WO2020129095A1

WO2020129095A1 - Galvanic bath for making a corrosion- and oxidation-resistant palladium and nickel alloy-based plating, preparation and use thereof

Info

Publication number: WO2020129095A1
Application number: PCT/IT2018/000168
Authority: WO
Inventors: Lorenzo BERTOCCHI
Original assignee: Top Finish 2002 S.R.L.
Priority date: 2018-12-20
Filing date: 2018-12-20
Publication date: 2020-06-25

Abstract

The present invention relates to a solution/a galvanic bath for making a plating of an article, wherein said plating is palladium and nickel alloy-based corrosion- and oxidation-resistant. The bath consists of an aqueous solution buffered at a substantially basic pH, comprising: A) an effective amount of at least one water-soluble palladium complex salt; B) an effective amount of at least one water-soluble nickel complex salt; C) an effective amount of at least one corrosion- and oxidation- resistant derivative of an element belonging to the non-metal group; D) an effective amount of one conductor salt; E) an effective amount of at least one primary brightening agent. The present invention relates also to the relative method for preparing said solution/galvanic bath and the use thereof.

Description

TITLE

GALVANIC BATH FOR MAKING A CORROSION- AND OXIDATION- RESISTANT PALLADIUM AND NICKEL ALLOY-BASED PLATING,

PREPARATION AND USE THEREOF

Field of the invention

The present invention relates to a solution/a galvanic bath for making a plating of an article, wherein said plating is palladium and nickel alloy-based corrosion- and oxidation-resistant (thereinafter, defined palladium-nickel inox alloy, for convenience) .

The present invention relates also to the relative method for preparing said solution/galvanic bath and the use thereof.

Brief outline of the prior art

The palladium and nickel-based galvanic bath has been known for a long time and in use in the field of galvanic technology in many industrial fields such as, for example, car, electronic field and so on.

In the last 25 years, it has been introduced and used also in the field of galvanic technology applied to the fashion field (for example, various accessories, zipper pullers, bells, sequins, and so on) . However, clients have been recently requesting accessories resistant to corrosion and oxidation by various external agents (such as environmental, mechanical agents and so on) . This request led to the search of new types of galvanic deposits, in compliance with resistance tests in accordance with various standards (such as ISO; ASTM) , always considering metals suitable for being used as galvanic deposit (for example, lead-based alloys have been prohibited, as well as other toxic and polluting metals such as chrome, cadmium and others) . As a consequence, it is necessary to make a deposit/a plating by means of a palladium and nickel-based alloy which proves to be more corrosion- and oxidation-resistant than the commonly known and already used ones.

Technical Problem

Therefore, the possibility to make a plating of an article which is particularly corrosion- and oxidation- resistant, for example usable, among others, in the field of fashion accessories, is particularly requested in the field .

In particular, it is still necessary to have a galvanic solution/bath for making the plating of an article using a palladium-nickel-based alloy which is more corrosion- and oxidation-resistant than conventional palladium-nickel alloys and maintaining, possibly improving, the characteristics of brightness and uniformity of deposit, and the lack of the inevitable aesthetic imperfections typical of conventional palladium- nickel alloys.

The aim of the present invention is to provide an adequate response to the technical problem described above .

Summary of the invention

The applicant has unexpectedly found that an aqueous solution of i) one suitable palladium complex salt, ii) one suitable nickel complex salt and iii) suitable additives, is able to solve efficaciously the technical issue described above.

Therefore, the object of the present invention is an aqueous solution/galvanic bath comprising or consisting of effective amounts of one palladium complex salt, one nickel complex salt and suitable additives, as described in the attached independent claim and the dependent claims thereof . An additional object of the present invention is the process for preparing the solution/galvanic bath as described above, as described in the attached independent claim.

An additional object of the present invention is the use of the solution as described above for the corrosion- and oxidation-resistant plating of an article, as described in the attached independent claim.

An additional object of the present invention is also the said corrosion- and oxidation-resistant palladium and nickel inox alloy-based plating, as described in the attached independent claim.

An additional object of the present invention is also an article plated with said corrosion- and oxidation- resistant palladium and nickel inox alloy, as described in the attached independent claim.

Detailed description of the invention

Composition of the solution

The solution/galvanic bath of the present invention for making the corrosion- and oxidation-resistant inox palladium and nickel alloy-based plating of an article comprises :

A) an effective amount of at least one water-soluble palladium complex salt.

