JP5675590B2 - Coated article and associated method - Google Patents

Description

  The present invention relates generally to coated articles and related methods, and more particularly to metal-coated articles formed using an electrodeposition process.

  Often, a coating is used to impart a unique function to the surface of the article. For example, articles are often provided with a metal coating that is electrodeposited by immersion in an electroless bath or an electrolytic bath to impart one or more high performance surface properties to these articles, as these high performance surface properties include: Among others, mention may be made of high hardness, abrasion resistance, gloss, high reflectivity, color development or other good appearance, abrasion resistance, and high lubricity. Such coatings are also frequently applied to the material surface to improve corrosion resistance. This typically exposes one or more surfaces of the article to the environment, whether the article is being processed, stored, or in use, and is exposed to an environment that may accelerate the corrosion process. It is necessary when it comes to. One common example in this regard is a surface that can come into contact with a liquid medium, which can include an aqueous solution, an acidic or basic solution, or an alcoholic solution. Corrosion is usually a problem when the environment contains fluids, but corrosion occurs quite commonly in a steam environment.

  Corrosion processes generally can affect the structure and composition of the surface of an article that is exposed to a corrosive environment. For example, in corrosion, atoms dissolve directly from the surface of the article, the article's surface chemistry is altered by selective dissolution or dealloying, or the article's surface chemistry and structure is altered, for example, by the formation of an oxidizing or passive film. Change. Some of these processes can change the shape, irregularities, properties, or appearance of the article surface. For example, the rust formation process can affect the appearance and properties of iron or steel surfaces. Metal articles are often placed in corrosive environments.

  Coatings applied to such articles can affect surface corrosion in several ways. In many cases, the coating can form a barrier to protect the underlying substrate from corrosion and / or prevent the underlying substrate from coming into direct contact with the corrosive medium. For example, a uniform coating can completely cover the substrate so that almost no part of the substrate is exposed to a corrosive environment, in which case the coating functions as a protective barrier. Thus, it is desirable for the barrier coating to exhibit a higher corrosion resistance (ie, lower corrosion rate) to the corrosive environment than the substrate, reducing the overall corrosion rate of the article. However, defects in the barrier coating such as cracks, voids, or through holes that penetrate the coating can expose the substrate to a corrosive environment. This will result in a generally undesirable local corrosion process.

  Another common coating function is to achieve an article surface that hardly reacts in the target environment (eg, inert to the target environment); or may change the surface properties of the article The realization of an outermost surface that undergoes little local chemical reaction. For example, a coating that fades, discolors, dissolves or degrades in a corrosive medium is undesirable, particularly when the coating is applied at least partially for aesthetic purposes. The passivation process may be used to achieve a less reactive surface or a more “passivated” surface that can withstand chemical erosion, degradation, fading, or discoloration.

  The tungsten-based coating is usually formed by an electrodeposition method. For example, such a coating can be a tungsten alloy that includes one or more of the elements Ni, Fe, Co, B, S, and P. These coatings often exhibit desirable properties including high hardness, wear resistance, high gloss, abrasion resistance, low coefficient of friction in sliding applications, and the like. Although tungsten-based coatings provide sufficient substrate protection, the outer surface of the coating is often subject to chemical erosion, degradation, fading, or discoloration when exposed to corrosive media. Accordingly, there is a need to improve tungsten-based coatings that render the coating surface chemically more inert in corrosive environments and prevent fading, discoloration, or degradation.

The present invention relates generally to coated articles and related methods.
In one aspect, an article is provided. The article comprises a substrate and a coating formed on the substrate. The coating has a first portion and a second portion. The second portion includes nickel, tungsten, and oxygen. The weight percentage of tungsten contained in the second part is 1 to 20 percent. In this aspect, the second portion may be formed on the first portion. In that case, the second part is the upper layer part of the coating. The coating is substantially free of chromium or chromium oxide. The coating may further contain a metal oxide. At least one of the first and second portions has a nanocrystal structure. The first portion is substantially free of oxygen. The first portion includes nickel and tungsten. The weight percentage of nickel contained in the second portion is at least 50 percent. More preferably, it is at least 70 percent. The second portion of the coating has a thickness of 10 nm to 500 nm. The first portion has a thickness that is more than five times the thickness of the second portion. Furthermore, a third part is provided. The second portion may be basically composed of nickel, tungsten, and oxygen.

In another aspect, an article is provided. The article comprises a substrate and a coating formed on the substrate. The coating includes nickel and tungsten. The article has a CASS corrosion life of at least 2 hours. In this embodiment, the coating is substantially free of chromium or chromium oxide. The substrate includes a metal. The coating has a first portion and a second portion formed on the first portion. The second portion includes nickel, tungsten, and oxygen, and the second portion
The weight percentage of tungsten contained in the part is 1 to 20 percent. The first portion includes a nickel-tungsten alloy. The coating is electrodeposited. The coating has a nanocrystalline structure. The article has a CASS corrosion life of at least 10 hours.

In another aspect, a method for electrodepositing a coating is provided. In the method, an anode, a cathode, an electrodeposition bath in which the anode and the cathode are immersed, and a power source connected to the anode and the cathode are provided. The method further includes electrodepositioning the coating by driving the power source to generate a waveform. The waveform includes a segment including at least one forward pulse and at least one reverse pulse. The at least one forward pulse has a period and an average forward current density, and the at least one reverse pulse has a period and an average reverse current density. The ratio of the average forward current density integrated over the period of the forward pulse to the average reverse current density integrated over the period of the reverse pulse is 0.5-5. In this aspect, the at least one reverse pulse immediately follows the at least one forward pulse. The segment includes a plurality of forward and reverse pulses. The forward current pulse integrated over the period of each forward current pulse relative to the sum of the average reverse current density of each reverse current pulse integrated over the period of each reverse current pulse; The ratio of the total average forward current density is 0.5-5. The waveform includes a preceding segment before the segment. The preceding segment includes only one forward pulse. The segment forms a second portion of the coating, and the preceding segment forms a first portion of the coating having a different composition than the second portion of the coating, the second portion being the first portion. Formed on the part. The second portion includes nickel, tungsten, and oxygen, and the weight percentage of tungsten contained in the upper portion is 1 to 20 percent. The coating includes a metal alloy. The coating includes a nickel tungsten alloy. The segment of the waveform has a period of 10 seconds to 180 seconds. The electrodeposition bath includes a tungsten species and a nickel species.

