloy was 0.5cm². An aluminum alloy on a silicon wafer was produced as in example 1. Samples with a conventional cadmium-based corrosion protection coating (Cd + chromium coating) and samples with a layer formed exclusively from aluminum (Al) were additionally examined.

Fig. 1 (fig. 1) shows the measured current, which is a measure of galvanic corrosion, for various uncoated and coated substrates. Al1Sn and Al1Sn-Al (50:100) coatings showed similar and very high galvanic corrosion. This can lead to defects or more active dissolution after a shorter time. Al1Sn-Al (100:100) and Al1Sn-Al (25:100) have lower currents. Cd (CrVI), Al1Sn-Al (5:100) and Al1Sn-Al (9:100) have similar currents. Al1Sn-Al (16:100) has a slightly elevated current compared to Cd (Cr (VI). in IVD Al, compacted or not by shot blasting with glass spheres, the current is very low the intensity of the current is an indication of the corresponding rate of dissolution (i.e. consumption) of the sacrificial anode.

Example 2:

after immersion in Harrison's solution (0.05% NaCl + 0.35% (NH)₄)₂SO₄) The mixing potential between the steel (1.7734.5) and various coatings formed of aluminum alloys on silicon wafers was measured three hours later. The Harrison solution is a typical solution used in corrosion protection testing. An Ag/AgCl electrode was used as reference electrode. The surface area of the steel was 0.01cm²And the surface area of the coating layer formed of the aluminum alloy was 0.5cm². An aluminum alloy on a silicon wafer was produced as in example 1. Samples with a conventional cadmium-based corrosion protection coating (Cd + chromium coating) and samples with a layer formed exclusively from aluminum (Al) were additionally examined.

In order to effectively protect steel from corrosion in a Harrison solution, a potential having a value of about-730 mV Ag/AgCl, i.e., as measured for a common cadmium-containing corrosion protection coating (Cd (CrVI)), or greater, is required. For some applications, for example for effective corrosion protection in media with relatively high chloride concentrations (for example concentrations corresponding to the chloride concentration in seawater), mixed potential values of about-800 mV to-900 mV are required. A significantly higher mixing potential may in some applications achieve less desirable and unnecessary consumption of the sacrificial anode. The coating Al1Sn-Al (16:100) has a potential slightly higher than-800 mV and therefore has a mixed potential in the above-mentioned particularly desirable range.