NL1013706C1 - Object provided with a cover. - Google Patents

Description

Title: Object with a cover.

The invention relates to decorative and protective coatings.

It is common practice today with various copper based objects such as lamps, tripods, 5 candlesticks, taps, doorknobs, door handles, door shields and the like to first polish and polish the surface of the object to a high degree of shine and then a protective organic apply a coating to the polished surface, for example, one consisting of acrylic, urethane, epoxy and the like. This system has the drawback that the required brushing and polishing, especially if the object has a complex shape, is labor intensive. Also, the known organic coatings are not as durable as one would wish and wear out.

These drawbacks are avoided with a coating containing a nickel base coating and a non-noble refractory metal compound such as zirconium nitride, titanium nitride and a zirconium titanium alloy nitride. However, it has been found that when titanium is present in the coating, for example in the form of titanium nitride or a nitride of a zirconium titanium alloy, the coating can undergo galvanic corrosion in a corrosive environment. This galvanic corrosion makes the coating really useless. It has surprisingly been found that the presence of a tin-nickel alloy layer between the nickel base layer and the top layer of a titanium compound or a titanium alloy compound reduces or eliminates galvanic corrosion. A coating 30 comprising a tin-nickel alloy layer between a nickel base coating and a refractory metal compound top coat is described in U.S. Patent No. 5,667,904. This coating consists of a nickel layer, a tin-nickel alloy layer and a top layer of a zirconium compound or a titanium compound. Although generally quite excellent, this type of coating has a number of drawbacks. The type of coating is not sufficiently resistant to chemical attack. The coating is particularly susceptible to attack from acids and bases. Another problem is that this type of coating sometimes cracks.

According to the invention, the drawbacks outlined are overcome and a coating is provided which exhibits an improved resistance to chemical attack as well as a resistance to cracking and which is resistant to galvanic corrosion.

The invention is directed to a protective and decorative coating for a substrate, in particular a metallic substrate. More particularly, the invention is directed to a substrate, in particular a metallic substrate such as copper or bronze, with a coating on at least a part of the surface consisting of a number of superimposed layers of certain specific types of metal or metal compounds . The upholstery is decorative and is also resistant to corrosion, wear and chemicals. In one embodiment, the coating provides a polished copper appearance with a golden hue, i.e., has a gold copper hue. Thus, an object surface with the coating on it simulates polished copper of a gold color.

A first layer deposited directly on the surface of the substrate consists of nickel. The first layer can be monolithic, i.e. a single nickel layer, or it can consist of two different nickel layers such as a semi-clear nickel layer deposited directly on the surface of the substrate and a clear nickel layer applied over the semi-clear nickel layer. A layer consisting of an alloy of tin and nickel is deposited over the nickel layer. Over the tin and nickel alloy layer is a composite layer 1013706 3, consisting of layers of titanium or a titanium alloy alternated with a titanium compound or a titanium alloy compound.

The composite layer is arranged such that a layer of titanium or titanium alloy is on the tin-nickel alloy layer, i.e., the bottom layer, and the layer of the titanium compound or compound of a titanium alloy is the top or exposed layer.

In another embodiment of the invention, over the layer of the titanium compound or the compound of a titanium alloy there is a layer consisting of titanium oxide or oxide of a titanium alloy, or a layer consisting of the reaction products of titanium or a titanium alloy and oxygen and nitrogen.

The invention is elucidated with reference to the drawing, in which: fig. 1 is a cross-sectional view, but not to scale, of a multilayer coating on a substrate.

The substrate 12 can consist of any plastic material, metal or metallic alloy.

Examples of metal and metal alloy substrates are copper, steel, bronze, tungsten, nickel alloys and the like. In one embodiment, the substrate is made of bronze.

