EP2215286B1 - Provision of water-carrying components made from brass alloys which release reduced quantities of metal ions - Google Patents

Description

The invention relates to a process for the production or supply of water-bearing components made of brass alloys with reduced metal ion release and the corresponding components themselves.

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 metallic metal ions from these components or coatings applied to those components will be absorbed by the component Water are discharged. 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 and lead ions, into the water, which comes into contact with the component in use as intended, in particular the component flows through, but is tolerated less and less. 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.

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.

The publication of Valcarce MB et al. JOURNAL OF MATERIALS SCIENCE, Vol. 41., No. 7, 17 February 2006 (2006-02-17), pages 1999-2007, XP 019211720 KLUWER ACADEMIC PUBLISHERS , discloses an investigation of brass discs placed in contact with (artificially produced) drinking water. The study investigated the formation of corresponding surface layers using different methods. A key focus was the incorporation of zinc ions in the corresponding surface films on the brass.

The JP 61117282 A shows the formation of copper oxide films on the surfaces of conductive materials consisting of copper or copper alloys.

In the WO 97/06313 A1 Although the water-contacting surfaces of a chrome-plated brass fitting are passivated in a second process step. The reduction of the metal ion release, however, takes place in a first method step by etching with acidic solutions.

Finally, the shows JP 61221378 A the application of a copper oxide film on a non-chromed, water-bearing pipe system by strongly alkaline, oxidizing solutions.

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 completely coated, preferably chrome-plated component should be able to 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 5.
The wording of all claims is hereby incorporated by reference into the content of this specification.

The above-mentioned method for producing or providing water-conducting components, which are made of brass alloys and have reduced metal ion release in use, is designed so that at least on the surfaces of the components in contact with water in use, at least partially, a copper oxide layer is formed. This copper oxide 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.

In 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 layers are applied to the decorative surfaces of the brass part, these layers, for example nickel layers, are "scattered" into the water-bearing parts of the component. As a rule, these will therefore be nickel layers which are located (partially) on the water-contacting surfaces of the component.

Preferably, the surfaces of the components coated according to the invention, which come into contact with water in use, are the (inner) exposed brass surfaces. These are those inner surfaces where the original brass material from which the component is made is substantially unchanged, d. H. For example, it is not provided with any coating, for example an interspersed nickel layer. These exposed brass surfaces are then according to the invention preferably completely provided with the copper oxide layer, so that from them no or substantially no metal ions (copper, zinc, lead and optionally other alloying constituents) can be released.

To form the copper oxide layer, according to the invention, at least one 80 ° C. hot solution containing 250 g / l of sodium chloride (NaClO ₂ ) and 300 g / l of sodium hydroxide (NaOH) is used over a period of 10 minutes.

It is a strongly alkaline solution with a pH> 11.

In the method according to the invention for the formation of the copper oxide layer, a strongly alkaline sodium chlorite solution is used. This can be prepared, for example, by introducing sodium hydroxide into an aqueous sodium chlorite solution.

The alkalinity of the strongly alkaline solution is achieved by addition of a suitable, for example, solid base, such as sodium hydroxide, by adding, for example, sodium hydroxide platelets in appropriate concentration to the sodium chlorite solution.

With respect to the obtained copper oxide layer, it is considered that this is CuO (cupric oxide). As explained in connection with the example, this is a black, resistant layer, which forms closed on the corresponding surface and is firmly anchored on this surface.
However, a restriction to the form CuO should not be made. It is not excluded that in addition partially Cu ₂ O (copper (I) oxide) is formed.

The layer thicknesses of the copper oxide layer obtained, depending on the treatment, are generally less than 50 .mu.m, whereby higher layer thicknesses can also easily be achieved. Preferably, the layer thicknesses are less than 25 .mu.m, wherein in particular layer thicknesses between 0.05 .mu.m and 5 .mu.m are more preferred.

In preferred embodiments, the 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 .

