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    • 专利摘要:
    A chromium coating precipitated from a chromium bath based on chromium in oxidation step +3 on a tin / nickel surface. This surface is very corrosion resistant and will not emit nickel in amounts estimated to be able to provoke hypersensitivity according to EU Directive 94/27 / EC. The surface will also contribute to reduced use of the toxic chromium baths based on chromic acid (chromium in oxidation state +6) in industry. And thereby also reduce the environmental and health risks associated with the production of decorative chrome-plated items.
    公开号:DK201300334A1
    申请号:DK201300334
    申请日:2013-05-31
    公开日:2014-12-15
    发明作者:Susanne Köhler；Nicklas Lütken
    申请人:Elplatek As；Susanne Köhler；Nicklas Lütken；
    IPC主号:
    专利说明:

    Description
    It is known to deposit glossy chromium on a coating of electrolytically precipitated nickel to obtain a glossy surface for decorative purposes while at the same time promoting the corrosion resistance of the surface. This surface is known by the term gloss chrome and highly sought after in many areas such as furniture design, lamps, plumbing fixtures for decorative surfaces on cars. However, the surface has the major disadvantage that it is very difficult to avoid corrosion in the long term. Cracks and defects in the chromium layer cannot be avoided due to stresses in the precipitated chromium layer, which causes corrosion to be introduced into the underlying nickel layer. This is because the chromium oxide will significantly raise the electrochemical potential relative to the underlying nickel corrosion potential, which will cause the nickel layer to act locally as an anode and corrode at increased speed. The chromium layer will act as an oxygen reduction cathode, as a plausible cathode reaction.
    Anode Reaction: Ni = Ni + 2 + 2e Cathode Reaction: O2 + 2H20 + 4e "= 40H" In microprorous or microwaveable chromium coatings, several artificially produced defects are introduced into the chromium layer and the corrosion preferably takes place evenly throughout the surface.
    By depositing several nickel layers (duplex nickel) typically two with varying sulfur content under the microprorous or microwaveable chromium coatings, controlled differences in the corrosion potentials between the different nickel layers can be achieved, allowing a cathodic protection of the lower nickel coating to occur as well as cathode action. on the chrome surface via the defects in the chromium layer can uniformly distribute the corrosion on the underlying nickel layer, which in turn cathodically protects the nickel layer closest to the steel.
    In any case, this construction of the coating system leads to a limited life of gloss chrome-plated items. Furthermore, the corrosion can cause problems with nickel hypersensitivity (nickel allergy) as the underlying nickel coating will dissolve.
    Alternatives to this process have long been sought to get rid of these problems without sacrificing the appearance of the surface. Some of these are; cobalt / tin, nickel / tungsten / cobalt and nickel / tungsten. The problem with these alloys is that, despite good corrosion properties on some of the surfaces, they do not get rid of the hypersensitivity problems, as cobalt presents many of the same problems as nickel, and none of the coatings prove stable enough to not provoke a hypersensitivity reaction. by prolonged skin contact.
    Figure 1 The corrosion potential of various metals and galvanic coatings in an oxygenated NaCl solution 30 g / l at room temperature.
    Surprisingly, it has been found that depositing a chromium coating on a tin / nickel surface will completely avoid these problems. The corrosion potential between the applied Cr layer and as plated tin / nickel is slightly higher than the corrosion potential of the tin / nickel coating alone measured in oxygenated seawater (see Figure 1).
    Tin / nickel is an electrolytically precipitated alloy consisting of 65wt% tin and 35wt% nickel, which corresponds to a one to one ratio of tin to nickel. The phase cannot be prepared by a pyrotechnic forming process and will be divided into phases consisting of Ni3Sn2 and Ni3Sn4 if heated to above 350 ° C. Tin / nickel is gray with a color close to some stainless steels, with a slightly smoky or reddish tone. The hardness is around 750 HV and the ductility is very low.
    Figure 2 Phase diagram for nickel and tin. Note that the tin / nickel phase is not present.
