EP2097557B1 - Provision of water-conducting components made of brass alloys with reduced metal ion release - Google Patents

Description

The invention relates to a process for the production of water-bearing components from brass alloys with reduced metal ion release. Components made of brass alloys are used for very different purposes. Particularly important are those applications in which these components come in contact with water as intended, especially with drinking water. These are in the broadest sense the areas of sanitary engineering, water and drinking water production and water treatment. There brass alloys are used for the production of water-bearing or water-storing components. Conventional production methods for such components are, for example, drawing, turning, hot pressing (forging) or casting. The corresponding components are then, for example, pipes, valves, fittings and the like.

In principle, a wide variety of brass alloys can be used for the purposes mentioned. These alloys are known in the art. Particularly noteworthy here are the lead-containing brass alloys, in which case the lead is generally added for better mechanical workability of the components produced therefrom.

In the case of all components of brass alloys which come into contact with water, and in particular water, it must be borne in mind that these components or coatings applied to water these components are applied, are given in use metal ions to the water. In the case of brass alloys, these are copper ions and zinc ions, which are regularly included in brass. Added to this are the lead ions, which are often included as an alloy constituent. Next, nickel ions can be released to the water, these nickel ions usually come from coatings that are applied in the further processing of brass parts, in particular galvanically. As is known, components made of brass alloys, in particular in the field of sanitary technology, are provided with coatings, in particular metallic coatings. Such coatings are preferably applied to the so-called decorative surfaces, ie those (outer) surfaces which are accessible to the user of the component, for example the sanitary fitting. The coatings mentioned have either a technical function, eg. B. corrosion protection, or a decorative function, eg. Gloss, or both. The best known example of such coatings is the so-called chrome plating, ie the application of a, usually final, chromium layer on the component. This chromium layer is usually applied by electroplating, wherein below the chromium layer, various other coatings can be located, which usually conclude with a nickel layer. Although the said coatings are to be applied only to the decorative surfaces of the component, it is usually unavoidable that such coatings (partially) also deposit in the water-bearing (inner) surfaces of the component. It is said here that these layers "scatter" into the water-bearing parts of the component and their surfaces. From such interspersed layers then come, for example, the above-mentioned nickel ions, which can be detected in the water flowing through the component.

The release of metal ions, in particular the mentioned copper, zinc, lead and nickel ions, in the water, which comes into contact with the component in use as intended, in particular flows through the component, but is less tolerated. This is especially true for the drinking water sector. For example, there are already limit values for such metal ions in the case of product approval, or the introduction of corresponding limit values is to be expected. For example, for the drinking water sector in brass alloys in the USA, there is already the so-called NSF61 standard, which defines limit values.

JP 2003 264053 A discloses a method of making sanitary water heaters of copper having improved corrosion resistance, ie, reduced metal ion release, especially nickel, which components are provided with a copper sulfide coating (10).

GB-A-1 403 157 discloses a method of making components (eg, copper tubes) from brass that have improved corrosion resistance, ie, reduced metal ion release, with these components being provided with a copper sulfide coating.

US-A-2,842,435 discloses a method of making components (eg, copper tubes) from brass, which components are first desalted and then provided with a copper sulfide coating, and then the copper sulfide coating is removed.

In order to comply with the corresponding limit values, therefore, various coating methods are already proposed in order to prevent a transfer of the corresponding metal ions into the water, in particular drinking water. For example, components are chemically copper-plated or chemically tinned. However, this approach has the disadvantage that always the entire component is provided with the appropriate layers. Therefore, such layers must be removed, for example, in sanitary fittings on their decorative surfaces (field of view) again, for example, by grinding or polishing. This is understandably very expensive. In addition, only after these additional coating process and polishing process, the brass part can then be electroplated further, for example by the usual nickel plating and subsequent chrome plating.

Accordingly, it is an object of the invention to provide a novel method of reducing metal ion release from water-bearing components made from brass alloys. In particular, this method should be easily incorporated into existing production or coating processes for such components, in particular for sanitary fittings. Ideally, an already largely coated, preferably Chromed component can be treated by such a new method.

