ES2339614T3 - SOLUTION AND METHOD TO ELECTROCHEMICALLY DEPOSIT A METAL ON A SUBSTRATE. - Google Patents

Abstract

To electroplate a metal layer which has silica particles dispersed therein, a solution and a method for electrochemically depositing a metal on a substrate are provided, wherein the solution contains ions of the metal to be deposited and silica particles, wherein at least one silicon containing organic moiety is provided to said silica particles , said silicon containing organic moiety comprising at least one functional group selected from the group comprising amino, quaternized ammonium, quaternized phosphonium and quaternized arsonium which imparts the silica particles a positive electric charge while being in contact with the solution.

Description

Solution and method to deposit electrochemically a metal on a substrate.

Field of the invention

The present invention relates to a method of form a corrosion-resistant nickel multilayer on a substratum. Such multi-layer systems of nickel resistant to corrosion, eg in the automotive industry, industry sanitary, furniture accessories industry, furniture industry Glasses and jewelry.

Background

Now it is the state of the art to get the corrosion resistance of articles provided with a layer of metallic coating (= metallized) mainly in the automotive industry by deposition of a multilayer of nickel on a substrate and on it a thin layer of chromium. The last nickel layer of such a system produces tiny pores (micropores) in the chrome layer, invisible to the naked eye,  but which are the starting points of a corrosive attack.

The nickel multilayer is usually formed by two or three layers of nickel: an optional first layer that has a noble (positive) electrical potential, a second layer of nickel which is a layer of bright nickel and that is less noble than the first layer of nickel and a third layer of nickel that is metallized on top of the second layer (shiny) nickel. The second layer of nickel can also be divided into two layers of nickel: a layer of high sulfur nickel, which is very active and deposited on the first layer of nickel and other Active layer of active nickel, bright and high leveling effect. The deposition of the outermost nickel layer (the third) is performed co-depositing particles that are incorporated into this third layer of nickel. Finally a chrome layer is metallized on top of the third layer of nickel. The layer of Chrome contains holes (pores), due to the particles that are incorporate the third layer of nickel. All attacks corrosives take place through these holes and first will cause the dissolution of the second layer of nickel (bright) less noble Until the third layer of nickel (the upper one) and the chrome layer do not collapse, corrosion continues to be invisible. Corrosion is interrupted in the first layer of nickel, more noble, which protects the base material against any corrosion and progresses laterally until it has dissolved all the less noble nickel of the second layer of nickel (sparkly).

The described system works on articles of metallized plastic, in which the metallic layer deposited in firstly it is usually copper, just like on articles of steel. Its properties are evaluated with the CASS test (test Accelerated spray of acetic acid and salt on copper, ASTM B368: Copper-Accelerated Acetic Acid-Salt Spray Testing). The results of this assay are indicated with a score between 1 and 10, in which the "10" means: no change is observed by comparison with a surface without corrosive attack and the "1" means that the surface has been destroyed. The essay also distinguishes between the appearance of a surface after corrosion Prolonged and corrosion of the base material. To do this use a couple of numbers, eg 10/9 means: no attack of the material of the material base, but a little change is observed important in the appearance of the surface. With only 48 hours of CASS test, a multi-layer nickel and chrome system properly adjusted should be able to fully protect the surface, leading to a 10/10 result. The CASS trial is related to the number of pores produced in the chromium layer, which in turn due to the incorporation of inert particles in the third layer of nickel (E.P. Harbulak et al., "Chromium Microporosity and Active Sites ", Plating and Surface Finishing, 58-61, (1989)).

Corrosion becomes visible holes produced are getting older, or when the protective action of the third layer of nickel and the chrome layer will collapse, because there is not enough bright nickel layer to support them.

There are various parameters that influence the multilayer nickel system. These are mainly the thickness of the metallic layers, their individual electrical potentials relative and pores produced in the top layer of chromium. Because the second layer of nickel (shiny) is what self-sacrifice, if this layer were thicker, then it would resist the attacks for a longer time. If the third layer of nickel or chrome layer are very thin, then the layers Protectors will collapse before. One of the main influences consists of the different electrical potentials of the nickel layers. Organic additives that have double bonds or which contain chlorides can make electrodeposited nickel Be more noble. Well-known additives, suitable for this purpose, they are for example vinyl sulfonic acid, allylsulfonic acid and the hydrated chloral. Other organic additives, which increase the sulfur content embedded in the nickel layer, convert it In less noble. Another member of this group is saccharin. Normally, using suitable additives, the difference between the electrical potentials of the first layer of nickel (semi-gloss) and the second layer of nickel (bright) for that is in the range between 90 mV and 140 mV. He electrical potential and the resulting potential difference can determined with the STEP test (simultaneous thickness determination and of the electrochemical potential of individual layers of a reservoir multi-layer nickel, ASTM B764: "Simultaneous Thickness and Electrochemical Potential Determination of Individual Layers in Multilayer Nickel Deposit "). Like the first layer of nickel, the third layer of nickel has to be more noble than the second layer of nickel, because the third layer of nickel with its thin pores have to cover the second layer of nickel (bright) without suffering any dissolution once it has started corrosion In order to achieve this, it usually fits the potential difference between the third layer of nickel and the second nickel layer in a range between 20 mV and 60 mV.

Without ensuring that the thin pores of the two last metal layers are evenly distributed, the corrosion takes place less evenly, somewhat early, producing holes that are few but large, visible to simple sight, which will soon be layers even to destroy the layer of Semi-gloss nickel and attack the base material. To do this, the corrosive attack should be distributed evenly (M. Häp and col., "DUR-NI 4000 - Verbesserter Korrosionsschutz mit größerer Prozesssicherheit "= better corrosion protection with greater process safety, Galvanotechnik, 894-897, (2004)). This is achieved with the use of a non-conductive material that is contained in the solution of deposition for the third layer of nickel. Non-conductive material causes such thin pores ("microporous" surface). By therefore, the third layer of nickel (discontinuous) is called "microporous nickel". Aluminum oxide particles, titanium oxide, filter earth, iron oxide, chromium oxide and molybdenum oxide are indicated in US Patent 3,449,223 as suitable for this purpose.