It should also be noted that the method according to the invention can be varied. So it is conceivable in principle to integrate further process steps, in which not only on the exposed brass surfaces a copper oxide layer is formed, but additionally a Entnickeln and / or a dezincing takes place. Such dezincing causes the corresponding surfaces in contact with water when used to deplete the surface of zinc and, accordingly, may therefore release less zinc ions into the water / drinking water. Detangling is similarly the removal of nickel layers from the surfaces of the component in contact with water when in use. As mentioned above, such nickel layers can be formed by the so-called scattering in a decorative coating of the outer surfaces, such as a chrome plating.

The advantages of the method according to the invention will become apparent from the previous versions. The copper oxide layer formed on the surfaces of the components in contact with water upon use prevents metal ions from being released from the copper oxide 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.
A further advantage is to be emphasized that the method steps according to the invention are 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.

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

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 10 minutes in an 80 ° C, strongly alkaline sodium chlorite solution. 250 g of sodium chlorite (NaClO ₂ ) and 300 g (sodium hydroxide (NaOH)) were contained per liter of aqueous solution. After this treatment, a copper oxide layer resulted on this surface.

It was found by spectroscopic examination that a copper oxide layer had formed on the surface of the treated sample. The resulting brown-red to deep black oxidation layer, which had a very good adhesion to the base material brass, is mainly CuO (cupric oxide).

Example 2

A total of 6 specimens of a sanitary fitting (single lever mixer) already chrome plated in a galvanic plant were made available. 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.

Three of these six valves were not further treated and served as comparison fittings.

The three other fittings were exposed to a 80 ° C, strongly alkaline sodium chlorite solution over a period of 10 minutes (Immersion with movement of the fittings), wherein the composition of the solution corresponded to that of Example 1. By this treatment, these three fittings were treated according to the invention, namely, a copper oxide layer was formed on the surfaces in contact with water (inner surfaces) of the fittings, namely the exposed brass surfaces there.

To compare the metal ion release in the three untreated fixtures and in the three treated fixtures, all six fixtures were filled with demineralized water, sealed with appropriate plugs and then allowed to stand for a few hours. The fittings were then emptied and filled again with demineralized water and allowed to stand for a few hours. This was repeated over a period of a total of 19 days. The water samples obtained during the emptying were spectroscopically, z. B. using an ICP-OES system (Inductively Coupled Plasma Optical Emission Spectrometry) examined, namely on the ions of copper and lead.

The investigation found that the release of lead in the treated fittings was significantly reduced compared to untreated fittings. The copper release is also significantly reduced in the treated fittings compared to the untreated fittings, whereby the US applied limit for copper release (130 ug / l) was exceeded.

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 due to the formed copper oxide layer.

Claims (5)

1. A method for the production or provision of water-conducting components made from brass alloys such as fittings and the like, showing decreased release of metal ions when used, wherein a copper oxide coating is formed at least partially on at least the surfaces of components that come into contact with water during use, wherein when applying the method, the components have already been chromed on their decorative surfaces and in order to form the copper oxide coating a hot solution of 80 °C, including 250 g/l sodium chlorite (NaClO₂ ) and 300 g/l sodium hydroxide (NaOH), is applied for a period of 10 minutes.
2. The method according to claim 1, characterized in that the components are chromed by means of electro-plating on their decorative surfaces.
3. The method according to claim 1 or 2, characterized in that the surfaces of the component coming into contact with water during use are partially provided with a nickel coating, preferably with an electro-plated nickel coating.
4. The method according to any of the preceding claims, characterized in that the copper oxide coating has a thickness of less than 50 µm, particularly less than 25 µm, preferably a thickness between 0.05 µm and 5 µm.
5. The method according to any of the preceding claims, characterized in that the brass alloy is a lead-containing brass alloy, preferably the lead-containing brass alloy is CuZn ₃₇ Pb or CuZn ₃₉ Pb ₃.