    The alloy is not affected by halogen ions and passivates efficiently, even at potentials up to 1200mV relative to SHE in a 250mg / L chloride solution.
    The tin / nickel coating is typically applied to a gloss copper coating (see Cu in Figure 1), which is electrolytically deposited on a steel, zinc, aluminum, magnesium, copper or copper alloy strike surface to produce a glossy decorative surface without defects ( pinholes). It has also surprisingly been found here that the difference between the potential of copper and the tin / nickel coating is vanishing in a similar environment, which reduces the galvanic coupling activity between copper and tin / nickel (Figure 3). Here it is seen that the Faraday current is in the region of 0.2µ A / cm2 which corresponds to a corrosion rate in the region of 2µm per year. Instinctively, it should be the copper that behaved most nobly, but the graph shows that this is not actually the case. This may be due to the fact that the potential difference between copper and tin / nickel under the given conditions is very small, and therefore it can be difficult to predict which of the two will act as a cathode and which as anode at a coupling. For the remaining couplings, the current measured for the majority goes to a passivation of the tin / nickel layer. Furthermore, it should be made clear that the measurement uncertainty at such low currents is of the same or almost the same magnitude as the magnitudes of the currents, and therefore the graph first and foremost gives an image of the magnitude of the current, and thereby the magnitude of the current.
    Figure 3 Galvanic tin / nickel couplings with selected metals.
    Surprisingly, it has been found that the conventional glossy chromium-based process containing chromic acid (hexavalent chromium) is not useful in the application of thin layers of chromium to tin / nickel. The surface is not chrome-plated with glossy chrome; as o the surface after application appears to appear partially untreated. The reason for this must be sought in that the tin / nickel alloy is passivated due to the strong oxidation from the chromic acid.
    However, it would be possible to apply tin / nickel chromium coating from a hexavalent chrome bath if the tin / nickel surface was activated via a nickel strike during chromium coating. The problem with this method is that it introduces the risk of nickel release to the environment during use and thus does not release nickel allergy coating system.
    Instead, by using an electrolyte based on trivalent chromium, it has surprisingly been found to be possible to precipitate a chromium layer directly onto tin / nickel with the same or better coverage as with the precipitation of hexavalent chromium on nickel.
    This combination turns out to be a very corrosion resistant surface. Among other things, items made in this way (10-15μιη tin / nickel) have been able to withstand salt mist chamber tests (ASTM B1 17) for four months without visible initiated corrosion on the surface. This property can be explained by the fact that tin / nickel forms an oxide layer, of the type SnxNiO2X + 2y, which turns out to be chemically very stable (passive), and therefore will exhibit no or very little corrosion in an oxidizing environment. At the same time, the potential for tin / nickel is close to, but lower than, the chromium oxide. This causes the chromium oxide to be cathodically protected by the underlying tin / nickel layer, thereby not corroding, while the tin / nickel layer, as previously mentioned, will passivate. The observations are confirmed via electrochemical polarization measurements (Figure 4). It can be stated here that tin / nickel exhibits its own corrosion resistance identical to the best stainless steels. After the experiment, tin / nickel coating appears without significant damage - the slightly increased corrosion current in the passive area is due to minor defects in the tin / nickel coating which allows selective dissolution of the underlying 100 nm thick wood nickel layer that is necessary to apply due to adhesion to the passive 254 SMO steel. In tests with tin / nickel applied to stainless steel such as 904L and 254 SMO, corrosion at greatly increased electrochemical potential (1500 mV) will typically always occur as pitting in the steel while the tin / nickel coating appears intact after the test.
    Figure 4 Polarization measurement of tin / nickel plated 254 SMO base material compared to 254 SMO base material.
    Tin / nickel is never directly plated on steel - but is often plated on an electrolytic copper layer which ensures an optimal, homogeneous and pore-free substrate that protects the base material against corrosion by cracks or pores in the outer layers. In most circumstances, this copper layer, like the chromium oxide, would be cathodically protected by the tin / nickel layer and thus not be subjected to corrosion.
