FI102908B - Corrosion resistant copper alloy - Google Patents

Description

102908

Corrosion resistant copper alloy. - Korrosionsbeständig kopparlegering.

The present invention relates to a corrosion-resistant copper alloy consisting of copper and at least two alloys of lower electrochemical potential than copper, which together with copper form an adherent, non-porous surface layer of oxides, oxide hydrates and / or hydroxides, wherein the mixture is under technical refrigeration conditions in the region of a solid solution.

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One such mixture is known, for example, from DE-OS 3.605.796. However, due to the high concentration of the additives, there is a risk of precipitation and thus of further processing difficulties.

15 Most corrosion damage in copper plumbing pipes is caused by uniform surface corrosion or pitting. In addition, improper installation may result in corrosion corrosion at the soldering points and joints. However, the corrosion resistance of copper can, in principle, be increased by forming an adherent continuous oxide surface layer. This is achieved by 20 special fabrication processes on the inner surface of the tube, which, however, are technically detailed and labor-intensive. A more advanced method is to form: · 'alloy additives' to form a self-healing * · · '· 1' oxide surface layer.

It is an object of the invention to provide a corrosion-resistant material which is characterized in particular by an improved surface layer and reduced solubility of copper in relation to non-oxidized copper and without any risk of pitting. The mass wear should then be reduced.

The problem is solved according to the invention by the characters of the claims 1-3.

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The formation of a valence pair from divalent to trivalent positive ions, divalent to tetravalent ions, or monovalent to tetravalent ions forms an adherent and largely non-anhydrous surface layer. It has surprisingly been found that the valence pair select-5 nanoparticles influence the structure of the Cu20 phase so that the surface layer is formed both faster and also in that the resulting surface layer has a more effective protective effect,

It is preferred to add up to 0.04% by weight of phosphorus to the mixture. Phosphorus improves valet-10 and also acts as a deoxidant.

According to a preferred embodiment of the invention, said elements are added in an amount of at least 0.1% by weight.

Preferably, the composition of the invention is used as a material for pipes in installation and sanitary engineering and for plumbing pipes.

The invention will be described in more detail in connection with the following embodiments: Tubes of 18x1 mm dimensions were made of anoxic copper 20 (SF-Cu) and three reference alloys having the following compositions.

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Material

SF-Cu soft, 50-70 HB

Fight 5, 100-120 HB

Cu MgO, 7TiO, 2 soft, 50-70 HB eg 1 (Parity 2 + / 4 +) hard, 100-120 HB eg 2 10 ____

Cu AIO, 5ZnO, 5 soft, 50-70 HB eg 3 (Parity 3 + / 2 +) hard, 100-120 HB eg 4 15

CuLiO, 6SiO, 1 soft, 50-70 HB eg 5 (Parity 1 + / 4 +) hard, 100-120 HB eg 6

In order to evaluate the corrosion behavior, the current density-potential curves (Fig. 1) and the electrochemical polarization resistance (Rp) were measured in the tube models, respectively: or the polarization conductivity (Rp1) according to Figs.

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More in detail: • «· 25 • · ·

Figure 1 shows a current-density potential curve for Cu-Mg-Ti, Cu-Al-Zn and Cu-Li-Si alloy systems compared to anoxic copper • ♦ · YY sf-cu.

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Reference electrode: saturated calomel electrode.

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Figures 2a to 2g show the polarization conductivity Rp 1 as a function of the test time.

M .: (a) SF-Cu, soft state, 50-70 HB or hard, 100-120 HB

(b) CuMgO, 7TiO, 2, soft state, 50-70 HB

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(c) CuMgO, 7TiO, 2, state hard, 100-120 HB

(d) CuAIO, 5ZnO, 5, soft state, 50-70 HB

(e) CuAIO, 5ZnO, 5, hard state, 100-120 HB

(f) CuL10, 6SiO, 1, soft state, 50-70 HB

5 (g) CuLiO, 6SiO, 1, hard state, 100-120 HB

Figure 3 shows the weight loss on the surface after 1000 hours.

Figure 1 shows current density potential curves for CuMgO, 7TiO, 2, CuA10, 5ZnO, 5, CuLiO, 6SiO, 1010 and SF-Cu. It can be seen that the alloyed elements clearly extend the corrosion resistance range. The passive current density is reduced compared to SF-Cu, which indicates a better cover layer quality. Breakthrough potentials have shifted towards more positive potentials.

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The polarization resistance Rp or the inverse, respectively, the polarization conductivity Rp'1 is a measure of the corrosion rate. The lower the polarization conductivity, the greater the resistance to smooth corrosion. Figures 2a to 2g compare the polarization conductances of the materials Cu-MgO, 7TiO, 2, CuA10, 5, ZNO, 5, and CuLiO, 6SiO, 1 in different states (soft / hard) with those of SF-Cu. Unalloyed copper: not only shows inferior behavior, but also exhibits considerable disintegration.