This object is achieved by the method having the features of claim 1. Preferred embodiments of this method are shown in the dependent claims 2 to 8.

The wording of all claims is hereby incorporated by reference into the content of this specification.

The aforementioned method for producing or providing water-conducting components, which are made of brass alloys and have reduced metal ion release in use, according to the invention is designed such that at least on the surfaces of the components in contact with water in contact with a copper sulfide layer is formed. This copper sulfide layer prevents metal ions from the underlying surfaces from entering the water present in or traversing the device. The advantages of the invention will be explained in more detail below.

The method according to the invention is additionally designed in such a way that the surfaces of the component which come into contact with water during use are partially desiccated. This dezincification causes the corresponding surfaces to deplete of zinc, which in particular form the finest channels in the surface. The copper sulfide can then be formed in these channels by reaction between the copper ions present there and the reagent used for copper sulfide formation. The resulting copper sulfide closes (blocks) the channels formed by the dezincification reliable, so that from there no metal ion release to the environment and thus into the water / drinking water can take place. For this reason, a combination of forming the copper sulfide layer with partial dezincification is particularly preferable.

In the last-mentioned embodiments, the surfaces which come into contact with water during use are simultaneously desensitized and provided with the copper sulfide layer in a single process step.

This approach is therefore preferred because a process step can be saved.

In further preferred embodiments of the method according to the invention, the components are already chrome-plated on their decorative surfaces when carrying out the method. In particular, these may be galvanically applied chromium layers. This procedure has the particular advantage that the method steps according to the invention can be easily integrated into an already existing process sequence. In addition, no additional treatment of the decorative surfaces, such as a grinding or Abpolieren necessary.

In a further development, the method according to the invention is designed such that the surfaces of the component which come into contact with water during use are partially provided with a nickel layer. Again, it is preferably a plated nickel layer.

Such embodiments are associated with the explanations made in the introduction. As described there, when applying of layers on the decorative surfaces of the brass part, these layers, such as nickel layers, in the water-bearing parts of the component "interspersed". As a rule, these will therefore be nickel layers which are located (partially) on the water-contacting surfaces of the component.

When the said nickel layer is removed and a copper sulfide layer is also formed on the respective surfaces where the nickel is then removed. Accordingly, the copper sulfide layer is then formed not only on the surfaces where the brass alloy was freely accessible from the outset, but also on those surfaces where the nickel layer was initially present and removed.

In the same way, it is necessary according to claim 1 that with such an approach in a process step at the same time also the already mentioned dezincification of the passing in use with water in contact surfaces occurs.

Accordingly, in accordance with the foregoing, particularly preferred process guides in the invention may be defined as follows.

On the one hand, an inventive method according to claim 1 is such that in which a water-conducting component of a brass alloy on its decorative (outer) surfaces is already chrome and this In this process, the component is dezincified on its (inner) surfaces in contact with water when in use and provided with a copper sulfide layer.

On the other hand, a method according to the invention is such that a water-conducting component made of a brass alloy is already chrome-plated on its decorative (outer) surfaces, at least partially having a nickel layer on its surfaces in contact with water during use. This component is at the points where the nickel layer is exposed, taken out and on the surfaces in contact with water coming into contact with water where the brass is exposed from the outset or after the Entnickeln surfaces, and provided with a copper sulfide layer.

To form the copper sulfide layer, it is possible according to the invention to use a sulfidic solution or a solution having a sulfide-forming constituent. Such solutions are known in the art. This may be, for example, a sodium sulfide (Na ₂ S) solution.

For dezincification, at least one acid or at least one acid-forming salt can be used according to the invention. Such substances are also known to the person skilled in the art. In this context, it should be understood that as a rule no reagents are to be used here, which also strongly attack the copper contained in the brass alloy. The dezincification (conversion of the zinc into zinc ions) should proceed much faster than the decoloration (transfer of the copper into copper ions). Accordingly, for example, no nitric acid will be used for dezincification, for example.

