EP4212647A1 - Method for coating an object with a multi-layer system comprising a nickel-phosphorus alloy - Google Patents

Abstract

A method for coating an object (1), wherein a surface (3) of the object (1) is at least partially coated with a coating (4) having a plurality of layers (5, 6, 7, 8, 9), wherein at least one layer (5, 6, 7, 8, 9) of the coating (4) consists of a nickel-phosphorus alloy and the proportion by mass of the phosphorus in the nickel-phosphorus alloy is at least 8%.

Description

The present invention relates to a method for coating an object with a multi-layer system. Such multi-layer systems are used, for example, as protection against corrosion and/or as decorative coatings. The method specified here is intended to be used in particular to produce or finish items from sanitary facilities, such as sanitary fittings, for example.

Multilayer systems based on electrochemically deposited metal layers can form corrosion products depending on the substrates used, layer materials, surrounding media and reaction conditions. The corrosion process also depends on geometric conditions (e.g. resulting in crevice corrosion) and mechanical influences (e.g. friction). The causes of corrosion can be varied and usually occur in combination. Electrochemical potential differences between the layers and base material defects (e.g. over-rolling) are mentioned here as examples.

Multilayer systems based on electrochemically deposited copper layers, nickel layers and chromium layers are known from the prior art. Here, different nickel layers are usually used as a multi-layer structure (semi-bright nickel, bright nickel, microporous nickel). The corrosion protection of the coated component is enhanced by subsequent chrome plating using an electrolyte containing chromium(VI) or chromium(III). Almost without exception, nickel layers are protected from rapid corrosion by a chromium layer. Damaged chromium coatings, but also those with incompletely closed, too thinly deposited or porous chromium layers lead after a short time (depending on the external conditions such as use, cleaning and surrounding media) to corrosion products that are visually unattractive and can lead to component failure in susceptible base materials.

The object of the invention is therefore to at least partially solve the problems described with reference to the prior art and in particular to specify a method for coating an object, in particular a sanitary object, with which both corrosion-inhibiting and decorative surfaces can be produced.

This object is achieved with a method according to the features of the independent patent claim. Further advantageous refinements of the invention are specified in the dependently formulated patent claims. It should be pointed out that the features listed individually in the dependently formulated patent claims can be combined with one another in any technologically meaningful manner and define further refinements of the invention. In addition, the features specified in the patent claims are specified and explained in more detail in the description, with further preferred configurations of the invention being presented.

In the method according to the invention for coating an object, a surface of the object is at least partially coated with a coating which has a plurality of layers, at least one layer of the coating consisting of a nickel-phosphorus alloy and a mass fraction of the phosphorus in the nickel - Phosphorus alloy is at least 8%.

The object is a substrate of any solid material that has a surface, but is preferably a sanitary object, such as a sanitary fitting, which is used in particular in connection with washbasins, sinks, showers and/or bathtubs. Such sanitary fittings are used in particular to remove water and can have actuators for a water temperature and/or a removal quantity of the water and are regularly used in a user's field of vision, so that on the one hand they should have a decorative surface and on the other hand they have to be effectively protected against corrosion. The surface of the article is at least partially or completely coated with a coating having a plurality of layers. The coating is a multi-layer system with which, in particular, decorative and/or functional surfaces can be produced. For this purpose, the individual layers are in particular formed sequentially and/or differ in their material composition. The individual layers preferably each have a layer thickness of 5 μm (microns) to 100 μm, preferably 8 μm to 80 μm. At least one of the plurality of layers of the coating is made of a nickel-phosphorus alloy, with a mass fraction of phosphorus in the nickel-phosphorus alloy being at least 8%. The mass fraction of phosphorus in the nickel-phosphorus alloy is preferably 8% to 14%, particularly preferably 10% to 12%. At least the nickel-phosphorus alloy layer is electrolytically deposited on the article. In addition, further layers or all layers of the coating can also be electrolytically deposited on the object. For this purpose, the object is in particular at least partially immersed in an electrolytic solution. The nickel-phosphorus alloy takes on the function of corrosion protection in the multi-layer system. Thus, the nickel-phosphorus alloy prevents corrosion of the object to a large extent and thus improves the corrosion properties, in particular of decorative coatings with a functional character. Damage, incompletely closed or porous coatings therefore lead to a significantly reduced corrosion process of the object, so that component failure and/or optical impairments are avoided.

