US20130277225A1 - Method to Produce Golden Bronze by Diffusion of Tin Into Copper Under Controlled Conditions - Google Patents

Method to Produce Golden Bronze by Diffusion of Tin Into Copper Under Controlled Conditions Download PDF

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US20130277225A1
US20130277225A1 US13/992,924 US201113992924A US2013277225A1 US 20130277225 A1 US20130277225 A1 US 20130277225A1 US 201113992924 A US201113992924 A US 201113992924A US 2013277225 A1 US2013277225 A1 US 2013277225A1
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layer
tin
annealing
copper
bronze
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Toan Dinh Nguyen
Hieu Cong Truong
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Royal Canadian Mint
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Royal Canadian Mint
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Assigned to ROYAL CANADIAN MINT reassignment ROYAL CANADIAN MINT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: TRUONG, HIEU CONG, NGUYEN, TOAN DINH
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
    • C25D5/505—After-treatment of electroplated surfaces by heat-treatment of electroplated tin coatings, e.g. by melting
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated

Definitions

  • the present invention relates to the production of bronze objects having a golden appearance. More particularly, the present invention provides a multi-layer plating method to produce a golden bronze alloy layer on substrates, comprising non-cyanide plating of successive metals.
  • Bronze is commonly defined as an alloy of copper and tin.
  • other metals can be used, defining different bronze alloy variations such as commercial bronze (copper, zinc), architectural bronze (copper, zinc, lead) or aluminum bronze (copper, aluminum, nickel).
  • the color of the bronze depends on the exact composition of the different metals used in the fabrication of the alloy. For instance, a copper-rich bronze alloy may have a reddish appearance whereas a tin-rich bronze alloy may have a silvery-white appearance. The golden appearance of bronze is then the result of a specific metallic composition.
  • Bronze can be obtained as a solid alloy by pyrometallurgy or as a plated material.
  • bronze made of copper and tin is traditionally obtained by using cyanide plating baths. Bronze can be deposited directly as an alloy if cyanide chemicals are used. The product is thus formed by co-depositing copper and tin as plating takes place. More particularly, cyanide plating solutions are used during the electroplating of coinage blanks to obtain a golden bronze alloy layer.
  • the American U.S. Pat. No. 4,579,761 (Ruscoe at al.) provides a method of making aureate colored coins, medallions and tokens and products so made. The product is electroplated with alkaline cyanide copper-tin plating bath and then introduced in an annealing furnace at a constant temperature. After further cleaning treatment, Ruscoe et al. obtain a product coated with a shiny gold colored bronze.
  • Non-cyanide bronze by the plating process can be obtained by proprietary commercial formulations but the results are usually poor because the plated products come out in a reddish color, resembling very much copper, rather than goldish as one would expect when bronze is desired.
  • the non-cyanide plating solutions tend to be unstable, expensive and difficult to control for consistent results and color. This is the reason why non-cyanide bronze plating is not popular and not used, particularly, when plating is done for large quantities of industrial products, such as coinage blanks.
  • the resulting coins have a regular surface exempted of surface pinholes which is normally an inherent problem of successive metals electroplating followed by annealing diffusion.
  • the use of non-cyanide plating solution has then been successful in the successive coating of nickel, copper and nickel.
  • Brass is also made by plating copper, then plating zinc on top of copper with non-cyanide plating solutions.
  • This non-cyanide brass alloy is commercially done at the Royal Canadian Mint.
  • tin does not easily diffuse into the copper matrix because of its low melting point.
  • golden bronze cannot be produced.
  • McDaniel discloses a method which includes the steps of electroplating a layer of a first metal onto a substrate, electroplating a second layer of a second metal onto the first electroplated layer, and heating the combination of the substrate to produce an alloy finish including a bronze alloy.
  • the teaching of McDaniel is very general in nature and vague, with no specific data and samples to show how it is done. It does not allow the production of commercially suitable golden bronze. Without being specific and precise, the teaching of that reference is inapplicable and unworkable for a person skilled in the art searching a solution for the production of non-cyanide golden bronze.
  • An object of the present invention is to provide a method to produce bronze which satisfies the above-mentioned need. More particularly, the present invention provides a multiply-electroplating method to produce golden bronze by diffusion of tin into copper under controlled conditions.
