CLAIMS

1.

A method of manufacturing a brazing sheet product, comprising the step of plating a layer comprising nickel onto a surface of a sheet comprising a core sheet and a clad layer on the core sheet, the clad layer being made of an aluminium alloy containing silicon in an amount in the range 2 to 18% by weight and said surface being a surface of the clad layer, the method including a pre treatment of said surface before the plating step, characterised in that the pretreatment comprises the step of applying a bonding layer comprising zinc or tin on said surface.

2.	A method according to claim 1, wherein said bonding layer is applied by a zincate treatment or a stannate treatment.

3.	A method according to claim 2, wherein said bonding layer is applied by an immersion zincate treatment or an immersion stannate treatment.

4.	A method according to claim 2 or 3, wherein the duration of the zincate or stannate treatment is in the range 1 to 300 s.

5.	A method according to any one of claims 2 to 4, wherein the temperature of the zincate or stannate treatment is in the range of 10 to 50°C.

6.	A method according to any one of claims 1 to 5, wherein said bonding layer has a thickness of not more than lm, preferably not more than 0.3m.

7.	A method according to claim 6, wherein said bonding layer has a thickness in the range 10 to 150nm.

8.	A method according to any one of claims 1 to 7, wherein said layer comprising nickel is applied by electroplating.

9.	A method according to claim 8, wherein said electroplating is carried out in a sulfamate solution.

10.	A method according to claim 9, wherein said sulfamate solution contains lead, whereby said nickel layer contains lead.

11.

A method according to any one of claims 8 to 10, wherein said layer comprising nickel is applied by electroplating in which one or more process parameters are selected from: (a) electroplating bath temperature 2070°C, preferably 2030°C; (b) electroplating bath pH 7.012.0, preferably pH 10.012.0, and more preferably about 10.5; (c) current density of 0.110.0 A/dm2, preferably 0.5 4.0 A/dm2; (d) plating time 1 to 300 s, preferably 30 to 100 s; (e) bath composition comprising 3200 g/1 nickel sulfate, 10100 g/1 nickel chloride, 60300 g/1 sodium citrate, preferably 100 g/1 sodium citrate, 0.0510.0 g/1 lead acetate, and 5150 ml/1 ammonium hydroxide (calculated as 30% ammonium hydroxide solution).

12.

A method according to claim 8, wherein said layer comprising nickel is applied by electroplating in which one or more process parameters are selected. from: (a) electroplating bath temperature 2070°C, preferably 2030°C; (b) electroplating bath pH in the range of 3 to 5, preferably 3 to 4, and more preferably about 3; (c) current density of 0.110.0 A/dm2, preferably 0.5 to 5.0 A/dm2; (d) plating time 1 to 300 s, preferably 20 to 100 s; (e) bath composition comprising 5400 g/1 nickel sulphate, preferably 240300 g/1 nickel sulphate, 10100 g/1 nickel chloride, preferably 4060 g/1 nickel chloride, 5100 g/1 boric acid, preferably 2540 g/l boric acid.

13.	A method according to any one of claims 1 to 11, wherein the amount of silicon in said clad layer is in the range 7 to 18% by weight.

14.

Brazing sheet product having a core sheet (1), a clad layer (2) on said core sheet (1) made of an aluminium alloy containing silicon in an amount in the range 2 to 18% by weight, and a layer (3) comprising nickel on the outer surface of said clad layer, characterised by a layer (4) comprising zinc or tin as a bonding layer between said outer surface of said clad layer and said layer comprising nickel.

15.

Brazing sheet product according to claim 14, wherein said clad layer (2) has discrete siliconrich particles exposed at said outer surface thereof, and said layer (3) comprising nickel is bonded both to said siliconrich particles and to the areas of said outer surface between said siliconrich particles, so as to form a continuous layer on said outer surface.

16.	Brazing sheet product according to claim 14 or 15, wherein said bonding layer (4) is an electroplated layer.

17.	Brazing sheet product according to any one of claims 14 to 16, wherein said bonding layer (4) has a thickness of not more than 0.5pm, preferably not more than 0.3pu.

18.	Brazing sheet product according to claim wherein said bonding layer (4) has a thickness in the range 20 to 150nm.

19.	Brazing sheet product according to any one of claims 14 to 18, wherein said layer (3) comprising nickel has a thickness of not more than 2.0pm, preferably not more than l. Om.

20.

Brazing sheet product according to any one of claims 14 to 19, wherein taken together said clad layer and all layers exterior thereto, have a composition containing at least one of the following elements, Bi in the range 0.01 to 0.5% by weight, preferably 0.05 to 0.5% Mg in the range 0.2 to 2.0% by weight Sb in the range 0.01 to 0.5% by weight, preferably 0.05 to 0.5%.

21.	Brazing sheet product according to any one of claims 14 to 20, wherein said bonding layer (4) contains by weight an amount not more than 50%, and preferably not more than 25%, in total of one or more elements selected from bismuth, lead, lithium and antimony.

22.	Brazing sheet product according to any one of claims 14 to 21, wherein said clad layer (2) contains by weight Mg in an amount in the range of up to 8%, preferably in the range of 0.5 to 5%.

23.	Brazing sheet product according to any one of claims 14 to 22, wherein said clad layer (2) contains by weight Zn in an amount in the range of up to 5%, preferably in the range of 0.5 to 3%.

24.	Brazing sheet product according to any one of claims 14 to 23, wherein said core sheet (1) is an aluminium alloy.

25.	Brazing sheet product according to claim 24, wherein said core sheet (1) is an aluminium alloy comprising Mg in an amount in the range of up to 8%.

26.	Brazing sheet product according to any one of claims 14 to 25, wherein said core sheet (1) is coupled to said clad layer (2) via an intermediate layer (5).

27.	An assembly of components joined by brazing, at least one said components being a brazing sheet product according to any one of claims 14 to 26.

28.

Method of manufacturing an assembly of brazed components, comprising the steps of: (a) forming said components of which at least one is made from brazing sheet product according to any one of claims 14 to 27; (b) assembling the components into an assembly; (c) brazing the assembly under a vacuum or in an inert atmosphere in the absence of a brazingflux at elevated temperature for a period long enough for melting and spreading of the clad layer; (d) cooling the brazed assembly.