EP3445582A1 - Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals - Google Patents

Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals

Info

Publication number
EP3445582A1
EP3445582A1 EP17731631.2A EP17731631A EP3445582A1 EP 3445582 A1 EP3445582 A1 EP 3445582A1 EP 17731631 A EP17731631 A EP 17731631A EP 3445582 A1 EP3445582 A1 EP 3445582A1
Authority
EP
European Patent Office
Prior art keywords
precious metal
alloy
nickel
cobalt
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP17731631.2A
Other languages
German (de)
French (fr)
Inventor
Leandro Luconi
Lorenzo Cavaciocchi
Giacomo PIZZICORI
Serena CINOTTI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BLUCLAD S.P.A.
Original Assignee
Bluclad Srl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bluclad Srl filed Critical Bluclad Srl
Publication of EP3445582A1 publication Critical patent/EP3445582A1/en
Pending legal-status Critical Current

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Classifications

    • 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
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • 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
    • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C9/00—Alloys based on copper

Definitions

  • Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals
  • the present invention relates to the field of metal alloys used for coating metal bodies, particularly small metal parts.
  • small metal objects which constitute the so-called small metal objects or jewelry (such as buckles, rings, bracelets, self-locking devices, chains, sliders, zippers, hooks, shoe clamps etc.).
  • These objects typically consist of a non-precious metal body coated with a layer of precious metal such as gold or palladium.
  • one or more preparatory layers are deposited which are selected according to a method known to the man skilled in the art as a function of the metal constituting the body of the object to be treated, the desired type of finish (e.g. glossy, satin finish) and the type of chemical and physical tests that the object undergoes during quality monitoring.
  • a phosphorous-cobalt-nickel alloy is described, and the use thereof in plating processes of non-precious metal objects with precious metals.
  • the present invention allows to overcome the above problem with a process that uses a phosphorous-cobalt-nickel alloy.
  • an alloy consisting of: 10-20% phosphorus, 10-50% cobalt and nickel as much as needed up to 100%, allows to maintain the features of oxidation resistance of the traditional nickel-phosphorus alloy, virtually eliminating the release of nickel or bringing it to levels below the limits imposed by law.
  • a concentration thereof greater than 50% lowers the resistance of the deposition, thereby increasing the release of nickel and producing dark oxidation points on the objects when tested with the conventional oxidative tests.
  • the alloy layer applied is at least 0.5 microns; using amounts of cobalt near the maximum value of the range allows to deposit layers of thickness up to 5-10 microns.
  • the alloy described above is therefore used in plating of non-precious metal objects that need to be coated with a layer of precious metal according to methodologies known in the art.
  • Non-precious metal objects according to the invention are objects of brass, copper, zinc, iron, steel, stainless steel, nickel silver, tin-bismuth, silver, aluminum, magnesium, or alloys thereof.
  • Precious metals are, for example: gold, palladium, ruthenium, platinum, rhodium.
  • one or more preparatory layers may be applied on the object to be plated, normally consisting of deposits of copper, bronze and tin for hypoallergenic cycles and nickel, nickel- phosphorus for those that do not require such a specification.
  • the alloy according to the invention may be deposited directly on the non-precious metal body and then coated with the precious metal layer.
  • one or more preparatory layers may be deposited on the non- precious metal body on which the layer of alloy according to the invention and then that of precious metal are deposited in succession.
  • a layer of bronze and then the layer of precious metal may be applied.
  • baths consisting of aqueous solutions comprising a nickel salt, a cobalt salt, a compound of the phosphorus with low oxidation number (equal to or lower than +4), a suitable buffer system, one or more complexing agents that, in addition to modulating the behavior of the metals in the alloy, ensure its stability in solution, a surfactant and other organic additives acting as brighteners.
  • the nickel salt used may be nickel sulfate and/or nickel chloride at various degrees of hydration.
  • concentration of nickel as metal ranges from 15 g/L to 90 g/L, more preferably from 40 g/L to 70 g/L depending on the desired alloy percentage.
  • the cobalt salt used may be selected from cobalt sulfate, cobalt chloride, cobalt acetate, cobalt sulfamate and other water-soluble salts at various degrees of hydration, as well as a combination thereof.
  • the concentration of cobalt as metal ranges from 1 g/L to 40 g/L, more preferably from 5 g/L to 20 g/L depending on the desired alloy percentage.
  • the phosphors compounds used as source of phosphorus for the alloy may be phosphorous acid, hypophosphorous acid, sodium or potassium phosphite, sodium or potassium hypophosphite and other phosphorus compounds capable of increasing the content of the element in the alloy in the working deposition conditions.
