EP1780311A1 - Manufacturing process for satin-matt surface - Google Patents

Abstract

A method for the production of satin-finish metal surfaces on a workpiece (1) involves (a) making a smooth surface (2) on (1), (b) applying a matt nickel coating (3) by electroplating without using organic delustering agents and then (c) applying a sulfamate-nickel coating (4).

Description

The present invention relates to the production of satin surfaces of workpieces, in particular automotive parts.

It is known to produce metal surfaces on a wide variety of workpieces by galvanic processes. Both glossy surfaces and matt surfaces are possible.

In certain applications, especially decorative surfaces in the automotive sector, semi-gloss metal surfaces are of interest. In the galvanic production of such surfaces, there is the problem of being able to reproducibly adjust the degree of dullness or gloss and thus the exact shape of the desired compromise between gloss and mattness in silk-matt surfaces.

Galvanic processes are also known in which galvanic Ni layers are given an adjustable silk mattness by adding to the galvanic solution an organic additive which drops onto the surface like a droplet and leads to disturbances of the surface structure. The degree of dullness or silk gloss must be set relatively inconveniently over the added amounts before starting a process and the organic additives must be filtered out in a process interruption before a new process start so as not to disturb the new process. The setting mentioned must therefore be repeated with each new process start-up and is therefore complicated and disadvantageous in terms of reproducibility.

Furthermore, it is known to sandblast surfaces, such as Cu-coated surfaces, and then to electroplate with Ni, for example. The silk gloss can be adjusted badly. Furthermore, slight optical defects of the sandblasting process, such as sharp spots due to particles resting on the workpiece during the sandblasting process, are easily apparent. Other surface defects are also comparatively obvious.

The invention is based on the technical problem of specifying an alternative method for producing satin matt metal surfaces on workpieces.

To solve this problem, a method is provided with the steps of: producing a smooth surface on a workpiece, applying a matt Ni layer by electrodeposition without organic matting additives, applying a sulfamate-Ni layer.

Preferred embodiments are specified in the dependent claims and are explained in more detail below.

The basic idea of the invention is to apply a matt Ni layer on a smooth workpiece surface and to adjust the mattness over the thickness of the Ni layer. The invention is directed to galvanic Ni layers in which no organic matting additives are used. Rather, in a preferred embodiment of the invention may be a known Wattsche Ni layer, which is technically simple and easy to control.

On the matte Ni layer then another sulfamate-Ni layer should be applied. This has the advantage and the function of the invention to round the more or less grain-like structure of the matte Ni layer something and thus to make something less rough and sensitive to contamination.

Overall, the result of the interaction of depending on the strength of the matte Ni layer still by a more or less pronounced residual appearing smooth surface on the workpiece with the conferred by the matte Ni layer dullness and finally the explained rounding by the sulfamate -Ni-layer a visually attractive and above all well reproducible silk gloss. In its optical quality, this is in no way inferior to the mentioned Ni layers with organic matting additives. Moreover, in the method according to the invention, the degree of gloss or degree of matting can be determined by various galvanic parameters, in particular by treatment time and / or Amperage, easy and well adjustable control. The need to filter the solutions for filtering organic matting additives is also eliminated.

The abovementioned sulfamate-Ni layer is preferably protected against environmental influences by means of a further finishing layer, it being understood that this finishing layer can also have a decorative function. Particularly preferred is a galvanic Cr layer, which may have a thickness between 0.1 and 3 microns, with a lower limit of 0.5 microns or an upper limit of 1 micron is particularly preferred. Here, a conventional and available through commercially available solutions gloss chrome process can be used because the satin finish of the surface is already present.

However, the invention is not limited to Cr layers. Other decorative layers may also be used, such as Ag, Au or Pt metals. Also suitable are black chrome layers, Ti layers, in particular sputtered Ti layers, or else non-metallic layers such as (clear) lacquers or (sputtered) ceramic layers.

