Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
  • C25D3/14—Electroplating: Baths therefor from solutions of nickel or cobalt from baths containing acetylenic or heterocyclic compounds
  • C25D3/16—Acetylenic compounds

Definitions

• the present invention relates generally to semi-bright nickel plating baths that provide good properties with respect to leveling, ductility and stress and that are virtually sulfur-free.
• Bright nickel plating baths are used in the automotive, electrical, appliance, hardware and other industries. The most important functions of bright nickel plating are as an undercoating for chromium plating, helping finishers achieve a smooth bright finish and providing a significant amount of corrosion protection.
• semi-bright nickel deposits are almost always used in conjunction with subsequent deposits of bright nickel and chromium.
• the semi-bright nickel deposit is typically between about 60 and 70 percent of the total nickel deposited on the part, which offers the highest level of basis metal corrosion protection with the lowest total nickel thickness and the best appearance.
• the most common nickel plating bath is a sulfate bath known as a Watts bath.
• a typical Watts bath contains about 20-40 oz/gal nickel sulfate, 3-12 oz/gal nickel chloride, and 4-6 oz/gal boric acid and operates at a pH in the range of about 2.0-5,2, a temperature in the range of 90-160°F and a current density in the range of about 10-60 ASF.
• the large amount of nickel sulfate provides the necessary concentration of nickel ions, nickel chloride improves anode corrosion and increases conductivity, and boric acid is used as a weak buffer to maintain pH.
• organic and inorganic agents are often added to the electrolyte.
• the types of added brighteners and their concentrations determine the appearance of the nickel deposit, i.e., brilliant, bright, semi-bright, satin, etc.
• a semi-bright nickel finish is semi-lustrous, as the name implies, but it was specifically developed for its ease of polishing and buffing. In the alternative, if subsequently bright nickel is plated, buffing can be eliminated. Brightness and smoothness are dependent on operating conditions.
• One of the reasons that semi-bright nickel finishes are so easily buffed and/or polished is that the structure of the deposit is columnar, whereas the structure of a bright nickel finish is plate-like (lamellar).
• the structure of the deposit can be changed with various additives, a change in pH, current density or an increase in solution agitation, which is not a problem unless it affects properties of the deposit such as internal stress.
• Internal stress of the plated nickel deposit can be compressive or tensile. Compressive stress is where the deposit expands to relieve the stress. In contrast, tensile stress is where the deposit contracts. Highly compressed deposits can result in blisters, warping or cause the deposit to separate from the substrate, while deposits with high tensile stress can also cause warping in addition to cracking and reduction in fatigue strength.
• coumarin as an additive in nickel electroplating baths, especially semi- bright nickel processes, to produce ductile, lustrous deposits with excellent leveling is well known. It is also known that the degree of leveling obtained is generally proportional to the concentration of coumarin in the plating bath, A full coumann bath typically contains about 150 to about 200 mg/L of coumann and about 30 nig/L of formaldehyde. Thus, it can be seen that a high concentration of coumann in the bath gives the best leveling.
• aqueous acidic nickel electroplating bath comprising a coumarin compound and an aryl hydroxy! carboxylic acid compound in a combined amount, as described for example in U.S. Patent No. 4,441,969 to Tremme!, the subject matter of which is herein incorporated by reference in its entirety.
• the bath described in Tremniel still requires a relatively high concentration of coumarin to provide good leveling characteristics. While the bath required less frequent batch carbon treatments, the need for said treatments was not eliminated.
• Another problem with coumarin is odor. The amount of coumarin required for a plating bath produces an offensive odor that can irritate eyes and mucous membranes.
• Leveling refers to the ability of the deposit to fill in and smooth out surface defects such as scratches or polish lines. It is also important to provide these highly leveled deposits without sacrificing deposit ductility and stress, it is further preferable that the nickel deposit contain less than 0.004% sulfur.
• the present invention relates generally to a nickel plating bath for plating a semi-bright nickel deposit on a substrate, the nickel plating bath comprising: a) a source of nickel ions;
• the nickel plating bath is preferably substantially free of coumarin, and preferably substantially free of aldehydes.