  • the concentration of these compounds may vary widely depending on the oxidation state of phosphorus in the compound. The lower the oxidation number of phosphorus, the easier it is to deposit it and therefore it will require lower concentrations. For example, using sodium hypophosphite allows to work between 5 and 40 g/L while using phosphorous acid requires the use of from 40 to 120 g/L of acid.
  • Some examples of these compounds are ethylenediaminetetraacetic acid, etidronic acid, nitrilotriacetic acid, ethylenediamine tetra methylene phosphonic acid, nitrilotrismethylenetriphosphonic acid, citric acid, acetic acid, in the form of free acids or in the form of salts.
  • the surfactant is selected from the sodium salts of soluble alkyl sulfonates and alkyl phosphonates stable at the working pH of the invention, and is placed in amounts no greater than 2 g/L, added as pre-diluted aqueous solution to prevent solubility problems.
  • the pH of the solution is a critical parameter from which the stability in solution of the selected components and the amount of phosphorus alloyed depend.
  • It may be between 1 .5 and 7, more preferably between 1 .8 and 2.8 and is adjusted with sodium or potassium hydroxide or with inorganic acids such as, but not limited to, sulfuric acid, phosphoric acid.
  • a higher working pH corresponds to a lower content of phosphorus in the alloy.
  • the pH is kept stable by a buffer system selected between the acid/salt pairs of acids such as gluconic, oxalic, citric, tartaric, malonic, malic, phosphoric, sulfamic and others.
  • a buffer system selected between the acid/salt pairs of acids such as gluconic, oxalic, citric, tartaric, malonic, malic, phosphoric, sulfamic and others.
  • the complexing agents are suitably used both for the stability of metals in solution and as a buffer system for maintaining the stability of the pH.
  • the preferred working temperature of the solution ranges from 55 to 75 °C; an increase in temperature causes an increase of nickel in the deposition, at the expense of the cobalt content.
  • the preferred current density ranges from 2.5 A/sq.dm to 6 A/sq.dm, an excessive increase in the applied current density may cause a localized precipitation at the cathode of the metals caused by the strong increase in the pH, resulting in the incorporation of the precipitate in the deposition and loss of the desired gloss.
  • Brighteners are organic additives; brighteners commonly used and well known to the man skilled in the art that are intended to enhance the appearance of the deposition, by increasing the brightness and/or leveling thereof, may be added; the addition of these additives is not relevant to the release of nickel and thus not even to the hypoallergenicity of the alloy.
  • NiSO4-6H 2 O nickel sulfate hexahydrate
  • CoSO4-7H 2 O cobalt sulfate heptahydrate
  • 60 g/L phosphorous acid 50 g/L potassium citrate
  • 50 g/L citric acid 100 ppm sodium lauryl sulfate.
  • the working pH is brought to 2.4 with sulfuric acid.
  • the bath thus formulated was used to produce parts which were subsequently tested.
  • a buckle as described in the example was subjected to wear test of a ceramic material with instrument Turbula T2F Mixer (reference standard ISO23160) and subsequently it underwent an oxidation test "Wet heat with leather, 96 hours" (reference standards UNI EN ISO 461 1/UNI EN ISO 17228) that includes keeping the part for 96 hours in a climatic chamber at constant temperature and humidity while in close contact with leather according to the test. The tests showed no oxidation phenomena.
  • a second galvanized buckle with the same galvanic cycle was subjected to oxidation test SO2/N y Ox (where y is 1 or 2 and x ranges from 1 to 5) (internal method LBS 004 of luxury Brand Services s.r.l. much widespread to test galvanic cycles containing nickel-phosphorus alloys) which involves keeping the part for 2 hours in a climatic chamber in contact with vapors containing a high concentration of sulfur and nitrogen oxides.
  • a third galvanized buckle with the same galvanic cycle was subjected to wear test and subsequently it underwent a nickel release test (reference wear standard UNI EN 12472 and nickel release standard UNI EN 181 1 ).
  • the release was lower than the LoD (Limit of Detection) value.
  • NiSO4-6H 2 O nickel sulfate hexahydrate
  • CoSO4-7H 2 O cobalt sulfate heptahydrate
  • 40 g/L Na2HPO2 sodium hypophosphite
  • 30 g/L acetic acid 30 g/L sodium malonate, working pH 2.0.
  • Working temperature 65 °C, fast stirring, direct current 4 A/sq.dm.
  • the deposition analyzed with a scanning electron microscope, consists of 70.7% nickel, 8.3% cobalt and 21 .0% phosphorus.
  • the bath thus formulated was used to produce parts which were subsequently tested.
  • example no. 1 The tests of example no. 1 were conducted on the three buckles. While the oxidative tests were all successful, the release of nickel exceeded the limit imposed by law, equal to 0.88 ⁇ g/cm 2 per week.
  • NiCI 2 -6H 2 O 100 g/L CoCI 2 -6H 2 O, 10 g/L Na 2 HPO 2 , 15 g/L sodium citrate, 15 g/L citric acid, working pH 2.5.
  • Working temperature 60 °C, fast stirring, direct current 4 A/sq.dm.
  • the deposition analyzed with a scanning electron microscope, consists of 45.9% nickel, 51 .3% cobalt and 2.8% phosphorus.
  • the bath thus formulated was used to produce parts which were subsequently tested.
  • example no. 1 The tests of example no. 1 were conducted on the three buckles. Both the oxidative tests and the nickel release tests were negative.