  • golden bronze includes any bronze having a yellow gold color resembling gold, in other words a golden tone or gold appearance.
  • a multilayer plating method for producing a golden bronze comprising the following steps. First, the methods comprises providing a copper plated substrate comprising a core plated with at least one copper layer having a copper layer thickness. Then, the method comprises plating the copper plated substrate with a tin layer having a tin layer thickness representing 3.5 to 12% of the copper layer thickness. A multiple-layer substrate is thereby obtained. The method further comprises annealing the multiple-layer substrate at a gradually increasing annealing temperature. This gradual increase of temperature allows a complete diffusion of the tin layer into the at least one copper layer for producing an inter-diffused outer bronze layer on the multiple-layer substrate, the inter-diffused outer bronze layer having a golden appearance. Additionally, the method comprises burnishing the inter-diffused outer bronze layer to remove undesired oxide formations.
  • cleaning/rinsing and/or drying steps may be inherent to the method and performed between each of the above-mentioned step of the method.
  • the progressive annealing temperature rise advantageously enables the tin layer to gradually diffuse into the copper layer to produce a dull yellow bronze layer and to prevent the tin from vaporising by sublimation or from forming puddles on the surface of the plated substrate.
  • the burnishing enables to reveal a bright yellow gold colored bronze layer.
  • the annealing step is performed in an annealing furnace comprising a plurality of heating zones to ensure the gradual increase of the annealing temperature from 425° C. to 815° C.
  • the gradual increase of the annealing temperature is in accordance with an annealing residence time inside the furnace. More preferably, the last heating zone of the furnace has an annealing temperature ranging from 600° C. to 815° C.
  • the annealing furnace may comprise at least five heating zones, the first heating zone ranging from 425° C. to 500° C., the second heating zone ranging from 500° C. to 650° C., the third heating zone ranging from 600° C. to 700° C., the fourth heating zone ranging from 700° C. to 775° C. and the fifth heating zone ranging from 775° C. to 815° C.
  • the annealing residence time in the furnace is chosen in function of the loading of the substrate which affects the heat transfer rate and thus, the formation of bronze alloys by tin diffusion.
  • the method further may comprise etching the copper plated substrate with an acidic solution.
  • the adhesion of the tin layer on the copper layer is optimized by this etching.
  • the substrate may be a coinage blank.
  • the plating of the substrate may be an electroplating using electroplating solutions comprising acidic, cyanide, non-cyanide, neutral or slightly basic electroplating solution. More preferably, the electroplating may be done by using non-cyanide electroplating solutions.
  • FIG. 1 is a block diagram showing the method steps for the formation of a bronze alloy layer on coinage blanks according to a preferred embodiment of the present invention.
  • FIG. 2 is the binary phase diagram of the Cu—Sn alloy.
  • FIG. 3 is a photography of a coinage blank with tin puddles.
  • FIG. 4 is a photography of a coinage blank with a gold-like color bronze surface produced by a method according to an embodiment of the present invention.
  • FIG. 5 is a schematic sectional view of three configurations of tin diffusion into copper.
  • FIG. 6 is a table representing different steps of tin diffusion into copper in corresponding heating zones of an annealing furnace according to an embodiment of the present invention.
  • FIG. 7 is a cross sectional view of a coinage blank plated with 1 ⁇ m of tin, annealed until 650° C. during 45 minutes according to an embodiment of the present invention.
  • FIG. 8 is a schematic view of a furnace suitable to perform the method according to an embodiment of the present invention.
  • the present invention provides a multilayer plating method to produce bronze with a golden appearance by using electroplating of copper and tin, followed by diffusion of tin into copper under controlled conditions.
  • the further examples will be based on the production of a bronze layer on coinage blanks.
  • the present invention is not reduced to the only use of coinage blanks but concerns generally all metallic substrates that can be electroplated.
  • the substrate may thus have a core comprising steel, zinc, copper or a low cost alloy such as cartridge brass.
  • Bronze is an alloy of copper and tin.
  • a layer of bronze can be plated on substrates by electroplating.
  • an electrolytic cell is used.
  • the electrolytic cell comprises electrodes composed of a cathode and an anode.