• the present invention relates generally to a nickel plating bath for plating a semi-bright nickel deposit on a substrate, the nickel plating bath comprising:
• nickel ions such as from a mixture of nickel sulfate and nickel chloride
• a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid and c) at least one diol selected from the group consisting of hexyne diol, butyne diol and combinations of the foregoing,
• nickel plating bath is preferably substantially free of coumarin and preferably substantially free of aldehydes .
• the present invention relates generally to a method of plating a substrate to produce a sulfur-free semi-bright nickel deposit thereon comprising the steps of:
• a) providing a nickel plating bath comprising:
• nickel ions such as from a mixture of nickel sulfate and nickel chloride
• a halide substituted i) acetic acid, (ii) proprionic acid, or (iii) salts of any of the foregoing, or a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid;
• the nickel plating bath is preferably substantially free of eoumarin and preferably substantially free of aldehydes.
• the present invention relates generally to a nickel plating bath that includes a halide substituted (i) acetic acid, (ii) proprionic acid, or (iii) salts of any of the foregoing, or a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid in combination with hexyne diol and/or butyne diol and that is able to provide good leveling characteristics without the addition of coumarin.
• a halide substituted i) acetic acid, (ii) proprionic acid, or (iii) salts of any of the foregoing, or a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid in combination with hexyne diol and/or butyne diol and that is able to provide good
• the present invention relates generally to a coumarin-iree nickel plating bath which provides the leveling characteristics that are achievable with a coumarin-contatning nickel plating bath.
• the present invention relates generally to a nickel plating bath for plating a serai-bright nickel deposit on a substrate, the nickel plating bath comprising: a) a source of nickel ions;
• the nickel plating bath is preferably substantially free of coumarin and preferably substantially free of aldehydes.
• the nickel plating bath contains nickel sulfate and nickel chloride.
• boric acid is typically added to control the pH of the solution.
• the plating bath contains a halide substituted (i) acetic acid, (ii) propriomc acid or (iii) salts thereof.
• MonocMoroacetic acid is preferred, however dicMoroacetic acid or trichloroacetic acid are also suitable.
• the aforementioned acids are generally added as sodium, potassium, lithium, magnesium and nickel salts because the addition of the acids tends to make the pH of the bath too low.
• the concentration of the soluble salt, such as sodium mono ch!oroacetate, is preferably beiween about 2.0 to 4.0 g/l but can range from as little as 0.5 g/1 to as much as 20 g/l.
• the hexyne diol concentration should preferably be between 100 to 200 mg/1, but can range from 50 mg/1 to 500 mg/1.
• the preferred range for the butyne diol is 60 to 120 mg/I but can range from 30 to 300 mg/1.
• both hexyne diol and butyne diol are used together, however, the inclusion of one of the two will work well. Even higher concentrations of these compounds can be used if they are used alone. If both diols are used the aggregate concentration can range from 50 mg/1 to 600 mg/1.
• Supplementary additives include ethoxylated (or propoxylated) butyne diol, ethoxylated (or propoxylated) hexyne diol, ethoxylated (or propoxylated) acetylemc alcohols, and/or acetylenic alcohols.
• the present invention relates generally to a nickel plating bath comprising:
• a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid b) a soluble salt of chloroacetic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid; and c) at least one diol selected from the group consisting of hexyne diol, butyne diol and combinations of the foregoing,
• nickel plating bath is preferably substantially free of coumarin and preferably substantially free of aldehydes.
• soluble salts of salicylic acid are preferred, such as sodium salicylate.
• the soluble salts of acetic acid, chloroacetic acid, glycolic acid, proprionic acid, benzoic acid and chlorobenzoic acid are also usable in the practice of the invention.
• the aforementioned acids are generally added as sodium, potassium, lithium, magnesium and nickel salts because the addition of the acids would make the pH of the bath too low.
• the concentration of the soluble salt, such as sodium salicylate is preferably between about 1.0 to 2.0 g/1 but can range from as little as 0.3 g/1 to as much as 20 g/1.
• the semi-bright nickel plating bath is preferably substantially free of coumarin and is most preferably free of coumarin. What is meant by substantially free is that the bath contains no functional amounts of coumarin. Free of coutnarin means that no detectible amounts of coumarin have been added to the bath.
• aldehydes are not required in the nickel plating bath to provide acceptable STEP results.