Abstract

A phosphorus-cobalt-nickel alloy is described, and the use thereof in plating processes of non-precious metal objects with precious metals; said plating processes and the objects thus obtained are also described.

Description

Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals
Field of the invention
The present invention relates to the field of metal alloys used for coating metal bodies, particularly small metal parts.
Prior art
It is known that metal objects have to be normally protected from oxidation.
The problem is particularly felt for small metal objects which constitute the so- called small metal objects or jewelry (such as buckles, rings, bracelets, self-locking devices, chains, sliders, zippers, hooks, shoe clamps etc.).
These objects typically consist of a non-precious metal body coated with a layer of precious metal such as gold or palladium.
Normally, before applying the layer of precious metal on the non-precious metal body, one or more preparatory layers are deposited which are selected according to a method known to the man skilled in the art as a function of the metal constituting the body of the object to be treated, the desired type of finish (e.g. glossy, satin finish) and the type of chemical and physical tests that the object undergoes during quality monitoring.
Since these objects are intended to come into contact with the user's skin, they must meet strict non-allergenic criteria.
This requirement adds up to the request by the fashion houses to use processes that allow to obtain products that are hypoallergenic but that still meet all quality standards, both aesthetic and physical and chemical needed for marketing and also have low precious metal deposition thicknesses, thus reducing costs.
Prior to the non-allergenic request, most processes used for coating of this type of metal objects with layers of precious metal comprised glossy plating baths (high leveling of flaws and high gloss but low testing resistance) and deposition baths of nickel-phosphorus alloys capable of withstanding the most extreme acidic and oxidative conditions.
They were normally applied in sequence, so polished nickel first as preparatory layer with a high gloss and mirror finish, and nickel-phosphorus directly on top of it, capable of preserving the non-precious underlying depositions from oxidation. Finally, the deposition of precious metal that characterizes the appearance of the object.
With the advent of the non-allergenic request, acid copper plating baths were used as a replacement process of polished nickel which, like nickel, have an excellent leveling and specularity capacity but have more oxidizable deposits.
In order to protect the copper deposit, prior to the final deposition of the precious metal, the use of bronze has become widespread, which is certainly more resistant than copper to oxidation but not enough to leave the thicknesses of precious material unchanged.
For this reason, bronze also having the need to be partially protected, manufacturers were forced to double and sometimes triple the thickness of precious metal which was previously deposited on the same metal accessory. It is therefore of paramount importance to introduce a new deposition in replacement or in sequence to bronze that has features similar to nickel- phosphorus but without releasing nickel.
Summary of the invention
A phosphorous-cobalt-nickel alloy is described, and the use thereof in plating processes of non-precious metal objects with precious metals.
Detailed description of the invention
The present invention allows to overcome the above problem with a process that uses a phosphorous-cobalt-nickel alloy.
In particular, it was surprisingly found that an alloy consisting of: 10-20% phosphorus, 10-50% cobalt and nickel as much as needed up to 100%, allows to maintain the features of oxidation resistance of the traditional nickel-phosphorus alloy, virtually eliminating the release of nickel or bringing it to levels below the limits imposed by law.
The percentages indicated are essential to achieve the desired result; in fact, it was found that percentages of phosphorus lower than 10% reduce the oxidation resistance of the deposition, causing a simpler oxidation/dissolution of the nickel contained in the alloy with consequent increase of its release while above 20% there is a significant lowering of the deposition efficiency; in fact, much of the current is used to bring hypophosphite to phosphorus, an extremely small and lightweight element if compared with metal elements.
Likewise, as regards cobalt, a concentration thereof greater than 50% lowers the resistance of the deposition, thereby increasing the release of nickel and producing dark oxidation points on the objects when tested with the conventional oxidative tests.