Many attempts have been made to achieve a uniform distribution of pores and a reliable count of same. It is believed that the number of pores should be greater than 10,000 cm -2 (E.P. Harbulak et al., cited place). The number is counted of pores after depositing copper on a specimen in a Acid copper electrolyte, which does not deposit copper to chromium, but only on nickel (Dubpernell test, ASTM B604, B456). Normally the inorganic material is added to the third solution of Nickel electrolyte to produce pores. This material can be silica (US Patent 3,825,478, in combination with ions of At +++ [ex. I]), titanium oxide (EP 0 431 228 A1, in combination with Ca ++), titanium oxide coated with Al 2 O 3 or SiO 2 (JP 04371597 A) or a product of insoluble reaction, for example a nickel compound that is insoluble in the bath solution (US Patent 3,736,108). They have employed organically non-electrically conductive fibers, which they are also incorporated into a nickel layer (GB patent 1,118,167).

There are substantial drawbacks in inorganic particles that are used to incorporate the third layer of nickel: particles of finely ground inorganic material have a specific density greater than water and that of nickel electrolyte, so they have a strong tendency to settle on the bottom of the deposition tank. To avoid sedimentation, strong agitation is carried out with air, which, in turn, is an inconvenience, because all the particles that come into contact with the surface of the article to be metallized are immediately expelled, although they should remain there. in order to join the nickel layer. A drawback of the SiO2 particles has been defined as the risk involved in sealing the anode bags. This is believed to be due to SiO2 particles having a negative network charge when they are in the electrodeposition bath. G. Vidrich et al. (dispersion behavior of the Al 2 O 3 and SiO 2 nanoparticles in nickel sulfamate deposition baths of different compositions, "Dispersion Behavior of Al_ {2} 3 and SiO_ {2} Nanoparticles in Nickel Sulfamate Plating Baths of Different Composition ", J. Electrochem. Soc., 152 (5), C294-C297, 2005) have published the co-deposition of metal ions and dispersed particles of Al_ {2} 3 and SiO_ {2}. They indicate that one reason for the lack of investigations dedicated to the deposition of the SiO2-nickel matrix material may be the negative network charge that is often observed in the SiO2 even when the ionic concentrations are low in the aqueous solution, whose pH is in numbers greater than 3 or 4.

In order to reverse the surface charge of the silica, C.J. Brinker and G.W. Scherrer (science sol-gel: physical and chemical process sol-gel, "Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing ", 1st ed., Academic Press, 1990, pp. 410-415) have indicated the absorption of the material loaded on the surface of the same, but without referring to the electrodeposition of nickel. He loaded material suitable for inverting silica charge to positive indicates that they are eg tri- and tetravalent metals, for example the Al, Cr, Ga, Ti and Zr. In place of these metals silica can also be absorbed organic cations versatile In an alternative, WO 2005/106106 A1 describes an aqueous dispersion that can be used as a finishing agent for textiles, said dispersion contains a dioxide powder aggregate, produced by pyrogenically, and a cationic polymer, which is soluble in the dispersion. In addition, in EP 1 894 888 A1, describes an aqueous dispersion of silica, which is stabilized with cations Said dispersion is mentioned for the one painting that applied on paper, sheets or on print media, such as a coating on a substrate, for example wood, plastic, metal, textile and sheets, to improve the mechanical properties and optics thereof, as a coating on sheets to improve the separation of two sheets from each other and also for agents grinding and polishing.

In addition, DE 24 32 724 A1 describes a nickel deposition solution containing metal silicates alkali and kaolin to form particles in the deposited layer of nickel. It is indicated that alkali metal silicates change the loading of the kaolin particles in order to make possible the incorporation of them to the nickel deposit.

US 4,655,882 A describes a process for manufacture metallized steel with a compound of zinc-silica The galvanization bath contains Zinc ions, for example ZnSO4, and silica particles. After electrochemical deposition of the compound of zinc-silica on steel a treatment is performed with alkoxysilane for the addition of silane.

In GB 1 421 975 A a process for the deposition of a metallic coating on a surface. The deposition is performed with an aqueous bath, more specifically by electrodeposition The solution contains metal ions, by example NiSO4 and a finely divided solid, for example silicon carbide or other non-metallic compounds, for example oxides The aqueous bath contains a compound of amino-organosilicon, which contains at least one group H 2 N. The amino organosilicon compound it is reacted preferably with the solid.

Object of the present invention

After seeing the above, an object of the present invention is to provide a solution to deposit electrochemically a metal on a substrate. Another object of the present invention is to provide a method for depositing electrochemically a metal on a substrate. Another object over the present invention is to provide a method for forming a corrosion resistant nickel multilayer on a substrate. A further object of the present invention is to provide a means to improve the uniformity of resistance to corrosive attack against the surface of a metallic coating, in particular a nickel plating, even more particularly a Nickel coating coated with a chrome coating. More especially, another object of the present invention is provides means to improve pore uniformity formed in the chrome coating and in particular provide means to improve the uniformity of distribution of non-conductive particles incorporated into the nickel layer that deposits directly below the chrome coating. From very specific way, an object of the present invention consists in provide a solution and a method to deposit electrochemically a metal, more specifically nickel, about a substrate containing silica particles that are deposited simultaneously with nickel.