  • the substrate to be plated is the cathode and the anode is made up with the metal to be plated on the substrate.
  • the electrodes are immersed in an electroplating solution containing ions, cations and anions, and preferably corresponding cations of the metal to be plated.
  • the electroplating solution may be copper sulphate (CuSO 4 ) based, which contains Cu 2+ cations and SO 4 2 ⁇ anions in solution.
  • cyanide electroplating solutions are well known and efficient.
  • a cyanide electroplating solution contains cyanide anions CN ⁇ which are very toxic.
  • the electrosolution has to conduct the current supplied by a power supply connected to the electrodes.
  • the metal of the anode is oxidized and releases corresponding metallic cations which interact with the anions of the electroplating solution. These cations are then reduced at the cathode and form the desired metallic deposit thereon.
  • the present invention provides a multilayer plating method to produce a bronze with a golden appearance.
  • the substrate is not limited to a mere copper plated substrate but generally includes any substrate plated with at least one copper layer.
  • the substrate may be plated with three layers comprising a nickel layer, a copper layer and a tin layer.
  • the substrate may also be plated with four layers comprising a nickel layer, a copper layer, a tin layer and a zinc layer. Therefore, the present method may comprise a step of plating a copper layer or another metallic layer on the substrate.
  • the method is valid when, besides acid copper and cyanide copper solutions, non-acidic, non-cyanide, neutral or slightly basic copper solution is used to deposit the copper needed for the bronze formation by the diffusion process, directly on the steel core. It should be noted that the present method enables to advantageously avoid the use of cyanide electroplating solutions which are commonly encountered despite their toxicity.
  • FIG. 1 shows the steps of the method to successively deposit nickel, copper and tin and ultimately produce a bronze alloy layer on coinage blanks formed from metal coils. Steps 2 to 6 are performed to obtain cleaned blanks before proceeding to the electroplating of nickel in step 7 . Copper and tin are respectively plated in step 9 and 12 . After each plating step, blanks needs to be rinsed (steps 8 , 10 , 13 ).
  • the nickel layer and the copper layer have to be etched (step 8 and 11 ) to promote and contribute to the adhesion of copper on nickel, and the adhesion of tin on copper during the electroplating of step 9 and 12 .
  • the multiple-layer blanks are then submitted to a heat treatment under an annealing temperature allowing diffusion of tin into copper so as to form an inter-diffused outer bronze layer on the blanks (step 15 ).
  • the blanks are then burnished in step 16 and dried in step 17 .
  • the plated bronze obtained by the diffusion of step 15 after cleaning and burnishing, has a nice bright yellow gold color or a dull yellow.
  • the succession of the method steps is insufficient to obtain the desired golden appearance of bronze.
  • the present invention provides controlled conditions used in the above mentioned steps to force the copper-tin alloy equilibrium to take place.
  • the heat treatment is preferably performed in an annealing furnace. It should be understood that the annealing furnace includes any furnace allowing diffusion between metallic layers upon heat treatment.
  • the formation of a yellow gold-like color bronze by diffusion of tin into copper depends heavily on three factors.
  • a particular care has to be given to the relationship between the annealing residence time in the furnace and the annealing temperature.
  • An appropriate annealing residence time allows a complete diffusion of tin to take place under gradual increase of the annealing temperature (as in step 15 ), thereby forming an inter-diffused outer bronze layer on the multiple-layer substrate.
  • the annealing residence time ranges from 10 to 90 minutes and more preferably, from 20 to 30 minutes. It should be understood that the annealing residence time may be set or controlled with a precision of more or less 5 minutes.
  • the annealing atmosphere composition has to be controlled because it influences the transformation of excess tin to tin oxide or a combination of tin and tin oxide, which in turn makes the burnishing (as in step 16 ) of the final product, easy or difficult, effective or ineffective.
  • the annealing furnace has therefore preferably a controlled atmosphere composition comprising atmosphere, nitrogen, or a mixture of nitrogen and hydrogen. This kind of composition results in a reducing (non-oxidizing) atmosphere.
  • the phase diagram of bronze alloy shows that bronze can exist in an infinite composition combination depending on the temperature and the proportion of copper and tin.
  • the percentage of tin in the bronze alloy should be between 8% and 20%.