A nickel layer 13 is deposited on the surface of the substrate 12 using conventional and known electrolytic coating methods. These methods include the use of a conventional electrolytic coating bath, such as, for example, a Watts bath 30 as a coating solution. Such baths typically contain nickel sulfate, nickel chloride and boric acid dissolved in water. All chloride, sulfamate and fluoroborate coating solutions can also be used. These baths can optionally contain a number of known and conventional compounds such as flattening agents, polishing agents and the like. To produce a mirror clear nickel layer, at least one Class I polishing agent and at least one Class II polishing agent are added to the coating solution. Class I polishes are organic compounds that contain sulfur.

Class II polishes are organic compounds that do not contain sulfur. Class II polishes can also cause flattening and when added to the coating bath without class I sulfur-containing polishes result in semi-clear nickel deposits. The class I polishes include alkylnaphthalene and benzenesulfonic acid, benzene and naphthalene di- and trisulfonic acid, benzene and naphthalene sulfonamide and sulfonamides such as saccharin, vinyl and allylsulfonamides and sulfonic acid. The class II polishes are generally unsaturated organic materials such as, for example, acetylene or ethylene alcohol, ethoxylated and propoxylated acetylene alcohol, coumarin and aldehydes. These Class I and Class II polishes are known to those skilled in the art and are commercially available. They are described, inter alia, in U.S. Patent 4,421,611.

The nickel layer 13 may consist of a single nickel layer such as, for example, clear nickel, or it may consist of two different nickel layers, such as a semi-clear nickel layer and a clear nickel layer. In the figure, the layer 14 consists of semi-clear nickel, while the layer 16 consists of clear nickel. This double nickel deposition provides improved corrosion protection to the underlying substrate. The semi-clear sulfur-free coating 14 is deposited directly on the surface of the substrate 12 by conventional electrolytic coating methods. The substrate 12 containing the semi-clear nickel layer 14 is then placed in a clear nickel plating bath and the clear nickel layer 16 is also deposited on the semi-clear nickel 14 by conventional electroplating methods.

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The thickness of the nickel layer 13 is generally in the range from about 250 millionth (0.00025) cm, preferably from about 380 millionth (0.00038) cm to about 8800 millionth (0.0088) cm.

In the dual nickel layer embodiment, the thickness of the semi-clear nickel layer and of the clear nickel layer is a thickness effective to provide improved corrosion protection. Generally, the thickness of the half-10 clear nickel layer 14 is at least about 127 millionth (0.000127) cm, preferably at least about 250 millionth (0.00025) cm, and more preferably at least about 380 millionth (0.00038) cm. The upper limit of the thickness is generally not critical and is governed by secondary considerations such as cost and appearance. Generally, however, a thickness of about 3800 millionth (0.0038) cm, preferably about 2500 millionth (0.0025) cm, and more preferably about 1880 millionth (0.0188) cm should not be overwritten. The clear nickel layer 16 generally has a thickness of at least about 125 millionth (0.000125) cm, preferably at least about 315 millionth (0.000315) cm and more preferably at least about 625 millionth (0.000625 ) cm. The upper limit of the thickness of the clear nickel layer is not critical and is generally governed by considerations such as cost. Generally, however, a thickness of about 6250 millionth (0.00625) cm, preferably about 5000 millionth (0.005) cm, and more preferably about 3750 millionth (0.00375) cm should not be overwritten. The clear nickel layer 16 also serves as a smoothing layer that tends to cover or fill imperfections in the substrate.

The clear nickel layer 16 is coated with a tin-nickel alloy layer 20. More particularly, the layer 20 consists of an alloy of nickel and tin. The 1 0 1 37 06 6 layer of tin-nickel alloy surprisingly appears to reduce or eliminate galvanic corrosion when titanium is present in the vapor deposited layers. The layer 20 is deposited on the layer 16 using conventional and known tin-nickel alloy electrolytic coating methods. These methods and coating baths are conventional and known and are described, inter alia, in U.S. Patents 4,033,835, 4,049,508, 3,887,444, 3,772,168, and 3,940,319. The tin-10 nickel alloy layer preferably consists of about 50-80 wt% tin and about 20-50 wt% nickel, more preferably about 65% tin and 35% nickel, which represents the SnNi atomic composition. The plating bath contains sufficient amounts of nickel and tin to provide an alloy of tin and nickel of the described composition.