Said palladium complex salt is, for example, selected from the group consisting of: dichloro-tetraamine- palladium ( Pd (NH_{3) 4}CI₂₎ , dibromo-tetraamine-palladium (Pd (NH_{3) 4}Br2) , diiodo-tetraamine-palladium ( Pd (NH3) 4I2) , tetraamine-palladium dinitrate ( Pd (NH_{3) 4 (}NO_{3) 2)} , tetraamine-palladium dinitrite (Pd (N¾) _{4 (}NO_{2) 2)} , tetraamine-palladium disulphite (Pd (NH_{3) 4 (}SO3) 2) , tetraamine-palladium disulphate (Pd (NH_{3) 4 (}SO_{4) 2)} , dichloro- diamine-palladium (Pd (NH_{3) 2}CI₂₎ , dibromo-dianaine-palladium ( Pd (NH_{3) 2}Br2) , diiodo-diamine-palladium (Pd (NH_{3) 2}I2) , diamine-palladium dinitrite ( Pd (NH_{3) 2 (}NO_{2) 2)} , diamine- palladium dinitrate (Pd (Nfi ) _{2 (}NO3) ₂) diamine-palladium disulphite (Pd (NH₃) 2 (SO3) ₂) , diamine-palladium disulphate (Pd (NH3) 2 (SO4) 2) tetraamine-palladium sulphate ( Pd (NH₃) 4SO4) , the similar or analogous ones thereof, or a mixture thereof. These are the suitable salts commonly available on the market, however, also other suitable palladium salts, similar or analogous to the previous ones, can be used.

Preferably, said palladium complex salt is selected from dichloro-tetraamine-palladium or tetraamine-palladium sulphate or a mixture thereof.

Said at least one palladium complex salt of the present invention is present in the solution in an amount from 0,1 to 20 g/1, in terms of palladium metal in the solution; preferably, in an amount comprised from 1 to 15 g/1; more preferably, in an amount comprised from 3 to 6 g/1; even more preferably, in an amount comprised from 4 to 5 g/1.

The solution/galvanic bath of the present invention as per the description above further comprises:

B) an effective amount of at least one suitable water-soluble nickel complex salt.

Said nickel complex salt is a nickel salt complexed with ammonia. For example, said salt is selected from the group consisting of: nickel sulphate, nickel chloride, nickel nitrate, nickel phosphate, nickel carbonate, or a mixture thereof, all of them complexed with ammonia.

Preferably said nickel complex salt is selected from: nickel sulphate, nickel chloride or a mixture thereof, all of them complexed with ammonia.

Said at least one nickel complex salt of the present invention is present in the solution in an amount from 0,1 to 20 g/1, in terms of nickel metal in the solution; preferably, in an amount comprised from 0,1 to 10 g/1, preferably, in an amount comprised from 1 to 8 g/1; more preferably, in an amount comprised from 2 to 6 g/1; even more preferably, in an amount comprised from 3 to 5 g/1.

C) an effective amount of at least one suitable corrosion- and oxidation-resistant derivative of an element belonging to the non-metal group, which is corrosion- and oxidation-resistant.

Said element belonging to the non-metal group is phosphorus (P), preferably in the form of one suitable corrosion- and oxidation-resistant hypophosphite salt.

Said element belonging to the non-metal group (P) , that is the hypophosphite salt described above, is selected from the group consisting of: sodium hypophosphite, potassium hypophosphite, magnesium hypophosphite, calcium hypophosphite, nickel hypophosphite, or a mixture thereof.

Preferably, said derivative of an element belonging to the non-metal group (P) , hypophosphite, as described above, is selected from: sodium hypophosphite, potassium hypophosphite or a mixture thereof.

Said at least one derivative of an element belonging to the non-metal group (P) , of the present invention, as described above, is present in an amount comprised from 1 to 1000 g/1; preferably, in an amount comprised from 1 to 500 g/1; more preferably, in an amount comprised from 1 to 50 g/1; even more preferably, in an amount comprised from 20 to 40 g/1; for example, in an amount comprised from 25 to 30 g/1.

D) an effective amount of one suitable conductor salt .

Said conductor salt as above, is, for example, selected from the group consisting of: ammonium sulphamate, potassium sulphamate, sodium sulphamate, ammonium chloride, potassium chloride, sodium chloride, potassium sulphate, sodium sulphate, ammonium nitrate, potassium nitrate, sodium nitrate, sodium nitrite, potassium nitrite, sodium tartrate, potassium tartrate, ammonium tartrate.

Preferably, said conductor salt as above is ammonium sulphamate .

Said conductor salt as above is present in the solution in an effective amount for adjusting the solution density to about 13 °Be (Baume degrees; corresponding to 1,100 g/cm³); preferably, comprised from 12 °Be to 14 Be; more preferably, comprised from 12,5 °Be to 13,5 °Be; or 13 °Be.