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In all the materials examined, the weight loss was significantly reduced with respect to SF-Cu as shown in Figure 3.

• · * • * · • · ·,. In all cases, the compositions of the invention exhibit clearly better behavior than SF-Cu. Not only does the surface layer improve in quality, but also · · · affects the rate of formation and, above all, expands I I ·; ' 30 corrosion resistance potential ranges. The formation of this passive layer

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As a result, the solubility of Cu is clearly reduced.

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It remains to be seen as a decisive advantage that the combination of certain mandatory components expands the pH range for the formation of the surface layer. While certain dopants are capable of forming reaction products also in acidic materials and thus contribute to the formation of an effective barrier layer, the same applies to other substances in basic substances, according to the Pourbaix diagram. Thus, the materials of the invention are not only usable in neutral waters. Certain pH changes do not negatively affect the corrosion behavior.

Furthermore, if the breakthrough potential is shifted so far in the positive direction that it is no longer in the free corrosion potential range, then there is additional protection against pairing, such as, for example, contact or aeration pairs. In addition, the tested tube models showed no risk of pitting.

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Claims (6)

1. Corrosion-resistant copper mixture consisting of copper and at least two alloys which, to their electrochemical stress potential, are more noble than copper and together with copper form an adhesive, non-porous surface layer of oxides, oxide hydrates and / or hydroxides, the amount of the individual elements being within such intervals, where the mixture under technical cooling conditions occurs within the range of a rigid solution, characterized by the following features: the melting point of the rigid solution is above 400 ° C, the copper mixture contains at least 99% by weight copper, two or more alloys with different valves selected from group A and B, wherein at least one substance from group A consisting of zinc, cadmium, beryllium, calcium, strontium, barium, man, iron, cobalt or nickel, in the surface layer forms thermodynamically stable chemical substances of said type in the form of divalent positive ions, and at least one alloy of group B, consisting of boron, aluminum, gallium, indium, scandium, yttrium, lanthanum, cerium, alloy metal, chromium, iron or cobalt, forms in the surface layer thermodynamically stable chemical substances of the type in the form of three-value positive ions. 2. Corrosion-resistant copper mixture consisting of copper and at least two alloys which, to their electrochemical stress potential, are more noble than copper and together with copper form an adherent, non-porous surface layer of oxides, oxide hydrates and / or hydroxides, wherein the amount of the individual elements is within such ranges where the mixture under technical cooling conditions occurs within the range of a rigid solution, characterized by the following characteristics: the melting point of the rigid solution is above 400 ° C, copper mixture. The composition contains at least 99% by weight of copper, the remainder of two or more alloys having different valves selected from group A and C, wherein at least one substance from group A consisting of zinc, cadmium, beryllium, calcium, stronium, barium, manganese, iron, cobalt or nickel, in the surface layer form thermodynamically m * »stable chemical substances of said type in the form of divalent positive ions, and:, · at least one alloy. from the group C consisting of silicon, germanium, titanium, zirconium or hafnium, form in the surface layer thermodynamically stable chemical substances of said type in the form of quadruple positive ions. 3. Corrosion-resistant copper mixture consisting of copper and at least two alloys which, to their electrochemical stress potential, are more noble than copper and together with copper form an adhesive, non-porous surface layer of oxides, oxide hydrates and / or hydroxides, the amount of the individual elements being within such intervals where, under technical cooling conditions, the mixture occurs within the range of a rigid solution, characterized in that the melting point of the rigid solution is above 400 ° C, the copper mixture contains at least 99.0% by weight copper, the remainder two or more alloying agents having different valves selected from the group D and C, wherein at least one substance from the group D consisting of lithium, sodium, potassium, rubidium or cesium, in the surface layer forms thermodynamically stable chemical substances of the type 15 in the form of monovalent positive ions and at least one alloy of group C consisting of silicon, germanium, titanium, zirconium or hafnium, forms in the surface layer thermodynamically stable chemical substances of said type in the form of quadruple positive ions. 4. Corrosion-resistant copper mixture according to claim 1,2 or 3, characterized in that it contains up to 0.04% by weight of phosphorus. v .: Corrosion-resistant copper mixture according to one or more of claims 1-4, characterized in that the element is present in at least 0.1% by weight. : 25 The use of corrosion-resistant copper mixture according to one or more of claims 1-5 as material for pipes in mounting and sanitation technology and drinking water pipes. • · · • · «« «· · MH ·« · V