Definitions

For use in this description the following definitions:

"Alkyl" means any saturated or unsaturated, monovalent or divalent moiety having a hydrocarbon chain. Therefore, alkyl can be a monovalent saturated hydrocarbon chain which, if unsubstituted, has the general chemical formula C n H 2 n + 1, in which n is an integer greater than zero, for example methyl , ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, tert-pentyl, neo-pentyl, hexyl, heptyl, octyl and the like, with special preference methyl, or a divalent saturated alkyl chain, which, if unsubstituted, has the general chemical formula C n H 2 n, in which n is an integer greater than zero, for example methylene (-CH_ { 2}-),
ethylene (-CH 2 -CH 2 -), n-propylene (-CH 2 -CH 2 -CH 2 -), isopropylene (-CH (CH 3) - CH_ { 2} -) and the like. In addition, the alkyl can be a monovalent unsaturated hydrocarbon chain, that is, a hydrocarbon chain having at least one double bond or at least one triple bond or both, at least one double bond and at least one triple link. Monovalent hydrocarbon chains that have at least one double bond, if unsubstituted, have the general chemical formula C n H 2 n-1, in which n is an integer greater than zero, for example ethenyl ( -CH = CH2) and propenyl (-CH = CH-CH3, -CH2 -CH = CH2). Divalent hydrocarbon chains having at least one double bond, if unsubstituted, have the general chemical formula C n H 2n-2, for example ethenylene (-CHCH-). Hydrocarbon chains that have at least one triple bond, if unsubstituted, have the general chemical formula C n H 2 n-3, in which n is an integer greater than zero, for example ethynyl ( -C \ equivCH). Divalent hydrocarbon chains, which have at least one triple bond, if unsubstituted, have the general chemical formula C n H 2n-4, for example ethylene (-C \ equivC-). In the above definitions, n may be an integer from 1 to 16, more preferably from 1 to 12, even more preferably from 1 to 10, more preferably still from 1 to 6, more preferably still from 1 to 5 and with special preference from 1 to 4. With regard to these definitions, n in an alternative embodiment may be at least 2 or at least 3. Therefore, alkyl may be C 1 -C_ { 6 or C 1 -C 5 alkyl or C 1 -C 4 alkyl.

The alkyl may be substituted, in that case at least one hydrogen atom is replaced by any residue, for example aryl, heteroaryl, OR, NR'R '', COOR, CONR'R '', in which R, R 'and R' 'are independently chosen from hydrogen, alkyl, aryl and heteroaryl.

"Aryl" means a hydrocarbon residue C5-C12 aromatic which is substituted or without replace. In the substituted aryl, at least one atom of hydrogen has been replaced by any remainder, for example alkyl, aryl, heteroaryl, OR, NR'R '', COOR, CONR'R '', in which R, R ', R' 'are independently chosen from each other among hydrogen, alkyl, aryl and heteroaryl. The most preferred aryl is the phenyl.

"Heteroaryl" means an aromatic moiety which has 5 to 12 links in the ring and as links it has, in addition to carbon atoms, at least one atom of N, S or O. Heteroaryl moieties may be unsubstituted or substituted. In the heteroaryl substituted at least one hydrogen atom has been replaced by any functional group of the alkyl, aryl type, heteroaryl, OR, NR'R '', COOR, CONR'R '', in which R, R ', R' 'is independently choose between hydrogen, alkyl, aryl and heteroaryl. The most preferred heteroaryl is pyridyl, pyrrile, thiophenyl, furanyl, pyrazolyl and the like.

"Amino" means a remainder -NR'R '', in the that R 'and R' 'are independently chosen from each other among the group formed by hydrogen, alkyl, aryl, heteroaryl or, as alternatively, they can form a single divalent group, which together with the atom of N forms a ring.

"Imino" means the remainder -NR- or = NR, in which R is hydrogen, alkyl, aryl, heteroaryl, and can form two bonds with two other atoms (-NR-) or a double bond with another atom (= NR).

"Silica" in a broad sense is the dioxide of silicon. Silica particles may vary, depending on the method of production, in terms of particle size, agglomeration degree, degree of crystallinity, specific area per unit weight, porosity and the like. According to the present invention, "silica" it can also be understood as a material formed by particles of any other material, for example alumina, when the particles of the other material are completely coated with silica, for example when the surface of the particles behaves so predominantly as if it were a silica surface. Silica is a  commercial product supplied with names of the Aerosil® type (Evonik Degussa), HDK® (Wacker Chemie) and Cab-O-Sil® (Cabot). Silica can Be crystalline or amorphous. Silica can also be supplied in colloid form.

Description of the present invention

The aforementioned objects are achieved with the method of forming a multilayer of nickel resistant to corrosion on a substrate according to claim 1. The forms Preferred embodiments of the invention are indicated in the secondary claims.

Now it has been discovered that the distribution uniform pores in the outer layer of chrome can be achieved  easily if the nickel layer is deposited with particles of silica deposited simultaneously, said silica particles confer a positive electric charge large enough to ensure that these particles are effectively transferred to the surface of the piece. Therefore, the invention uses the particles that have better properties in terms of their behavior in metallic electrolytes, preferably in nickel electrolytes and in an electric field. The particles allow the creation of large numbers of pores and a wide pore size range. The positive electrical charge of the silica particles are imparted to said silica particles providing them with at least one organic residue that contain silicon, giving silica particles this charge positive electrical while in contact with the solution.

An aspect of the present invention is thus provide a solution for electrochemically depositing nickel on a substrate, said solution contains nickel ions at deposit and silica particles, in which it is provided so less an organic residue that contains silicon that imparts to silica particles a positive electrical charge while they are in contact with the solution. At least one of said remains organic containing silicon contains at least one group Functional chosen from the group consisting of amino, ammonium quaternary, quaternary phosphonium and quaternary arsonium and is attached preferably silica particles. Said functional group, at least one, imparts to the silica particles the charge positive electrical required while in contact with said solution.

