WO2019215287A1

WO2019215287A1 - Nickel comprising layer array and a method for its manufacturing

Info

Publication number: WO2019215287A1
Application number: PCT/EP2019/061938
Authority: WO
Inventors: Berkem Özkaya; Philipp Wachter; Torsten Voss; Philip Hartmann
Original assignee: Atotech Deutschland GmbH and Co KG
Current assignee: Atotech Deutschland GmbH and Co KG
Priority date: 2018-05-09
Filing date: 2019-05-09
Publication date: 2019-11-14
Anticipated expiration: 2020-11-09

Abstract

The present invention concerns a new nickel comprising layer array preferably having a reduced nickel ion release and a method for its manufacture. Further, it relates to the use of the layer array as decorative coating on a surface of the substrate. The use of the new layer array reduces the risk of nickel caused dermatitis due to lower release of nickel ions compared to conventional decorative coatings.

Description

Nickel comprising layer array and a method for its manufacturing

Field of the Invention

The present invention concerns nickel comprising layer arrays on a surface of a substrate, in par ticular a nickel comprising layer arrays on a surface of a substrate with reduced nickel ion release and a method for its manufacturing. These layer arrays are of particular interest in the decorative coating of appliances such as car interiors and shower heads.

Background of the Invention

Nickel is being widely used in various industries, both as metal and as alloy. One important market is the galvanic deposition of nickel and its alloys together with further layers, e.g. a chromium outer surface layer in the manufacturing of decorative articles for white good industry as metallic surfac- es of refrigerators; articles for sanitary industry such as shower heads and for automotive industry as decorative car parts as emblems, front grilles (radiator grilles), and door handles. The different metal layers form a nickel comprising layer array onto a substrate, wherein this layer array gives the resulting article a decorative appearance and also prevents the substrate and/or the e.g. a chromium outer surface layer from corrosion.

Conventionally, plated parts sequentially coated with a substantially non-sulfur semi-bright nickel plating layer, a bright nickel plating layer, an eutectoid nickel plating layer (a distributed strike nickel plating layer), and a chrome plating film on a substrate have been disclosed as chrome-plated parts.

It is an ongoing demand by the industry to provide parts which will show decorative appearance for as long as possible time. In order to provide good optical appearance and corrosion resistance at least one of the nickel layers functions as sacrificial layer which will fully or partly dissolved to nickel ions in order to prevent corrosion of the e.g. chromium outer surface layer leading to a undesired optical appearance. EP2396455B1 relates to a chrome-plated part represented by a decorative part such as an emblem or a front grille of an automobile, comprising a substrate, different nickel plating layers and a trivalent chrome plating layer having a microporous structure and a microcrack struc ture. The chrome-plated parts will show improved optical appearance and corrosion resistance. Unfortunately Nickel is also known to be a potent contact allergen and causes a contact dermatitis to sensitized individuals. In the EU, it is estimated that approximately 65 million people suffer from nickel allergy. Therefore, in early 2018 the European Chemicals Agency (ECHA) has published a new draft guideline concerning nickel containing articles that are to come into direct and prolonged contact with the skin. This draft guideline effectively regulates the allowable amount of nickel leach ing from articles during contact. Many known nickel comprising articles, however, fail the required tests, and too high amounts of nickel are being set free during contact with the skin, potentially causing a contact dermatitis.

Objective of the present Invention

It is therefore an objective of the present invention to provide deposits for decorative purposes with good optical appearance as long as possible while on the other side fulfilling environmental and/or regulatory requirements. It is another objective underlying the present invention to provide a nickel comprising layer array on a surface of a substrate having a reduced nickel ion release, in particular for decorative purposes while maintaining its corrosion protection functionality and the optical ap- pearance of the decorative articles.

Summary of the Invention

The objectives underlying the present invention are solved by the nickel comprising layer array on at least one surface of a substrate having a reduced nickel ion release according to the invention, the nickel comprising layer array comprising

A) a semi-bright nickel layer;

B) an intermediate nickel layer selected from bright nickel layers and satin nickel layers;

C) a non-porous nickel layer, wherein the non-porous nickel layer is free of particulate mat ter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the electrical potential difference between the non-porous nickel layer and the in termediate nickel layer ranges from 10 to 150 mV;

D) a chromium layer,

wherein the layers are located on each in the given order.

The objectives are further solved by the inventive method for manufacturing a nickel comprising layer array on at least one surface of a substrate, comprising the method steps in the given order: a) providing a substrate having the at least one surface;

b) depositing a semi-bright nickel layer;

c) depositing an intermediate nickel layer selected from bright nickel layers and satin nickel layers;

d) depositing a non-porous nickel layer, wherein the non-porous nickel layer is free of par ticulate matter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the electrical potential difference between the non-porous nickel layer and the intermediate nickel layer ranges from 10 to 150 mV; and e) depositing a chromium layer.

The invention leads to a nickel comprising layer array having a reduced nickel ion release and to a nickel comprising layer array on at least one surface of a substrate.

Preferred embodiments of the present invention are described in the dependent claims and in this specification hereinafter.

Detailed Description of the Invention

Percentages throughout this specification are weight-percentages (wt.-%) unless stated other-wise. Concentrations given in this specification refer to the volume or mass of the entire solutions / com- positions unless stated otherwise. The terms“deposition” and“plating” are used interchangeably herein. Also,“layer” and“deposit” are also used synonymously in this specification.

The terms“bright”,“semi-bright” and“satin” are well-known to the skilled person and describe dif ferent optical appearance of the produced nickel layers. The optical appearance depends on the different surface roughness of the produced nickel layers wherein the different surface roughness will be adjusted by the different additives in the nickel plating baths. In this context, the terms “bright”,“semi-bright” and“satin” can defined relatively to each other by their surface roughness as “bright” refers to a bright nickel layers having lower surface roughness (lowest surface roughness compared to semi-bright and satin),“semi-bright” refers to a semi-bright nickel layers having medi um surface roughness (medium surface roughness in between to bright and satin), and“satin” re- fers to a satin nickel layers having higher surface roughness (highest surface roughness compared to bright and semi-bright).

The embodiments described hereinafter can be combined without restraints unless this is techni cally not feasible or specifically excluded. Preferred embodiments described for one aspect of the present invention are applicable mutatis mutandis to all the other aspects of the present invention unless stated otherwise herein.

The nickel comprising layer array comprises a semi-bright nickel layer. The semi-bright nickel layer is located on the surface of the substrate. Preferably, it is located directly on the surface of the sub strate. The surface of the substrate is preferably selected from those described hereinafter.

Preferably, the thickness of the semi-bright nickel layer ranges from 5 to 16 pm, preferably from 6 to 15 pm.