In another aspect, a method for electrodepositing a coating is provided. In the method, an anode, a cathode, an electrodeposition bath in which the anode and the cathode are immersed, and a power source connected to the anode and the cathode are provided. The method further includes electrodepositioning the coating by driving the power source to generate a waveform. The waveform includes a segment including at least one forward pulse and at least one reverse pulse. Wherein the at least one forward pulse has a duration of about 1ms~ about 100 ms, the average forward current density of about ^{0.01A / cm 2 ~1A / cm 2} . Wherein the at least one reverse pulse has a duration of about 1ms~ about 100 ms, the average reverse current density of about ^{0.01A / cm 2 ~1A / cm 2} . In this aspect, the at least one reverse pulse immediately follows the at least one forward pulse. The segment includes a plurality of forward and reverse pulses. The coating includes a nickel tungsten alloy. The coating includes a first portion and a second portion formed on the first portion;
The second portion includes nickel, tungsten, and oxygen, and the weight percentage of tungsten contained in the upper portion is 1 to 20 percent. The electrodeposition bath includes a tungsten species and a nickel species.

  In another aspect, a method for forming a coated article is provided. In the method, an anode, a cathode, an electrodeposition bath in which the anode and the cathode are immersed, and a power source connected to the anode and the cathode are provided, and the electrochemical bath includes nickel species and tungsten. Including species. The method further includes forming an article to be coated by driving the power source to generate a waveform to electrodeposit a coating onto the substrate. The coating includes nickel and tungsten. The article has a CASS corrosion life of at least 2 hours.

In another aspect, a method for forming a coated article is provided. In the method, an anode, a cathode, an electrodeposition bath in which the anode and the cathode are immersed, and a power source connected to the anode and the cathode are provided, and the electrochemical bath includes nickel species and tungsten. Including species. The method further includes driving the power source to generate a waveform to electrodeposit a coating onto a substrate to form an article to be coated, the coating having a first portion and a second portion. The second part includes nickel, tungsten, and oxygen, and the weight percentage of tungsten contained in the second part is 1 to 20 percent.

  Other aspects, embodiments and features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. The accompanying figures are schematic and are not drawn to scale. In order to make the figures easier to understand, not all components are labeled in all figures, and the illustrations are necessary in order to allow the person skilled in the art to understand the invention. If not, not all components of each embodiment of the invention are shown. All patent applications and patents that are hereby incorporated by reference are hereby incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

1 is a schematic diagram of an article to be coated according to one embodiment of the present invention. FIG. For a panel sample coated with Ni-W alloy using a two-step reverse pulse electrodeposition process, and (b) a panel sample coated with Ni-W alloy using a one-step reverse pulse electrodeposition process A photograph after a standard CASS corrosion test for 14 hours. XPS spectrum of sample E nickel. XPS spectrum of sample F nickel. XPS spectrum of sample E tungsten. XPS spectrum of sample F tungsten. XPS spectrum of sample E oxygen. 2 shows the XPS spectrum of sample F oxygen. FIG. 4 shows an example of a waveform including an inverted pulse sequence according to one embodiment of the present invention. FIG. 4 illustrates an example of a waveform including (i) a segment including a single forward pulse and (ii) a segment including an inverted pulse sequence according to one embodiment of the present invention.

  The present invention relates generally to coated articles and related methods. The coating achieves advantageous properties such as high strength, high hardness, high brightness, high wear resistance, high corrosion resistance, low density macroscopic defects (eg, cracks, voids). In some cases, the coating comprises an alloy such as a nickel-tungsten alloy. Some embodiments of the present invention are advantageous because they provide the ability to adjust various coating properties such as chemical composition, particle size, and the like. For example, the coating can include multiple portions having different chemical compositions that impart different properties. For example, the coating can include an upper layer portion that enhances corrosion resistance, and this upper layer portion is formed on a lower layer portion having high strength. As described further below, the coating or portions of the coating can be formed by an electrodeposition process, in which the article is coated in an electrodeposition bath containing the appropriate chemical species. Can do.

  The article to be coated can include a substrate and a coating formed on the substrate. In some cases, the coating can be formed on at least a portion of the substrate surface. In other cases, the coating covers the entire substrate surface.

  The coating includes one or more metals. For example, the coating can include an alloy (eg, a nickel-tungsten alloy). Examples of suitable alloys can include two or more elements from the following group of elements: Ni, W, Fe, B, S, Co, Mo, Cu, Cr, Zn, and Sn, among others. In some cases, alloys containing tungsten (eg, nickel-tungsten alloys) are particularly preferred. Some special examples of alloys include Ni-W, Ni-Fe-W, Ni-B-W, Ni-S-W, Co-W, Ni-Mo, Co-Mo, and Ni-Co-W. Can be mentioned.

In some embodiments, it is advantageous for the coating to be substantially free of elements or compounds having high toxicity or other defects. In some embodiments, it is advantageous for the coating to be substantially free of elements or compounds that are electrodeposited using highly toxic or other deficient species. For example, in some cases, the coating is often free of chromium (eg, chromium oxide) because chromium is often electrodeposited using a toxic chromium ion species (eg, Cr ⁶⁺ ). There is a need to. Such coatings can provide various processing, health and environmental benefits that are superior to previous coatings.

  Some embodiments can include a coating having one or more portions, each portion including chemical composition, thickness, microstructure (eg, crystallinity, particle size), corrosion resistance, and the like. Different features and / or characteristics may be indicated. For example, the coating can have a first portion and a second portion, where the first portion is on the underlying substrate and the second portion is on the first portion. The second portion can also be expressed as a top portion. For example, as shown in FIG. 1, the article 10 includes a substrate 20 on which a coating 30 is formed. The coating includes a first portion 40 that contacts the substrate and a second portion 50 formed on the first portion.