A commercially available tin-nickel plating process is the Ni-Colloy ™ process which is marketed ATOTECH and is described in a Technical Information Sheet No: NiColloy dated October 30, 1994.

The thickness of the tin-nickel alloy layer 20 is a thickness effective to reduce or eliminate galvanic corrosion. This thickness is generally at least about 25 millionth, (0.000025) cm, preferably at least about 50 millionth (0.00005) cm, and more particularly at least about 127 millionth (0.000127) cm. The upper limit of thickness is not critical and generally depends on economic considerations. Generally, a thickness of about 5000 millionth (0.005) cm, preferably about 2500 millionth (0.0025) 30 cm and even more particularly about 1270 millionth (0.00127) cm should not be overwritten.

A sandwich layer 26 consisting of layers 30 composed of titanium or a titanium alloy alternating with 35 layers 28 consisting of a titanium compound or a compound of a titanium alloy is provided over the layer 20 of a tin-nickel alloy. Such a structure is shown in the 1 01 37 06 7 figures, in which 2 designates the sandwich layer, 28 represents a layer consisting of a titanium compound or a compound of a titanium alloy and 30 indicates a layer consisting of titanium or a titanium alloy.

The metals alloying with titanium to form the titanium alloy or the compound of a titanium alloy are the non-precious refractory metals. These include zircon, hafnium, tantalum and tungsten. The titanium alloys generally comprise about 10 to 90% by weight of titanium and about 90 to 10% by weight of another non-noble refractory metal, preferably about 20 to 80% by weight of titanium and about 80 to 20% by weight of another refractory metal. The titanium or titanium alloy compounds include oxides, nitrides, carbides and carbonitrides. In an embodiment, the layers 28 consist of nitrides of a titanium zirconium alloy and the layers 30 of a titanium zirconium alloy. In this embodiment, the titanium zircon alloy nitride layer has a brass color with a golden hue.

The sandwich layer 26 has a thickness effective to resist abrasion, scratches and abrasion and to provide the requirement, for example, a brass color with a golden tint. Generally, the layer has an average thickness of from about 5 millionth (0.000005) cm to about 100 millionth (0.0001) cm, preferably from about 10 millionth (0.00001) cm to about 88 millionth (0, 000088) cm er) more preferably from about 15 millionth (0.000015) cm to about 75 millionth (0.000075) cm.

Each of the layers 28 and 30 generally has a thickness of at least about 0.025 millionth (0.0000000025) cm, preferably at least about 0.63 millionth (0.000000063) cm, and more particularly at least about 1.25 millionth 35 (0.000000125) cm. In the algae, layers 28 and 30 should be no thicker than about 38 millionth 1 01 3706 8 (0.0000038) cm, preferably about 25 millionth (0.0000025) cm and more preferably about 13 millionth (0.0000013) ) cm.

In the sandwich layer, the bottom layer is the layer 30, i.e. the layer consisting of titanium or a titanium alloy. The bottom layer 30 is applied to the tin-nickel alloy layer 20. The top layer of the sandwich layer is the layer 28 '. The layer 28 'consists of a titanium compound or a titanium alloy compound and the layer 28' is the color layer. That is, the layer provides the color to the coating. In the case of titanium zirconium alloy nitride, it is a copper shade with a golden hue.

The layer 28 'has a thickness that is at least effective to provide the required color, i.e., copper color with a golden hue. Generally, the layer 28 'may have a thickness approximately equal to the thickness of the sandwich layer. The layer 28 'is the thickest of the layers 28 and 30 that form the sandwich layer. Generally, the layer 28 'has a thickness of at least about 5 millionths, and preferably at least about 13 millionths of an inch. Generally, a thickness of about 127 millionth and preferably about 76 millionth of an inch should not be exceeded.