Said conductor salt can optionally have also a buffer and regulator function against the pH of the solution; said value of the pH of the solution having to be substantially basic.

Preferably, said pH value of the solution is comprised from 7 to 12; more preferably, from 8 to 9.

In any case, preferably, the regulation of the pH of the solution within the limits defined above is carried out by adding a sufficient quantity of ammonium hydroxide.

E) an effective amount of at least one primary brightening agent.

Said at least one primary brightening agent is, for example, selected from the group consisting of: organic compounds having hydroxy functional groups -OH, for example, alcohols, ethanol, butanediol, hexanediol, methanol, 2-propenol, allyl, saccharine, isobutyl alcohol, saccharose, glucose, fructose, maltose, xylitol, sorbitol, mannitol; organic compounds having the -CHO functional group, for example, formaldehyde, acetaldehyde, acrolein, butyraldehyde; organic compounds having the -CO functional group, for example, pinacolin and acetone; organic compounds having the N functional group, for example, amines, such as methylamine, triethanolamine, pyridine and bipyridine, isopropylamine, diethylamine, triethylamine, methylamine; inorganic sulphurated compounds, for example, sodium sulphite, potassium sulphite, and/or mixtures thereof .

Preferably, said brightening agent as above is selected from: allyl, saccharine, sodium sulphite, potassium sulphite or mixtures thereof.

Said at least one brightening agent is present in the solution in an amount from 1 to 100 g/1, preferably, in an amount comprised from 10 to 90 g/1; more preferably, in an amount comprised from 20 to 80 g/1; even more preferably, in an amount comprised from 30 to 70 g/1; for example, in an amount comprised from 40 to 60 g/1.

In a preferred embodiment, the solution/galvanic bath of the invention consists of an aqueous solution buffered at a substantially basic pH, comprising:

A) an effective amount of at least one water- soluble palladium complex salt;

B) an effective amount of at least one water- soluble nickel complex salt;

C) an effective amount of at least one corrosion- and oxidation-resistant derivative of an element belonging to the non-metal group;

D) an effective amount of one conductor salt;

E) an effective amount of at least one primary brightening agent.

Preferably, the pH of the aqueous solution is comprised from 7 to 12, more preferably from 8 to 9, preferably by addition of ammonium hydroxide, and the characteristics of ingredients from A) to E) are as described above. In another preferred embodiment, the solution/galvanic bath of the invention consists of an aqueous solution buffered at a substantially basic pH, consisting of:

A) an effective amount of at least one water- soluble palladium complex salt;

B) an effective amount of at least one water- soluble nickel complex salt;

D) an effective amount of one conductor salt;

E) an effective amount of at least one primary brightening agent.

Preferably, the pH of the aqueous solution is comprised from 7 to 12, more preferably from 8 to 9, preferably by addition of ammonium hydroxide, and the characteristics of ingredients from A) to E) are as described above.

Process for preparing the solution and plating of an article

The preparation of the solution/galvanic bath of the present invention is carried out (into a suitable mixer commonly used in the field, made from glass, steel or plastic; or also directly into the vessel intended for containing the galvanic bath of the invention and making the plating of the desired article) by simply mixing at room temperature and under stirring, in water at pH comprised from 7 to 12 (obtained by adding the needed amount of ammonium hydroxide) the ingredients as described in points A-E, added in the order as described above or also in any order, maintaining everything under stirring for the time needed for obtaining the desired final solution .

Provided as a non-limiting example of the wide application potential of the present invention, the following experimental example explains a preferred way for preparing the said solution/galvanic bath, as well as for the application of the same.

In any case, in the light of the present document, the skilled person will make appropriate changes, depending on reactants and/or the substrate to be used, without exceeding the scope of the present invention.

Experimental example

The solution for plating a number of test samples (in this case, one or more brass lattens 10 x 7,5 cm) with the palladium-nickel inox alloy is directly prepared into the vessel of the galvanic bath (made from glass, 2 liters) by mixing the elements as described above for making a buffered solution at a pH comprised from 7 to 12, with the use of ammonium hydroxide, containing from 50 to 300 g/1 of one conductor salt (ammonium sulphamate) , from 1 to 20 g/1 in terms of palladium metal (from dichloro- tetraamine-palladium) , from 0,1 and 10 g/1 in in terms of nickel metal (from nickel sulphate complexed with ammonia) , from 1 to 1000 g/1 of a derivative of an element (P) belonging to the non-metal group, making it corrosion- resistant (sodium hypophosphite, for example, 28 g/1) , and from 1 to 100 g/1 of a brightening agent (allyl) .

