Coating for functional parts made of metal

1. A baking plate for the industrial manufacture of baked products, whereby a baking surface of the baking plate is formed with a moulding forming a baking mould and engraving and whereby the baking surface is a coated metal surface, wherein at least one coating comprising an alloy is applied galvanically to the metal surface from an electrolyte bath, wherein:

the coating comprises a surface layer which consists of a galvanically applied alloy which contains nickel, phosphorus and tin, wherein the alloy contains 0.05 to 10.0 wt. % tin and 1.0 to 15 wt. % phosphorus and the remainder up to 100 wt. % nickel,

wherein the pH-value of the electrolyte bath is 1.0 to 5.5 and the bath temperature of the electrolyte bath is 25° C. to 75° C.

wherein the surface layer is an alloy layer obtained by pulsed deposition,

wherein the surface layer has a roughness, the Ra value of which is less than 5 μm,

wherein the layer is produced by:

a unipolar pulse sequence as follows:

pulse current density from 0.5 to 15 A/dm 2 ;

cathodic pulse time from 5 to 100 ms; and

off time from 0 to 25 ms,

or the layer is produced by:

a bipolar pulse with a base current as follows:

cathodic pulse current density from 0.5 to 20 A/dm 2 with a pulse time from 5 to 100 ms;

cathodic base current density from 0.5 to 12 A/dm 2 with a pulse time from 5 to 100 ms;

anodic pulse current density from 0.5 to 20 A/dm 2 with a pulse time from 5 to 100 ms;

with a repetition rate of the cathodic sequence of 1 to 50 before the anodic pulse current.

2. The baking plate of claim 1 , wherein the pulsed deposition is inverse pulsed deposition from a galvanic bath.

3. The baking plate of claim 1 , wherein the Ra value is less than 3 μm.

4. The baking plate of claim 1 , wherein the Ra value is less than 2 μm.

5. The baking plate according to claim 1 , wherein the surface layer contains phosphorus in the range of 1 to 15 wt. %, and the remainder up to 100 wt. % nickel.

6. The baking plate according to claim 1 , wherein the surface layer additionally contains molybdenum.

7. The baking plate of claim 1 , wherein the surface layer contains molybdenum up to 10 wt. %.

8. The baking plate of claim 1 , wherein the alloy contains 0.01 to 10 wt. % molybdenum.

9. The baking plate according to claim 1 , wherein the layer thickness of the surface layer is at least 5 μm.

10. The baking plate according to claim 1 , wherein the layer thickness of the surface layer is between 10 μm and 50 μm.

11. The baking plate according to claim 1 , wherein one or more underlayers are disposed between the surface layer and the metal surface.

12. The baking plate according to claim 11 , wherein the underlayers are nickel layers applied electrolytically or without external current.

13. The baking plate according to claim 11 , wherein the hardness gradient runs in an ascending manner from the metal surface to the surface layer.

14. The baking plate according to claim 11 , wherein the one or more underlayers comprise two underlayers that are double-layer and a first underlayer nearest the metal surface consists of a nickel layer or copper and a second underlayer consists of a nickel layer.

15. The baking plate according to claim 1 , wherein the coated baking plate is annealed at a temperature between 150° C. and 700° C. and the coated baking plate is tempered for a duration in the range of one hour to six hours.

16. The baking plate according to claim 1 , wherein a baking plate body of the baking plate consists of cast iron, steel, aluminum, aluminum alloys or copper and its alloys.

17. A method for making the baking plate according to claim 1 , wherein a metal substrate is coated with the surface layer via a pulsed method from a galvanic electrolyte bath.

18. The method according to claim 17 , characterized in that the electrolyte bath contains salts and acids selected from the following group:

a) nickel sulphate hexahydrate in the range of 250-700 g/l

b) nickel chloride hexahydrate in the range of 5-50 g/l

c) tin (IV) chloride hydrate in the range of 1-40 g/l

d) tin (II) sulphate in the range of 1-30 g/l

e) tin (II) chloride dihydrate in the range of 1-40 g/l

f) sodium molybdate dihydrate in the range of 1-30 g/l

g) molybdatophosphoric acid in the range of 1-30 g/l

h) sodium citrate in the range of 1-90 g/l

i) boric acid in the range of 25-45 g/l

j) phosphorous acid in the range of 1-25 g/l

k) phosphoric acid in the range of 1-5 g/l

l) sodium hypophosphite in the range of 5-40 g/l

m) sodium gluconate in the range of 40-90 g/l

n) potassium sodium tartrate in the range of 10-50 g/l.

19. The method according to claim 17 , comprising the further following steps:

washing the coated metal surface,

optionally drying the coated metal surface,

annealing the coated metal surface for a time in the range from one hour to six hours, at a temperature in the range of 100° C. and 700° C.

20. The method according to claim 17 , characterized in that the coating has a hardness in the range of 400 Vickers and 800 Vickers.

21. The method according to claim 19 , characterized in that the coating after annealing is 700 to 1000 Vickers.