Preferred reagents for dezincification are copper chloride, sulfuric acid or organic acids, preferably citric acid.

For de-nickeling, it is preferred according to the invention to use at least one oxidizing acid, in particular at least one sulfonic acid. Of the sulfonic acids, in particular aromatic sulfonic acids, preferably 3-nitrobenzenesulfonic acid, should be emphasized.

In accordance with the foregoing, it is preferred to use reagents which exhibit several of the desired effects in one process step.

In this connection, it is advantageous according to the invention if the same reagent, in particular at least one sulfonic acid, preferably the already mentioned 3-nitrobenzenesulfonic acid, is used for (simultaneous) de-nipping and forming the copper sulfide layer.

In a corresponding manner, a mixture of at least two reagents can be used according to the invention for simultaneously de-nipping, dezincing and forming the copper sulfide layer. In particular, it is a mixture of at least two acids, wherein a mixture of sulfuric acid and 3-nitrobenzenesulfonic acid is particularly preferred.

In the latter case, one of the acids, preferably the sulfuric acid mentioned, serves for dezincing, and a second acid, preferably the 3-nitrobenzenesulfonic acid, serves to simultaneously de-nickel and form the copper sulfide layer.

The concentration ranges for all reagents used can be varied within wide limits and can be determined by the skilled person depending on the used brass alloy and depending on the application of the component in a corresponding manner. In case of used Acids are to be mentioned as preferred a range of 2% to 30% acids, in particular 5% to 20%, preferably 5% to 10%, acids. In the case of a mixture of sulfuric acid and 3-nitrobenzenesulfonic acid, the sulfuric acid is used as 5% to 10% acid and the 3-nitrobenzenesulfonic acid as 5% to 20% acid.

With respect to the obtained copper sulfide layer, it is considered that this is CuS (copper (II) sulfide). As explained in connection with the example, this is a black, resistant layer, which forms closed on the corresponding surface and is particularly firmly anchored within this surface in the case of dezincification.

However, a restriction to the form CuS should not be made. It is not excluded that in addition partially Cu ₂ S (copper (I) sulfide) is formed.

The treatment time, during which the corresponding reagents are in contact with the corresponding surfaces for forming the copper sulfide layer, is basically not critical in the invention. In order to usefully integrate the method steps according to the invention into already existing methods, the corresponding periods should usually not exceed several hours. Accordingly, in the method according to the invention at elevated temperatures, usually up to 80 ° C, worked. A preferred temperature is for example at about 70 ° C. Then usual process times are between a few, for example 5 minutes and 5 hours, in particular between 30 minutes and 3 hours.

The layer thicknesses of the copper sulfide layer obtained, depending on the treatment, are generally less than 50 .mu.m, whereby higher layer thicknesses can also be readily achieved. Preferably amount the layer thicknesses less than 25 microns, with particular layer thicknesses between 0.05 microns and 5 microns are more preferred.

Although the inventive method is limited according to claim to water-bearing components made of brass alloys, it is also possible in principle to carry out the method steps according to the invention with copper or copper alloys. However, as the main claim expresses, components of brass alloys are preferred.

In preferred embodiments, this brass alloy may be a leaded brass alloy. Preferably, the lead contents of such brass alloys are below 10%, preferably below 5%. In this context it should be mentioned that in the field of sanitary technology in the USA lead-containing brass alloys with a lead content of about 7% are used. For Europe, mention may be made of preferred lead-containing brass alloys CuZn ₃₇ Pb or CuZn ₃₉ Pb ₃ .

The layer thickness of the copper sulfide layer present on the component is preferably less than 50 μm, in particular less than 25 μm. Particularly noteworthy are layer thicknesses of copper sulfide between 0.05 microns and 5 microns.

The component is a water-bearing sanitary object. Preferably, it is a so-called sanitary fitting, d. H. around a mixer or the like.