• STEP is an acronym for "simultaneous thickness and electrolytic potential” and is measured with a special device called a STEP tester, which measures not only the thickness of the given deposits but also the electrical potential difference between the bright and semi-bright nickel layers. This difference is very important because it relates to the corrosion protection of these duplex nickel layers.
• a STEP of at least 100 mv is required and 120 mv or higher is desirable. Normally, the addition of aldehydes is used to accomplish this end.
• the plating bath described herein is preferably substantially free of aldehydes, and most preferably is free of aldehydes. What is meant by substantially free is that the bath contains no functional amounts of aldehydes. Free of aldehydes means that no detectible amounts of aldehydes have been added to the bath.
• the semi-bright nickel plating bath described herein also provides a nickel deposit that exliibits perfect ductility of 0.5 according to the Chrysler ductility method and exceptionally low internal stress ranging from about 1,000 compressive to about 4,000 tensile.
• the leveling of deposits plated from the plating bath of the invention are comparable to a freshly made coiimarin/formaldehyde bath.
• leveling characteristics of various processes there have been no coumarin-free plating processes thai have come close to the leveling of a fresh coumarin bath.
• the STEP results achieved by the plating bath of this invention are completely unexpected. Until now, only the addition of aldehydes, such as chloral hydrate or formaldehyde, would increase the STEP to the required levels. Furthermore, previously the addition of other acids, such as salicylic acid and benzoic acid, was shown to reduce STEP.
• Stress of the deposit is measured using various methods and is typically desired to be within the range of 15,000 psi tensile or less. The lower the internal stress, the better.
• Ductility is normally measured using the Chrysler ductility method.
• a stock semi-bright nickel bath was prepared having 40 oz/gal nickel sulfate hexahydrate, 4.5 oz/gal nickel chloride hexahydrate and 5.5 oz/gal of boric acid.
• the solution was carbon and peroxide treated and filtered and the pH adjusted to 3.8 to 4.0, Thereafter, 0.3% v/v of a solution of 6% by weight di ⁇ hexy1sulfosuccinate was added to prevent pitting in the subsequent deposits.
• a scratched hull cell panel is one where the bottom 0.75 inch of the panel has been polished with a 200 grit belt. This leaves polishing lines and allows the researcher to evaluate leveling across a wide current density range.
• the overall deposit was over-lustrous semi-bright from about 0 to 50 ASF and slightly dull above 50 ASF and very dull along the HCD edge.
• This panel was then plated in a bright nickel bath directly across from the anode (not a hull cell) at 25 ASF for 5 minutes.
• the bright nickel under these conditions did not provide much levelmg but made the deposit bright enough to evaluate leveling of the initial nickel deposit.
• the leveling of the deposit was about 65% of a commercial coumarin bath, ft should be noted that the HCD area of the panel was still cloudy because the semi-bright deposit was dull.
• a fresh semi -bright stock solution was added to the air agitated hull cell.
• Example 2 was repeated but the bath pH was increased to 4,6. The resulting deposit was a little brighter than that in Example 2, It was over-plated with bright nickel as above and leveling evaluated. The leveling of the deposit was almost equal to one plated from a full coumarin bath. The concentration of the mixture of hexyne diol and butyne diol was increased such that the aggregate concentration was 0.45 g/1. The leveling of the deposit was now equal to one plated from a commercial coumarin bath.
• Example 1 was repeated at a bath pH of 4.6, and the results were the same.
• Example 3 A one liter solution of the bath of Example 3 was placed in a beaker equipped with air agitation. A foil was plated from this bath which had a thickness of about 1.0 mil. This was done by plating the deposit on a stainless steel panel at an average current density of 40 ASF. Because the substrate is passive, the deposit is readily removed by cutting the edges of the panel which releases the deposit. This allows the plater to cut strips of foil and measure the ductility. The ductility (T/2R value) of this deposit was 0.5.
• Example 3 A one liter solution of the bath in Example 3 was again placed in an air agitation beaker. This time, stress was measured using the strip method. This is done by measuring the deflection of a beryllium - copper strip before and after plating and plugging the data into a formula which uses deposit thickness, deflection and a constant to determine stress in units of pounds per square inch (psi). The stress of the deposit was determined to be 1560 psi tensile. As mentioned above, the lower the stress, the better, and most semi-bright nickel deposits have stress values of about 8,000 to about 15,000 psi tensile.
