Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
  • C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites

Definitions

• Chemical nickel plating commonly referred to as electroless nickel plating, is a well known technique highly useful in depositing uniform nickel surfaces upon solid substrates.
• the technique involves contacting the substrate with a bath containing nickel ions, hypophosphite ions and a buffer.
• the technique is applicable to plating substrates of a conductive, e.g., metals, or non-conductive nature such as, for example, plastics, rubber, wood or ceramics. In the latter case, however, it is necessary first to prepare or condition the substrate surface prior to contact with the plating bath.
• My chemical nickel plating compositions comprise aqueous solutions of a nickel salt, an alkali metal h ypophosphite, a buffer in the form of a salt of an organic acid and an alkali metal lignosulfonate.
• the lignosulfonate has a molecular weight ranging from about 1,000 to about 20,000.
• an electroless nickel bath composition comprising 0.095 mole per liter (m./l.) nickel sulfate, 0.236 m./l. sodium hypophosphite, 0.127 m./1.
• nickel ion to hypophosphite ion ratio is 0.4.
• the term ion as employed herein includes the total quantity of element or radical present in the bath; that is, both on the associated and disassociated material. Thus, association is assumed when the term ion is used in connection with molar ratios and concentrations in the bath.
• the lignosulfonates useful in my compositions are those alkali metal sulfonate salts made from the lignin of sulfite pulp-mill liquors selected from the group con.- sisting of sodium and potassium. They are a light tan to dark brown powder having no pronounced odor and which are stable in dry form and relatively stable in aqueous solution. It is preferred to use the de-sugarized alkali metal lignosulfonates.
• the products are commercially available.
• the compositions have an average molecular weight in the range of 1,000 to 20,000 and have a bulk density of 20-50 lbs/cubic foot. The practical solubility limit is 100 grams/100 cc. of water.
• the advantages of my invention are realized by the addition of the lignosulfonates to conventional chemical nickel plating baths.
• Such baths are characterized by a nickel to hypophosphite ion ratio, expressed as molar concentrations, falling within the range of from about 0.25 to about 1.60.
• the absolute concentration of hypophosphite ions in the bath expressed in mole/liter is within the range from about 0.15 to about 1.20 and the absolute concentration of the buffer is approximately equal to 2 carboxyl groups of any nickel ion that can be deposited.
• the buffer employed in the system can be a soluble salt of a simple short chain aliphatic mono-, or dicarboxylic acid.
• acetic acid, butyric acid, propionic acid, malonic acid, succinic acid, glutaric acid and the like, as Well as their salts can be employed.
• the bath can contain, and in the baths of my invention preferably does contain, additional buffers which also serve as chelating or complexing agent, to prevent the precipitation of undesirable metal compounds.
• additional buffers which also serve as chelating or complexing agent, to prevent the precipitation of undesirable metal compounds.
• exemplary of such agents are nitrilotriacetic acid, ethylene diamine tetraacetic acid, and the like known complexing agents or their salts.
• the term bulfer as used herein encompasses such agents.
• Example 1 A bath is formulated by mixing the following compositions with distilled or deionized water:
• Example 2 The bath described in Example 1 is prepared in a suitable container and the pH adjusted to 4.75 with sodium hydroxide.
• the bath temperature is brought within the preferred operating range of 120-210 E, the particular temperature chosen dependent on the specific application.
• properly prepared thermoplastic polymers can be plated in the range of 120140 F. to avoid heat distortion.
• Metallic substrates can be plated at any temperature within the preferred operating range without the close temperature control required by most electroless nickel processes to obtain satisfactory deposits and deposition rates. A bright deposit is obtained with this bath at any temperature within the range cited above.
• Example 3 The rate of deposition of nickel on a metal substrate using the bath of Example 1 was compared to the deposition rate of a bath containing all the components of Example 1 except the sodium lignosulfonate. The results are as follows:
• Example 4 The bath of Example 1 was altered by using NiCl -6H O in lieu of the NiSO '6H O and tested in the same manner as Example 3. The results achieved paralleled the results of Example 3.
• Example 5 The stability of the bath of Example 1 was compared to a bath containing no sodium lignosulfonate. The bath Without sodium lignosulfonate was observed to decompose after two days while the bath with sodium lignosulfonate did not decompose after three months.
• a chemical nickel plating bath having a acidic pH and which comprises an aqueous solution of a nickel salt, an alkali metal hypophosphite, a buffer in the form of an organic acid selected from the group consisting of aliphatic monocarboxylic and aliphatic dicarboxylic acids and salts thereof, the improvement which comprises the presence in said bath of an alkali metal lignosulfonate in a amount effective to permit the use of said bath for low temperature operations.
• composition of claim 1 wherein said nickel salt can be selected from the group consisting of nickel sulfate and nickel chloride and mixtures thereof.
• composition of claim 2, wherein said hypophosphite is sodium hypophosphite.
• composition of claim 3 wherein said buffer is succinic acid and the trisodium salt of nitrilotriacetic acid monohydrate.
• composition of claim 4, wherein said alkali metal lignosulfonate can be selected from the group consisting of sodium lignosulfonate, potassium lignosulfonate and mixtures thereof.
• a solid substrate in form suitable for nickel plating, which comprises contacting said substrate with a bath having an acidic pH and comprising an aqueous solution of a nickel salt, an alkali metal hypophosphite, a buffer in the form of an organic acid, selected from the group consisting of aliphatic .monocarboxylic and aliphatic dicarboxylic acids and salts thereof, the improvement which comprises the introduction into said bath of an alkali metal lignosulfonate in an amount effective to permit said process to be conducted at low temperatures.
• nickel salt can be selected from the group consisting of nickel sulfate and nickel chloride and mixtures thereof.
• hypophosphite is sodium hypophosphite.
• alkali metal lignosulfonate can be selected from the group consisting of sodium lignosulfonate, potassium lignosulfonate and mixtures thereof.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25038878

Family Applications (1)

Country Status (4)

Cited By (7)

Families Citing this family (1)

Citations (2)

• 1968
  • 1968-08-26 US US755377A patent/US3531301A/en not_active Expired - Lifetime
• 1969
  • 1969-08-05 GB GB39069/69A patent/GB1217309A/en not_active Expired
  • 1969-08-22 CH CH1278269A patent/CH516648A/de not_active IP Right Cessation
  • 1969-08-25 BE BE737929D patent/BE737929A/xx unknown

Patent Citations (2)

Also Published As

Similar Documents