  It should be understood that in other embodiments, the coating can include more than two portions having different characteristics and / or properties. Also, in some embodiments, the coating may include only one portion that generally has the same characteristics and properties.

  In some cases, the first portion of the coating includes more than one metal, such as nickel and tungsten. For example, the first portion can be a nickel and tungsten alloy. In some cases, the first portion includes nickel and tungsten, and the weight percentage of nickel included in the first portion is at least 30 percent, at least 40 percent, at least 50 percent, at least 60 percent, or greater. Percent. In an exemplary embodiment, the first portion can include about 60 weight percent nickel and about 40 weight percent tungsten. In some embodiments, the first portion can be substantially free of oxygen, ie, the weight percentage of oxygen contained in the first portion is less than 1 percent.

The coating can further include a second portion formed over the first portion. For example, the second portion can include oxygen and one or more metals. In some cases, the second portion includes nickel, tungsten, and oxygen. Some embodiments are advantageous because they contain only a small amount of tungsten. For example, if the second portion includes nickel, tungsten, and oxygen, the weight percentage of tungsten contained in the second portion can be less than the weight percentage of nickel contained in the second portion. In some cases (eg, when the second portion includes nickel, tungsten, and oxygen), the weight percentage of tungsten contained in the second portion is 1 to 20 percent; in some cases, the weight percentage Is 5
15 percent (eg, about 10 percent). The second portion can include a relatively large amount of nickel. For example, if the second portion includes nickel, tungsten, and oxygen, the second portion can include at least 50 weight percent nickel; and in some cases, includes at least about 70 weight percent nickel. Or in some cases at least 80 weight percent nickel. In some embodiments, the ratio of weight percent nickel to weight percent tungsten is greater than 15: 1 or greater than 20: 1. As further described below, the corrosion resistance can be increased by the composition of the second portion.

  The second portion can include one or more metal oxide species. Examples of these metal oxide species include nickel oxide, tungsten oxide, nickel-tungsten oxide, and the like. The composition of the coating, or portions of the coating, can be characterized using a suitable method such as Auger Electron Spectroscopy (AES) known in the art. For example, AES can be used to characterize the chemical composition of the surface of the coating.

  The various portions of the coating can be arranged in any configuration suitable for use in a particular application. In some cases, the second portion can be placed as the upper layer portion of the coating. That is, the surface of the article can be defined by the surface of the second portion, and no further portion of the coating can be provided over the second portion. For example, the second portion can be disposed as an upper layer portion of the coating to provide anti-corrosion properties. In some embodiments, the second portion can be located within the inner portion or inner layer of the coating. In some cases, the coating can include multiple portions that include nickel, tungsten, and oxygen, which can be disposed as the upper layer portion of the coating and / or the interior of the inner portion of the coating. Can be arranged. In one embodiment, the coating can have a layered structure with alternating layers of first and second subgroups.

  As noted above, the coatings described herein can include one or more metals. One of ordinary skill in the art will be able to select an appropriate metal group or combination of metal groups that imparts the desired characteristics or properties to the article, including corrosion resistance.

  The coating, and portions of the coating, can have any thickness suitable for a particular application. For example, the total coating thickness can be 10 nm to 1 mm; in some cases, 100 nm to 200 microns; and in some cases, 100 nm to 100 microns. In some embodiments, the first portion can be thicker than the second portion when the coating includes a first portion and a second portion formed over the first portion. For example, the first portion can have a thickness that is greater than 2 times, 5 times, or 10 times the thickness of the second portion. The second portion can be, for example, 1 nm to 500 nm, or 10 nm to 500 nm, or 50 nm to 250 nm.

However, it should be understood that the coating, and portions of the coating, may have other thicknesses outside the ranges stated above.
In some cases, the coating can have a specific microstructure. For example, at least a portion of the coating can have a nanocrystalline microstructure. As used herein, a “nanocrystalline” structure refers to a structure in which the number average size of crystal particles is less than 1 micron. The number average size of crystal grains is calculated by giving equal and statistical weight to each particle and dividing the total value of all equivalent spherical particle diameter groups by the total number of particles contained in the representative volume of the body. Is done. In some embodiments, at least a portion of the coating can have an amorphous structure. As is known in the art, an amorphous structure is an amorphous structure characterized by a lack of long-range symmetry at atomic positions. Examples of the amorphous structure include a glass structure or a glassy structure. Some embodiments can provide a coating having a nanocrystalline structure over substantially the entire coating. Some embodiments can provide a coating having an amorphous structure over substantially the entire coating.

In some embodiments, the coating can include various portions having different microstructures. The coating can include, for example, one or more portions having a nanocrystalline structure and one or more portions having an amorphous structure. In a series of embodiments, the coating includes nanocrystalline particles and other portions that exhibit an amorphous structure. In some cases, the coating or portion of the coating can include a portion having a group of crystal particles, most of these crystal particles having a particle size greater than 1 micron in diameter. In some embodiments, the coating can include other structures or other phases, alone or in combination with nanocrystalline or amorphous portions. For example, metallic particulates, ceramic particulates, intermetallic particulates, solid lubricant graphite particles or MoS ₂ particles, or other materials are included in coatings having nanocrystalline or amorphous portions. Can do. One skilled in the art will be able to select other structures or other phases suitable for use in connection with the present invention.

  As described herein, various substrates can be coated to form a coated article. In some cases, the substrate can include a conductive material such as a metal, metal alloy, or intermetallic material. Suitable substrates include, among others, steel, copper, aluminum, brass, bronze, nickel, polymers having a conductive surface and / or surface treatment, transparent conductive oxides.

  In some embodiments, the present invention provides a coated article that can resist corrosion in one or more potential corrosive environments and / or can protect the underlying substrate material from corrosion. Examples of such corrosive environments include, but are not limited to, aqueous solutions, acidic solutions, alkaline or basic solutions, or combinations of these solutions. For example, the coated articles described herein resist corrosion when exposed to a corrosive environment such as a corrosive liquid, vapor, or humidity atmosphere (eg, when touched, immersed, etc.). be able to. In some cases, the metal coatings described herein (eg, Ni-W alloy coatings) can be, for example, saline (NSS) sprays, other salt sprays or salt mists, acetic acid containing solutions, copper sulfate containing solutions. Or, it can resist corrosion when exposed to other salt-containing solutions, citric acid-containing solutions or other acid-containing solutions, alkaline component-containing solutions, basic component-containing solutions, and the like.