Another aspect of the present invention is provide a method to electrochemically deposit a metal on a substrate, said method consists of the following steps: (a) contact the substrate and at least one anode with the solution to electrochemically deposit a metal according to the present invention and (b) apply a flowing electric current through the substrate and at least one anode, so that the metal It is deposited on the substrate.

A layer of nickel produced with according to the method of the present invention and using the solution of the present invention as part of a multilayer structure of nickel, eg, a multilayer of two, three or four layers of nickel, which is finished off preferably with a layer of superimposed chrome.

Therefore, another aspect of the present invention is to provide a method for forming a multilayer of corrosion resistant nickel on a substrate, said method It consists of the following steps: (a) deposit a first layer of nickel that has a first electrical potential, (b) deposit a second nickel layer that has a second electrical potential plus negative than the first electrical potential (i.e. the second nickel layer is less noble than the first nickel layer) on the first layer of nickel, and (c) deposit a third layer of nickel using the solution to electrochemically deposit a metal of the invention on the second layer of nickel.

In water, silica will normally develop a negative network charge and therefore will not be transferred to the cathode, in which is intended to produce pores. Instead it will be transferred to anode and, in high concentrations, can even block the anode bags. Providing at least one organic residue that imparts a positive electrical charge to silica particles when in contact with the solution, you get a number uniform and elevated pores in the chrome layer. This advantage is combines with the silica that has other advantages over particles of other materials that can be incorporated into the third nickel layer, these additional advantages are that silica is very porous and has a hydrophilic surface. Hydrophilic silica porous (or glass particles) that are commercial products that are supplied in almost any size and desirable porosity) is chosen instead of ground alumina or talc type minerals, because it can be dispersed in water or electrolyte more easily and for a longer time. The high porosity of silica particles offer the additional benefit of attributing to particles a low specific gravity, which, in turn, produces a more uniform distribution of the same in the solution of deposition due to its lower tendency to settle. This in turn does unnecessary and complicated injection of air into the bath solution, which in other cases is required to maintain the suspended particles.

Silica particles tend to precipitate in Water. For this reason, silica particles can be applied to an electrolyte solution in suspension form, which makes The replacement is very simple and reliable. Other materials inorganic, especially talc, in a concentration of pores slightly elevated (e.g.,> 20,000 cm -2) produces a cloudy chromium deposit, the new invention powder does not produce no visible turbidity when the number of pores is much greater than 100,000 cm -2.

Another great advantage of the present invention is that a large number of different types of silica are products commercial. Silica particles that have a porosity and size in a wide range are products commercial and can be easily obtained with organic remains They contain silicon as desired. Since the particles later of modification with organic remains have a burden positive electrical defined, the number of pores can be adjusted simply by choosing the current density and adjusting the concentration of the modified silica particles in the metal electrolyte, in particular in the nickel electrolyte. It is not necessary to build a sophisticated or complicated architecture for agitation with air, which could lead to results unpredictable.

Silica particles coated with alumina they have, for example, a positive network charge at the pH at which Process the nickel electrolyte (pH = 3.5 to 5.5) to ensure that these particles will be transferred to the piece. In addition, said Coated particles are more hydrophilic than solid alumina, it they moisturize and disperse more easily in the solution of electrolyte than solid alumina particles. But nevertheless, these particles do not have the same amount of surface charge than the silica particles that are obtained by providing the same with the organic moiety according to the present invention.

Organic remains are organic remains that They contain silicon. Silanes and siloxanes or the like, such as organic compounds that contain silicon, react easily with organic residues that contain silicon and are united, with preference by covalent bond, to the surface of the silica particles

According to a preferred form of execution of the present invention, the organic moiety, at least one, is bonded to silica particles. This means that a chemical bond (covalent) between reactive centers corresponding to the organic residue on the one hand and the surface of The silica on the other hand. The chemical bond ensures that the remains that impart the possible positive charge to silica particles they are not desorbed or otherwise torn from the particles of silica. Therefore, the positive charge contributed to the particles of silica by organic remains is constant and does not depend on no surface effect, for example the balance that forms in the electrolyte deposition solution.

In order to impart to the particles of silica a positive electrical charge, the organic remains have a positive electric charge in at least one of its atoms, is that is, in a nitrogen, phosphorus or arsenic atom. Load positive electrical can be provided with a chemical residue that forms part of the organic residue that forms or has an electric charge positive. The last form of execution of chemical remains has a permanent positive electrical charge, that is, the remains ammonium, phosphonium and arsonium. The chemical remains form this charge positive electrical only in the conditions of the deposition of the metal, that is, due to the existing pH conditions in the metal deposition solution. The chemical remains that form said positive electric charge are for example amine residues. For the therefore, the positive electrical charge is formed or contributes at least through a functional group chosen from the group formed by amino, quaternary ammonium, quaternary phosphonium and arsonium quaternary. Quaternary ammonium, quaternary phosphonium and arsonium quaternary possess a permanent positive electrical charge while that the amino has a positive electrical charge only when the pH of the metal deposition solution is below a certain threshold value, which can be defined as pH around 7, with more preferably pH around 6, more preferably pH in around 5.5, more preferably still pH around 5 and with Special preference pH around 4.5. Therefore, if the pH is below any one of the upper limits here mentioned, the amino will be protonized to form ammonium ions and by consequently it will impart a charge to the silica particles positive electrical The lower pH limit of the solution metal deposition will depend on the type of deposition solution of the metal and will be a pH around 0, more preferably around to 1, even more preferably a pH around 2, with greater preference still a pH around 3, more preferably still a pH around 3.5 and with special preference a pH in around 4.