A method of forming the sandwich layer 26 is to use known and conventional vapor deposition methods such as physical vapor deposition or chemical vapor deposition. Physical vapor deposition methods include sputtering and cathodic arc vapor deposition. In a method of the invention, sputtering or cathodic arc vapor deposition is used to deposit a layer 30 of an alloy of zirconium titanium or titanium, followed by reactive sputtering or reactive cathodic arc vapor deposition around a layer 28 of a zirconium-titanium alloy compound such as a nitride or a titanium compound such as a nitride.

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To form the sandwich layer 26 in which the titanium compound and the titanium alloy compound are nitrides, the flow rate of the nitrogen gas is varied (pulsed) during vapor deposition such as reactive sputtering or reactive cathodic arc evaporation between zero (no nitrogen gas pf becomes a reduced amount introduced) to introduce nitrogen of a desired value to form multiple alternating layers of metal 30 and metal nitride 28 in the sandwich layer 26.

The number of alternating layers of metal 30 and layers 28 of refractory metal compounds in the sandwich layer 26 is a number effective to reduce or eliminate cracks. This number is generally at least about 4, preferably at least about 6, and more preferably at least about 8. Generally, the number of alternating layers of refractory metal 30 and refractory metal compound 28 in the sandwich layer 26 should be about 50, at preferably about 40 and more preferably about 20 30./

In one embodiment of the invention, a layer 34 consisting of the reaction products of a titanium metal or titanium alloy, an oxygen-containing gas such as oxygen and nitrogen is deposited on the sandwich layer 26.

The reaction products of the metal or metal alloy, oxygen and nitrogen generally consist of oxide of the metal or metal alloy and nitride of the metal or metal alloy. The reaction products of titanium, oxygen and nitrogen therefore include, for example, titanium oxide and titanium nitride. These metal oxides and metal nitrides and their preparation and deposition are conventional and known and are described, inter alia, in U.S. Patent 5,367,285.

The layer 34 can be deposited using known and conventional vapor deposition techniques, including reactive sputtering and reactive kachodic arc evaporation.

In another embodiment of the invention, the layer 34, instead of the reaction products 5 of titanium or a titanium alloy, oxygen and nitrogen consists of titanium oxide or oxide of a titanium alloy. These oxides and their preparation are known and common.

The layer 34 containing (I) the reaction products of titanium or a titanium alloy, oxygen and nitrogen or (II) titanium oxide or titanium alloy oxide is generally very thin. The layer has a thickness that makes the layer 34 non-opaque or translucent or transparent, so that the layer 28 is visible therethrough. The layer also has a thickness that is at least effective to provide improved chemical resistance. Generally, the thickness is at least about one hundredth of a millionth (0.000000125) cm, preferably at least one quarter of a millionth (0.00000025) cm, and more preferably at least about 0.38 of one millionth (0 , 000000038) cm. Generally, the layer 34 should be no thicker than about twelve and a half millionth (0.00000125) cm, preferably about five millionth (0.0000005) cm, and more preferably about 2.5 millionth (0.00000025) cm.

The layer 34 can be deposited using known and conventional vapor deposition methods including physical vapor deposition and chemical vapor deposition such as, for example, reactive sputtering and reactive cathodic arc vapor deposition.

Sputtering methods and equipment therefor are described, inter alia, in the publications J. Vossen and W. Kern "Thin Film Processes II", Academy Press, 1991; R. Boxman et al. "Handbook of Vacuum Arc Science and Technology", Noyes Pub., 1995; and U.S. Patents 35 4,162,954 and 4,591,418.

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Briefly, in the sputter deposition process, a refractory metal target (e.g., of titanium or zircon), which is the cathode, and the substrate are placed in a vacuum chamber. The air in the chamber is extracted to create vacuum conditions in the chamber. An inert gas, such as argon, is introduced into the chamber. The gas particles are ionized and accelerated to the target to release titanium or zircon atoms. The detached target material is then deposited as a coating on the substrate.

In cathodic arc evaporation, an electric arc of typically several hundred amperes is applied to the surface of a metal cathode, for example, of zircon or titanium. The arc evaporates the cathode material, which then condenses on the substrates to form a coating.