    The life of such a surface, in a corrosive environment such as seawater or in contact with the skin under the influence of body sweat, will have far better durability than conventional gloss chromed surfaces, whether based on duplex nickel with microporous or microwaveable chrome or conventional gloss chrome coatings. Thus, the new coating combination will be a unique alternative to "high quality" gloss chromium and may thus provide a new method that allows the phasing out of hexavalent chromium from many processes which so far have not done so due to poor performance from trivalent chromium baths used as topcoat on glossy nickel coated surfaces. The new coating combination also allows for the use of POP (plating of polymers) and can ensure that Cr + 3 can be used for all chrome coating in the automotive industry, including areas where Cr + 3 pt. is not currently accepted.
    The initial preprocessing of polymer (primarily ABS) before plating with chemical Cu or Ni, typically an etching, can be done in several ways, but is often done with chromium-sulfuric acid, since at least one chromic acid bath is present in the process line. If this is changed to a trivalent chromium bath, it will be very attractive to use other etching methods for the pretreatment, as it is possible to completely remove hexavalent chromium from production in the automotive field, and thus the health problems associated with this.
    Other advantages of using tin / nickel directly under the chrome layer will be that you can save a lot of material especially nickel compared to normal chrome plating processes, since a tin / nickel layer with a thickness of 5μιη - 1 Ομιη provides adequate corrosion protection in most applications . In addition, the coating will not be particularly sensitive to mechanical impact; as the copper coating is ductile and by galvanic coupling is not very active (see Figure 1). Furthermore, the number of processes associated with gloss chrome will be greatly reduced. Now that you have up to four nickel layers with a total thickness of up to 70μιη for a gloss chromed surface, you will be able to settle with a layer of tin / nickel applied to a good quality copper coating and at the same time obtain better corrosion protection than possible when laying chrome on nickel. Copper plating can generally achieve much better material distribution than is known from nickel. In addition, the tin / nickel process is among the galvanic processes that can provide the best macro dispersion. This opens the possibility that even complex geometries can be optimally coated with the specified process.
    Different subjects would have to be treated differently based on material before applying a surface as described here. The following are examples of how some materials could be prepared. Between all processes should be cleaned with deionized water.
    A metal blank would typically be pre-treated as follows: • Mild alkaline dipping degreaser. For example, SLOTOCLEAN AK 90.
    • Electric degreaser. For example, SLOTOCLEAN EL DCG.
    o For brass, cathodic degreasing should be used and steel blanks should be degreased anodically according to recommendations in the data sheet.
    • Decapitation.
    o Dry or sulfuric acid should be used here as the subsequent copper process may be sensitive to chloride contaminants.
    • If you work with a steel blank you should apply a nickel strike here. • Copper plating o Depending on the geometry of the workpiece and the desired surface, a wide range of processes can be used. For example, for a glossy surface from an acid bath, Schlutter's gloss copper bath TB 10, which has a copper content of 43 - 50 g / l, a sulfuric acid content of 70 - 100 g / l and a chloride content of 50 - 120 mg / l, could be used, in addition to a variety of additives called TB 11, TB 12 and TB 13, or SLOTOCOUP TB 50, or CUPRUM 10 if an alkaline copper bath is desired or required. One could also imagine that a matte surface is desired for a copper bath with a matte precipitate.
    • Tin / nickel plating o For example, GalvanLoy NS 11 from Galvanord, which has a tin (II) content of 20 - 25 g / l, a nickel content of 55 - 65 g / l, a fluoride content high enough to complex all the tin in the bath, besides some glossy additives.
    • Chromium o Different trivalent chromium baths can be used depending on the properties of the surface. For a classic gloss surface, SLOTOCHROM DR 60 from Schlotter could be used.
    If a plastic item is desired to be plated, the process could be as follows: • Pickling o Here picking processes that do not contain chromic acid could obviously be used to avoid the health risks associated with this.