The coated articles described herein can exhibit much superior corrosion resistance that is much higher than other conventional coated articles. For example, corrosion resistance can be evaluated using a copper acetate spray (CASS) test, a common corrosion test that provides an environment that can cause corrosion, fading, discoloration, and degradation of the coating. The CASS corrosion test is performed based on the test standard defined in the standard ASTM B368 entitled “Standard Test Method for Copper Accelerated Acetate Spray (Fog) Test (CASS Test)”. In this test, a procedure is generally performed in which a sample of a substrate to be coated is brought into a corrosion test room under special standard conditions and exposed to a corrosive atmosphere. The exposure time can be variable and is usually specified by the end user of the product or coating being tested.
After a predetermined length of exposure time, the panel is visually inspected by the human eye for signs of surface appearance change resulting from discoloration and / or fading and / or corrosion. Depending on the coating and substrate used in the test, any or all of these effects may appear. For example, steel surfaces can develop red rust after exposure to a corrosive atmosphere. Many glossy coatings are tested to assess the ease of discoloration or fading of these coatings. Usually, the change in surface appearance as a result of corrosion and / or discoloration and / or fading of the coating is non-uniform, some parts have changed, and others have not changed. Thus, only a certain percentage of the exposed surface area is considered to have corroded and / or discolored and / or faded, and this area percentage is a quantifiable corrosion indicator. It can be said that the smaller the area ratio, the higher the corrosion resistance or discoloration resistance of the coating or product.

  CASS corrosion test results can be reported using a simple pass / fail approach. In this method, the critical surface area ratio is specified together with the specified time. After the CASS test has been performed for a specified time, if the percentage of the coating's surface area that changes appearance as a result of discoloration and / or fading and / or corrosion falls below a specified critical value, the result is considered acceptable. If a change in appearance appears as a result of discoloration and / or fading and / or corrosion on the surface area above the critical percentage, the result is considered to be rejected.

  As used herein, “CASS corrosion lifetime” refers to corrosion and / or as known to those skilled in the art at a surface area of 1% of the exposed coating surface area. Refers to the time until a visual change in appearance as a result of discoloration and / or fading. In some cases, the coated articles of the present invention can exhibit a CASS corrosion life that exhibits resistance of greater than 2 hours, greater than 5 hours, or greater than 10 hours. In some cases, the coated article can exhibit a much longer CASS corrosion life. For example, some coated articles can exhibit a CASS corrosion life of greater than 50 hours, greater than 75 hours, or greater than 96 hours. In an exemplary embodiment, a Ni-W alloy coating that includes portions containing Ni, W, and oxygen can have a CASS corrosion life of greater than 2 hours, and often has the life described above. You can have a much longer lifetime including. Without wishing to be bound by theory, the corrosion resistance properties of the article to be coated can be improved by including in the coating the upper layer portion described above (eg, metal oxide).

  Some embodiments of the invention include a method of electrodepositing (eg, electroplating) a coating. In electrodeposition, the material is usually immersed on a substrate, the substrate is immersed in an electrodeposition bath, and an electric current is passed between the two electrodes through the electrodeposition bath, i.e. using the potential difference between the two electrodes. Electrodeposition (for example, electroplating). For example, in the methods described herein, an anode, a cathode, an electrodeposition bath (also known as an electrodeposition fluid) in which the anode and cathode are immersed (eg, wet the anode and cathode), and And a power source connected to the anode and the cathode. In some cases, the coating can be formed by driving a power supply to generate a waveform, as described more fully below. In some embodiments, at least one electrode can function as a substrate to be coated.

Electrodeposition conditions can be achieved by changing the potential applied between the electrode groups (eg, potential control or voltage control), or by changing the current or current density that can be passed (eg, current control or current density control). ) Can be changed. In some embodiments, the coating can be formed (eg, electrodeposited) using direct current (DC) plating, pulse current plating, reverse pulse current plating, or a combination of these plating methods. Pulses, oscillations, and / or other changes in voltage, potential, current, and / or current density can also be incorporated during the electrodeposition process, as described more fully below. For example, voltage control pulses can be applied alternately with current control pulses or current density control pulses. In general, during the electrodeposition process, a potential can be generated on the substrate to be coated and the applied voltage, current, or current density can be varied to effect a change in the potential on the substrate. In some cases, a waveform including one or more segments can be used in the electrodeposition process, each segment having a specific set of electrodeposition conditions (e.g., as described more fully below) Current density, current period, electrodeposition bath temperature, etc.).

  Some embodiments of the present invention include electrodeposition methods that can control the particle size of electrodeposition materials (eg, metals, alloys, etc.). In some embodiments, a coating having a desired particle size can be achieved by selecting a specific coating (eg, electroplating) composition, such as the composition of the alloy electrodeposit. For example, electrodeposition alloys such as Ni-W, Ni-P, etc. have a relatively fine nanocrystal particle size by containing a relatively large amount of W or P, or in some cases A coating having an amorphous structure can be formed. In some embodiments, the particle size of the electrodeposition material can be controlled by selecting the electrodeposition method (eg, electrodeposition conditions) described herein to form a particular composition. In the method of the present invention, a US patent entitled "Method of Forming an Electrodeposit of Alloy and Controlling Nanostructure of the Electrodeposit Using Negative Current Pulse Electrodeposition and Article Containing Such Alloy Electrodeposit". Certain aspects of the methods described in published application 2006/02722949 can be utilized, and this US patent application is hereby incorporated by reference in its entirety. Incorporated. US Patent Application Publication No. 2006, filed on Nov. 15, 2007 and entitled “Methods of adjusting the surface morphology of nanocrystalline metals or alloys, or amorphous metals or alloys, and articles formed by such methods” Other electrodeposition method embodiments are also suitable, including those described in US patent application Ser. No./0154084 and US application Ser. No. 11 / 985,569, which are hereby incorporated by reference herein, The entire contents of these patent applications are incorporated herein.