The smooth surface on the workpiece under the matte Ni layer may for example be a polished workpiece surface itself or even an applied metal layer. If an inventively preferred gloss Ni layer is used here, this has the particular advantage of very well leveling any surface defects and defects. Thus, it can improve the quality of the final gloss content of the finished metal surface according to the invention. Galvanic processes for bright Ni layers are well known and need not be detailed here. There are commercial solutions available which may include, for example, Ni sulfate, organic brighteners and so-called levelers. Suitable current densities in this range are 1 to 3 A / dm ² . It may also be advantageous to provide a shiny metal layer, for example a Cu layer, below the glossy Ni layer.

The matte galvanic Ni layer is preferably applied as a known and technically well-controlled Wattsche Ni layer, ie as a galvanic Ni layer without organic matting additives. This creates a microscopic bulbous layer structure, in which the tuber sizes and tuber intervals can be set via the current intensity and / or coating time, which ultimately determine dullness. A maximum dullness arises when the tubers are practically close to each other. Current strengths in the range of 0.1 to 2 A / dm ² , better 0.1 to 1 A / dm ² , are preferred here. The layer thickness of the matt layer should be comparatively low and may be between 0.05 and 5 .mu.m, with upper limits of 4 .mu.m, 3 .mu.m, 2 .mu.m and more preferably 1 .mu.m and lower limits of 0.075 .mu.m and more preferably 0.1 .mu.m even cheaper. The layer thickness is ultimately determined by optical / aesthetic considerations.

The electrodeposition of a sulfamate-Ni layer is also conventional and known. The corresponding solutions contain nickel sulfamate, that is, the salt of amidosulfuric acid. Although the sulphamate Ni layer rounds and reinforces the aforementioned bulbous or otherwise matte Ni layer, it does not really level it. In particular, the sulfamate-Ni layer also enhances the grain size without changing fundamentals on the granularity described above as "nodular". It thus receives the matte character, possibly only slightly increases the gloss, but above all provides increased material strength for reasons of stability and resilience and for better wiping sensitivity or better dirt-repellent properties. The roughness reduced by the rounding provides less grip to soiling. A favorable thickness for the suifamate Ni layer is in the range of 5 and 20 microns, with a lower limit of 10 and an upper limit of 15 microns are more preferred. It has already been mentioned that a protective topcoat is preferred. If the metallic Ni color is of interest, a clearcoat can also be used here.

A particular advantage of the invention, in addition to the good optical properties and the good resilience and dirt resistance of surfaces according to the invention is that can be adjusted by galvanic parameters in a very simple manner, the degree of gloss or matte degree. Different optical properties can be generated with one and the same basic process, that is, the same solution compositions, identical baths, etc. In particular, from batch to batch simply over the amperage, or even cheaper about the treatment time, the dullness are set. The thicker the matte Ni layer, the higher the matte degree.

The invention will be explained in more detail below with reference to an exemplary embodiment, which is shown schematically in the figures.

Figures 1 - 5 show various intermediate stages of a method according to the invention.

As an exemplary embodiment, an inner door handle of a passenger car made of plastic is metallized silk matt. FIG. 1 schematically shows a surface of the plastic door handle 1. On this surface, according to FIG. 2, a glossy Ni layer 2 is deposited in a manner known per se. For this purpose, the surface of the plastic door handle can be previously germinated and prepared, for example, with a chemically deposited thin metal layer for the electroplating process.

The glossy Ni layer 2 is deposited in a standard electroplating process at 2 A / dm ² from an aqueous solution containing about 180 g / l nickel sulfate, about 150 g / l nickel chloride and about 50 g / l boric acid as a pH buffer and at Gloss Ni baths contains commercially available organic brighteners. For example, the bath Slotonik-50 of the company Schlötter comes into consideration.

The purpose of the glossy Ni layer 2 is to provide a glossy base that is as error-free as possible, and is distinguished by its good ability to level initially existing imperfections. Their thickness is not really essential to the subsequent process and depends, on the one hand, on the overall material thickness targeted, especially with regard to durability, and on the surface defects to be leveled. Typical orders of magnitude are in the range of 10-30 microns.

On the glossy Ni layer 2, according to FIG. 3, a matt wadding Ni layer 3 is applied. This is carried out at a current density of about 0.5 A / dm ² from an aqueous solution containing 210 g / l nickel sulfate, 35 g / l nickel chloride and 40 g / l boric acid without further additives. The preferred layer thickness range is between 0.1 and 1 μm, wherein the mattness of the finally resulting layer is adjusted via the layer thickness. In this embodiment, 0.2 microns are deposited.