  • the color is pinkish gold when the tin content in the alloy is 8% or less.
  • the copper plating thickness should be such that it is compatible with the tin layer to form a complete alloy between the two.
  • the important consideration is that the copper layer must be thick enough to absorb all the available tin as the diffusion takes place. There is an optimum ratio between the copper and tin layer thicknesses. If there the thickness of the copper layer is insufficient or the thickness of the tin layer is in excess, the bronze is formed as an inner inter-diffused layer but the excess tin will form puddles on the outer surface of the coinage blank.
  • the right ordinate of the binary phase diagram shows that alloys with copper can be formed as the temperature is raised.
  • the annealing temperature increase above 231.9° C., which is the melting point of tin
  • Tin then coalesces and forms droplets which can falls off the coinage blank surface or/and upon cooling, forms puddles.
  • an outer inter-diffused layer of bronze there are puddles of tin on the copper layer surface as the temperature is raised too fast.
  • a multi-layer plated coinage blank is plated with 5 microns of nickel, 20 microns of copper and 10 microns of tin, it will look grey (tin finish look) at the end of the plating process. Indeed, as can be seen in FIG. 2 , upon heating in an annealing furnace up to 600° C., and upon cooling, the blank may appear slightly yellow, but with a strong indication of tin grey still present on the surface; almost all tin has diffused into the copper and the composition on the surface would be about 86% copper and 14% tin, enough to give the yellow gold color (Point B in FIG. 2 ).
  • FIG. 3 shows the plated coinage blank with excess tin having formed tin-rich alloy large puddles on the surface of the blank, relating to the above-mentioned alloy behaviour at points B and D of FIG. 2 .
  • FIGS. 2 and 4 if a blank is plated with multiple layers including 5 microns of nickel, 20 microns of copper and 2 microns of tin, it will look grey (tin finish look) at the end of the plating process.
  • the composition of the outer alloy may be about 88% copper and 12% tin (Point C in FIG. 2 ).
  • FIG. 4 shows the blank appearing with a nice yellow gold like bronze color.
  • the present invention therefore contributes to a better control of the composition of the bronze alloy through the relative thickness of plated copper and tin.
  • FIG. 5 schematically shows substrate with a steel core and plated with nickel, copper and finally tin in different configurations A, B and C corresponding to different annealing residence time in the annealing furnace.
  • the residence time is appropriate and when there is enough copper and tin in the right proportion to give an alloy in the range of 8 to 14% tin, the inter-diffused outer bronze layer has a good golden color.
  • a residual layer of copper may be present when the copper has not completely reacted with the tin (A in FIG. 5 ).
  • the alloy formed on the surface is slightly less yellow and some residual copper may not have been alloyed yet with the tin (C in FIG. 5 ).
  • the annealing residence time is correct, when the copper and the tin are in the right ratio and when the annealing temperature is correctly set or controlled, a single outer layer of bronze is obtained with varying alloying ratios of copper and tin (B in FIG. 5 ).
  • the combination of controlled operating conditions comprising the relative layer thicknesses and the annealing residence time is crucial but insufficient to guaranty a gold-like color bronze for a given loading of substrates such as coin blanks. Indeed, a right balance has to be achieved between annealing temperature, annealing residence time (related to the diffusion rate) and right combination of copper and tin layer thicknesses, to form a bronze alloy with the proper yellow gold color without creating pockets of tin rich puddles on the substrate surface.
  • the substrate has to be plated with copper and tin in appropriate thicknesses, and then the multiple-plated substrate is submitted to an annealing treatment (heat treatment) during a sufficient annealing residence time.
  • the annealing furnace used for the annealing treatment comprises a plurality of heating zones which are set with an increasing temperature gradient, in order to succeed in facilitating the diffusion of tin into copper to produce a gold like colored bronze.
  • different controls are used to regulate the amount of energy available for heating, which results in very well defined heating zones.
  • a belt furnace long enough to allow at least five heating zones is preferred.
  • the five heating zones have respectively a temperature of 425° C., 550° C., 675° C., 725° C., 800° C. According to the shade of gold-like appearance desired, the temperature of the last two heating zones may be the same.
  • the annealing temperature may be set or controlled to increase incrementally from one heating zone to another heating zone.