In a more preferred form of execution of the In the present invention, positive charges are introduced into the silica particles joining a silane, for example an aminosilane, to the surface of the silica particles. As an alternative binds a silane to the surface of the silica particles that have at least one of the ammonium, phosphonium and arsonium groups or not it has such groups when the silane is attached to the surface of the silica particles, but in which said onium groups are subsequently formed, that is, when the silanes are already united to the surface of the silica particles.

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Even more preferred, the rest organic, at least one, is formed by reaction of the particles of silica with a reagent, said reagent has the formulas General chemicals I, II, III or IV:

one

in the that

Q is N (nitrogen), P (phosphorus) or As (arsenic), Q is preferably N;

R1 and R2, independently of each other, they are unsubstituted or substituted alkyl or unsubstituted aryl or substituted, preferably unsubstituted or substituted alkyl, said R1 is more preferably alkyl C 1 -C 5 and R 2 is more preferably C 1 -C 6 alkyl, R 1 can also be hydrogen;

R 3, R 4 and R 5 are hydrogen, unsubstituted or substituted alkyl, unsubstituted aryl or substituted, said R 3, R 4 and R 5, independently each other, they can also contain at least one functional group containing amino and imino residues.

Silica particles provided with the rest Organic have an overwhelming effect: only 50 mg / l of silica modified with this material can produce more than 100,000 pores per square centimeter when deposited simultaneously with a layer of nickel. While other material particles require a concentration of> 300 mg / l and a distribution careful of the air inside the electrolyte, the porous silica provided with the organic rest does not need any care special in terms of agitation with air or the distribution of air.

More specifically, the organic rest, so minus one, is formed by reacting the silica particles with the (3-aminopropyl) triethoxysilane. It is believed that this reaction is a condensation reaction on the surface of silica particles, which, by hydrolysis, normally have Si-OH groups exposed on its surface. This condensation reaction of the compound having the chemical formula general I with the SiOH groups of the surface of the particles of silica could be the following:

Si-OH + (R 1 O) 3 Si-R 2 -NR 3 R 4 \ rightarrow Si-O-Si (OR 1) 2 -R 2 -NR 3 R 4  + R1 -OH

It is believed that other reaction steps may have place with the Si-OH surface groups, by example the following:

2

Y:

3

Silica particles provided with the rest Organic can be produced by reaction of silica particles with a silane compound by mixing them in a non-aqueous solvent, by example acetone or chloroform and letting the reaction mixture react for a short period of time, for example for one hour. Then the precipitate formed within the reaction mixture, for example by filtration. As an alternative, a silane is mixed with an acid in an aqueous medium. Later disperses the silica in this reaction mixture, preferably keeping the reaction mixture under stirring. More products from transformation and various forms of execution and examples of obtaining the silica particles modified by the union of one or more of different aminosilanes with the surface thereof have been described in EP 1 894 888 A1, whose various sources and types of silica, of solvent used for the reaction of the particles  of silica with aminosilanes, the acid used in the mixture reactant as well as the predominant pH during the passage of reaction, types of aminosilane compounds (R_ SiX (4-a)), in which one or several aminosilanes are used to join the surface of the silica particles, concentration and proportion of concentrations of silica and aminosilanes, the operations for reaction of silica particles with aminosilanes (mixing, stirring), the concentration of silica particles suspended in the reaction mixture, the type of additives used in the product obtained and similar described in EP 1 894 888 A1 are incorporated into the description herein request.

The silica particles used according to the present invention preferably have a surface specific per unit weight of 300 m2 / g. Lower limit of the specific surface area per unit of weight is preferably 40 m 2 / g. More preferably, the upper limit is 250 m 2 / g and the lower limit is 140 m 2 / g. Limits upper and lower of the indicated intervals can be combined to produce any interval. The previous values of the specific surface area per unit of weight are chosen to achieve the optimal positive surface charge after the particles of silica have reacted to join the organic residue with the surface of it. The specific area per unit weight It is determined by applying the BET method.

In addition, silica particles have with preferably an average diameter between 0.3 µm and 15 µm, more preferably between 0.6 µm and 12 µm and with special preference between 0.6 µm and 5 µm. The expression "mean diameter" is used here to indicate the value d_ {50} of the resulting particle size distribution, which is obtains, for example, by measuring the dynamic laser dispersion. The experts already know these methods of determining the particle size distributions. Therefore, the lower limit of the average diameter is preferably 0.3 µm and more preferably 0.6 µm. The upper limit is with preferably 15 µm, more preferably 12 and preferably special 5 µm. The upper and lower limits of the average size can be combined to obtain any interval that has these limits. The average values above the average diameter are chosen to obtain optimum dispersibility (uniform distribution) in the dispersant (metal deposition bath).

The silica may be contained in the solution. of electrolyte of the invention at a concentration of 2 mg / l at 10 g / l, more preferably from 10 mg / l to 1 g / l, more preferably still from 20 to 500 mg / l and with special preference from 35 to 100 mg / l Therefore, the lower limit of this concentration may be 2 mg / l, more preferably 10 mg / l, more preferably still 20 mg / l and with special preference 35 mg / l and the limit higher than this concentration can be 10 g / l, with higher preference 1 g / l, more preferably still 500 mg / l and with special preference 100 mg / l. The upper limit values e bottom can be combined anyway to get a preferred range of concentrations. Silica concentration in the electrolyte solution it can be around 50 mg / l.