FIG. 3 illustrates that this layer thickness only makes sense in terms of averaging. In fact, the growth is very grainy or "bulbous", the individual grains shown schematically in Figure 3 with increasing average layer thickness are larger and have decreasing average distances. At significantly greater layer thicknesses, the grains are finally close, resulting in a matte layer that does not let the gloss of the underlying gloss Ni layer 2 through.

In the next step, illustrated in FIG. 4, a sulfamate Ni layer 4 is deposited on the Watt Ni layer 3. The grains are thereby reinforced, rounded the corners a bit and in particular the niches and angles lying on the edge of the grains filled.

Here, a 12 μm thick layer is deposited at a galvanic current density of 1 A / dm ² . The aqueous solution contains 36% by volume of 60% by weight nickel sulphamate solution. The galvanic solution contains 5 g / l nickel chloride and 35 g / l boric acid. Considered, for example, the bathroom Schlötter MS.

Finally, as shown in FIG. 5, a finishing layer is optionally applied. In this embodiment, this is a conventional gloss Cr layer 5 of thickness 1.5 .mu.m. Here is the Schlötter-Bad slotochrome GC10 with hexavalent Cr or Slotochrom 50 with trivalent Cr into consideration.

As a result of the properties of the Cr surface, the overall layer is well protected against environmental influences and resistant to oxidation. It ultimately shows a metallic Cr gloss, which is desirable here. Due to the somewhat rounding properties of the sulfamate-Ni layer, the sensitivity to dirt and the roughness are significantly improved and well suited for applications in the interior of motor vehicles.

If desired, of course, other top coats and thus other colors can be used. This changes the basic principle of generating a Silky sheen through the interaction of a shiny metal layer, here the glossy Ni layer, and a lying on top of it matte Ni layer of comparatively low strength, nothing.

Overall, the exemplary embodiment is a simple process control with a control of the essential layer properties over the treatment time, in particular a control of the mattness of the resulting silk gloss over the time of the Watt's nickel process. The described disadvantages of organic matting additives omitted. The process is thus practicable, easy to reproduce and inexpensive.

Claims (14)

Method of producing a semi-matt metal surface on a workpiece (1) comprising the steps: - producing a smooth surface (2) on a workpiece (1), Application of a matt Ni layer (3) by electrodeposition without organic matting additives, - Applying a sulfamate-Ni layer (4). The method of claim 1, further comprising the step of: applying a further capping layer (5) on the sulfamate Ni layer (4). The method of claim 2, wherein the cap layer is a Cr Cr layer (5). Method according to claim 2 or 3, wherein the finishing layer (5) is between 0.1 and 3 μm thick. Method according to one of the preceding claims, in which the smooth workpiece surface is produced by electrodeposition of a bright Ni layer (2). Method according to Claim 5, in which the current density on the workpiece during the electrodeposition is between 1 and 3 A / dm ² . Method according to one of the preceding claims, in which the matt Ni layer is applied as a wadding Ni layer (3). A method according to claim 7, wherein the current density on the workpiece during the application of the Watt-Ni layer (3) is between 0.1 and 2 A / dm ² . Method according to one of the preceding claims, in which the matt Ni layer (3) is between 0.05 and 5 μm thick. Method according to one of the preceding claims, wherein the current density on the workpiece during the application of the sulfamate-Ni layer (4) is between 0.1 and 2 A / dm ² . A method according to any one of the preceding claims, wherein the sulfamate Ni layer (4) is between 5 and 20 μm thick. A method according to any one of the preceding claims, wherein the workpiece is an automobile part (1) and the semi-gloss metal surface is a decorative surface of the automobile part (1), especially for the interior of an automobile. Method for producing semi-matt metal surfaces on a plurality of workpieces (1) comprising a method according to one of the preceding claims, wherein the metal surfaces (1) produced are differently matted and the different mattnesses are adjusted by different thicknesses of the matt Ni layer (3). A method according to claim 13, wherein the respective thicknesses of the matte Ni layer (3) are adjusted over the period of the electrodeposition.

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