  In some embodiments, the coating or portion of the coating can be electrodeposited using direct current (DC) plating. For example, a substrate (eg, an electrode) can be placed so as to be immersed (eg, immersed) in an electrodeposition bath that includes one or more chemical species to be electrodeposited on the substrate. A constant steady current can be passed through the electrodeposition bath to form a coating or part of a coating on the substrate.

  In some cases, in the electrodeposition method, the coating is electrodeposited by driving a power source to generate a waveform. The waveform can have any shape including a square waveform, an arbitrarily shaped non-square waveform, and the like. As described further below, in some methods, such as forming a coating having different portions, the corrugation can have different segments, and these segments are used to form different portions. However, it should be understood that not all waveforms use waveforms having different segments.

  In some cases, bipolar waveforms can be used that include at least one forward pulse and at least one reverse pulse, ie, an “inverted pulse sequence”. In some embodiments, the at least one reverse pulse immediately follows the at least one forward pulse. In some embodiments, at least one forward pulse follows immediately after at least one reverse pulse. In some cases, the bipolar waveform includes multiple forward and reverse pulses. Some embodiments can include a bipolar waveform that includes multiple forward and reverse pulses, each pulse having a specific current density and duration. In some cases, the composition of the coating formed and / or the particle size can be varied by using an inversion pulse sequence.

  In some embodiments, the reverse pulse sequence is integrated over the period of the forward current pulse (s) so that the forward (eg, positive) current density is over the period of the reverse current segment. It can be applied to have the same absolute value as the integrated reverse (eg, negative) current density. FIG. 6 shows an example of the inversion pulse sequence (the vertical axis indicates the intensity and the horizontal axis indicates the time), and a plurality of portions A are the reverse current integrated over the period of the reverse current pulse (group). The density B represents the forward current density integrated over the duration of the forward current pulse (s). In some cases, integration over the period of forward current pulse (s) (eg, part B) relative to the sum of the average reverse pulse integrated over the period of the reverse pulse (part A). The total ratio of average forward current density achieved is 0.5-5, 1-5, or in some cases 1-2.

In a series of embodiments, the at least one forward pulse has a duration of about 1 to about 100 ms, the average forward current density is about 0.01 to 1 A / cm ² , and the at least one reverse pulse Has a period of about 1 to about 100 ms, and the average reverse current density is about 0.01 to 1 A / cm ² .

In some embodiments, an inversion pulse sequence is used to form a coating composition having specific properties such as corrosion resistance. In a series of embodiments, the forward current density is about 0.09 A / cm ² and after the first pulse with a pulse duration of 12 ms, the reverse current density is about 0.075 A / cm ² and the pulse A waveform configured with a second pulse of duration 8 ms is used to form a coating as described herein.

In some cases, the product of forward current density and forward current period is about 1.08 A · ms / cm ² , while the product of reverse current density and reverse current period is about 0.6 A ···. ms / cm ² . These two values have the same absolute value, in which case the ratio of the forward value and the backward value is about 1.8. Other ratios may be used, including ratios in the range of about 0.5 to about 5.

  As mentioned above, some embodiments can include a waveform having more than one segment, each segment including a specific series of electrodeposition conditions. That is, the waveform is different in different segments. For example, the waveform comprises at least one forward pulse and one segment (eg, a bipolar waveform or an inverted pulse sequence) that includes at least one reverse pulse, and a single forward or reverse pulse. Including another segment. In some cases, a segment with a single pulse can be placed before a segment with an inverted pulse sequence. For example, FIG. 7 illustrates an example of a waveform including (i) a first segment that includes a single forward pulse and (ii) a second segment that includes an inverted pulse sequence according to one embodiment of the present invention. Show. In some cases, the second segment is similar to the waveform shown in FIG. It should be understood that the waveform can have many more segments in addition to the first and second segments.

In some methods, as shown in FIG. 1, the first portion 40 of the coating can be formed using the first segment of the corrugation, and the second portion 50 of the coating can be the second portion of the corrugation. Can be formed using. Select parameters for the first and second segments (eg, pulse type, pulse duration, etc.) and select the desired features (eg, composition, particle size) and corresponding coating portions formed during these segment durations. Can be granted. In some cases, the second (eg, upper) portion can include nickel, tungsten, and oxygen, and the weight percentage of tungsten included in the upper layer portion is 1-20 percent. The method using waveforms described herein provides the ability to form a wide variety of coatings in a relatively short time and without the need to change either the composition or temperature of the electrodeposition bath can do.

  In some cases, the second segment used to form the second (eg, upper layer) portion can be an inverted pulse sequence applied over a period of seconds to many minutes. In some cases, a second segment (eg, an inverted pulse sequence) is applied for at least 1 second, at least 5 seconds, at least 10 seconds, or in some cases at least 20 seconds, to achieve the desired surface. Forming an upper layer portion having properties and corrosion resistance. In some cases, the second segment (eg, the inverted pulse segment) is applied for a period of at least 1 minute or longer. In some cases, the second segment (eg, an inverted pulse sequence) is applied over a period of less than 5 minutes, or less than 3 minutes, or less than 2 minutes, or less than 1 minute. The time length of the second segment can be shorter than the time length of the first segment. The duration of the second segment (eg, the inversion pulse segment) can be varied to form the desired coating.

  In general, the time length of the first segment is not limited. For example, the first segment can be between 1 minute and 10 hours; it should be understood that other time lengths may be used.

  In some cases, the present invention provides a method of forming a coating having a specific microstructure. For example, coatings containing nanocrystalline portions are formed by a variety of electrodeposition methods including the addition of atomizing additives, electrodeposition of alloys that take at least the nanocrystalline form, the use of pulsed currents, or the use of inverted pulsed currents. be able to. Another method for changing the microstructure of the coating is described in US 2006/02722949.

  As described herein, some embodiments of the invention use an electrodeposition bath. An electrodeposition bath typically includes chemical species that can be electrodeposited onto a substrate (eg, an electrode) upon application of an electric current. For example, electrodeposition baths containing one or more metal species (eg, metals, salts, other metal sources) can be used for electrodeposition of coatings containing metals (eg, alloys). In some cases, the electrodeposition bath includes a nickel species (eg, nickel sulfate) and a tungsten species (eg, sodium tungstate) and can be useful, for example, in forming a nickel-tungsten alloy coating.