The temperature of the subsequent process of deposition/plating of the palladium-nickel inox alloy of the present invention is comprised from 20°C to 35°C; the cathodic current density (in this case formed by a net of rare-earth mixed oxides) is varied from 0,5 A/dm² to 10 A/dm². Depending on the current used, the resistance of the deposit to the oxidizing agents may vary. The preferable current density for having a deposit with great resistance without losing brightness and the lack of aesthetic defects proved to be approximately, preferably, 3 A/dm², once identified, on a case by case basis, the optimum mix of the amount of the element of the bath. The thickness of palladium and nickel in the alloy proved to be variable depending on the amount of the metals in the solution, on pH, on current density used and on deposition time. On average, as regards the thickness of the deposited layer, a palladium-nickel inox alloy in accordance with the present invention has been obtained containing 0,6 palladium microns and 0,10 nickel microns.

The obtained alloy can be made up of 80% palladium and 20% nickel, to 50% palladium and 50% nickel.

Plated brass lattens obtained as described above, have been subsequently tested as follows in order to check the corrosion- and oxidation-resistance thereof.

Oxidation-resistance

HN03 rubbing test

A brass latten deposited with the palladium/nickel inox alloy is subjected to 10' with a current density of 3 A/dm² to a rubbing of concentrated HN03 (at 98%) along the deposited surface for a time of approximately 30''. The deposit is not subjected to corrosion along the whole rubbing from high current densities to low current densities for the observation time.

Salt spray test

A brass latten deposited with the palladium-nickel alloy is subjected to 10' with a current density of 3 A/dm² to the salt spray test (in accordance with NSS ISO 9227:2017) for 96 h at a pH of the saline solution between 6,5 and 7,2 and at a temperature of 35°C with RH of 50% and 1 Bar of pressure. No defects were visible after this time .

A brass latten deposited with the palladium-nickel alloy is subjected to 10' with a current density of 3 A/dm² to test the corrosion test with thioacetamide (in accordance with the TAA UNI EN ISO 4538: 1998). After the time set by standards, no evident aesthetic defect was found.

The solution of plating/galvanic bath of the present invention can be directly used onto any type of substrate, such as, for example, plastic, metal or other materials, such as a composite material which has to be coated by a corrosion- and oxidation-resistant plating (for example, usable in conventional industrial fields, but also, preferably, in the field of fashion accessories) , or as final layer for having a very good layer onto previous platings, corrosion- and oxidation-resistant, without losing a bright layer and lacking aesthetic/functional defects .

Consequently, a further object of the present invention is an article plated with the palladium-nickel inox alloy of the present invention, obtained by using onto said article the solution/galvanic bath of the present invention described above.

Moreover, another object of the present invention is an article plated with the palladium-nickel inox alloy of the present invention, obtained by depositing onto said article the solution/galvanic bath of the present invention described above.

Industrial applicability

In the light of the description above, it is possible to state that the plating of any article made with the palladium-nickel inox alloy of the present invention, obtained by using the solution/ galvanic bath of the previously described invention and claimed in the attached claims, with respect to a palladium-nickel conventional alloy, is better corrosion- and oxidation- resistant, both mechanical and environmental, thus maintaining the same aesthetic characteristics at the same time (brightness and uniformity of deposit, the lack of aesthetic imperfections of conventional palladium-nickel) . Therefore, it was possible to obtain articles, such as fashion accessories (zipper pullers, bells, sequins, and so on) which proved to be resistant to corrosion and oxidation by various external agents and owning excellent and long-lasting aesthetic qualities.

Claims

CLAIMS A solution/galvanic bath consisting of an aqueous solution buffered at a substantially basic pH, comprising :

A) an effective amount of at least one water-soluble palladium complex salt;

B) an effective amount of at least one water-soluble nickel complex salt;

D) an effective amount of one conductor salt;

E) an effective amount of at least one primary brightening agent.

