Method for making a black self-healing part having a precious metal substrate, and part thus obtained

Abstract

Disclosed is a method for making a part including a substrate made of a precious metal, including: a step of providing the substrate made of an alloy including between 94% and 99.5% of copper (Cu), between 0.5% and 6% of gold (Au), and between 0% and 4% of at least one added element, the substrate having a surface, called upper surface, and having a thickness of at least 100 μm starting from the upper surface; and a step of preparing a patina bath from a mixture including at least: between 3 g and 10 g of anhydrous or hydrated copper acetate (Cu(CH3COO)2), between 3 g and 20 g of anhydrous or hydrated copper sulphate (CuSO4), and between 0.5 g and 2 g of salt (NaCl); then a step of applying the patina bath over the upper surface of the substrate. A part obtained by such a method.

1 . A method for making a part including a substrate made of a precious metal, the method including:
 A step of providing the substrate made of an alloy including:
 Between 94 wt. % and 99.5 wt. % of copper (Cu), 
 Between 0.5 wt. % and 6 wt. % of gold (Au), 
 Between 0 wt. % and 4 wt. % of at least one added element, 
 The total amounting to 100%; 
 The substrate having a surface, called upper surface, and having a thickness of at least 100 μm starting from the upper surface; 
   A step of preparing a patina bath from a mixture including at least:
 Between 3 g and 10 g of anhydrous or hydrated copper acetate (Cu(CH 3 COO) 2 ), 
 Between 3 g and 20 g of anhydrous or hydrated copper sulphate (CuSO 4 ), and 
 Between 0.5 g and 2 g of salt (NaCl); then 
   A step of applying the patina bath over the upper surface of the substrate.   
     
     
         2 . The method according to  claim 1 , wherein the step of preparing a patina bath includes:
 A step of heating a litter of distilled or permuted water up to a temperature comprised between 80° C. and 100° C.;   A step of adding 3 g to 10 g of anhydrous or hydrated copper acetate, and   3 g to 10 g of anhydrous or hydrated copper sulphate in the heated water, producing a first mixture;   A step of stirring for a time period comprised between 30 minutes and 90 minutes of the first mixture; then   A step of adding 0.5 g to 2 g of salt (NaCl), in the first mixture;   A step of adding 3 g to 10 g of anhydrous or hydrated copper sulphate in the first mixture, producing a second mixture; then   A step of stirring the second mixture for a time period comprised between 30 minutes and 90 minutes, producing the patina bath.   
     
     
         3 . The method according to  claim 1 , including a step of forming the alloy of the substrate including:
 a step of mixing, in proportions, at least 45 g to 55 g of gold (Au) with between 800 g and 1,200 g of pure copper (Cu).   
     
     
         4 . The method according to  claim 1 , including a step of forming the substrate over a base. 
     
     
         5 . The method according to  claim 4 , wherein the step of forming the substrate includes:
 a step of galvanic deposition or projection of the alloy on the base, configured to form a thickness of the substrate of at least 100 μm.   
     
     
         6 . The method according to  claim 1 , including prior to the step of applying patina:
 A step of pickling the upper surface of the substrate; then   A step of rinsing the substrate.   
     
     
         7 . The method according to  claim 1 , wherein the step of applying the patina bath includes a step of immersing the substrate into the patina bath, the immersion step having a duration comprised between 45 minutes and 90 minutes, and the patina bath having a temperature comprised between 80° C. and 100° C. 
     
     
         8 . A part obtained by a method according to  claim 1 , the part including:
 At least one substrate made of an alloy including at least:
 Between 94% and 99.5% of copper (Cu), 
 Between 0.5% and 6% of gold (Au), 
 Between 0% and 4% of at least one added element, 
 The total amounting to 100%; 
 The substrate having a surface, called upper surface, and having a thickness of at least 100 μm starting from the upper surface; and 
   And a patina applied over the upper surface of the substrate, the patina having a thickness of at least 5 μm, and the patina including at least:
 a copper oxide, and 
 gold (Au). 
   
     
     
         9 . The part according to  claim 8 , wherein the patina includes between 0% and of at least one amongst: carbon, oxygen, chlorine, potassium, calcium, or iron. 
     
     
         10 . The part according to  claim 8 , wherein the added element has a concentration comprised between 0% and 1%. 
     
     
         11 . The part according to  claim 8 , wherein the added element includes at least one amongst: silver (Ag); arsenic (As), zinc (Zn), lead (Pb), iron (Fe), or tin (Sn). 
     
     
         12 . The part according to  claim 8 , wherein the patina includes a gold concentration comprised between 5% and 15%. 
     
     
         13 . The part according to  claim 8 , wherein the alloy of the substrate includes 95.24% copper (Cu) and 4.76% gold (Au). 
     
     
         14 . The part according to  claim 8 , having a black surface characterised by colorimetry in the L*a*b* CIE 1976 colour space with a “L” value comprised between 10 and 50, an “a” value comprised between −1.5 and 1; and a “b” value comprised between −8 and 1. 
     
     
         15 . The method according to  claim 2 , including a step of forming the alloy of the substrate including:
 a step of mixing, in proportions, at least 45 g to 55 g of gold (Au) with between 800 g and 1,200 g of pure copper (Cu).   
     
     
         16 . The method according to  claim 2 , including a step of forming the substrate over a base. 
     
     
         17 . The method according to  claim 3 , including a step of forming the substrate over a base. 
     
     
         18 . The method according to  claim 2 , including prior to the step of applying patina:
 A step of pickling the upper surface of the substrate; then   A step of rinsing the substrate.   
     
     
         19 . The method according to  claim 3 , including prior to the step of applying patina:
 A step of pickling the upper surface of the substrate; then   A step of rinsing the substrate.   
     
     
         20 . The method according to  claim 4 , including prior to the step of applying patina:
 A step of pickling the upper surface of the substrate; then   A step of rinsing the substrate.