The nickel comprising layer array comprises an intermediate nickel layer selected from bright nickel layers and satin nickel layers. The intermediate nickel layer is located on the semi-bright nickel layer. Preferably, the intermediate nickel layer is located directly on the semi-bright nickel layer. According to this preference, no further layer is located between the semi-bright nickel layer and the intermediate nickel layer. Preferably, the thickness of the intermediate nickel layer ranges from 5 to 15 pm, preferably from 6 to 13 pm, more preferably from 7 to 12 pm.

Preferably, the semi-bright nickel layer is nobler than intermediate nickel layer selected from the bright nickel layer or a satin nickel layer; preferably, the electrical potential difference between the semi-bright nickel layer and the bright nickel layer or a satin nickel layer ranges from 80 to 250 mV.

This electrical potential difference allows for a further decrease of the nickel ion release.

The nickel comprising layer array comprises a non-porous nickel layer. The non-porous nickel layer is located on the intermediate nickel layer. Preferably, the non-porous nickel layer is located direct ly on the intermediate nickel layer.

Preferably, the thickness of the non-porous nickel layer ranges from 0.5 to 3.5 pm, preferably from 1 to 3, more preferably from 1 .2 to 2.5 pm. Generally, the preferred thickness of the nickel layers was found to decrease the amount of nickel ion release.

Preferably, the non-porous nickel layer is essential free of pores. Essential free means the non- porous nickel layer comprises 1000 pores per cm² or less, more preferably 100 pores per cm² or less and even more preferably 10 per cm² or less. In one embodiment of the invention, the non- porous nickel layer is free of pores. Essential free of pores according to the invention mean that the pores are not intentionally generated within the non-porous nickel layer by using intentionally add ed particulate matter into the plating bath (which not contains particulate matter) or special plating conditions during nickel plating. This further reduces the nickel ion release. The measurement of pores can be achieved with methods known to skilled person, e.g. with microscope analysis, wherein pores per area will be counted at one point and/or different points on the nickel surface. Counted pores of smaller areas can be extrapolated. In particular the non-porous nickel layer is free of particulate matter, especially free of non-conductive particulate matter. It is preferred that the particulate matter is free of particulate matter having a d50 (measured by X-ray diffraction) of 0.25 pm or greater.

Preferably the non-porous nickel layer is essential free of phosphor content. Essential free of phos phor content means that the non-porous nickel layer does contain less than 1 atom-%, preferably less than 0.5 atom-%, more preferably less than 0.1 atom-%. Most preferably the non-porous nickel layer does not contain phosphor.

The nickel comprising layer array comprises a chromium layer. The chromium layer is located on the non-porous nickel layer. Preferably, the chromium layer is located directly on the non-porous nickel layer.

Preferably, the chromium layer comprises 1000 pores per cm² or less, more preferably 100 per cm² or less and even more preferably 10 per cm² or less. In one embodiment of the invention, the chromium layer is (essentially) free of pores. Free of pores or having the mentioned small numbers of pores according to the invention mean that the pores where not intentionally generated within the chromium layer by using intentionally added particulate matter into the plating bath or special plating conditions during chromium plating or otherwise intentionally transferred into the chromium layer by e.g. underlying nickel layers, especially not by the underlying non-porous nickel layer. In particular the chromium layer is free of particulate matter, preferred is free of particulate matter having a d50 (measured by X-ray diffraction) of 0.25 pm or greater. This further reduces the nickel ion release. The measurement of pores can be achieved with methods known to skilled person, e.g. with microscope analysis, wherein pores per area will be counted at one point and/or different points on the chromium surface. Counted pores of smaller areas can be extrapolated. Pores can be made visible and counted also by known methods e.g. Dubpernell test method, Fuhrmann test or pore count test (e.g disclosed in DE 102016013792 A1). For chromium surfaces derived from chromium electroplating bath comprising chromium (VI) ions Dubpernell test method is preferred and for chromium surfaces derived from chromium electroplating bath comprising chromium (III) ions pore count test method is preferred.

Preferably, the thickness of the chromium layer ranges from 0.05 to 1 .0 pm, 0.08 - 0.8 pm, 0.1 - 0.6 pm. These thicknesses were found to further decrease the nickel ion release. Surprisingly, it was found that thicker chromium layers sometimes disadvantageously increase the nickel ion re lease.

In a preferred embodiment of the invention, the chromium layer is deposited from a chromium elec troplating bath.

In a more preferred embodiment of the invention, the chromium layer is deposited from a hexava- lent chromium electroplating bath comprising chromium (VI) ions.

In another preferred embodiment of the invention, the chromium layer is deposited from a trivalent chromium electroplating bath comprising chromium (III) ions. Preferably the nickel comprising layer array comprises a coating on the chromium layer derived from the trivalent chromium electroplating bath comprising chromium (III) ions. Preferably, the coating is located directly on the chromium layer.

The coating is preferably an electrolytically applied chromium passivation coatings (see un published international application PCT/EP 2018/053391 , in particular page 3, line 17 to page 19, line 19 and examples 7 to 10; JP 2009-235456 A, in particular paragraphs 8 to 24 and JP 2010- 209456 A in particular paragraphs 12 to 41 ).

Alternatively, albeit less preferred, the coating is selected from the group consisting of silica-based nanocoatings (sol-gel coatings) and UV-cured cathodic electrophoretic coatings, e.g. based on polyurethanes.

The thickness of the coating preferably ranges from 0.001 to 1.0 pm, more preferably from 0.005 to 0.5 pm, even more preferably from 0.01 to 0.4 pm.

In one embodiment of the invention, the overall thickness of all nickel layers and the chromium layer ranges from 10.6 to 30 pm, preferably from 12.5 to 28 pm, more preferably from 15 to 25 pm. This allows for a very thin and cost-effective layer array to be obtained whose nickel ion release is very low and often meets the requirement of the new ECHA guideline in this regard.

The amount of nickel ion release is 0.88 pg/cm²/week or less, preferably 0.5 pg/cm²/week or less according to EN 1811 :201 1 +A1 :2015. Occasionally, it is reported that a nickel ion release of 0.88 pg/cm²/week would be sufficient to meet the requirements set out in the ECHA draft guideline, es pecially when error margins are considered.

In another aspect of the present invention, the nickel comprising layer array is used as decorative coating on the surface of the substrate. Preferably, the nickel comprising layer array is used as decorative coating having a reduced nickel ion release, e.g. according to EN 1811 :2011 +A1 :2015. In particular, the nickel ion release of the nickel comprising layer array is 0.5 pg/cm²/week or less according to EN 1811 :2011 +A1 :2015.

The nickel comprising layer array according to the invention not only meets the requirements of low nickel ion release (see above) but also is sufficiently resistant to corrosion. It also is sufficiently resistant to abrasion. Thus, it can be used as decorative coating in car interiors and the like.