  Typically, the electrodeposition bath includes an aqueous fluid carrier (eg, water). However, it should be understood that other fluid carriers may be used in connection with the present invention including, but not limited to, molten salts, cryogenic solvents, alcohol baths, and the like. One skilled in the art will be able to select an appropriate fluid carrier for use in the electrodeposition bath. In some cases, the electrodeposition bath can be selected to have a pH (hydrogen ion concentration index) of about 7.0 to 9.0. In some cases, the electrodeposition bath can have a pH of about 7.6 to 8.4, or in some cases about 7.9 to 8.1.

  The electrodeposition bath can contain other additives such as wetting agents, brighteners, leveling agents and the like. One skilled in the art will be able to select the appropriate additive and use it for a particular application. In some cases, the electrodeposition bath includes citrate ions as an additive. In some cases, the citrate ion content can be about 35-150 g / L, 40-80 g / L, or in some cases 60-66 g / L.

The method of the present invention can be advantageous in that coatings with various compositions (eg, Ni-W alloy coatings) can be readily formed in a single electrodeposition step. For example, a coating comprising a layered composition, a stepped composition, etc. can be formed by selecting a waveform having an appropriate group of segments in a single electrodeposition bath and in a single electrodeposition process.
The coated article that is formed can exhibit high corrosion resistance and high functional surface properties.

  It is understood that the coating can be formed as described herein using other methods including vapor phase processes, sputtering, physical vapor deposition, chemical vapor deposition, thermal oxidation, ion implantation, and the like. I want.

The following examples should not be construed as limiting, but as exemplifications of particular features of the invention.
(Example 1)
In the following examples, articles coated with Ni-W alloy were formed by an aqueous electrodeposition bath. The article to be coated was immersed in the solution and electrodeposition was performed by applying an electric current. The components of the solution used for electrodeposition are listed in Table I along with some of the conditions used in the electrodeposition process. The pH of the solution was equilibrated to a value of 8.0 using ammonium hydroxide. An inversion pulse current was applied under the characteristic conditions shown in Table I. The inversion pulse scheme used in this case is similar to the scheme suggested by US Patent Application Publication No. 2006/0272249. Several coatings were formed on a brass substrate using a counter electrode made of stainless steel.
Table 1. Electrodeposition conditions for tests 1 and 2

  A first article to be coated, including a Ni-W alloy coating, Sample A, was made using the inversion pulse method detailed in Table 1. The coating was electrodeposited for 20 minutes and achieved a thickness of about 10-12 micrometers as measured by x-ray fluorescence (XRF). XRF measurements also provided the composition of this coating, which was about 40 wt.% W and the remaining Ni. The coating immediately after electrodeposition was bright and vivid and glossy. According to the line broadening measurement using X-ray diffraction, the particle size of this sample was about 10 ± 5 nm; the sample was a nanocrystal. Thus, the coating formed on Sample A in this test is formed using prior art methods as described in U.S. Patent Application Publication No. 2006/02722949.

  Sample A was subjected to a corrosion test in a copper accelerated acetate spray (CASS) chamber (see standard ASTM B368). After less than 2 hours in the CASS test, the coating showed fading due to corrosion erosion. The CASS corrosion life was significantly less than 1 hour. After 4 hours, the corrosion became significant and the coating was no longer bright and vivid or glossy.

A second coated article, Sample B, was made using the method described above to be approximately the same thickness as listed above for Sample A. In this example, the first step of Ni—W alloy electrodeposition was performed using the same conditions as in Sample A. At the end of the first electroplating step, another electrodeposition step was performed. In this electrodeposition step, the current waveform was a forward current for a period of 12 ms followed by a reverse current for a period of 8 ms. , Included. The current density applied in this step was 0.09 A / cm ² in the forward direction and 0.075 A / cm ² in the reverse direction. This waveform was applied for 1 minute and formed the second part (ie, the upper layer part) of the electrodeposition coating. This two-stage process was carried out in a single processing step, i.e. the sample was immersed in the same electrodeposition bath in both electrodeposition steps carried out in succession. A change in the applied current waveform occurred between the processes, but in this case, the electrodeposition processing step was only performed once.

  The coating formed on sample B was about the same as the coating formed on sample A with respect to thickness and composition as measured by XRF (x-ray fluorescence analysis) (about 40 wt.% W, and the rest subtracted). Ni). The coating of Sample B in the state immediately after electrodeposition is bright and vivid and shiny, and according to line broadening measurements using X-ray diffraction, the particle size of this sample is about 10 ± 5 nm; and The sample was a nanocrystal.

  Sample B was subjected to the same standard copper accelerated acetate spray corrosion test as in Sample A. After 4 hours, no discernable corrosion was observed on the coating surface. High corrosion resistance performance up to 96 hours was achieved. The CASS corrosion life was at least 4 hours and may have been significantly longer. It is interesting to note that the coatings in Sample A and Sample B look the same when viewed using a bulk measurement method such as XRF (x-ray fluorescence analysis) or X-ray diffraction. That is, the coatings of Sample A and Sample B have approximately the same thickness, composition, and particle size. However, the corrosion properties and surface properties of Sample A and Sample B are clearly different. The results obtained for sample A are typically Ni-W electrodeposits formed using conventional methods such as the DC plating method, pulse plating method described above, or even pulse reversal plating. It is. Such coatings are susceptible to CASS corrosion effects with only a short exposure time. In contrast, Sample B was highly resistant to CASS corrosion, suggesting that the coating containing the upper layer portion imparts high corrosion resistance to the article.

Furthermore, Sample B does not require a sub-step such as a passivation step and leaves a W alloy coating with a trace amount of Cr or chromium oxide in the coating or on the coating surface. ₃ can be produced without using the solution.
(Example 2)
The various properties of the sample group produced in Example 1 were then analyzed to understand the effect of the outermost surface characteristics and composition of the coating on the corrosion properties of the sample. The composition of the two samples, Sample A and Sample B, was measured using Auger electron spectroscopy prior to exposure to a corrosive environment. The results from Auger electron spectroscopy suggested that the near-surface regions of the two coatings were different.

