FR2504558A1 - Surface oxidation of metal, e.g. copper - using ammoniacal copper carbonate soln. to give aged appearance - Google Patents

Abstract

A metal workpiece (e.g. of copper) is surface oxidised by immersion in an aq. ammoniacal copper carbonate soln. and then drying and opt. brushing (to obtain a satin finish). The soln. contains about 5 l. (per 10 l. of soln.) of 10-35% ammonia soln., 50-500 (pref. about 250) g/l copper carbonate and opt. a small amount of a polysulphide (esp. calcium polysulphide). The workpiece, e.g. a brass component electroplated with copper, is immersed for 10-15 secs. in the soln. held at ambient temp. and then dried for about 24 hrs. To obtain a satin finish, the dried component is brushed with an abrasive material, esp. a plastics material. The process is useful for treating metal components to produce an aged appearance. The process is rapid and gives a surface having an excellent combination of hardness and adaptability to brushing.

Description

METHOD AND DEVICE FOR THE TREATMENT OF ME SEEFACE OF SUCH AS I2 COPPER BY ONDATION.

 The present invention relates to a method and a mixture for producing the surface oxidation of a part into a metal such as copper.

 The surface oxidation of metal parts is generally used to give them a particular color or appearance, and in particular an aged appearance. The methods currently used generally consist in immersing the metal part to be oxidized in an oxidizing bath at a relatively high temperature, for a relatively long period, for example from one to several hours.

All the known processes produce on the surface of the part an oxidized layer of more or less dark color and relatively regular.

The implementation of these methods is relatively long, which limits the throughput of mass production plants, and it is necessary to bring the baths to a relatively high temperature which is both a source of danger during of use and a source of loss of time during the commissioning of the installation. In addition, the surfaces thus obtained have a relatively regular appearance and little variation. The surfaces obtained are either too soft to withstand impacts or too hard. to allow further treatment by brushing
The present invention proposes in particular to obviate the drawbacks of the known methods by the use of a mixture allowing the treatment of copper-colored metal parts when cold, this treatment being particularly rapid, of the order of a few seconds.

 Another object of the invention is to provide a method and a mixture which make it possible to obtain surfaces having excellent mechanical qualities, and in particular achieving a good promised promise between hardness to resist impact and brittleness to allow subsequent mechanical treatment by brushing. .

 Another object of the invention is to propose a process making it possible to more particularly treat copper-clad metals such as brasses, or brasses previously coated with copper by electrolysis.

 To do this, the method consists in immersing the piece of metal to be treated in a bath containing ammonia and copper carbonate in aqueous solution, then removing the piece to dry it. This gives a relatively hard oxidized surface.

 According to another characteristic of the invention, the part is then subjected to dry brushing in order to partially remove the oxidized surface layer therefrom. The surface obtained has a satin appearance.

 According to another characteristic of the invention, the bath in which the part is immersed contains, for ten liters of mixture, approximately five liters of ammonia comprising from ten to thirty five percent of anhydrous ammonia, and fifty to five hundred grams of copper carbonate per liter of solution. We can for example use two hundred and fifty grams of copper carbonate per liter. Such a mixture makes it possible to carry out a surface oxidation of the metal and to obtain a surface layer allowing a very rapid and iridescent treatment of the metal part while leaving the possibility of a subsequent brushing to obtain a satin effect.

 According to another characteristic of the invention, and in particular for the treatment of metal parts 8 made of brass covered with copper, a small amount of polysulphide is incorporated into the preceding mixture. It has been determined that the treatment is thus significantly improved and faster.

 Other characteristics and advantages of the present invention will emerge from the following description of a particular embodiment, given by way of illustration but not limitation.

 To treat the surface of a copper-plated metal part with a view to giving it a satin and aged appearance, the present invention provides for several steps 2 - the part is immersed in a bath containing ammonia and copper carbonate in aqueous solution. ; the solution can be cold, ie at room temperature, and the dive can last from ten to fifteen seconds. the bay: could be made in a melgeaat, to obtain for example ten liters of mixture, approximately five liters of ammonia containing ten to thirty five percent of anhydrous ammonia, and fifty to five hundred grams per liter of copper carbonate.

Good results will be obtained with two hundred and fifty grams per liter of copper carbonate.

- the next step is to remove the piece from the bath to dry it. This stage can last around twenty four hours.

the next step consists in subjecting the piece thus treated to dry brushing intended to partially remove the oxidized surface layer therefrom. This brushing may be carried out using a brush made of abrasive material, in particular with a plastic material.

 The treatment of metallic pieces 8 of copper-plated brass may require the addition of a small amount of polysulphide, for example a proportion of five percent. We could in particular use a calcium polysalide.

 the previously described process allows the treatment of metal parts such as taps or other parts which we want to give an aged appearance.

 The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims (10)

 1 - Process for producing a surface oxidation of a part made of a metal such as copper, characterized in that it comprises the following steps 2 - immerse the part in a bath containing ammonia and copper carbonate in aqueous solution 3 - remove the part and dry it.  2 - Method according to claim 1 to give the piece a satin appearance, characterized in that it further comprises, at the end of the drying step, a dry brushing step of the piece to partially eliminate the oxidized surface layer.  3 - Method according to one of claims 1 or 2, characterized in that the bath contains, for ten liters of mixtures about five liters of ammonia comprising ten to thirty five percent of anhydrous ammonia,  4 - Process according to claim 3, characterized in that the bath contains from fifty to five hundred grams of copper carbonate per liter.  5 - Method according to claim 4, characterized in that the bath contains about two hundred and fifty grams of copper carbonate per liter.  6 - Method according to any one of claims 1 to 5, characterized in that the step of dipping the part in the bath is carried out for a period of between ten and fifteen seconds.  7 - Method according to any one of claims 1 to 6, characterized in that the drying step lasts about twenty four hours.  8 - Process according to any one of claims 3 to 7, characterized in that the mixture also contains a small amount of polysulfide.  9 - Process according to claim 8, characterized in that the mixture contains calcium polysulfide.  10 - Bath for the surface oxidation of a piece of coppery metal, characterized in that it contains, for ten liters of mixture, approximately five liters of ammonia comprising ten to thirty five percent of anhydrous ammonia, and fifty to five hundred glams per liter of copper carbonate.