  • the annealing temperature therefore gradually increases over a short transition from the exit of one heating zone to the entrance of the following heating zone. For instance, during this transition, the plated blanks entering the fifth heating zone will first stay at the annealing temperature of the fourth and then gradually reach the annealing temperature of the fifth zone after a short period.
  • the annealing furnace may comprise a belt conveyor or a rotational screw conveyor and may also comprise a forced convection system in order to ensure even heat conduction and distribution.
  • the annealing furnace may further comprise a belt conveyor or a screw conveyor with instant abrupt quenching at the end to control and stop the diffusion at the desired gold color shade.
  • the belt conveyor or rotational screw conveyor may also be set or controlled at a conveying speed which may vary from a heating zone to another heating zone, or which may be set to a constant conveying speed.
  • the conveyor is set or controlled at a constant conveying speed.
  • the annealing furnace 2 is provided with five temperature sensors 4 for each of the five heating zones.
  • the annealing temperature of the heating zones may be controlled according to these sensors 4 .
  • An evacuation duct 6 is connected to each zone of the furnace 2 and directs an exhaust gas upward to a filtration unit for removing gaseous metallic impurities from the annealing atmosphere.
  • the exhaust gas duct 6 reduces the condensation of metallic vapours in the furnace, thereby limiting time-consuming furnace shut down and hard work cleaning during operation.
  • the exhaust gas may contain zinc which has evaporated.
  • the zinc vapours may further be condensed in an external condenser and easily removed with a metallic filter.
  • the purified inert gas containing recycled hydrogen and/or nitrogen is returned to each heating zones of the furnace 2 through a recycling duct 8 .
  • the pure tin gradually diffuses into the copper layer to form a inter-diffused layer of tin-copper alloy, which in turn can sustain higher temperature which allows more diffusion of tin into the copper-rich alloy.
  • the tin can build up in the alloy to form the yellow gold color of bronze alloys.
  • the tin layer has completely disappeared and diffused into the copper layer so as to form a new inter-diffused outer bronze layer.
  • the copper layer may or may not disappear completely depending on the inter-diffused layer thickness of the copper-tin alloy.
  • a residual copper layer may subsist as seen on FIG. 5A and section 5 of FIG. 6 .
  • the inter-diffused outer bronze layer may also replace totally the tin and copper layers.
  • the present invention provides a method using an annealing furnace comprising a plurality of heating zones where three key parameters are set or controlled to allow the formation of golden bronze: the relative tin plated thickness to the copper plated thickness, the annealing temperature and the annealing residence time inside the furnace.
  • the temperature is gradually raised from 425° C. to 815° C. along the different heating zones of the annealing furnace, thereby providing effective diffusion.
  • a bronze alloy with a higher melting point than the tin melting point, is gradually formed by diffusing tin into copper and preventing it from vaporising by sublimation.
  • the tin layer thickness has to be in a proper ratio of 3.5% to 12% relatively to the copper layer thickness to obtain a final gold-like bronze according to the annealing residence time. For example, if the thickness of the copper layer is 14 microns, the tin layer to be deposited should have a thickness ranging from 0.49 to 1.68 microns.
  • the annealing residence time in the furnace is a function of the tin-copper loading which affect the heat transfer rate and thus, the formation of bronze alloys by tin diffusion.
  • the annealing temperature should be ranging from 650° C. to 850° C. in the last heating zone of the furnace.
  • the composition of the atmosphere in the diffusion annealing furnace may comprise atmosphere composition, nitrogen, or a mixture of nitrogen and hydrogen.
  • the method further comprises a step of burnishing the bronze formed by diffusion to remove oxide that may form during the annealing step.
  • the presence of residual tin oxide or other metallic impurities oxides can cause problems during further minting of coin blanks for example.
  • the burnishing step comprises polishing the outer bronze layer so as to reveal the bright yellow gold color of the bronze.
  • the blanks that were used in the experiments were Canada loon dollars.
  • the blanks had an edge thickness of 1.39 mm and a diameter of 26.1 mm.
  • the weight of each blank was approximately 6.31 grams.
  • the blanks have a steel core and are plated the same way with the same thickness of nickel and the same thickness of copper, but with different thicknesses of tin.