Preferably, according to the invention, the alloy layer applied is at least 0.5 microns; using amounts of cobalt near the maximum value of the range allows to deposit layers of thickness up to 5-10 microns.
The alloy described above is therefore used in plating of non-precious metal objects that need to be coated with a layer of precious metal according to methodologies known in the art.
Non-precious metal objects according to the invention are objects of brass, copper, zinc, iron, steel, stainless steel, nickel silver, tin-bismuth, silver, aluminum, magnesium, or alloys thereof.
Precious metals are, for example: gold, palladium, ruthenium, platinum, rhodium. As said, if necessary, prior to the plating with precious metal, one or more preparatory layers may be applied on the object to be plated, normally consisting of deposits of copper, bronze and tin for hypoallergenic cycles and nickel, nickel- phosphorus for those that do not require such a specification.
The alloy according to the invention may be deposited directly on the non-precious metal body and then coated with the precious metal layer.
Alternatively, one or more preparatory layers may be deposited on the non- precious metal body on which the layer of alloy according to the invention and then that of precious metal are deposited in succession.
According to a further embodiment of the process on the alloy layer according to the invention (irrespective of the presence or absence of the underlying preparatory layer(s)), a layer of bronze and then the layer of precious metal may be applied.
In order to obtain the alloy according to the invention, baths are used consisting of aqueous solutions comprising a nickel salt, a cobalt salt, a compound of the phosphorus with low oxidation number (equal to or lower than +4), a suitable buffer system, one or more complexing agents that, in addition to modulating the behavior of the metals in the alloy, ensure its stability in solution, a surfactant and other organic additives acting as brighteners.
The nickel salt used may be nickel sulfate and/or nickel chloride at various degrees of hydration. Preferably, the concentration of nickel as metal ranges from 15 g/L to 90 g/L, more preferably from 40 g/L to 70 g/L depending on the desired alloy percentage.
The cobalt salt used may be selected from cobalt sulfate, cobalt chloride, cobalt acetate, cobalt sulfamate and other water-soluble salts at various degrees of hydration, as well as a combination thereof.
Preferably, the concentration of cobalt as metal ranges from 1 g/L to 40 g/L, more preferably from 5 g/L to 20 g/L depending on the desired alloy percentage.
The phosphors compounds used as source of phosphorus for the alloy may be phosphorous acid, hypophosphorous acid, sodium or potassium phosphite, sodium or potassium hypophosphite and other phosphorus compounds capable of increasing the content of the element in the alloy in the working deposition conditions.
The concentration of these compounds may vary widely depending on the oxidation state of phosphorus in the compound. The lower the oxidation number of phosphorus, the easier it is to deposit it and therefore it will require lower concentrations. For example, using sodium hypophosphite allows to work between 5 and 40 g/L while using phosphorous acid requires the use of from 40 to 120 g/L of acid.
It is suitable to include one or more complexing agents in the bath formulation, preferably in concentrations of between 5 and 50 g/L.
Some examples of these compounds are ethylenediaminetetraacetic acid, etidronic acid, nitrilotriacetic acid, ethylenediamine tetra methylene phosphonic acid, nitrilotrismethylenetriphosphonic acid, citric acid, acetic acid, in the form of free acids or in the form of salts.
The surfactant is selected from the sodium salts of soluble alkyl sulfonates and alkyl phosphonates stable at the working pH of the invention, and is placed in amounts no greater than 2 g/L, added as pre-diluted aqueous solution to prevent solubility problems. The pH of the solution is a critical parameter from which the stability in solution of the selected components and the amount of phosphorus alloyed depend.
It may be between 1 .5 and 7, more preferably between 1 .8 and 2.8 and is adjusted with sodium or potassium hydroxide or with inorganic acids such as, but not limited to, sulfuric acid, phosphoric acid. A higher working pH corresponds to a lower content of phosphorus in the alloy.
In the working conditions, the pH is kept stable by a buffer system selected between the acid/salt pairs of acids such as gluconic, oxalic, citric, tartaric, malonic, malic, phosphoric, sulfamic and others.
The complexing agents are suitably used both for the stability of metals in solution and as a buffer system for maintaining the stability of the pH.