In one embodiment of the invention, the inventive nickel comprising layer array on a surface of a substrate having a reduced nickel ion release, comprises

A) a semi-bright nickel layer;

B) an intermediate nickel layer selected from bright nickel layers and satin nickel layers, preferably a satin nickel layer; and wherein the intermediate layer is preferably directly on the semi-bright nickel layer;

C) a non-porous nickel layer, wherein the non-porous nickel layer is free of particulate matter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the elec trical potential difference between the non-porous nickel layer and the intermediate nickel layer ranges from 10 to 150 mV, deposited from an electroplating bath for deposition of a non-porous nickel layer comprising nickel ions, boric acid, chloral hydrate and optionally, one or more of carri ers, brighteners and auxiliary brighteners;

wherein the temperature of said electroplating bath for deposition of a non-porous nickel layer dur ing deposition ranges from 45 to 75 °C, preferably from 50 to 67.5 °C, more preferably from 52 to 62.5 °C;

wherein the cathode density during deposition of the non-porous nickel layer preferably ranges from 1 to 8 A/dm², more preferably from 1.5 to 7 A/dm², even more preferably from 2 to 6 A/dm²; and wherein the electroplating bath for deposition of a non-porous nickel layer is preferably free of particulate matter having a d₅₀ (measured by X-ray diffraction) of 0.25 pm or greater ; and

D) a chromium layer deposited from a hexavalent chromium electroplating bath comprising chromi um (VI) ions and a catalyst (preferably in concentrations described below); wherein the temperature of the hexavalent chromium electroplating bath during deposition ranges from 32 to 52 °C, preferably from 35 to 47 °C, more preferably from 38 to 42 °C;

wherein the cathode density of the hexavalent chromium electroplating bath ranges from 6 to 30 A/dm², preferably from 8 to 20 A/dm², more preferably from 10 to 15 A/dm².

Surprisingly, it was found that above described layer array is particularly useful in decreasing the nickel ion release. However, it is not quite clear to date why thus constituted layer array performs better than those known in the art which comprise similar layer sequences, e.g. in terms of nickel ion release. Although many structural analyses have been carried out so far, the exact nature of the layers is not fully clear.

In another embodiment of the invention, the inventive nickel comprising layer array on a surface of a substrate, comprises

A) a semi-bright nickel layer;

wherein the temperature of said electroplating bath for deposition of a non-porous nickel layer during deposition ranges from 45 to 75 °C, preferably from 50 to 67.5 °C, more pref erably from 52 to 62.5 °C;

wherein the cathode density during deposition of the non-porous nickel layer preferably ranges from 1 to 8 A/dm², more preferably from 1 .5 to 7 A/dm², even more preferably from 2 to 6 A/dm²;

and wherein the electroplating bath for deposition of a non-porous nickel layer is preferably free of particulate matter having a d₅₀ (measured by X-ray diffraction) of 0.25 pm or great er;

in one embodiment of the invention, the final electroplating bath is free of aluminum and sil- icon based particles such as Al₂0₃ and Si0₂ particles; and

D) a chromium layer deposited from a trivalent chromium electroplating bath comprising chromium (III) ions ,

wherein the temperature of the trivalent chromium electroplating bath during deposition ranges from 25 to 65 °C, preferably from 30 to 60 °C; wherein the cathode density of the trivalent chromium electroplating bath ranges from 3 to 30 A/dm², preferably from 4 to 25 A/dm², more preferably from 5 to 20 A/dm²;

and

E) preferably, a coating on the chromium layer wherein the coating is selected from the group consisting of electrolytically applied chromium passivation coatings, silica-based nanocoatings (sol-gel coatings) and UV-cured cathodic electrophoretic coatings.

Surprisingly, it was found that above described layer array is particularly useful in decreasing the nickel ion release. However, it is not quite clear to date why the thus constituted layer array per forms better than those known in the art which comprise similar layer sequences, e.g. in terms of nickel ion release. Although many structural analyses have been carried out so far, the exact na ture of the layers is not fully clear.

In method step a) of the method according to the invention, a substrate having the at least one surface is provided.

A suitable surface of a substrate is usually a metallic surface, in particular a copper or copper alloy surface. Alternatively, a non-conductive surface of a substrate may be used after suitable pretreat ments such as deposition of a conductive activation layer and/or metallization in order to have a conductive surface at least on parts of the non-conductive surface. Non-conductive surfaces are typically made of or comprise one or more of the following plastic materials: acrylonitrile-butadiene- styrene copolymer (ABS copolymer), polyamide (PA), polycarbonate (PC), polyimide (PI), polyeth ylene terephthalate (PET) and mixtures of the aforementioned.

In so far surfaces are to be treated, it is also possible within the means of the present invention, to treat only one or more portions of a given surface or various portions of a given surface. The sub strates are made in their entirety of any of the listed materials or combinations thereof or they only comprise at least one surface made of one or more of the materials listed (above). In the latter case, the at least one surface is to be used in the inventive method.

Optionally, the method according to the invention comprises one or more pretreatment steps be tween method steps a) and b). Suitable known pretreatment steps are known in the art and include exemplarily cleaning (e.g. treatment with an aqueous solution comprising a surfactant to remove dirt from the at least one surface of the substrate), etching (e.g. treatment with an aqueous acidic or aqueous alkaline solution optionally comprising an oxidant such as hydrogen peroxide or per manganate to increase the surface area of the at least one surface of the substrate), activation (e.g. treatment with a palladium-tin colloid to render the surface suitable for plating), metallization steps (e.g. deposition of a copper or copper alloy layer by means of electroless or electrolytic dep osition) or reducing steps (e.g. treatment with a solution comprising a reducing agent such as NaBH₄). One or more pretreatment steps can optionally be included between all method steps of the inventive method if desired. In method step b) of the method according to the invention, a semi-bright nickel layer is deposited on the at least one surface of the substrate.

The semi-bright nickel layer is deposited from a semi-bright electroplating bath. Such baths are known in the art and useful guidance for their set-up and use are disclosed in e.g.“Modern Elec troplating”, edited by M. Schlesinger and M. Paunovic, 4^th ed., 2000, John Wiley & Sons, Inc., New York, pages 147, 149 to 151 . A particularly useful semi-bright electroplating bath is Mark 90 ob tainable from Atotech Deutschland GmbH.

Typically, the semi-bright nickel electroplating bath comprises nickel ions, boric acid and one or more organic levelling agents. Semi-bright nickel electroplating baths are typically free of sulfur- containing additives to avoid sulfur incorporation in the formed nickel layer.