  • the thickness of nickel and copper layers are approximately 8 ⁇ m and 14 ⁇ m respectively at the center of the blanks. Barrel plating was used for the experiments.
  • the first pre-treatment step was an alkaline electroclean called Tec-1000.
  • the bath (also referred herein as electroplating solution) composition was:
  • the neutral anode used for the electroclean was made in stainless steel.
  • the barrel was submerged in the solution and a current was passed through the barrel and stainless steel plates.
  • the conditions of the cleaning bath were:
  • the next step was the acid pickling (also referred herein as etching) that activates the copper surface of the blanks.
  • the solution used for the acid pickling is a solution of 5% sulphuric acid. The conditions are listed below.
  • the final step is the tin plating.
  • the plating solution that was used to plate tin on the blanks was Stannolume 160. This is a highly conductive acidic tin plating solution able to plate over a large range of current densities.
  • the solution composition is:
  • tin thickness that was deposited on the blanks ranged from 0.5 ⁇ m to 10 ⁇ m of tin. Either 125 or 250 blanks were used for each trial. The current density used to plate the blanks was 0.3 A/dm 2 . The plating time was calculated based on the theoretical thickness, the number of blanks and the current density. See Appendix.
  • the blanks were annealed in a belt conveyor annealing furnace with controlled heating zones, ranging from room temperature to progressively hotter diffusion temperatures to induce the diffusion of tin into the copper without prematurely melting the tin and causing the tin to congregate into a puddle and falling off the faces of the blanks.
  • the first factor is the annealing temperature which ranged between 300° C. to 800° C.
  • the second is the annealing time which varied between 10 to 90 minutes.
  • the last factor is the atmosphere in the furnace. The atmosphere of the furnace can be changed between air, nitrogen or a combination of nitrogen and hydrogen gas.
  • the final step is the burnishing of the blanks.
  • the blanks were first burnished in a 90 liter-tumbler with an acidic solution.
  • the acidic solution used was C24 or L243.
  • the blanks were rinsed and burnished in a basic solution.
  • the basic solution used was L300 or C45.
  • the blanks were rinsed for one final time and were then dried.
  • the optimum tin layer thickness is found to be between 0.5 ⁇ m to 1.5 ⁇ m. This range of layer thickness is the most successful to form the bronze alloys with a range of colours.
  • the tin layer thickness should represent 3.5% to 12% of the copper layer thickness. It is observed that only a small amount of tin can diffuse into the copper while any of the excess tin will melt and form a puddle of tin. Puddles of tin tend to be very hard to remove during burnishing. In the range of 0.5-1.5 ⁇ m of tin layer thickness, a consistent bronze alloy with a composition of about 10% of tin is obtained. Any thicker tin plated thickness (greater or equal to 2 ⁇ m) will result in large amounts of excess tin on the surface of the blanks.
  • the annealing atmosphere does not have an effect on the formation of bronze alloy, it does have some effect on the ability to obtain a bright bronze finish or a dull bronze finish after burnishing.
  • the blanks that were annealed in air gave the most successful results.
  • the oxide layer on the surface of the blanks was more easily removed during burnishing and the resulting blanks were very bright.
  • the nitrogen atmosphere also gave good results but was not as good as the blanks that were annealed in air.
  • the blanks that were hardest to burnish were the blanks that were annealed in a nitrogen and hydrogen atmosphere. The blanks were still dull after the burnishing.
  • the set of chemicals that best cleaned the surfaces of the blanks was the combination of C24 and C45.
  • the table 2 shows the results of the tin plating. After the tin was plated on the copper, the tin layer was light gray and very dull. The bent test revealed that an excellent adhesion was obtained. The tin plating is ranging from 0.5 ⁇ m to 10 ⁇ m. Two trials were used to calculate the efficiency of the tin plating. The calculation for the efficiency is done as follows.
  • the efficiency of the plating can also be calculated once the theoretical thickness is found.
  • the efficiency can be calculated using the theoretical thickness and the following equation:
  • the color as well as the thickness of the bronze alloy is influenced by three factors which are the plated tin layer thickness, the annealing temperature and the annealing residence time.
  • the tin layer thickness is increased, more tin is available to diffuse into the copper which results in a more yellow bronze alloy.