The advantages of the invention are already apparent from the previous versions. The copper sulfide layer, which is formed on at least the surfaces of the components in contact with water when used, prevents metal ions from being released from the copper sulfide layer itself and from the underlying surface areas. These metal ions are primarily the copper ions and zinc ions which are absolutely necessary in the brass and the ions of the optionally present further alloying metals, in particular lead ions. Furthermore, the copper sulfide layer prevents the release of any existing nickel ions, which originate from coatings that are applied to the actual brass component.

By dezincing the corresponding surface areas of the component, the anchoring of the copper sulfide layer on these surfaces is further improved. Simultaneous de-nipping of the surfaces further minimizes the release of nickel ions.

A further advantage is that the method steps according to the invention are already carried out on an already chrome-plated component.

Thus, the method according to the invention can be installed and integrated in a simple manner into already existing process sequences, for example a so-called electroplating.

In the previous statements on the method according to the invention and on the component according to the invention, it was assumed that the copper sulphide layer formed on the surfaces in contact with water when in use remains on the component. This leads to the combination of the described advantages of the invention.

However, it is now the case that at least part of these advantages can also be realized if the copper sulphide layer formed by the treatment with the corresponding reagents is subsequently removed again. Thus, as explained, with the use of appropriate reagents, a dezincification and a Entnickeln the corresponding surfaces instead, the effects obtained, of course, even after removal of the formed copper sulfide remain. The corresponding surfaces are indeed depleted, for example, of zinc and freed from nickel. Accordingly, of course, a then freed from the copper sulfide surface will have a reduced metal ion release, in the case described zinc and nickel. Accordingly, in special cases, the subsequent removal of the copper sulfide layer may be indicated. The fact that the method according to the invention has been used can then be determined, for example, by analyzing the surface of the component.

The described and other features of the invention will become apparent from the following examples and the drawings in conjunction with the dependent claims. The individual features can be realized alone or in combination with each other.

Fig. 1

das GDS (glow discharge spectroscopy)-Spektrum einer unbehandelten Messingoberfläche aus CuZn₃₇

Fig. 2

das GDS (glow discharge spectroscopy)-Spektrum einer erfindungsgemäß behandelten Messingoberfläche aus CuZn₃₇.

In the drawings show

Fig. 1

the GDS (glow discharge spectroscopy) spectrum of an untreated CuZn ₃₇ brass surface

Fig. 2

the GDS (glow discharge spectroscopy) spectrum of a brass surface of CuZn ₃₇ treated according to the invention.

example 1

Initially, two samples of brass, CuZn ₃₇ brass alloy, were made available. One of these samples was left untreated for comparison.

The surface of the other sample was treated for 15 minutes in a 40 ° C solution of sulfuric acid and a 3-nitrobenzenesulfonic acid. Per liter of solution while 25 ml of concentrated sulfuric acid (98%) and 40 g of 3-nitrobenzenesulfonic acid were included. After this treatment, a copper sulfide layer of 0.3 μm thick was formed on this surface.

In order to compare the surfaces of the two samples (untreated or treated), a so-called GDS (glow discharge spectroscopy) spectrum was created in each case. This process is known to the person skilled in the art. With the help of this method one can use the element distribution from atoms directly at the surface to the depth of the material.

The two spectra obtained are in the attached FIG. 1 (untreated brass sample) and FIG. 2 (treated brass sample).

According to FIG. 1 It can be seen that in the untreated sample to a depth of 0.3 microns essentially only copper and zinc, ie the constituents of the brass alloy, are detectable. The values obtained agree very well with the brass composition (CuZn ₃₇ ). Only on the surface are oxygen and carbon detectable in small quantities (in FIG. 1 not shown).