In addition, it is advantageous if the object consists of copper, zinc, aluminum, steel, plastic or an alloy that includes copper, zinc or steel. Sanitary items carrying water, such as single-lever mixers and/or spouts, can be made at least partially of copper alloys (brass, bronze). Many attachments in the sanitary industry are made of die-cast zinc (e.g. lever for single-lever mixer, housing and/or spouts). Decorative zinc die-cast parts are also used in the automotive industry (e.g. inside door handles, key parts and/or console elements). Plastics are decoratively chrome-plated in the sanitary area for caps, push plates, rosettes and/or sleeves. ABS (acrylonitrile butadiene styrene or a blend of ABS/PC (PC = polycarbonate) is used here in various proportions. In the automotive industry, these materials are also used in a chrome-plated state, for example for decorative strips, radiator grilles and/or operating elements here PA (polyamide) or PA/GF (glass fiber reinforced polyamide) decoratively coated with chrome for certain applications (e.g. inside door handles). There are also numerous applications for decorative chrome-plated objects in other industries (household, white goods, etc.). Galvanically chrome-plated steel parts can also be found in numerous industries, such as the furniture industry (chair frames), the automotive industry (attachments, ashtrays, headrest holders, etc.) Aluminum is used in the sanitary industry, for example in the area of shower stalls and bathroom furniture.

Furthermore, it is advantageous if a first layer of the coating consists of copper or nickel. The first layer of the coating is the layer that is applied directly to the surface of the base body. The copper or nickel layer can be used to achieve the optical surface quality that is required for the production of high-quality chrome surfaces. Both metals can be electrolytically deposited to level surface defects (scratches, fine lines, pores) and significantly increase the gloss of the finished surfaces. Furthermore, the corrosion resistance of the base body can be increased and, in the case of plastic base bodies, the adhesion of the finished coating on the base body can be significantly improved by the ductility of copper.

Furthermore, it is advantageous if a further layer of the coating consists of bright nickel, semi-bright nickel or matt nickel. The further layer is in particular applied directly to the first layer.

Bright nickel layers are the most important of all nickel layers. Here, the decorative application is in the foreground. Bright nickel baths contain various brighteners. These cause a fine crystalline structure and thus a brilliant, high-gloss layer. Chromium deposited on this layer gives a high gloss finish which is well known and most common.

Semi-bright nickel layers are not deposited because of their low degree of gloss, but to meet special corrosion requirements. Semi-bright nickel layers should always be considered together with the bright nickel layer. They are usually deposited before the bright nickel layer and improve the corrosion properties of the composite due to their electrochemical potential.

Matt nickel layers are nickel layers which, due to their composition, have largely anti-glare properties. Certain substances are usually added to the electrolyte, which influence the nickel deposition. Since the purpose of these layers is to achieve a specific appearance, these layers are usually deposited just prior to chrome plating (often as a replacement for bright nickel layers). With these methods, the color and the matt impression can be controlled to a certain extent by the process parameters.

It is also advantageous if a third layer of the coating consists of the proposed nickel-phosphorus alloy. In particular, the third layer is applied directly to the second layer.

It is also advantageous if a fourth layer of the coating is a chromium layer. In particular, the fourth layer is applied directly to the third layer.

Furthermore, it is advantageous if the chromium layer is deposited from hexavalent or trivalent chromium electrolyte. A chromium layer made from a hexavalent chromium electrolyte is particularly corrosion-resistant and provides very good optical surface qualities. A chromium layer made of a trivalent chromium electrolyte is particularly suitable and preferred from the point of view of occupational safety and for environmental reasons.

In addition, it is advantageous if a fifth layer of the coating comprises at least one zirconium compound, one chromium compound or one titanium compound. Mixtures of these compounds are also possible in the fifth layer. In particular, the fifth layer is applied directly to the fourth layer. The purpose of this coating is to create a specific color. For example, red tones, gold tones or a stainless steel look can be realized on electroplated chrome layers with this. The composition of these layers determines the color achieved. These layers mostly consist of zirconium nitride (ZrN), titanium nitride (TiN) and/or chromium nitride (CrN) in different proportions.

Furthermore, it is advantageous if the fifth layer is produced by physical vapor deposition (PVD method).

The fifth layer is preferably produced from an amorphous carbon layer. The amorphous carbon layer is in particular a diamond-like carbon layer (DLC=“diamond-like carbon”).

According to the invention, at least the nickel-phosphorus alloy is preferably applied electrolytically. Compared to, for example, autocatalytic application, this method can be carried out much more quickly and is therefore more suitable for industrial large-scale production. In addition to the nickel-phosphorus alloy, other layers, such as the chromium layer, can also be applied electrolytically.

Another very special advantage of the invention is achieved when the chromium layer is applied directly to the nickel-phosphorus alloy. This particularly improves the corrosion resistance of the chrome layer. If, in addition, a chromium layer from a trivalent chromium electrolyte is applied electrolytically to the nickel-phosphorus alloy, particularly good corrosion resistance can also be achieved with this electrolyte, which is significantly better than previously known coatings of trivalent chromium. These advantages are achieved through the direct combination of the nickel-phosphorus alloy with the chromium layer applied to it. This combination can be used at different points within the framework of a layer structure according to the invention and can achieve the above-described positive technical effect there. The pairing of layers can thus advantageously also be used, for example, as the first and second layer or as the second and third layer of a layer structure.