  • a tin layer thickness of 0.5 ⁇ m and 1.5 ⁇ m will result in different colours.
  • the blanks with 0.5 ⁇ m will be pinker than the blanks with 1.5 ⁇ m.
  • the most important factors for controlling the colour of the bronze alloy are the annealing temperature and annealing residence time.
  • FIG. 4 shows the golden successful result on a coinage blank plated with 1 ⁇ m of tin and annealed at 650° C. for 45 minutes, a golden bronze blank with a high tin composition and no excess amounts of tin is obtained.
  • the cross section of this same blank is shown on FIG. 7 , the multiply layer is easily observed.
  • This golden bronze blanks are obtained with an annealing temperature ranging from 650° C. to 700° C.
  • the optimum annealing residence time may be between 20 to 30 minutes in the whole heating zone of the furnace with a constant conveying speed.
  • the annealing temperature in the last heating zone was increased up to 750-800° C. or the annealing time was increased, the tin had more time to diffuse through the copper layer.
  • the bronze layer is thus thicker and has a lower composition of tin which resulted in a more pinkish bronze color.

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018066007A1 (en) * 2016-10-06 2018-04-12 Valmet Plating S.R.L. A galvanic and thermal process to obtain the coloration of metals, in particular precious metals

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014071493A1 (en) * 2012-11-08 2014-05-15 Monnaie Royale Canadienne / Royal Canadian Mint Enhanced techniques for production of golden bronze by inter-diffusion of tin and copper under controlled conditions
CN108707882B (zh) * 2018-06-01 2020-06-12 浙江伟星实业发展股份有限公司 一种青铜金齿色拉链及其制作方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2490700A (en) * 1943-08-24 1949-12-06 John S Nachtman Production of alloy coating on base metal material
US3729294A (en) * 1968-04-10 1973-04-24 Gen Electric Zinc diffused copper
US5089057A (en) * 1989-09-15 1992-02-18 At&T Bell Laboratories Method for treating copper-based alloys and articles produced therefrom

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2304709A (en) * 1940-10-31 1942-12-08 Thomas Steel Company Method of coating ferrous articles
JPS56298A (en) * 1979-06-11 1981-01-06 Toshiba Corp Plating method
CA1219708A (en) * 1984-05-01 1987-03-31 Michael J.H. Ruscoe Aureate coins, medallions and tokens
CA2013639C (en) * 1990-04-02 1998-06-23 Mitsuhiro Yasuda Electroplated blank for coins, medallions and tokens
US5151167A (en) * 1990-06-21 1992-09-29 Royal Canadian Mint Coins coated with nickel, copper and nickel and process for making such coins
US5139886A (en) * 1990-06-21 1992-08-18 Royal Canadian Mint Coins coated with nickel, copper and nickel
JPH056298A (ja) * 1991-06-20 1993-01-14 Fuji Xerox Co Ltd 電子情報共有化装置
JP4090483B2 (ja) * 2001-07-31 2008-05-28 株式会社神戸製鋼所 導電接続部品
US7296370B2 (en) * 2004-09-24 2007-11-20 Jarden Zinc Products, Inc. Electroplated metals with silvery-white appearance and method of making
US20060286400A1 (en) * 2005-06-17 2006-12-21 Jarden Zinc Products, Inc. Substrate with alloy finish and method of making
CN101368285A (zh) * 2008-08-28 2009-02-18 尼尔金属(苏州)有限公司 一种铝及铝合金基材上镀铜的工艺方法及其产品
CN101532155B (zh) * 2009-02-26 2010-08-11 上海造币有限公司 一种多层电镀造币材料的应用工艺及其产品

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2490700A (en) * 1943-08-24 1949-12-06 John S Nachtman Production of alloy coating on base metal material
US3729294A (en) * 1968-04-10 1973-04-24 Gen Electric Zinc diffused copper
US5089057A (en) * 1989-09-15 1992-02-18 At&T Bell Laboratories Method for treating copper-based alloys and articles produced therefrom

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018066007A1 (en) * 2016-10-06 2018-04-12 Valmet Plating S.R.L. A galvanic and thermal process to obtain the coloration of metals, in particular precious metals

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CA2820745A1 (en) 2012-06-14

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