Sample A had a surface composition comprising Ni (about 62 atomic%), W (about 22 atomic%), and oxygen (about 16 atomic%). When oxygen is excluded from the analysis, the metal ratio is about 75 atomic percent Ni: about 25 atomic percent W, or when expressed in weight percentage, about 49 weight percent Ni: about 51 weight percent. W. This composition is quite close to the bulk measurements obtained from the results by XRF (x-ray fluorescence analysis), and slight differences may be due to the presence of oxygen on the surface. Sample B is Ni (about 86 atomic%), W (about 4 atomic%)
And a very different surface composition including oxygen (about 10 atomic%). When oxygen is excluded from the analysis, the metal ratio is about 96: 4 (Ni: W) in atomic ratio or about 88:12 (Ni: W) in weight ratio. In any of these Auger measurements, the upper portion of the sample B coating was different from the upper portion of the sample A coating.

Thus, the special procedure used to obtain Sample B resulted in a coated article having a different surface chemistry than that contained in Sample A. In particular, the upper layer portion of the coating formed on Sample B (ie, the oxide layer, composite oxide, or oxygen-containing phase) had a composition different from the composition formed on Sample A. The oxide layer of sample A almost showed an atomic composition Ni ₆₂ W ₂₂ O ₁₆ with a small deviation, whereas the oxide layer of sample B showed an atomic composition close to Ni ₈₆ W ₄ O ₁₀ . From these measurements, the oxide layer included a single composite oxide phase, or a composite material or composite comprising a plurality of different metal oxides and / or metal phases, or an alloy phase containing dissolved oxygen. Whether it was not clear.

  It has been shown that the different surface chemistry obtained in Sample B may depend on the high performance surface properties we measured, including high corrosion resistance and high color fastness. Thus, in some cases, a coating comprising an oxide layer comprising less than about 20 atomic percent W, nickel, and oxygen is formed by known methods and contains a large amount of W. It can provide higher corrosion resistance than oxides and other desired surface properties.

CIE Lab color system specified by CIE (International Commission on Lighting)
In CIE Lab Color Scale), sample A had colorimetric values represented by L = 82.5; a = 0.28; b = 3.16, whereas sample B had L = 83 4; a = 0.41; and b = 5.26. This further demonstrates that the surface phase and / or surface properties differ between the two samples.

  As a control test, the coatings formed on Sample A and Sample B were further compared to coatings that did not contain W and were formed by other Ni plating methods known in the industry. A Ni coating (eg, a W-free coating) is applied to the same substrate as Sample A and Sample B, and the Ni coating is similar in thickness to Sample A and Sample B (about 10-12 microns) And in this case, a nominally pure Ni coating was formed, for example, by immersion in a normal bright nickel electroplating solution or in a nickel sulfamate bath. A CASS corrosion test was performed on the Ni coating, and in all cases the surface and corrosion properties of the Ni coating were less desirable than those of the Ni-W coatings in Samples A and B. Thus, the state in which at least a certain amount of W is contained in the coating is desirable for improving the characteristics and enhancing the corrosion protection.

While not wishing to be bound by theory, inclusion of W forms the desired complex oxide or oxygen-containing phase that includes both nickel and tungsten, or one of these metal species A composite material is formed which consists of several different oxide phases containing species, or both metal species. For example, Sample B contained about 4 atomic percent W in the oxide. In some cases, the desired effect can be achieved by including at least 1 atomic percent W in the coating. Further, in some cases it is desirable to form a coating that includes a portion that includes an oxide, where the oxide includes nickel and oxygen as well as about 1 to 20 atomic percent W. Such coatings can exhibit high functional surface properties, corrosion resistance, and resistance to discoloration or fading. These coatings can further comprise a group of regions consisting of a W alloy, in which case these regions can be at least nanocrystals or need not be at least nanocrystals. In some cases, these coatings can be substantially free of chromium or chromium oxide and can be formed without the need for additional processing steps after electroplating.
(Example 3)
Various additional coating samples were made and the characteristics of these samples were analyzed. For example, Sample C and Sample D in Example 1 except that organic additives (ie leveling agents, wetting agents, brighteners) were added to the electrodeposition bath in an amount of less than 1 g / L. Prepared using the methods described for making A and B, respectively. Those skilled in the art can use leveling agents, whitening agents, spreading agents, wetting agents, etc. in such small amounts in common in these electrodeposition baths, and their addition. It will be appreciated that many composites of agents can be included in different baths. In this example, inclusion of low concentrations of organic additives did not change the main results reported above for Samples A and B. Sample C showed CASS corrosion within only a few hours, with very large corrosion occurring after 4 hours. However, Sample D contained a corrosion resistant top layer portion and had a CASS corrosion life of at least 4 hours.
(Example 4)
In the following example, a Ni-W coating was formed using a conventional DC plating method. Sample E and Sample F are the same as Sample A and B in Example 1 except that the multiple layers are first electrodeposited under direct current (DC) conditions and at a constant applied current density of 0.09 A / cm ^2. Made using the method described for making. Sample E and Sample F both included a Ni-W coating less than about 20 microns thick. Sample E was removed from the bath after DC (direct current) plating to form a Ni-W coating. In contrast, after DC plating to form the Ni-W coating, another upper layer portion was formed on Sample F using the same DC current and procedure as used in Sample B (eg, 1 minute forward / reverse sequence of plating at a forward current density of 0.09 A / cm ² for 12 ms followed by plating at a reverse current density of 0.075 A / cm ² for 8 ms And plate over).

  Sample E and Sample F exhibited all of the same respective features as the coatings formed on Samples A and B. FIG. 2 shows (a) a panel sample coated with a Ni—W alloy using a standard DC electrodeposition process (eg, sample E); and (b) Ni using a two-step inversion pulse electrodeposition process. -Shows a copy of a photograph after a standard CASS corrosion test for 14 hours on panel samples coated with W alloy (e.g., Sample F). Sample E, made using conventional DC plating, corroded and faded almost completely after only 14 hours (FIG. 2A), whereas Sample F had the same exposure. After receiving, it was able to withstand the CASS test, showed little fading and did not cause obvious corrosion or obvious discoloration. From yet another test, a group of samples made using the same conditions as in Sample F were able to withstand CASS corrosion conditions and there was little corrosion over 88 hours. Thus, the CASS corrosion life was at least 88 hours for this sample.