The preferred working temperature of the solution ranges from 55 to 75 °C; an increase in temperature causes an increase of nickel in the deposition, at the expense of the cobalt content. The preferred current density ranges from 2.5 A/sq.dm to 6 A/sq.dm, an excessive increase in the applied current density may cause a localized precipitation at the cathode of the metals caused by the strong increase in the pH, resulting in the incorporation of the precipitate in the deposition and loss of the desired gloss.
Brighteners are organic additives; brighteners commonly used and well known to the man skilled in the art that are intended to enhance the appearance of the deposition, by increasing the brightness and/or leveling thereof, may be added; the addition of these additives is not relevant to the release of nickel and thus not even to the hypoallergenicity of the alloy.
Below are some examples of galvanic baths and resulting alloys as well as examples of plating of metal objects.
Example 1
250 g/L NiSO4-6H2O (nickel sulfate hexahydrate), 50 g/L CoSO4-7H2O (cobalt sulfate heptahydrate), 60 g/L phosphorous acid, 50 g/L potassium citrate, 50 g/L citric acid, 100 ppm sodium lauryl sulfate. The working pH is brought to 2.4 with sulfuric acid.
Working temperature 65 °C, fast stirring, direct current 4 A/sq.dm. The deposition, analyzed with a scanning electron microscope, consists of 56.7% nickel, 30.2% cobalt and 13.1 % phosphorus.
The bath thus formulated was used to produce parts which were subsequently tested.
The following galvanic deposits were deposited on three brass belt buckles, respectively:
• Deposition of polished copper plating, 20 μιη thick
• Deposition of nickel-cobalt-phosphorus alloy, 1 .5 μιη thick
• Deposition of a white bronze alloy, 1 μιη thick
· Gold plating, 0.25 pm thick
Wear tests
A buckle as described in the example was subjected to wear test of a ceramic material with instrument Turbula T2F Mixer (reference standard ISO23160) and subsequently it underwent an oxidation test "Wet heat with leather, 96 hours" (reference standards UNI EN ISO 461 1/UNI EN ISO 17228) that includes keeping the part for 96 hours in a climatic chamber at constant temperature and humidity while in close contact with leather according to the test. The tests showed no oxidation phenomena.
A second galvanized buckle with the same galvanic cycle was subjected to oxidation test SO2/NyOx (where y is 1 or 2 and x ranges from 1 to 5) (internal method LBS 004 of Luxury Brand Services s.r.l. much widespread to test galvanic cycles containing nickel-phosphorus alloys) which involves keeping the part for 2 hours in a climatic chamber in contact with vapors containing a high concentration of sulfur and nitrogen oxides.
The tests showed no oxidation phenomena.
A third galvanized buckle with the same galvanic cycle was subjected to wear test and subsequently it underwent a nickel release test (reference wear standard UNI EN 12472 and nickel release standard UNI EN 181 1 ).
The release was lower than the LoD (Limit of Detection) value.
Example 2
300 g/L NiSO4-6H2O (nickel sulfate hexahydrate), 30 g/L CoSO4-7H2O (cobalt sulfate heptahydrate), 40 g/L Na2HPO2 (sodium hypophosphite), 30 g/L acetic acid, 30 g/L sodium malonate, working pH 2.0. Working temperature 65 °C, fast stirring, direct current 4 A/sq.dm.
The deposition, analyzed with a scanning electron microscope, consists of 70.7% nickel, 8.3% cobalt and 21 .0% phosphorus.
The bath thus formulated was used to produce parts which were subsequently tested.
The following galvanic deposits were deposited on three brass belt buckles, respectively:
· Deposition of polished copper plating, 23 μιη thick
• Deposition of nickel-cobalt-phosphorus alloy, 1 .2 μιη thick
• Deposition of a white bronze alloy, 2 μιη thick
• Gold plating, 0.25 μιη thick
The tests of example no. 1 were conducted on the three buckles. While the oxidative tests were all successful, the release of nickel exceeded the limit imposed by law, equal to 0.88 μg/cm2 per week.
Example 3
200 g/L NiCI2-6H2O, 100 g/L CoCI2-6H2O, 10 g/L Na2HPO2, 15 g/L sodium citrate, 15 g/L citric acid, working pH 2.5. Working temperature 60 °C, fast stirring, direct current 4 A/sq.dm.
The deposition, analyzed with a scanning electron microscope, consists of 45.9% nickel, 51 .3% cobalt and 2.8% phosphorus.
The bath thus formulated was used to produce parts which were subsequently tested.
The following galvanic deposits were deposited on three brass belt buckles, respectively:
• Deposition of polished copper plating, 25 μιη thick
• Deposition of nickel-cobalt-phosphorus alloy, 2.1 μιη thick
· Deposition of a white bronze alloy, 2 μιη thick
• Gold plating, 0.5 μιη thick
The tests of example no. 1 were conducted on the three buckles. Both the oxidative tests and the nickel release tests were negative.