Nickel ions are usually added as nickel sulfate and/or as nickel chloride or hydrates thereof to the semi-bright nickel electroplating bath. Usual concentrations of nickel sulfate in the semi-bright nick el electroplating bath range from 200 to 400 g/L, preferably from 220 to 380 g/L, more preferably from 250 to 360 g/L.

Usual concentrations of nickel chloride in the semi-bright nickel electroplating bath range from 25 to 65 g/L, preferably from 30 to 60 g/L, more preferably from 35 to 54 g/L.

Usual concentrations of boric acid in the semi-bright nickel electroplating bath range from 30 to 60, preferably from 32 to 55 g/L, more preferably from 37 to 50 g/L.

Typical organic levelling agents for the semi-bright nickel electroplating bath comprise one or more olefinic and/or acetylenic bonds and are free of sulfur atoms. Preferable organic levelling agents are selected from the group consisting of coumarin; hydroxy cinnamic acid; diethyl maleate; 2- butyne-1 ,4-diol; ethyl cyanohydrin; p-amino azo benzene; polyethylene glycols; salts and mixtures of the aforementioned. Generally applied concentrations of the one or more organic levelling agents range from 0.005 to 0.2 g/L.

The semi-bright electroplating bath optionally further comprises chloral hydrate in a concentration ranging from 0 to 0.5 g/L, preferably from 0.0125 to 0.25 g/L, more preferably from 0.025 to 0.125 g/L. Further, the semi-bright electroplating bath optionally further comprises at least one aromatic acid such as benzoic acid or salicylic acid in a concentration ranging from 0.01 to 5 g/L, preferably from 0.05 to 4 g/L, more preferably from 0.1 to 3 g/L.

Further, the semi-bright electroplating bath optionally further comprises at least one or more wet ting agents such as fatty alcohol ether sulfates, fatty alcohol sulfates and/or sulfosuccinic acid de rivatives, preferably in a concentration ranging from 0.01 to 5 g/L, more preferably from 0.05 to 4 g/L, and even more preferably from 0.1 to 3 g/L.

The pH value of the semi-bright nickel electroplating bath preferably ranges from 3.4 to 4.8, more preferably from 3.6 to 4.6, even more preferably from 3.8 to 4.4. Typically, the temperature of the semi-bright nickel electroplating bath ranges from 45 to 75 °C, preferably from 50 to 67.5 °C, more preferably from 55 to 62.5 °C during deposition.

Any duration necessary to achieve the desired thickness of the semi-bright nickel layer can be em ployed. Usually applied duration ranges from 3 to 40 min, preferably from 4.5 to 30 min, more pref erably from 6 to 19 min.

The cathode density during deposition preferably ranges from 0.5 to 8 A/dm², more preferably from 1 to 6.5 A/dm², even more preferably from 2 to 5 A/dm².

Optionally, the semi-bright nickel electroplating bath is agitated during deposition, preferably by means of air injection, stirring, cathode movement or electrolyte circulation.

Preferably, the thickness of the semi-bright nickel layer ranges from 5 to 15 pm, more preferably from 6 to 14.5, even more preferably from 7 to 14.0 pm.

In method step c) of the method according to the invention, an intermediate nickel layer selected from bright nickel layers and satin nickel layers is deposited.

Preferably, the intermediate nickel layer is deposited directly on the semi-bright nickel layer. This allows for a more efficient production during manufacturing. Also, it was found that the nickel ion release is lower if a satin nickel layer is used instead of a bright nickel layer.

The bright nickel layer is deposited from a bright nickel electroplating bath. Such baths are known in the art.

Such baths are known in the art and useful guidance for their set-up and use are disclosed in e.g. “Modern Electroplating”, edited by M. Schlesinger and M. Paunovic, 4^th ed., 2000, John Wiley & Sons, Inc., New York, pages 147 to 150. A particularly useful bright electroplating bath is Supreme Plus obtainable from Atotech Deutschland GmbH.

Typically, the bright nickel electroplating bath comprises nickel ions, boric acid and one or more of carriers, brighteners and auxiliary brighteners.

Nickel ions are usually added as nickel sulfate and/or as nickel chloride or hydrates thereof to the bright nickel electroplating bath. Usual concentrations of nickel sulfate in the bright nickel electro plating bath range from 200 to 400 g/L, preferably from 210 to 380 g/L, more preferably from 220 to 360 g/L

Usual concentrations of nickel chloride in the bright nickel electroplating bath range from 20 to 100 g/L, preferably from 25 to 90 g/L, more preferably from 30 to 80 g/L.

Usual concentrations of boric acid in the bright nickel electroplating bath range from 30 to 60 g/L, preferably from 32 to 55 g/L, more preferably from 37 to 50 g/L.

Carriers are typically aromatic organic compounds. Preferable carriers are selected from the group consisting of benzene sulfonic acid; 1 ,3,6-naphthalene sulfonic acid; p-toluene sufonamide; sac charin (benzoic sulfonimide); thiophen-2-sulfonic acid; benzene sulfinic acid; allyl sulfonic acid; salts and mixtures of the aforementioned. A useful concentration of the carrier ranges from 0.5 to 15 g/L, preferably from 0.75 to 10 g/L, more preferably from 1 to 6 g/L.

Brighteners increase the brightness and ductility of the bright nickel layers and are preferably se lected from the group consisting of formaldehyde; o-sulfo benzaldehyde; allyl sulfonic acid; couma- rin; hydroxy cinnamic acid; diethyl maleate; 2-butyne-1 ,4-diol; 2-butyne-1 ,4-disulfonic acid; ethyl cyanohydrin; p-amino azo benzene; thiourea; allyl thiourea; polyethylene glycols; salts and mix tures of the aforementioned. A useful concentration of the brightener ranges from 0.001 to 0.5 g/L, preferably from 0.002 to 0.45 g/L, more preferably from 0.003 to 0.4 g/L.

Auxiliary brighteners further increase the brightness and levelling when used with carriers and brighteners. They are preferably selected from the group consisting of allyl sulfonate; zinc ions; cobalt ions; cadmium ions; 1 ,4-butyne 2-diol; pyridinium propyl sulfonate; salts and mixtures of the aforementioned. Zinc ions, cobalt ions and cadmium ions may be provided as water-soluble salts of zinc, cobalt and cadmium, respectively. More preferably for ecological and health reasons, the auxiliary brightener is selected from the group consisting of allyl sulfonate; 1 ,4-butyne 2-diol; pyri dinium propyl sulfonate; salts and mixtures of the aforementioned.

Further, the bright electroplating bath optionally further comprises at least one or more wetting agents such as fatty alcohol ether sulfates, fatty alcohol sulphates and/or sulfosuccinic acid deriva tives in a concentration ranging from 0.01 to 5 g/L, preferably from 0.05 to 4 g/L, more preferably from 0.1 to 3 g/L.