Prior to the corrosion test, Samples E and F were further analyzed and the surface chemistry of these samples and the oxides on the surface were evaluated using X-ray photoelectron spectroscopy (XPS). XPS analysis on sample E revealed that the surface consisted of nickel, tungsten and oxygen, ie the oxide layer (or oxygen-containing phase) contained nickel and tungsten. Furthermore, it is possible to perform a quantitative measurement of the metal content, which revealed that the surface of sample E had a Ni: W weight ratio of about 49% by weight: 51% by weight. The ratio was similar to the ratio measured by Auger spectroscopy for sample A (49:51). Both Sample A and Sample E were made using conventional methods. XPF analysis of Sample F further revealed that the surface oxygen-containing layer contained Ni and W and had different metal ratios on the surface, ie, the Ni: W ratio was 81 wt%: 19 wt%. This ratio was similar to the ratio measured by Auger spectroscopy for sample B (eg 88:12). Both Sample B and Sample F were produced using the inversion pulse method in the final plating step, and the upper layer portion was formed by this inversion pulse method.

  Thus, the XPS measurement on samples E and F confirms the above knowledge about samples A and B using Auger spectroscopy, and the upper layer portion formed on samples B and F is included in samples A and E. It was verified that it had a different surface composition that contained a smaller amount of tungsten than the tungsten that was produced. Comparing the corrosion properties of samples B and F with significantly improved CASS tests to those of samples A and E, the nature of the surface phase or various surface phases can affect the corrosion behavior and other surface properties I understand.

XPS analysis of Samples E and F further revealed clear evidence that not only oxygen was included in the coating, but metal-oxygen bonds were formed. FIG. 3 shows (a) the XPS spectrum of nickel of sample E, and (b) the XPS spectrum of nickel of sample F. As shown in FIG. 3, the XPS spectrum of nickel of sample E (FIG. 3A) and the XPS spectrum of nickel of sample F (FIG. 3B) are similar, and the two primary peaks are in the metallic state. This is caused by bonding of Ni. In the figure, “Binding Energy” indicates binding energy, and “Intensity” indicates strength. A plurality of relatively small secondary peaks are also observed, and two of these secondary peaks are associated with metallic Ni. A tertiary peak located at a binding energy of about 856 eV is associated with a metal oxide containing nickel. FIG. 4 shows (a) the XPS spectrum of tungsten of sample E, and (b) the XPS spectrum of tungsten of sample F. In both spectra, the two larger peaks can be associated with metallic tungsten bonds, and the smaller peaks can be associated with tungsten-containing oxides. Sample F showed a more pronounced oxide peak than Sample E. The peaks on the left side of these plots indicate that the binding energy is relatively high, that is, the atomic constituent groups are relatively strongly bonded. The data in FIG. 4 suggests that in sample F, the atomic groups are on average more strongly bonded than in sample E. FIG. 5 shows (a) the XPS spectrum of sample E, and (b) the XPS spectrum of sample F. There is a very clear difference between the two spectra, the spectrum of FIG. 5A shows a shoulder to the right of the primary peak, and the spectrum of FIG. 5B does not show this shoulder. The peaks on the left side of these plots indicate that the binding energy is relatively high, that is, the atomic constituent groups are relatively strongly bonded. The data in FIG. 5 suggests that in sample F, the atomic groups are on average more strongly bonded than in sample E.

  Thus, XPS analysis shows that there is a difference in the surface layers of samples E and F and that the oxide or oxygen containing phase located on top of these two samples is distinctly different. This correlates with the composition measurement results and the corrosion observation results by both XPS (X-ray photoelectron spectroscopy) and Auger spectroscopy methods. Further tests confirmed that these results were obtained for various substrates and for other changes in conditions. Other corrosive media including copper-free acetate spray (based on ASTM G-85), and neutral salt spray (based on NSS, ASTM G B-117) are also considered in detail. Tests have been performed on brass substrates and steel substrates having a variety of different geometric structures. Immersion corrosion tests that immerse in various corrosive media have also been performed. In each case, a sample having a unique upper layer portion composition, or a sample made using methods known to form a unique upper layer portion, may be coated with a coating made using previous methods. In comparison, it showed high corrosion resistance.

Claims (15)

A substrate,
A coating formed by electrodeposition on the substrate, the coating having a first portion and a second portion formed on the first portion ;
The first portion is made of nickel and tungsten and contains substantially no oxygen; and the first portion has a nanocrystalline structure;
Before Stories second portion nickel comprises tungsten, and oxygen, Ri weight percentage from 1 to 20 percent der tungsten contained in said second portion and said second portion has a nanocrystalline structure, the first An article comprising: the coating with a thickness of one part exceeding five times the thickness of the second part . The article of claim 1, wherein the second portion is an upper layer portion of the coating. The article of claim 1, wherein the coating is substantially free of chromium or chromium oxide. The article of claim 1, wherein the coating further comprises a metal oxide. The article of claim 1, wherein the weight percentage of nickel contained in the second portion is at least 50 percent. The article of claim 1, wherein the weight percentage of nickel contained in the second portion is at least 70 percent. The article of claim 1, wherein the second portion of the coating has a thickness of 10 nm to 500 nm. The article of claim 1, further comprising a third portion. The article of claim 1, wherein the second portion comprises nickel, tungsten, and oxygen. The article of claim 1, wherein the coating has a CASS corrosion life of at least 2 hours. The article of claim 10, wherein the coating has a CASS corrosion life of at least 10 hours. The article of claim 10, wherein the coating is substantially free of chromium or chromium oxide. The article of claim 10, wherein the substrate comprises a metal. The article of claim 1, wherein the substrate comprises a conductive material. The article of claim 14, wherein the conductive material comprises a metal.

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