The metal can be deposited on the substrate using a direct current or pulsating current, including the unipolar or bipolar pulsating current. As an alternative, metal can be deposited using a sequence of time period, in the time periods of direct current alternate with the periods of pulsating current time. In addition the deposition It can be done in a conventional plant using tanks immersion and racks to support the items to be metallized and immerse them inside the electrolyte solution of the invention contained in said anodes with respect to articles a metallize. Items may also be located within cylinders that are submerged in the deposition solution. How alternatively, the items to be metallized can be placed and treated in a deposition plant on conveyor belt, which uses trays for the accommodation of the articles. Anodes it can be placed in one or, preferably in the two articles to metallize and can be soluble anodes, that is, anodes that are dissolve due to the electrodeposition operation because they are substantially of the same metal as the metal that is intended to deposit. Or the anodes are manufactured with a material that is not dissolves during the electrodeposition operation, that is, a material that is inert in the solution and in the conditions of deposition The deposition is done by making a more agitation or less vigorous solution, including air injection.

The substrate can be any suitable piece for the metallization by deposition of a metallic layer, eg a metal part or a piece of plastic material or any other non-conductive material A non-conductive substrate can metallize firstly by deposition of any ground metal, with or without application of electric current, that is, by electrodeposition by immersion or by deposition without electrodes. TO The metal layer is then deposited using a solution according to the invention. And finally, more layers can be deposited metallic on the metallic layer deposited with the solution of the invention.

In addition to the metal ions to deposit and of the modified silica particles with organic residues that contain silicon, the deposition solution contains with preferably an agent for adjusting the pH, for example an acid or a tampon.

In a more preferred form of execution of the In the present invention, the metal to be deposited is nickel. Nickel can contribute with the solution of deposition of the metal that acts as source of nickel ions, more specifically as nickel salt and with special preference as nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, nickel borate, sulfamate of nickel, nickel methanesulfonate.

Preferably the deposition solution of metal, preferably nickel, may also contain less an acid, preferably an inorganic acid and with special preference an acid that has a counter-ion, which is the same as the counter-ion of the nickel salt, for example of acid sulfuric acid, sulfamic acid, methanesulfonic acid, boric acid and acetic acid. With special preference, the deposition solution metal, preferably nickel, of the invention contains acid boric acid or as a pH adjusting agent.

It is also assumed that the acid can be the same as an agent to adjust the pH or as part of the pH adjustment, the latter can be a buffer mixture.

In addition, the metal deposition solution, with Nickel preference, contains additives that serve to control the metal deposition bath, for example organic compounds that influence the properties of the metallic deposit, for example brightness, leveling, anticorrosive behavior (potential electrical corrosion) and the like. These compounds can be unsaturated compounds, for example acid vinyl sulfonic acid, allylsulfonic acid, also the hydrated chloral and organic compounds that have sulfur atoms in a low oxidation state, for example saccharin.

A multilayer of nickel can be deposited on the surface of a substrate. Optionally a chrome layer can be deposited on the top of the nickel multilayer. This nickel multilayer and chrome layer are well known in the art for being very resistant to corrosion. The nickel multilayer is generally formed by two or three layers of nickel: an optional first layer of nickel that has a noble (positive) electrical potential, a second layer of nickel that is a bright layer of nickel and that is less noble than the first layer of nickel and a third layer of nickel that is deposited on top of the second layer of nickel (bright). A chromium layer is deposited on top of the third layer of nickel, which also contains silica particles co-deposited therein. The corrosive attack will take place through the large number of pores created in the chrome layer and in the third layer of nickel and will progress first in the second layer of nickel (shiny) less noble. Therefore, a visible change in the metallic coating will not take place. The first nickel layer can be deposited using Watts called electrolyte containing nickel chloride, nickel sulfate and boric acid, for example approx. 60 g NiCl2 \ cdot6
H 2 O, 270 g of NiSO 4 • H 2 O and 45 g of boric acid per liter of deposition solution. Typically, apart from salicylic acid, this bath contains derivatives of ethyne, for example hexinodiol or butynediol or derivatives of propargyl alcohol as additives or a mixture of various additives. The second nickel layer can be deposited using a Watts electrolyte that differs from the electrolyte used to deposit the first nickel layer because it typically uses sulfur-containing compounds, for example toluenesulfonic acid or propargyl sulfonates and also saccharin instead of salicylic acid such as additives or mixture of various additives. The third nickel layer can be deposited using a Watts nickel electrolyte as in the case of the deposition of the first and second nickel layers, but also contains saccharin or a salt thereof and the hydrated chloral as a mixture of additives and also silica as described for the formation of pores. All of the electrolyte solutions mentioned can also contain other additives, for example a brightener or a wetting agent, for example ethylhexyl sulfate. The pH of the electrolyte solution can be between 2.5 and 6, more preferably between 3 and 4.5 and with a special preference at 4.0. The temperature of the electrolyte during the operation of the electrodeposition of the nickel can be high, for example 40-70 ° C, more specifically 50-60 ° C and with special preference 55 ° C.

The invention is described below with greater clarity through the examples that follow. The forms of execution presented in the figures and in the examples shall not be taken as limiting the scope of the invention.

Figure 1 shows the relationship between the number of pores and the current density for the solution of electrolyte according to the invention (P305b) and for a solution of prior art electrolyte containing alumina and silica particles that have not been modified with an organic residue (GZZ).

Figure 2 shows the relationship between the number of pores and the concentration of dust particles using modified silica particles.

Figure 3 shows a scheme of a curved panel used to investigate the distribution of pores

Figure 4 shows a diagram of a curved steel panel used to investigate the distribution of the pores.

Figure 5 shows a piece metallized according to the invention.

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Example 1 Obtaining modified silica particles joining a aminosilane to their surface and use them in a nickel electrodeposition bath

3.0 ml of dissolved (3-aminopropyl) triethoxysilane in 200 ml of dry acetone The solution is poured onto 15 g of powder SD-530 (Porous silica from Hang Tian SaiDe / Beijing, R.P. China, volume peak of 26.2% in particle size of 5 \ mum). The mixture is reacted at room temperature for one hour. The powder is washed with acetone and dried at temperature ambient until reaching a constant weight.