    • Activation in colloidal palladium • Accelerator (Removal of tin ions from the activation process) • Autocatalytic precipitation of nickel o An alkaline nickel bath should be used as these typically have a lower working temperature than an acidic chemical nickel bath.
    • Copper plating • Tin / nickel plating • Chromium plating
    These factors taken into account will not only achieve better corrosion protection, but also have lower material costs and production time, using tin / nickel in gloss chromium rather than the traditionally used nickel. At the same time, an optimum opportunity to completely phase out hexavalent chromium from the decorative chrome plating - at the same time as the surfaces can be considered safe in relation to nickel release according to EU Directive 94/27 / EC, which sets a limit of o 0.5pg / cm / week in artificial sweat according to standard EN 1811 for things that are exposed to prolonged skin contact, and 0.2pg / cm2 / week for things to be inserted into the body such as piercings, ear rings etc. In the article “Nickel-containing alloys and platings and their ability to cause dermatitis” -
    British Journal of Dermatology 1996; 134: 193 - 198, the nickel release from tin / nickel in such a test is set to 0, lpg / cm2 / week.
    权利要求:
    Claims (7)
    [1]
    1. An electrolytically precipitated decorative chrome plating on a tin / nickel surface. Characterized by the fact that the chromium electrolyte does not act oxidatively on the tin / nickel coating.
    [2]
    A tin / nickel chrome coating according to claim 1, characterized in that, in addition to serving decorative purposes, it can also be applied to promote a technical, chemical or physical property of the surface.
    [3]
    A chrome plating on tin / nickel according to claims 1 and 2, characterized in that the surface of the chrome plating exhibits a corrosion potential primarily higher than the tin / nickel coating alternatively up to 50 mV lower than tin / nickel.
    [4]
    A tin / nickel chrome coating according to claims 1, 2 and 3, characterized in that the chromium coating may contain alloying elements such as iron, nickel, cobalt, manganese, tungsten or sulfur.
    [5]
    A tin / nickel chromium coating according to claims 1, 2, 3 and 4, characterized in that the tin / nickel alloy composition has a nickel content in the range of 45-55 atom% and correspondingly a tin content in the range 55-45 atom%.
    [6]
    A tin / nickel chrome coating according to claims 1, 2, 3, 4 and 5, characterized in that the base material is metallic, a polymer, ceramic, or a composite arbitrarily composed of these.
    [7]
    A tin / nickel chromium coating according to claims 1, 2, 3, 4, 5 and 6, characterized in that nickel does not dissolve in the case of galvanic coupling that can exceed the limits set by the EU of 0.5μg / cm2 / week in artificial sweat according to standard EN 1811 for items exposed to o prolonged skin contact and 0.2μg / cm / week for items to be inserted into the body according to EU Directive 94/27 / EC.
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    同族专利:
    公开号 | 公开日
    DK178476B1|2016-04-11|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JPS58161794A|1982-03-19|1983-09-26|Nippon Steel Corp|Surface treated steel plate for can manufacture with superior corrosion resistance after coating|
    JPH032960B2|1982-12-10|1991-01-17|Kawasaki Steel Co|
    CA1240949A|1983-07-08|1988-08-23|Kyoko Yamaji|Surface treated steel strip with coatings ofiron-nickel alloy, tin and chromate|
    GB0407619D0|2004-04-02|2004-05-05|Jing Mei Ind Holdings Ltd|Chromium plating|
    DE102010055968A1|2010-12-23|2012-06-28|Coventya Spa|Substrate with corrosion-resistant coating and process for its preparation|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    DKPA201300334A|DK178476B1|2013-05-31|2013-05-31|Decorative chrome surface that eliminates the use of hexavalent chromium electrolytes in production, and minimizes nickel release from the surface|
    DK201300334|2013-05-31|DKPA201300334A| DK178476B1|2013-05-31|2013-05-31|Decorative chrome surface that eliminates the use of hexavalent chromium electrolytes in production, and minimizes nickel release from the surface|
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