Furthermore, it is advantageous if a brush structure is introduced into the coating. A brush structure is usually applied in conjunction with the PVD coating already mentioned. Resulting finishes are for example "brushed stainless steel" or "brushed nickel". Brushing is performed by pressing objects against rotating disks. These discs can be, for example, polishing rings with the appropriate polishing pastes, fiber brushes or sisal brushes. This step is carried out before the PVD coating or even before the chrome plating.

Fig. 1:

einen mit dem erfindungsgemäßen Verfahren beschichteten Gegenstand in einem Längsschnitt,

Fig. 2:

einen mit dem autokatalytischen Verfahren nach dem Stand der Technik beschichteten Gegenstand in einem Längsschnitt, und

Fig. 3:

einen mit dem erfindungsgemäßen elektrolytischen Verfahren beschichteten Gegenstand in einem Längsschnitt.

The invention and the technical environment are explained in more detail below with reference to the figure. It should be pointed out that the figure shows a particularly preferred embodiment variant of the invention, but that it is not limited thereto. It shows as an example and schematically:

Figure 1:

an object coated with the method according to the invention in a longitudinal section,

Figure 2:

a longitudinal section of an article coated with the prior art electroless process, and

Figure 3:

an object coated with the electrolytic process according to the invention in a longitudinal section.

The 1 shows a coated object 1 in a longitudinal section, which has a base body 2 with a surface 3 . The surface 3 is coated with a coating 4 which has a first layer 5 , a second layer 6 , a third layer 7 , a fourth layer 8 and a fifth layer 9 . In the embodiment variant of the invention proposed here, for example, the base body 2 is steel, the first layer 5 is copper, the second layer 6 is matt nickel, the third layer 7 is a nickel-phosphorus alloy and the fourth layer 8 is one chrome layer. The fifth layer 9 includes a zirconium compound.

In 2 a coated object 1 with a coating according to the prior art is shown. The coating 4 is applied using an autocatalytic coating process. The autocatalytic coating process is very slow and therefore time-consuming. In addition, the autocatalytic coating process results in constant layer thicknesses over the entire contours. This layer thickness is in the 2 represented by the bold line.

In 3 is the coated object 1 according to 2 shown again, in which case the coating 4 has been applied by means of an electrolytic coating process. It can be clearly seen that the outer contour 10 no longer follows the contour of the coated object. Rather, deposits of the coatings on the surface of the coated object of varying strength result, which essentially follow the field lines of the electrical fields in the electrolyte bath. It is clearly evident here that a significant reduction in the distance between the edge regions 11 can be achieved by the electrolytic coating, in particular in the edge regions 11 . Compared to coating with an autocatalytic process, significantly smoother surfaces can be created by filling up existing gaps or pores or making them significantly smaller. Overall, this leads to a significantly higher quality surface of the finished coated object 1.

The electrolytic coating method is also advantageous in that not the entire component or the entire object 1 to be coated is coated. Rather, it is possible to selectively coat areas of the object 1 to be coated, as a result of which unwanted coatings of water-bearing sections can be avoided entirely or at least to the greatest possible extent. This is not possible in this form with an autocatalytic coating without taking otherwise necessary and extremely complex covering or sealing measures on the object 1 to be coated.

The present invention is characterized in particular by a high level of protection against corrosion in decorative multi-layer systems.

Reference List

1

coated object

2

body

3

surface

4

coating

5

first layer

6

second layer

7

third layer

8th

fourth layer

9

fifth layer

10

outer contour

11

edge area

Claims (5)

Method for coating a sanitary item (1), wherein a surface (3) of the item (1) is at least partially coated with a coating (4) having a plurality of layers (5, 6, 7, 8, 9), wherein the individual layers (5, 6, 7, 8, 9) are formed sequentially, with either a first layer (5) of the coating (4) made of copper, a second layer (6) of the coating (4) made of a nickel-phosphorus alloy and a third layer (7) of the coating (4) consists of a chromium layer or a first layer (5) of the coating (4) of bright nickel, semi-bright nickel or matt nickel, a second layer (6) of the coating (4) of a nickel-phosphorus alloy and a third layer (7) of the coating (4) consists of a chromium layer or a first layer (5) of the coating (4) consists of a nickel-phosphorus alloy and a second layer (6) of the coating ( 4) consists of a chromium layer, with a mass fraction of phosphorus in the nickel-phosphorus alloy being at least 8% and with at least the nickel-phosphorus alloy being applied electrolytically. Method according to claim 1, wherein the sanitary article (1) consists of copper, zinc, aluminium, iron, plastic or an alloy comprising copper, zinc or steel. Method according to one of the preceding claims, in which the chromium layer is deposited from hexavalent or trivalent chromium electrolyte. Method according to one of the preceding claims, in which the chromium layer is applied directly to the nickel-phosphorus alloy. Method according to one of the preceding claims, in which a fifth layer (9) is produced from an amorphous carbon layer (DLC).

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