A rectangular PVC tank equipped is filled with two nickel anodes on opposite sides with 2 l of an electrolyte  nickel Watts (60 g / l NiCl2 \ cdot6 H2O, 270 g / l of NiSO 4 • 6 H 2 O, 45 g / l boric acid). Be heats the electrolyte at 55 ° C. It is then adjusted by adding 0.2 ml / l of a solution of a sulfate-based wetting agent of ethylhexyl, 0.7 g / l sodium sucrate, 50 mg / l hydrated chloral and a brightener. After the additions it is found that the pH of the electrolyte is pH = 4.0. The 2 l of electrolyte are given add 100 mg of modified silica. The solution continues transparent, without noticeable turbidity. The agitation of the solution only with a moderate injection of air.

Panels are pretreated properly rectangular steel and are metallized with approximately 10 µm of semi-gloss nickel and approximately 10 µm nickel sparkly. These prepared panels are then metallized in the electrolyte described above with a current density of 3 A / dm 2 for three minutes and then for three minutes with a chromium electrolyte that is a commercial product (Unichrome® 843 from Atotech).

It is found that the average thickness of the layer Chrome is 0.23 µm at the edges of the panels and 0.16 \ mum in the center of the panels. The total thickness of all Nickel layers is 17 µm / 25 µm.

The electrical potential between the nickel layer semi-gloss and the bright nickel layer is between 121 mV and 135 mV and the potential between the last two layers of nickel (between the second and third layer of nickel) is between 28 mV and 35 mV. The average number of pores is 55,000 cm -2. After a CASS trial of 198 CASS hours, the score (average of score awarded by five independent inspectors) of brightness It is 9.33 and the protection is 9.72.

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Example 2 Obtaining modified silica particles by joining a aminosilane to their surface

Syloid 244FP dries (Grace, peak volume 15.2% at 3.3 µm) in an oven at 110 ° C for two hours. Dust of silica loses 4.2% by weight. 5.0 ml of the (3-aminopropyl) triethoxysilane in 100 ml of chloroform (HPLC quality, water <0.001%) and poured over 15 g of the silica powder in a PP jar, which is then closed hermetically. After a short reaction time, the opaque gel It becomes a suspension. After an hour the suspension on a filter paper in a Buchner funnel, it removes the chloroform by vacuum suction and the material is washed remaining carefully with chloroform. It dries again resulting material at 110 ° C until its weight no longer changes. He weight gain after the reaction is 9.5%

Example 2.1

The test of example 2 is repeated with SD-530

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For different concentrations of aminosilane, The resulting weight gain is only slightly different:

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Example 3 Obtaining modified silica particles with the union of a aminosilane to their surface and use them in a nickel electrodeposition bath

Two types of particles are compared: a SD-530 modified as described in example 1, but with 5 ml of aminosilane for 15 g of powder and a silica Alumina modified which is a commercial product. From a standard solution of 5 l of Watts nickel electrolyte, a liter fits with saccharin, surfactant and brightener, from mode described in the previous example 1. In a 250 Hull cell ml the electrolyte is used to metallize with nickel microporous with a cell current of 2 A for three minutes.  The amount of pores is calculated against the current. In the figure 1 represents the relationship obtained between the number of pores and the current density for the electrolyte solution according to the invention (A) and for an electrolyte solution of the art anterior containing alumina and silica particles that are not modified with an organic moiety according to the invention. The number of pores made in the material containing alumina does not obey the increasing density of the current while the behavior of pore number / current density of the modified material With amino groups it is linear. Therefore, it can influence the number of pores to achieve high values of number of desired pores increasing the density of the current. For example, the number of pores for conventional silica particles in The nickel electrodeposition bath is approx. in 27,000 cm -2 for a current density of 5 A / dm 2, while that the pores obtained with silica particles modified with organic residues containing silicon according to the invention are situated at 50,000 cm -2 for the same current density.

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Example 4 Use of modified silica in an electrodeposition bath of nickel

They are introduced in a rectangular tank 2 liters of nickel electrolyte described in example 1 and are used to metallize panels with a layer of microdiscontinuous nickel, pre-metallized with approximately 10 µm nickel bright, with different concentrations of dust SD-530 modified with aminosilane as described in example 1. A relationship between the number of pores and the dust concentration shown in figure 2. This ratio is linear to high dust concentration values and pore numbers, respectively. It is found that the number of pores increases to approx. 200,000 cm -2 when a powder concentration of 100 mg / l and is expected to continue to increase When the concentration increases.

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Comparative example 5

Use of unmodified silica in an electrodeposition bath of nickel

An electrolyte is prepared as described. in example 1. Repeat the deposition in the same tank of deposition This time SD-530 powder is used without Modification with silane. The electrolyte contains 2 g / l of powder. Be finds that the number of pores is only 2,300 cm -2.

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Example 6 Use of modified silica in an electrodeposition bath of nickel

In a tank of 250 a solution of Watts nickel (concentrations of the main components: NiCl2, NiSO4, boric acid, as described in the Example 1). The solution is heated to 55 ° C and adjusted in the manner described in example 1 with organic additives, for example surfactant, saccharin and brightener. After adjusting the pH to 4.2 and add 50 mg / l of modified silica powder, fix a curved panel (figure 3) in the center of the tank, parallel to the anodes and deposition begins with a current density of 5 A / dm 2. The deposition takes place for three minutes. After the panel is rinsed and the chrome layer is deposited. Then the panel is divided into pieces and the pores of the chrome surface after copper deposition (test of Dubpernell). The numbers of pores collected in the table are obtained one.