A solution/galvanic bath consisting of an aqueous solution buffered at a substantially basic pH, consisting of:

A) an effective amount of at least one water-soluble palladium complex salt;

B) an effective amount of at least one water-soluble nickel complex salt;

D) an effective amount of one conductor salt;

E) an effective amount of at least one primary brightening agent. The solution/galvanic bath according to claim 1 or 2, in which the aqueous solution pH is from 7 to 12 and in which:

A) said at least one palladium complex salt is selected from the group consisting of: dichloro- tetraamine-palladium (Pd (NH₃) ₄CI₂) , dibromo-tetraamine- palladium ( Pd (NH₃) ₄Br₂) , diiodo-tetraamine-palladium

( Pd (NH₃) 4I2) , tetraamine-palladium dinitrate

( Pd (NH₃) 4 (NO3) 2) , tetraamine-palladium dinitrite ( Pd (NH₃) (NO2) 2) , tetraamine-palladium disulphite ( Pd (NH₃) ₄ (SO₃) 2) , tetraamine-palladium disulphate ( Pd (NH₃) 4 ( S0₄ ) 2 ) , dichloro-diamine-palladium ( Pd (NH3) 2CI2) , dibromo-diamine-palladium ( Pd (NH3) 2Br2) , diiodo-diamine-palladium ( Pd (NH₃) ₂I₂) , diamine- palladium dinitrite (Pd (NH₃) ₂ (NO₂) ₂) , diamine-palladium disulphite (Pd (NH₃) ₂ (SO₃) 2) , diamine-palladium disulphate (Pd (NH₃) ₂ (SO₄) ₂) , tetraamine-palladium sulphate ( Pd (NH₃) ₄SO₄ ) , or a mixture thereof;

B) said at least one nickel complex salt is complexed with ammonia and is selected from the group consisting of: nickel sulphate, nickel chloride, nickel nitrate, nickel phosphate, nickel carbonate, or a mixture thereof, all of them complexed with ammonia;

C) said at least one derivative of an element belonging to the non-metal group is a hypophosphite salt selected from the group consisting of: sodium hypophosphite, potassium hypophosphite, magnesium hypophosphite, calcium hypophosphite, nickel hypophosphite, or a mixture thereof;

D) said conductor salt is selected from the group consisting of: ammonium sulphamate, potassium sulphamate, sodium sulphamate, ammonium chloride, potassium chloride, sodium chloride, potassium sulphate, sodium sulphate, ammonium nitrate, potassium nitrate, sodium nitrate, sodium nitrite, potassium nitrite, sodium tartrate, potassium tartrate, ammonium tartrate;

E) said at least one primary brightening agent is selected from the group consisting of: organic compounds having hydroxy functional groups -OH, alcohols, ethanol, butanediol, hexanediol, methanol, 2-propenol, allyl, saccharine, isobutyl alcohol, saccharose, glucose, fructose, maltose, xylitol, sorbitol, mannitol; organic compounds having the -CHO functional group, formaldehyde, acetaldehyde, acrolein, butyraldehyde; organic compounds having the -CO functional group, pinacolin and acetone; organic compounds having the N functional group, amines, such as methylamine, triethanolamine, pyridine and bipyridine, isopropylamine, diethylamine, triethylamine, methylamine; inorganic sulphurated compounds, sodium sulphite, potassium sulphite, or mixtures thereof.

4 The solution/galvanic bath according to claim 3, in which said pH of the aqueous solution is obtained by adding the needed amount of ammonium hydroxide.

5 The solution/galvanic bath according to anyone of the preceding claims in which:

A) said at least one palladium complex salt is present in the solution in an amount from 0.1 to 20 g/1, in terms of palladium metal;

B) said at least one nickel complex salt of the present invention is present in the solution in an amount from 0.1 to 20 g/1, in terms of nickel metal;

C) said at least one derivative of an element belonging to the non-metal group is present in the solution in an amount from 1 to 1000 g/1;

D) said conductor salt is present in the solution in an effective amount for adjusting the solution density to about 13 °Be;

E) said at least one brightening agent is present in the solution in an amount from 1 to 100 g/1.

6 A process for preparing the solution/galvanic bath according to anyone of claims from 1 to 5, comprising: into a mixer or into the vessel intended for containing said solution/galvanic bath and making the plating of the desired article, mixing, at room temperature and under stirring, in water at pH from 7 to 12, obtained by adding the needed amount of ammonium hydroxide, the ingredients as described in the preceding claims from 1 to 5, added in any order, and

- maintaining under stirring for the needed time to obtain the final solution.

7 Use of the solution/galvanic bath according to anyone of claims from 1 to 5, for making the plating of an article by forming on the same a corrosion- and oxidation-resistant palladium-nickel inox alloy.

8 A plating of an article by forming on the same a corrosion- and oxidation-resistant palladium-nickel inox alloy, obtained by deposing on said article the solution/galvanic bath according to anyone of claims from 1 to 5.

9 An article plated with a corrosion- and oxidation- resistant palladium-nickel inox alloy, obtained by deposing on said article the solution/galvanic bath according to anyone of claims from 1 to 5.