Claims

1 . An alloy consisting of: 10-20% phosphorus, 10-50% cobalt and nickel as much as it is needed up to 100%.
2. Use of an alloy according to claim 1 in plating processes of non-precious metal objects with precious metals.
3. Use according to claim 2, wherein said non-precious metal is selected from: brass, copper, zinc, iron, steel, stainless steel, nickel silver, tin-bismuth, silver, aluminum, magnesium, or alloys thereof and the precious metal is selected from gold, palladium ruthenium, platinum, rhodium.
4. A process for obtaining an alloy according to claim 1 , wherein baths are used consisting of aqueous solutions comprising a nickel salt, a cobalt salt, a compound of the phosphorus with oxidation number equal to or lower than +4, a suitable buffer system, one or more complexing agents, a surfactant and other organic additives acting as brighteners.
5. A process according to claim 4, wherein the nickel salt used is nickel sulfate and/or nickel chloride and the concentration of nickel as metal ranges from 15 g/L to 90 g/L, preferably between 40 g/L and 70 g/L.
6. A process according to claim 4, wherein the cobalt salt is selected from sulfate, cobalt chloride, cobalt acetate, cobalt sulfamate and the concentration of cobalt as metal ranges from 1 g/L to 40 g/L, preferably between 5 g/L and 20 g/L depending on the desired alloy percentage.
7. A process according to claim 4, wherein the phosphors compounds used as source of phosphorus for the alloy can be phosphorous acid, hypophosphorous acid, sodium or potassium phosphite, sodium or potassium hypophosphite.
8. A process for plating non-precious metal objects wherein a layer of alloy according to claim 1 is deposited directly onto the non-precious metal body and then coated with the precious metal layer.
9. A process for plating non-precious metal objects wherein one or more preparatory layers are deposited on the non-precious metal body on which the layer of alloy according to claim 1 and then that of precious metal are deposited in succession.
10. A process for plating non-precious metal objects on which a layer of alloy is deposited on the non-precious metal body irrespective of the presence or absence of underlying preparatory layer/s, then a brass layer and then the precious metal layer are applied
1 1 . Objects of non-precious metal plated with precious metal and comprising a layer of alloy according to claim 1 .
12. Objects according to claim 1 1 produced by the processes according to claims 8 - 10.
13. Objects according to claims 1 1 and 12, wherein the alloy layer applied if at least 0.5 micron.
EP17731631.2A 2016-04-19 2017-04-19 Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals Pending EP3445582A1 (en)

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ITUA2016A002707A ITUA20162707A1 (en) 2016-04-19 2016-04-19 Phosphorus-Cobalt-Nickel alloy and its use in the processes of plating with noble metals of non-noble metal objects.
PCT/IB2017/052232 WO2017182957A1 (en) 2016-04-19 2017-04-19 Phosphorous-cobalt-nickel alloy and use thereof in plating processes of non-precious metal objects with precious metals

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IT202000011203A1 (en) * 2020-05-15 2021-11-15 Bluclad S P A STAINLESS BRONZE ALLOY AND ITS USE IN GALVANIZED PRODUCTS
IT202100003281A1 (en) 2021-02-15 2022-08-15 Bluclad S P A HYPOALLERGENIC ELECTRODEPOSITED PT-NI ALLOY AND RELATED BATH AND GALVANIC CYCLE

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US6335107B1 (en) * 1999-09-23 2002-01-01 Lucent Technologies Inc. Metal article coated with multilayer surface finish for porosity reduction
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