• Example 1 was repeated using 2 g/l of sodium formate in place of the sodium acetate.
• the resulting deposit with the diols was overall lustrous over the entire current density range but the deposit had fair to poor leveling. While increasing the pH improved leveling, leveling was still less than 50% of a commercial coumarin bath.
• a stock semi-bright nickel bath was prepared having 40 oz/ga! nickel sulfate hexahydrate, 4.5 oz/gal nickel chloride hexahydrate and 5.5 oz/gal of boric acid.
• the solution was carbon and peroxide treated and filtered and the pH adjusted to 3.8 to 4.0. Thereafter, 0,3% v/v of a solution of 6% by weight di-hexy!sulfosuccinate was added to prevent pitting in the subsequent deposits.
• a scratched hull cell panel is one where the bottom 0.75 inch of the panel has been polished with a 200 grit belt. This leaves polishing lines and allows the researcher to evaluate leveling across a wide current density range.
• the overall deposit was over-lustrous semi-bright from about 0 to 80 ASF and dull above 80 ASF and somewhat dull along the HCD edge, This panel was then plated in a bright nickel bath directly across from the anode
• the bright nickel under these conditions did not provide much leveling but made the deposit bright enough to evaluate leveling of the initial nickel deposit.
• the leveling of the deposit was about 65% of a commercial coumarin bath.
• a fresh semi-bright stock solution was added to the air agitated hull cell. Thereafter, 2.0 g/1 of sodium salicylate was added to the bath and 0.2% of the mixture of hexyne diol and butyne diol was added such that the aggregate concentration was 0.35 g/1, A scratched brass panel was plated at 2 amps for 15 minutes. The resulting deposit was overall lustrous semi-bright with some slight dullness in the extreme HCD edge of the panel. The panel was over-plated with 5 minutes of bright as described above in Example 9 and the leveling was about 75% of a commercial coumarin bath.
• Example 11 Example 11:
• Example 10 was repeated but the bath pH was increased to 4.6. The resulting deposit was a little brighter than that in Example 10. It was over-plated with bright nickel as above and leveling evaluated. The leveling of the deposit was equal to one plated from a commercial coumarm bath.
• Example 11 A one liter solution of the bath of Example 11 was placed in a beaker equipped with air agitation. A foil was plated from this bath which had a thickness of about 1.0 mil. This was done by plating the deposit on a stainless steel panel at an average current density of 40 ASF. Because the substrate is passive, the deposit is readily removed by cutting the edges of the panel which releases the deposit. This allows the plater to cut strips of foil and measure the ductility. The ductility (T/2R value) of this deposit was 0.5.
• Example 11 A one liter solution of the bath in Example 11 was again placed in an air agitation beaker. This time, stress was measured using the strip method. This is done by measuring the deflection of the strip before and after plating and plugging the data into a formula which uses deposit thickness, deflection and a constant to determine stress in units of pounds per square inch (psi). The stress of the deposit was deterrnrned to be 1920 psi tensile. As mentioned above, the lower the stress, the better, and most semi- bright nickel deposits have stress values of about 8,000 to about 15,000 psi tensile.
• Example 3 was repeated using 1.5 g/1 of sodium benzoate in place of sodium acetate.
• the resulting deposit was overall semi-bright to lustrous over the entire current density range.
• the leveling of the deposit was comparable to deposits from a commercial coumarm bath.
• Example 3 was repeated using 1.5 g/1 of sodium chlorobenzoate in place of sodium acetate.
• the resulting deposit was overall lustrous over the entire current density range.
• the leveling of the deposit was comparable to deposits from a commercial coumarm bath.
• the semi-bright nickel plating baths described herein produce sulfur-free semi-bright deposits over a very wide current density range.
• the nickel plating baths described herein are the only non ⁇ coumarin semi-bright baths known to produce leveling equal to a full commercial coumarin bath.
• the baths also require no aldehydes to achieve STEP and, as a result, the deposit has extremely low stress and excellent ductility.

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• 2011
  • 2011-03-09 US US13/043,783 patent/US20110155582A1/en not_active Abandoned
• 2012
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  • 2012-02-08 EP EP12754802.2A patent/EP2683853B1/de not_active Revoked
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