# US 9,752,243 B2 · Method of fabricating a bath of electrolyte for plating a platinum-based metallic underlayer on a metallic substrate

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- Number: US 9,752,243 B2
- Document ID: US9752243B2
- Status: Granted
- Kind: B2
- Application number: 14/395,190
- Filed: 2013-04-18
- Published: 2015-03-19
- Granted: 2017-09-05
- Earliest claimed: 2012-04-19
- Assignees: Snecma
- Applicants: Snecma
- Inventors: Juliette Hugot; Frederic Lagrange; Herve Molet
- Web page: https://patentgrep.com/patent/US9752243B2

## CPC

- C25D 3/52: characterised by the organic bath constituents used
- C25D 3/50: of platinum group metals
- C25D 5/34: Pretreatment of metallic surfaces to be electroplated
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR

## Abstract

The invention relates to a method of fabricating a bath of electrolyte for plating a platinum-based metal underlayer on a metallic substrate, comprising: a) providing a first system having ligands and amine functional groups, the first system being constituted by an aqueous solution of an amino ligand comprising at least one compound X—(NH2)n, where X belongs to the group constituted by (CH3, CH3—CH2, CH3—(CH2)m), or NH3 or an xP−(NH4)+p salt where x is an acid radical belonging to the group constituted by (PO43−, HPO42−, H2PO4−, HPO42−and H2PO4−, SO42−, HSO4−, H2SO4, HSO4−, and H2SO4, CH3COO−, CH3COOH, and CH3COO−), or H2SO4, or CH3COOH, and where n, m, and p are non-zero integers; b) providing a second system forming a buffer system; c) providing a third system providing a metallic salt, and constituted by an aqueous solution of platinum; d) providing a fourth system suitable for imparting the conduction property to the medium; and e) mixing together the four systems so as to obtain the electrolyte bath.

## Claims

### Claim 1

A fabrication method for a bath of electrolyte, the method comprising:
a) providing a first system having ligands and amine functional groups, said first system comprising an aqueous solution of an amino ligand comprising:
(i) at least one compound X—(NH2)n, where X is selected from the group consisting of (CH3, CH3—CH2, CH3—(CH2)m;
(ii) NH3; or
(iii) an xP−(NH4)+p salt where x is an acid radical selected from the group consisting of PO43−, HPO42−, H2PO4−, SO42−, HSO4−, and CH3COO−, where n, m, and p are non-zero integers;
b) providing a second system forming a buffer system;
c) providing a third system providing a metallic salt, and comprising an aqueous solution of platinum; the metallic salt being at least one salt of platinum of degree of oxidation IV;
d) providing a fourth system suitable for imparting the property of conduction to the bath of electrolyte;
forming a first solution B by grouping the first system, the second system, and the fourth system together in a single solution;
forming a second solution A comprising sodium hydroxide and the least one salt of platinum of degree of oxidation IV of the third system; and
e) mixing together the four systems so as to obtain the electrolyte bath of electrolyte;
wherein
the mixing comprises:
e1) covering the first solution B and raising the first solution B to a temperature of at least 50° C. for at least 1h30 and
e2) adding the second solution A to the first solution B and mixing the second solution A with the first solution B thereby forming a platinum amino complex and thus obtaining said bath of electrolyte.

### Claim 2 (depends on 1)

The method according to claim 1, the first solution B comprises the xp−(NH4)+p salt, where x=HPO42− and p=2, and/or x=H2PO4− and p=1.

### Claim 3 (depends on 2)

The method according to claim 2, further comprising
f) heating the bath of electrolyte to a temperature of 80° C. to 97° C. for at least two hours; and
g) electroplating a deposit of platinum on a metallic substrate using said heated bath of electrolyte.

### Claim 4 (depends on 3)

The method according to claim 3, wherein prior to e2), the first solution B is raised to a temperature of 60° C.

### Claim 5 (depends on 3)

The method according to claim 3, wherein the molar ratio of sodium hydroxide (NaOH) to the salt of platinum of degree of oxidation IV is 2.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said salt of platinum of degree of oxidation IV is Y2PtM6 with Y═NH4+, H+, or K+, and M=Cl− or OH−.

### Claim 7 (depends on 6)

The method according to claim 6, wherein in the second solution A, said salt of platinum of degree of oxidation IV is diammonium hexachloroplatinate of formula (NH4)2PtCl6.

### Claim 8 (depends on 1)

The method according to claim 1, wherein x of the xp−(NH4)+p salt is an acid radical selected from the group consisting of HPO42− and H2PO4−; and wherein the first system comprises diammonium hydrogen phosphate (NH4)2HPO4, ammonium dihydrogen phosphate NH4H2PO4, or a mixture thereof.

### Claim 9 (depends on 8)

The method according to claim 8, wherein a molar ratio between the ammonium dihydrogen phosphate NH4H2PO4 and the diammonium hydrogen phosphate (NH4)2HPO4 is 2.

### Claim 10 (depends on 1)

The method according to claim 1, wherein said second solution A is heated before step e2).