Reactive cathodic arc evaporation and reactive sputtering are generally similar to ordinary sputtering and cathodic Yoke vaporization except that a reactive gas is introduced into the chamber which reacts with the released material from the target. Therefore, in the case where the layer 34 consists of titanium oxide and the cathode consists of titanium oxygen, reactive gas 25 is introduced into the chamber.

The invention is illustrated by the following example, which is for illustrative purposes and does not limit the invention.

EXAMPLE I

A number of copper faucets are placed in a conventional cleaning bath, which contains the common known soaps, cleaning agents, flocculants and the like, and which is maintained at a pH of 8.9 - 9.2 and a temperature of about 50 to 91 ° C for 10 minutes. The copper faucets are then placed in a conventional ultrasonic alkaline cleaning bath. The ultrasonic cleaning bath has a pH of 8.9 to 9.2 and is maintained at a temperature of about 70 to 81 ° C and contains the usual and known soaps, cleaning agents, flocculants and the like. After the ultrasonic cleaning, the faucets are rinsed and placed in a conventional alkaline electro-cleaning bath for about 50 seconds. The electrical cleaning bath is maintained at a temperature of about 60-71 ° C at a pH of about 10.5-11.5 and contains conventional and standard cleaning agents. The faucets are then rinsed and placed in a conventional acid activator bath for about 20 seconds. The acid activator bath has a pH of about 2.0-3.0, is maintained at ambient temperature and contains an acid salt based on sodium fluoride.

The faucets are then rinsed and placed in a clear nickel plating bath for about 12 minutes. The clear nickel bath is generally a conventional bath which is maintained at a temperature of about 55-65 ° C, a pH of about 4.0-4.8, and contains NiSO 4, NiCl 2, boric acid, and brighteners. A clear nickel layer with an average thickness of about one thousandth of an inch is deposited on the taps. The clear nickel-coated faucets are rinsed twice in a tin-nickel coating bath for about 7 minutes. The bath is kept at a temperature of about 29-60 ° C and a pH of about 4.5-5.0. The bath contains tin chloride, nickel chloride, ammonium bifluoride and other known and common complex humectants.

A tin-nickel layer with an average thickness of about 500 millionth cm is deposited on the surface of the clear nickel layer. The taps nickel and tin-nickel coated are rinsed thoroughly in deionized water and then dried.

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The electrolytically coated taps are arranged in a vessel for coating by cathodic arc vapor deposition. The vessel is generally a cylindrical housing with a vacuum chamber, which is arranged to be pressurized using pumps. A source of argon gas is connected to the chamber by an adjustable valve for varying the flow rate of the gas.

A cylindrical zirconium-titanium alloy cathode is mounted in the center of the chamber and connected to the negative poles of a variable DC voltage source. The positive side of the voltage source is connected to the wall of the room. The cathode material contains zircon and titanium.

The electrolytically coated valves are mounted on 15 bobbins, 16 of which are arranged as a ring around the outside of the cathode. The entire ring rotates around the cathode as each bobbin rotates about its own axis, resulting in a so-called planetary motion that provides uniform exposure to the cathode for all valves mounted on each bobbin. The ring typically rotates at a number of revolutions per minute, while each spool makes a number of revolutions per revolution of the ring. The bobbins are electrically insulated from the chamber and provided with rotatable contacts so that a bias can be applied to the substrates during coating.

The vacuum chamber is placed under a reduced pressure of about 5x103 millibars and heated to 150 ° C.

The electrolytically coated faucets are then subjected to high bias arc plasma cleaning, with a (negative) bias of about 500 V applied to the electrolytically coated faucets, while an arc of about 500 amps is applied to and maintained on the cathode. The cleaning time is about five minutes. Argon gas is then introduced at a rate sufficient to maintain a pressure of 1 01 3706 14 approximately 3x1O2 millibars. A layer of zirconium-titanium alloy with an average thickness of about 10 millionth centimeters is deposited on the tin-nickel coated taps over a three minute period. The cathodic arc deposition process includes applying DC voltage to the cathode to achieve a current of about 500 amps, introducing argon gas into the vessel to maintain the pressure in the vessel at about 1 × 10 2 millibars, and rotating the cranes according to the planetary motion described above.