The pH value of the bright nickel electroplating bath preferably ranges from 3.4 to 4.8, more prefer ably from 3.6 to 4.7, even more preferably from 3.8 to 4.6.

Typically, the temperature of the bright nickel electroplating bath ranges from 45 to 75 °C, prefera bly from 50 to 67.5 °C, more preferably from 55 to 62.5 °C during deposition.

Any duration necessary to achieve the desired thickness of the bright nickel layer can be em ployed. Usually applied durations range from 3 to 40 min, preferably from 4.5 to 30 min, more pref erably from 6 to 19 min.

The cathode density during deposition of the bright nickel layer preferably ranges from 0.5 to 8 A/dm², more preferably from 1 to 6.5 A/dm², even more preferably from 2 to 5 A/dm².

Satin nickel layers are deposited from a satin nickel electroplating bath electroplating bath. Such baths are known in the art. Typically, the satin nickel electroplating bath comprises nickel ions, boric acid and one or more of additives as basis brighteners, etc. Exemplarily, WO 01/88227 A1 discloses a satin nickel electroplating bath electroplating bath (see in particular page 6, line 1 to page 19, line 23). Further relevant information can be found in the technical datasheet of Satilume Plus.

Nickel ions are usually added as nickel sulfate and/or as nickel chloride or hydrates thereof. Usual concentrations of nickel sulfate range from 330 to 550 g/L. Usual concentrations of nickel chloride range from 30 to 150 g/L.

Preferably, the concentration of chloride ions in the satin nickel electroplating bath is 20 g/L or more.

Usual concentrations of boric acid range from 30 to 60 g/L, preferably from 32 to 55 g/L, more pref erably from 37 to 50 g/L.

In principle sulfosuccinic acid compounds may be added to the bath without any other bath addi tives to be added too. However, sufficient long-time stability of the baths can only be achieved if a combination of the sulfosuccinic acid compounds is used together with quaternary ammonium compounds and if necessary with additional basic brighteners. Under these circumstances an ex cellent satin-finish of nickel or nickel alloy surfaces is achieved over the entire current density range operable under practical conditions. Unsaturated, in most cases aromatic sulfonic acids, sulfona mides, sulfimides, N-sulfonylcarboxamides, sulfinates, diarylsulfones or the salts thereof are to be understood as basic brighteners. The most familiar brightners are for example m-benzenedisulfonic acid, benzoic acid sulfimide (saccharin), trisodium-1 , 3, 6-naphthalenetrisulfonate, sodium benzene monosulfonate, dibenzene sulfonamide and sodium benzene monosulfinate. The basic brighteners are normally added to the electrolyte bath at a concentration of from 5 mg/1 to 10 g/1 , preferably of from 0.5 to 2 g/1 .

The pH value of the satin nickel electroplating bath preferably ranges from 3.7 to 4.7, more prefer ably from 3.8 to 4.5, even more preferably from 3.9 to 4.3.

Typically, the temperature of the satin nickel electroplating bath ranges from 45 to 65 °C, preferably from 47 to 60 °C, more preferably from 51 to 53 °C during deposition.

Any duration necessary to achieve the desired thickness of the satin nickel layer can be employed. Usually applied durations range from 3 to 40 min, preferably from 4.5 to 30 min, more preferably from 6 to 19 min.

The cathode density during deposition of the satin nickel layer preferably ranges from 1 to 8 A/dm², more preferably from 2 to 7 A/dm², even more preferably from 3 to 6 A/dm².

Preferably, the thickness of the intermediate nickel layer ranges from 5 to 15 pm, more preferably from 5.5 to 14, even more preferably from 6 to 13 pm.

In method step d) of the method according to the invention, a non-porous nickel layer is deposited, wherein the non-porous nickel layer is free of particulate matter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the electrical potential difference between the non-porous nickel layer and the intermediate nickel layer ranges from 10 to 150 mV.

The non-porous nickel layer is deposited from a nickel electroplating bath suitable to deposit the non-porous nickel layer. Said electroplating bath (hereinafter referred to as“final nickel electroplat ing bath”) comprises nickel ions, boric acid, chloral hydrate and one or more of carriers, brighteners and auxiliary brighteners. Nickel ions are usually added to the final nickel electroplating bath as nickel sulfate and/or as nickel chloride or hydrates thereof. Usual concentrations of nickel sulfate in the final nickel electroplating bath range from 200 to 400 g/L, preferably from 210 to 380 g/L, more preferably from 220 to 360 g/L.

Usual concentrations of nickel chloride in the final nickel electroplating bath range from 20 to 100 g/L, preferably from 25 to 90 g/L, more preferably from 30 to 80 g/L.

Usual concentrations of boric acid in the final nickel electroplating bath range from 30 to 60 g/L, preferably from 32 to 55 g/L, more preferably from 37 to 50 g/L.

The final electroplating bath comprises chloral hydrate in a concentration ranging from 0.001 to 2 g/L, preferably from 0.1 to 1 .5 g/L, more preferably from 0.2 to 1 g/L.

The final electroplating bath is free of particulate matter (also referred to as particles) having a d₅₀ (measured by X-ray diffraction) of 0.25 pm or greater. In one embodiment of the invention, the final electroplating bath is free of aluminum and silicon based particles such as Al₂0₃ and Si0₂ parti cles. Such particulate matter increases the number of pores of the chromium layer which is unde sired.

First experimental results have indicated that the increase of the number of pores is disadvanta- geously increases nickel ion release.

Carriers are typically aromatic organic compounds. Preferable carriers for the final nickel electro plating bath are selected from the group consisting of benzene sulfonic acid; 1 ,3,6-naphthalene sulfonic acid; p-toluene sufonamide; saccharin (benzoic sulfonimide); thiophen-2-sulfonic acid; benzene sulfinic acid; allyl sulfonic acid; salts and mixtures of the aforementioned. A useful con centration of the carrier ranges from 0.01 to 10 g/L, preferably from 0.5 to 7.5 g/L, more preferably from 1 to 5 g/L.

Brighteners increase the brightness and ductility of the non-porous nickel layer and are preferably selected from the group consisting of formaldehyde chloral hydrate; o-sulfo benzaldehyde; allyl sulfonic acid; coumarin; hydroxy cinnamic acid; diethyl maleate; 2-butyne-1 ,4-diol; 2-butyne-1 ,4- disulfonic acid; ethyl cyanohydrin; p-amino azo benzene; thiourea; allyl thiourea; polyethylene gly cols; salts and mixtures of the aforementioned. A useful concentration of the brightener ranges from 0.001 to 0.25 g/L, preferably from 0.002 to 0.2 g/L, more preferably from 0.003 to 0.15 g/L.