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Example 7 Use of modified silica in an electrodeposition bath of nickel

A multilayer of nickel and a layer is deposited chrome over the top of the nickel multilayer on a curved steel plate (shown in figure 4). The tests are carried out in tanks of 100 l.

In the first step of nickel deposition, deposit a layer of semi-gloss nickel on the steel plate 16 µm thick (20 min with 4 A / dm 2) using a bath deposition of semi-gloss nickel which is a commercial product (Duplalux® Step, Atotech). Then on top a nickel layer is deposited from the first nickel layer bright about 8 µm thick (10 min with 4 A / dm 2) employing a bright nickel deposition bath which is a commercial product (Makrolux® NF, Atotech). The electrical potential of this second layer of nickel and is which is 140 mV with respect to the first nickel layer. Next, on top of the shiny nickel layer a layer of nickel about 2 µm thick is deposited (4 min with 3 A / dm 2) simultaneously incorporating silica into this third layer of nickel. The solution to deposit this layer of nickel is the same as in example 1, but the solution of deposition instead of containing as sulfate additives ethylhexyl, sodium saccharide and hydrated chloral now contain a unsaturated carboxylic acid (acid allyl carboxylic acid vinyl carboxylic), saccharin and a brightener (Makrolux®, Atotech). The different types of silica used in this case is shown in table 2. The potential is determined electrical of this third layer of nickel and is found to be 30 mV with respect to the second nickel layer. The anodes used in all the steps of nickel deposition are pieces of nickel that They contain sulfur, which are housed inside baskets. Finally, in the top of the third layer of nickel is deposited a layer of chrome about 0.4 µm thick (4 min with 10 A / dm 2) with a chrome deposition bath which is a commercial product (Glanzchrombad Cr 843, Atotech).

To determine the number of pores the Fuhrmann-Tester automated program (program: 30 s with 1.0 V; 30 s with 0 V; 30 s with -0.4 V; pores> 4 \ mum, 50 x; Markus Häp et al., Place cited). The results of the numbers of pores found in the chrome layer are collected in the table 3.

From table 3 it is clear that the number of pores is much larger in the case of the solution of the invention than in the case of prior art solutions. In addition, the variations in pore numbers are much larger in the case of the prior art solutions than in the case of the solution of the invention. Therefore, with the solution of the invention you get much more consistent results in terms of distribution of pore numbers on the curved plate of steel than the compositions than the prior art.

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Example 8 Use of modified silica in an electrodeposition bath of nickel

Another test is performed in a plant production of larger dimensions using 1400 l tanks. The Pieces to be metallized are shown in Figure 5. The procedure deposition of the first nickel layers (semi-gloss), second (bright) and third and the chrome layer is as described in example 7. To deposit the third layer of nickel that Contains particles, the composition used is also described in example 7. The particles used in this case are collected in table 4.

To determine the number of pores the Fuhrmann-Tester automated program (program: 30 s with 1.0 V; 30 s with 0 V; 30 s with -0.4 V; pores> 4 \ mum, 50 x; Markus Häp et al., Place cited). The results of the numbers of pores found in the chrome layer are collected in the table 5.

From table 5 it is clear that the number of pores is much larger in the case of the solution of the invention than in the case of prior art solutions. In addition, the variations in pore numbers are much larger in the case of the prior art solutions than in the case of the solution of the invention. Therefore, with the solution of the invention you get much more consistent results in terms of distribution of pore numbers on the curved plate of steel than the compositions than the prior art.

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TABLE 1 Pore numbers in the curved panel of the example 6

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TABLE 2 Particle types of example 7

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TABLE 3 Number of pores [cm -2] of the example 7

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TABLE 4 Particle types from Example 8

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TABLE 5 Number of pores [cm -2] of the example 8

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Claims (5)

1. A method to form a nickel multilayer corrosion resistant on a substrate, said method consists of the following steps: (a) deposit a first layer of nickel that has a first electrical potential, (b) deposit a second layer of nickel, which has a second electrical potential that is more negative than the first electrical potential, over the first layer of nickel and (c) deposit a third layer of nickel on the second layer of nickel using a solution to deposit electrochemically a metal on a substrate, said solution it contains ions of the metal to deposit and silica particles, so that at least one organic residue containing silicon provides to said silica particles, said organic residue containing Silicon contains at least one functional group chosen from among the group consisting of amino, quaternary ammonium, quaternary phosphonium and quaternary arsonium that gives silica particles a positive electrical charge while in contact with said solution. 2. The method for forming a corrosion-resistant nickel multilayer on a substrate according to claim 1, characterized in that at least one organic residue is formed by reacting the silica particles with a reagent having the general chemical formula I, II, III or IV: 13 in the that Q is N (nitrogen), P (phosphorus) or As (arsenic); R1 and R2, independently of each other, they are unsubstituted or substituted alkyl; R 3, R 4 and R 5 they are hydrogen, unsubstituted or substituted alkyl, aryl without substitute or substituted, said R3, R4 and R5, with independence from each other, they can also contain at least one group functional that contains amino and imino residues. 3. The method for forming a corrosion-resistant nickel multilayer on a substrate according to any one of the preceding claims, characterized in that at least one organic moiety is formed by reacting the silica particles with (3-aminopropyl) triethoxysilane. 4. The method for forming a corrosion-resistant nickel multilayer on a substrate according to any one of the preceding claims, characterized in that the silica particles have a specific surface area per unit weight of up to 300 m 2 / g. 5. The method for forming a corrosion-resistant nickel multilayer on a substrate according to any one of the preceding claims, characterized in that the silica particles have an average diameter within the range between 0.3 µm and 15 µm.