In contrast, shows FIG. 2 in the treated sample, a copper sulfide layer is formed on the surface. It can also be clearly seen that significant dezincification of the surface by the 3-nitrobenzenesulphonic acid is effected at least to a depth of 0.2 .mu.m, with the zinc content settling again only at a depth of 0.3 .mu.m in the direction of the actual alloying value. The copper is depleted to a depth of 0.3 microns compared to the actual alloy, but to a much lesser extent than is the case with zinc. That the proportion of copper (based on CuS (copper (II) sulfide)) is higher than the corresponding stoichiometric sulfur content, may be due to the fact that not all the copper is present on the surface as copper sulfide, but preferably at the points where a Entzinkung has taken place.

Example 2

A total of 4 copies of a plumbing fixture already chrome plated in a galvanic plant (single lever mixer) will be provided. As already explained, in such fittings, a nickel layer is applied below the final chromium layer, wherein this nickel layer, due to the process, also scatters into the (inner) water-conducting parts of the fitting.

Two of these 4 fittings are not treated further and serve as comparison fittings.

The other two fittings are exposed over a period of 1 hour of a 70 ° C hot solution of sulfuric acid and 3-nitrobenzenesulfonic acid (immersion with movement of the valves), the composition of the solution corresponds to that of Example 1. By this treatment, these two valves are treated according to the invention, namely, a copper sulfide layer is formed by dezincing and Entnickeln on the water in contact surfaces (inner surfaces) of the fittings.

To compare the metal ion release in the two untreated fittings and in the two treated fittings, all 4 fittings are filled with demineralized water, sealed with suitable plugs and then placed in a furnace at a temperature of 70 ° C for 3 hours. Subsequently, the water inside the fixtures was analyzed for the ions of zinc, nickel, copper and lead using an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry) system. The results of this study are shown in the following table. sample Zn (mg) Ni (mg) Cu (mg) Pb (mg) 1 (untreated) 2.65 0.57 0.99 0.16 2 (untreated) 4.35 0.53 1.54 0.24 3 (treated) 0.08 0.13 0.17 0.08 4 (treated) 0.05 0.03 0.18 0.03

Without absolutely quantifying the results of the above table, it can be clearly seen that in the two treated valves, the release of all four metal ion species investigated is significantly reduced. This in particular, taking into account the error limits which are 0.03 for zinc, 0.01 for nickel and copper and 0.05 for lead.

Thus, it is clearly demonstrated on the basis of the examples that the method according to the invention is capable of significantly reducing the metal ion release in water-carrying components by the formed copper sulfide layer, optionally in conjunction with a dezincification and a Entnickeln.

Claims (8)

1. Process for producing or providing water-carrying components made from brass alloys, such as fittings and the like, which in use exhibit reduced release of metal ions,
   characterized in that
   a component, which has already been chrome-plated on its decorative surfaces and is at least partially provided with a nickel layer on those surfaces which in use come into contact with water, is denickeled, dezincified on the surfaces which in use come into contact with water and provided with a copper sulphide layer in one process step, wherein for simultaneous denickeling, dezincing and forming the copper sulphide layer a mixture of at least two acids is employed.
2. Process according to claim 1, characterized in that sulphuric acid or an organic acid, preferably citric acid, is employed as an acid for dezincing.
3. Process according to claim 1 or claim 2, characterized in that at least one sulphonic acid, preferably 3-nitrobenzenesulphonic acid, is employed as an acid for denickeling and for forming the copper sulphide layer.
4. Process according to any one of the preceding claims, characterized in that a mixture of sulphuric acid and 3-nitrobenzenesulphonic acid is employed.
5. Process according to any one of the preceding claims, characterized in that the decorative surfaces of the component are chrome-plated by electrodeposition.
6. Process according to any one of the preceding claims, characterized in that the copper sulphide layer has a layer thickness of less than 50 µm, in particular of less than 25 µm, preferably a layer thickness of between 0.05 µm and 5 µm.
7. Process according to any one of the preceding claims, characterized in that the brass alloy is a lead-containing brass alloy.
8. Process according to claim 7, characterized in that the lead-containing brass alloy is CuZn₃₇Pb or CuZn₃₉Pb₃.

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