Auxiliary brighteners further increase the brightness and levelling of the non-porous nickel layer when used with carriers and brighteners. They are preferably selected from the group consisting of allyl sulfonate; zinc ions; cobalt ions; cadmium ions; 1 ,4-butyne 2-diol; pyridinium propyl sulfonate; salts and mixtures of the aforementioned. Zinc ions, cobalt ions and cadmium ions may be provid ed as water-soluble salts of zinc, cobalt and cadmium, respectively. More preferably for ecological and health reasons, the auxiliary brightener is selected from the group consisting of allyl sulfonate; 1 ,4-butyne 2-diol; pyridinium propyl sulfonate; salts and mixtures of the aforementioned. Further, the electroplating bath optionally further comprises at least one or more wetting agents such as fatty alcohol ether sulfates, fatty alcohol sulfates and/or sulfosuccinic acid derivatives in a concentration ranging from 0.01 to 5 g/L, preferably from 0.05 to 4 g/L, more preferably from 0.1 to 3 g/L.

The pH value of the final nickel electroplating bath preferably ranges from 3.4 to 5.0, more prefera bly from 3.6 to 4.8, even more preferably from 3.8 to 4.6.

Typically, the temperature of the final nickel electroplating bath ranges from 45 to 75 °C, preferably from 50 to 67.5 °C, more preferably from 52 to 62.5 °C during deposition.

Any duration necessary to achieve the desired thickness of the non-porous nickel layer can be employed. Usually applied durations range from 0.5 to 10 min, preferably from 0.75 to 8 min, more preferably from 1 to 3.5 min.

The cathode density during deposition of the non-porous nickel layer preferably ranges from 1 to 8 A/dm², more preferably from 1.5 to 7 A/dm², even more preferably from 2 to 6 A/dm².

Preferably, the thickness of the non-porous nickel layer ranges from 0.5 to 3.5 pm, more preferably from 0.75 to 3 pm, even more preferably from 1 to 2.5 pm.

In method step e) of the method according to the invention, a chromium layer is deposited.

In a first embodiment, the chromium layer is deposited from a hexavalent chromium electroplating bath. As hexavalent chromium plating bath, Bright Chromium Bath CR 843 was used with astonish ingly good results in terms of nickel ion release.

Hexavalent chromium electroplating baths are known in the art and for example disclosed in“Mod ern Electroplating”, edited by M. Schlesinger and M. Paunovic, 4^th ed., 2000, John Wiley & Sons, Inc., New York, pages 298 to 311.

Hexavalent chromium electroplating baths comprise chromium (VI) ions and a catalyst. Chromium (VI) ions are usually added as chromic acid, chromates, dichromates, polychromates or mixtures of the aforementioned. The concentration of the chromium (VI) ions ranges from 90 to 230 g/L, pref erably from 110 to 210 g/L, more preferably from 130 to 190 g/L.

A typical catalyst to be used in a hexavalent chromium electroplating bath is sulfate ions. They may be added as sulfuric acid or as a sulfate salt such as sodium sulfate. Usual concentrations of sul fate range from 0.25 to 4 g/L, preferably from 0.5 to 3 g/L, more preferably from 1 to 2 g/L.

Further catalysts to be used in a hexavalent chromium electroplating bath are fluoride or SiF₆-ions. They may be added as alkaline or earth-alkaline salts. Usual concentrations of fluoride or SiF₆-ions range from 0 to 2 g/L, preferably from 0.1 to 1.5 g/L, more preferably from 0.2 to 1 .2 g/L.

Typically, the temperature of the hexavalent chromium electroplating bath ranges from 32 to 52 °C, preferably from 35 to 47 °C, more preferably from 38 to 42 °C during deposition. Any duration necessary to achieve the desired thickness of the chromium layer can be employed. Usually applied durations range from 0.1 to 30 min, preferably from 1 to 10 min, more preferably from 2 to or 7 or 8 min, even more preferably from 3 to 6 min.

The cathode density during deposition of the hexavalent chromium electroplating bath preferably ranges from 6 to 30 A/dm², more preferably from 8 to 20 A/dm², even more preferably from 10 to 15 A/dm².

In a second embodiment, the chromium layer is deposited from a trivalent chromium electroplating bath and the method preferably comprises the further method step after method step e):

f) depositing a coating on the chromium layer.

Various trivalent chromium electroplating baths are known in the art. They typically comprise either chromium (III) sulfate or chromium (III) chloride as source of chromium ions. Trivalent chromium electroplating baths based on chromium (III) sulfate are preferred as the nickel ion release of nickel comprising layer arrays comprising such deposited chromium layers are generally lower than those having layers from chromium (III) chloride based baths.

The principal components are known in the art and for example published in WO 2012/150198 (see in particular page 4, third paragraph to page 21 , first paragraph) Further, the trivalent chromium electroplating bath comprises boric acid, conductive salts such ammonium or alkaline halides, am monium or alkali sulfate; complexing agents such as mono-, di- or tricarboxylic acids.

The temperature of the trivalent chromium electroplating bath during deposition ranges from 30 °C to 60 °C, preferably from 30 °C to 40 °C, and more preferably from 50 °C to 60 °C. In one embodi ment of the invention, the temperature of the chloride based trivalent chromium electroplating bath is held during electroplating in a range from 30 °C to 40 °C, preferably 30 °C to 35 °C. In one em bodiment of the invention, the temperature of the chloride-free trivalent chromium electroplating bath is held during electroplating in a range from 50 °C to 60 °C, preferably 53 °C to 57 °C.

The cathode current densities during deposition of the trivalent chromium can range from 5 to 25 A/dm², preferably the current densities range from 5 A/dm² to 20 A/dm². Cathode current densities during deposition form from chloride based trivalent chromium electroplating baths can also range from 5 to 25 A/dm², preferably from 10 A/dm² to 20 A/dm². Cathode current densities during depo sition from chloride-free trivalent chromium electroplating baths can range from 5 to 10 A/dm².

Any time necessary to deposit a desired layer thickness can be applied. Preferably, the time of deposition from the trivalent chromium electroplating bath ranges from 0.1 to 30 min, preferably from 0.5 to 20 min, more preferably from 1 to 10 min.

Preferable coatings have been described before. In one embodiment of the invention, the coating is selected from the group consisting of electrolytically applied chromium passivation coatings, silica- based nanocoatings (sol-gel coatings) and UV-cured cathodic electrophoretic coatings. Suitable parameters for their deposition are principally known in the art. Preferably, an electrolytically ap- plied chromium passivation coatings is applied. Alternatively, albeit less preferred, the coating is selected from the group consisting of silica-based nanocoatings (sol-gel coatings) and UV-cured cathodic electrophoretic coatings (vide supra). These coatings further decrease the nickel ion re lease of the nickel comprising layer array according to the invention.