After the layer of zirconium-titanium alloy has been deposited, the sandwich layer is applied to the layer of zirconium-titanium alloy. A stream of nitrogen is periodically introduced into the vacuum chamber while the arc discharge continues at about 15 500 amps. The flow rate of the nitrogen is pulsed, ie periodically changed from maximum flow rate, sufficient to fully react the zirconium and titanium atoms arriving on the substrate to form a nitride compound of the zirconium titanium-20 alloy, and a minimum flow rate equal to zero or low value, which is not sufficient to provide complete reaction with all zirconium titanium alloy. The nitrogen flow pulsation period is one to two minutes (30 seconds to one 25 minutes on and then off). The total time for the pulsed deposition is about 15 minutes, resulting in a 10-layer sandwich stack with a thickness of about 2 to 3.8 millionth centimeters each.

The deposited material in the sandwich layer alternates between a fully reacted zirconium-titanium alloy nitride compound and a zirconium-titanium metal alloy (or substoichiometric ZrTiN with much lower nitrogen content).

After the sandwich layer is deposited, a flow rate of the nitrogen is maintained at maximum value (sufficient to produce a fully reacted nitride).

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15 to form a zirconium-titanium alloy compound) over a period of five to ten minutes to form a thicker "color layer" on the sandwich layer. After this zirconium-titanium alloy nitride layer is deposited, an additional flow of oxygen of about 0.1 standard liters per minute is introduced for thirty seconds to one minute, while the flow rates of nitrogen and argon are maintained at the aforementioned values. A thin layer of mixed reaction products are formed (oxy-nitride of 10 zirconium-titanium alloy) about 0.5 to 1.3 millionth centimeters thick. Finally, the arc is quenched at the end of this last deposition period, the vacuum chamber is vented and the coated substrates are removed.

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Claims (14)

1. Object provided with a substrate having a multilayer coating on at least a part of its surface comprising: at least one layer consisting of nickel, a layer consisting of an alloy of tin and nickel, a layer consisting of titanium or a titanium alloy, a sandwich layer consisting of layers comprising a titanium compound or a titanium alloy compound interspersed with layers comprising titanium or a titanium alloy, and a layer consisting of a titanium compound or a compound of a titanium alloy. Article according to claim 1, characterized in that the titanium compound is titanium nitride. Article according to claim 1, characterized in that the compound of a titanium alloy is nitride of titanium-zirconium alloy. Article according to claim 3, characterized in that the titanium alloy is a titanium zirconium alloy. Article according to claim 1, characterized in that the at least one nickel layer consists of clear nickel. 6. Article according to claim 5, characterized in that the titanium compound is titanium nitride. 1013706 Article according to claim 5, characterized in that the compound of a titanium alloy is nitride of a titanium zirconium alloy. Article according to claim 7, characterized in that the titanium alloy is an alloy of titanium and zircon. 9. Object having a substrate having a multilayer coating on at least a portion of the surface, comprising: a layer of semi-clear nickel, a layer of clear nickel, a layer of an alloy of tin and nickel, a layer of titanium or an alloy of titanium, a sandwich layer consisting of layers of a titanium compound or a compound of a titanium alloy interspersed with layers consisting of titanium or a titanium alloy, and a layer of a compound of zirconium or a compound of a zirconium-titanium alloy. Article according to claim 9, characterized in that the titanium compound is titanium nitride. Article according to claim 9, characterized in that the compound of a titanium alloy is a compound of a titanium-zirconium alloy. 12. Article according to claim 11, characterized in that the compound of titanium and zirconium is titanium-zirconium nitride. Article according to claim 11, characterized in that the titanium alloy is an alloy of titanium and zircon. 35 Article according to claim 12, characterized in that the titanium alloy is an alloy of titanium and zircon.