The method according to the invention optionally comprises further method steps before, between or after the named method steps. Such methods steps include rinsing steps (e.g. with deionized water), drying steps (e.g. by hot air drying or by subjecting the substrates to elevated temperatures like in an oven) or acid dip steps (e.g. treating the surface with an aqueous solution comprising an acid). The latter named acid dip step is preferably included between method steps a) and b) and/or b) and c) and/or c) and d) and/or d) and e). This acid dip step activates the respective surface prior to nickel or chromium plating and thereby improves plating performance. Additionally, due to this improved plating performance, it may further decrease to nickel ion release from a nickel compris ing layer array due to better plating outcome.

A preferable product to be used for this purpose is Uniclean 675, obtainable from Atotech Deutsch- land GmbH.

Generally, the electroplating baths described hereinbefore may be prepared by dissolving the indi vidual components in a liquid medium as solvent. A preferred solvent is water for its ecological benign character. Further, water often allows for easy solubilizing of the individual components. Other liquids that are miscible with water such as polar organic solvents may be added, e.g. as co- solvents if desired. However, it is preferred that the electroplating baths contain only water as sol vent (>99.0% of all solvents in the respective electroplating bath).

Generally, the electroplating baths described herein are aqueous solutions.

As a general concept, if the pH of a solution or composition such as an electroplating baths needs to be adapted to a certain value, it may be done so by addition of suitable acids, bases and buffers. The person skilled in the art can select suitable components based on routine experiments or his general knowledge.

Advantageously, the nickel comprising layer array is very corrosion resistant and typically with stands a CASS test (ISO 9227:2017). The nickel comprising layer array has a corrosion resistance of at least 24 h according to the standardized CASS test. In particular this corrosion resistance is achieved while non-porous nickel layer or the chromium layer has 100 pores per cm² or less.

Industrial Applicability

The present invention is particularly useful in the manufacturing of decorative coatings. Such coat ings are used for example in car interiors and as shower heads.

Examples

The invention will now be illustrated by reference to the following non-limiting examples. Commercial products were used as described in the technical datasheet available on the date of filing of this specification unless stated otherwise hereinafter.

Uniclean 151 , Adhemax^® Neutralizer Cr, Adhemax^® Activator SF, Adhemax^® Accelerator 1 , Adhe- max^® Ni LFS, Noviganth^® Immersion Copper, Cupracid^® 5000, Uniclean 675, Mark 90, Supreme Plus, Nickel MPS-300, Bright Chromium Bath CR 843, Trichrome ICE, Trichrome Plus, Supreme Plus Brightener, Nickel Carrier A-5 (2x), Nickel Additive SA-1 , Mark 90 M 904, MPS 300 Carrier, TriSeal 300, and CR 843 Additive are products produced and distributed by Atotech Deutschland GmbPI. These products were used according to the specification in the technical datasheets avail able at the date of filing unless stated otherwise herein.

The thickness of nickel layers and the electrical potential differences were measured as described in ASTM B 764-04:2014.

The thickness of chromium layers was measured at 10 positions of each substrate by XRF using the XRF instrument Fischerscope XDV-SDD (Helmut Fischer GmbH, Germany). By assuming a layered structure of the chromium layers, the layer thickness can be calculated from such obtained XRF data.

The number of pores per area was measured in accordance with ASTM B 456 (2011 ) and ASTM B 604 (2008).

Substrates

As substrates, ABS-PC caps were used which prior to deposition of nickel layers and chromium layer were pretreated as described hereinafter.

Table 1 : Pretreatment sequence of substrates.

AA: air agitation; MA: mechanical agitation; FL: flooding

Unless indicated otherwise, between each process step a rinsing step with deionized water (20 °C) and a final drying step were carried out. In cases where the concentration of an acid is given as volume percent, it refers to the volume of concentrated acid in water.

Comparative example 1 : a porous nickel layer on a bright nickel layer

Above pretreated substrates were further treated as follows:

The obtained nickel comprising array did not comprise a non-porous nickel layer but a porous nick el layer. The nickel ion release of the thus obtained nickel comprising array was then tested in ac cordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was 3.3 pg /cm² /week. This value exceeded the requirement described by ECHA by almost a magnitude.

Comparative example 2: a porous nickel layer on a satin nickel layer

Above pretreated substrates were further treated as follows:

The obtained nickel comprising array did not comprise a non-porous nickel layer but a porous nick el layer. The nickel ion release of the thus obtained nickel comprising array was then tested in ac cordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was 8.7 pg /cm²/week. This value exceeded the requirement described by ECHA by more than a magnitude.

Comparative example 3: no non-porous layer

Above pretreated substrates were further treated as follows:

The obtained nickel comprising array did not comprise any non-porous nickel layers. The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was 2.6 pg /cm²/week. This value exceeded the requirement described by ECHA by more than factor 5.

Inventive example 1 : satin nickel layer, chromium layer from hexavalent chromium electroplating

A nickel electroplating bath suitable to deposit the non-porous nickel layer was prepared by dissolv ing the following components in water:

The nickel electroplating bath suitable to deposit the non-porous nickel layer was free of particulate matter such as alumina or silica particles.

As hexavalent chromium plating bath, Bright Chromium Bath CR 843 was used with the parame- ters below. Surprisingly, this hexavalent chromium plating bath showed superior nickel ion releases when used in the nickel comprising layer arrays described hereinafter.

Above pretreated substrates were further treated as follows and above-described bath was used in step no. 16:

The layer thicknesses of the individual layers of the obtained nickel comprising array were:

A) the semi-bright nickel layer: 16 pm

B) the intermediate nickel layer: 8 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 222 nm

The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :201 1 +A1 :2015. The nickel ion release rate was 0.0 pg /cm²/week. This value was in accordance with the requirement described by ECHA. Inventive example 2: satin nickel layer, chromium layer from hexavalent chromium electroplating

Inventive example 1 was repeated but the electroplating for the satin nickel layer deposition (meth od step c) was exchanged for another satin nickel layer deposited from Satilume Plus (including 0.3 mL/L Satilume Plus LS1 and 0.3 mL/L Satilume Plus LS2).

A) the semi-bright nickel layer: 18 pm

B) the intermediate nickel layer: 8 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 243 nm

The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was <0.2 pg /cm²/week. This value was in accordance with the requirement described by ECHA.

Inventive example 3: satin nickel layer, thick chromium layer from hexavalent chromium electroplating

Inventive example 2 was repeated but the chrome layer deposition was carried out for 6 min (in stead of 3 min in inventive example 2).

A) the semi-bright nickel layer: 12 pm

B) the intermediate nickel layer: 8,5 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 473 nm

The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was <0.2 pg /cm²/week. This value was in accordance with the requirement described by ECHA. Inventive example 4: satin nickel layer, thick chromium layer chromium layer from hexavalent chromium electroplating

Inventive example 1 was repeated but the chrome layer deposition was carried out for 6 min (in stead of 3 min in inventive example 1 ).

A) the semi-bright nickel layer: 12 pm

B) the intermediate nickel layer: 8.5 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 496 nm

The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was 0.6 pg /cm²/week. This value was almost in accordance with the requirement described by ECHA. As described above, thicker chro mium layers in some cases result in a higher nickel ion release compared to otherwise identical nickel comprising layer array having thinner chromium layers.

Inventive example 5: bright nickel layer, chromium layer from hexavalent chromium electroplating

Inventive example 1 was repeated but the electroplating for the satin nickel layer deposition (meth od step c) was exchanged for a bright nickel layer deposition with the following parameters:

Supreme Plus, 55 °C, 4 A/dm², AA+MA, 25 min

A) the semi-bright nickel layer: 14 pm

B) the intermediate nickel layer: 8 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 244 nm The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 1811 :2011 +A1 :2015. The nickel ion release rate was <0.2 pg /cm²/week. This value was in accordance with the requirement described by ECHA.

Inventive example 6: bright nickel layer, thick chromium layer

Inventive example 5 was repeated but the chrome layer deposition was carried out for 6 min (in stead of 3 min in inventive example 2).

A) the semi-bright nickel layer: 14 pm

B) the intermediate nickel layer: 9 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 384 nm

Inventive example 7: deposition from a trivalent chromium plating bath

Inventive example 1 was repeated but for the chrome layer deposition a chloride based trivalent chromium plating bath was used (TriChrome Plus, plating time: 1.5 minutes, current density: 10 [A/dm²], temperature: 35 °C, air agitation).

A) the semi-bright nickel layer: 14 pm

B) the intermediate nickel layer: 8 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 161 nm The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 181 1 :201 1 +A1 :2015. The nickel ion release rate was 2.6 pg /cm²/week. However, when instead of the non-porous nickel layer deposition (method step d) a porous nickel layer deposition as described in comparative example 2 was used, the nickel ion release was increased to 9.7 pg /cm²/week.

A coating (TriSeal 300, an electrolytically applied chromium passivation coating) was placed on the chromium layer. Thereby, the nickel ion release was further decreased.

Inventive example 8: deposition from a trivalent chromium plating bath

Inventive example 7 was repeated but for the chrome layer deposition a chloride-free trivalent chromium plating bath was used (TriChrome ICE, plating time: 5 minutes, current density: 5 [A/dm²], temperature 50 °C, air agitation.

A) the semi-bright nickel layer: 16 pm

B) the intermediate nickel layer: 1 1 pm

C) the non-porous nickel layer: 1 .5 ±0.3 pm

D) the chromium layer: 197 nm

The nickel ion release of the thus obtained nickel comprising array was then tested in accordance with EN 181 1 :201 1 +A1 :2015. The nickel ion release rate was 1 .7 pg /cm²/week. However, when instead of the non-porous nickel layer deposition (method step d) a porous nickel layer deposition as described in comparative example 2 was used, the nickel ion release was increased to 5.1 pg /cm²/week.

Other embodiments of the present invention will be apparent to those skilled in the art from a con- sideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being defined by the following claims only.

Claims

1. A nickel comprising layer array on at least one surface of a substrate, comprising

A) a semi-bright nickel layer;

B) an intermediate nickel layer selected from bright nickel layers and satin nickel layers; C) a non-porous nickel layer, wherein the non-porous nickel layer is free of particulate mat ter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the electrical potential difference between the non-porous nickel layer and the in termediate nickel layer ranges from 10 to 150 mV;

D) a chromium layer,

wherein the layers are located on each in the given order.

2. The nickel comprising layer array of claim 1 characterized in that the chromium layer is deposited from a chromium electroplating bath.

3. The nickel comprising layer array of claim 2 characterized in that the chromium electroplat ing bath comprises chromium (VI) ions.

4. The nickel comprising layer array of claim 2 characterized in the chromium electroplating bath comprises chromium (III) ions und that the nickel comprising layer array comprises a coating on the chromium layer.

5. The nickel comprising layer array of any one of the preceding claims characterized in that non-porous nickel layer is free of particulate matter having a d50 (measured by X-ray dif- fraction) of 0.25 pm or greater.

6. The nickel comprising layer array of any one of the preceding claims characterized in that the semi-bright nickel layer is nobler than the intermediate nickel layer; preferably the elec trical potential difference between the semi-bright nickel layer and the intermediate nickel layer ranges from 80 to 250 mV.

7. The nickel comprising layer array of any one of the preceding claims characterized in that the semi-bright nickel layer is nobler than the non-porous nickel layer; preferably the elec trical potential difference between the semi-bright nickel layer and the non-porous nickel layer ranges from 70 to 240 mV.

8. The nickel comprising layer array of any one of the preceding claims characterized in that the chromium layer comprises 100 pores per cm² or less.

9. The nickel comprising layer array of any one of the preceding claims characterized in that the thickness of the non-porous nickel layer ranges from 0.5 to 3.5 pm, preferable 1 - 3, even more preferred 1 .2 - 2.5 pm.

10. The nickel comprising layer array of any one of the preceding claims characterized in that the thickness of the chromium layer ranges from 0.05 to 1.0 pm, 0.08 - 0.8, 0.1 - 0.6 pm.

11. The nickel comprising layer array of any one of the preceding claims characterized in that the amount of nickel ion release of the nickel comprising layer array is 0.88 pg/cm²/week or less according to EN 1811 :2011 +A1 :2015.

12. A method for manufacturing a nickel comprising layer array on at least one surface of a substrate according to any one of the preceding claims,, comprising the method steps in the given order:

a) providing a substrate having the at least one surface;

b) depositing a semi-bright nickel layer;

d) depositing a non-porous nickel layer, wherein the non-porous nickel layer is free of par ticulate matter and wherein the non-porous nickel layer is nobler than the intermediate nickel layer; wherein the electrical potential difference between the non-porous nickel layer and the intermediate nickel layer ranges from 10 to 150 mV; and

e) depositing a chromium layer.

13. The method of claim 12 characterized in that the chromium layer is deposited from a chro mium electroplating bath.

14. The method of claims 12 or 13 characterized in that the amount of nickel ion release of the nickel comprising layer array is 0.88 pg/cm²/week or less according to EN 1811 :2011 +A1 :2015.

15. Use of the nickel comprising layer array of any one of claims 1 to 1 1 as low nickel-releasing finish on at least one surface of a substrate, wherein the surface is a decorative surface for white goods articles or automotive articles.