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

• the present invention relates to a process for the chemical nickel-plating of non-metallic articles by means of a bath containing nickeland hypophosphite ions, and a complex former for stabilizing the bath and for accelerating the precipitation of nickel on the surface of the article.
• a process for the chemical nickel-plating of articles treated to have a catalytic surface has been described in German Patent 1,077,940, which process essentially comprises treating the articles by means of a bath containing nickeland hypophosphite ions.
• catalytic as used in this content is intended to mean that at least the surface material of the article is capable of catalyzing the oxidation-reduction reaction between the nickel ions and the hypophosphite ions, that causes the nickel to precipitate on the catalytic surface.
• the bath is primarily required to contain the reactants in specific proportions, i.e. the bath is required to contain:
• Ni++ and H PO --ions in a quantitative ratio between i 0.25 and 1.60;
• T PO in an absolute concentration between 0.15 and 1.20 mols/liter
• the bath is required to contain so-called activating agents formed of saturated, aliphatic dicarboxylic acids having 3 to 6 carbon atoms, such as succinic acid.
• the reaction is ultimately required to be carried out at a temperature be tween 95 and 99 C. .As the applicability of the above process is limited to the chemical nickel-plating of articles having a catalytic" surface, it cannot simply be used for metallizing nonmetallic articles, as proposed in the present invention.
• the surfaces of nonmetallic articles can be treated to receive, for example, a metallic nickel plating.
• the article is first purified to activate its surface which is roughened thereafter, and pre-treated by means of a palladium salt solution, for example a palladium chloride solution.
• the palladium chloride is reduced to palladium and the article so activated is immersed thereafter in a bath containing nickeland hypophosphite ions.
• the palladium chloride solution suitable for surface activation preferably has a concentration of 35 milligrams per liter.
• hypophosphite is the reducing agent, it is advantageous to dissolve it in the metallization bath in a concentration of 0.225 mol/liter.
• the palladium-activated article should preferably be nickel-plated first with the use of a dilute preliminary bath containing Ni++ and H PO in a molar concentration of about 0.25 and, after formation of a continuous nickel plating, the article should be treated further by means of a bath customary in nickel-plating.
• the preliminary nickel-plating bath is said to avoid the induction period usually needed for the nickel to precipitate on the dispersed palladium particles as the growthpromoting nuclei, and to improve the bond strength of the nickel plating.
• the preliminary nickel-plating bath may contain, for example, the following components:
• the preliminary bath used in carrying out the nickelplating should have a pH-value between 5.5 and 7 and a temperature between 10 and 30 C.
• the bath may be mixed with an ordinary,
• short-chain, saturated aliphatic monocarboxylic acid such as acetic, butyric or valeric acid, which is added in salt form.
• the disadvantage associated with the use of a preliminary bath in carrying out the nickel-plating is seen to reside in the relatively low precipitation velocity of the nickel on the surface of the article to be plated therewith, in the suggested temperature range of 10 to 30 C., so that a layer not thicker than 1 to 1.2 is produced per hour. In the event that the temperature is increased to a value higher than 30 C., the preliminary nickel-plating bath is found to undergo spontaneous self-decomposition with the resultant formation of colloidal nickel, and to become useless. h
• German Patent 1,077,940 mentioned above is not applicable to the direct nickel-plating'of nonmetallic articles, for example plastics.
• the reason is that thermoplastics, for example, undergo plastic deformation at a temperature of -99 C. needed for the nickel-plat lng bath, and that the precipitated layer of nickel would be found to have no more than a poor bond strength.
• the present process of the present invention for the chemical nickel-plating of non-metallic articles which are (a) purified by mechanical and/or chemical treatment,
• a buffer substance and is maintained at a pH-value' between 3 and 9, comprises nickel-plating the said articles in the presence of nitrilo-trismethylene-phosphonic acid, at a temperature between 30 and 70 C.
• the bath used for carrying out the nickel-plating contains the hypophosphite ions in a concentration of about 0.25 to 1 mol per liter, which is convenient. It is also 3 advantageous to provide for a molar ratio of Ni++-ions to H PO -ions of about 0.2 to 1.6 in the bath.
• the bath used for carrying out the nickel plating contains Ni++-ions and nitrilo-trismethylene-phosphonic acid in a molar ratio of about 0.7 to 2.0.
• a bath maintained at a pH- value of 3 to 9, preferably to 6, causes the nickel to precipitate under especially favorable conditions.
• Phosphate buffer containing, per liter, 0.02 to 0.1 mol, preferable 0.067 mol Na HPO -6H O, and 0.002 to 0.01 mol, preferably 0.0067 mol KH PO has proved very suitable for maintaining the above pH-values.
• the phosphate buffer is found to participate in the stabilization of the bath, at the pH-valnes indicated above.
• pH-values and temperatures higher than those specified above accelerate the precipitation of nickel, but they reduce the stability of the bath and impair the bond strength of the nickel plating
• a stabilizer such as lead sulfide or lead acetate, which is used in a proportion of 2 milligrams per liter.
• the bath temperature which should be conveniently used at a given pH-value, Where the bath is found to have a good stability and the nickel plating precipitated on the surface of the articles to be metallized is found to have the necessary bond strength.
• the precipitated nickel plating has a thickness of about 3 to 3.5
• the nickel plating which is really formed of a nickel-phosphorous alloy containing 5 to 15% phosphorus, adheres very tenaciously to non-metallic articles of which the surface has been activated in convenient manner, prior to the metallizationl
• the nickel plating precipitated by the process of the present invention can be used for reinforcing galvanic nickel, polished nickel and polished chromium coatings, or may receive a ductile copper coating as a first reinforcing coating.
• the steps of pre-treating the article to be plated in an attempt to activate its surface does not form part of the present invention.
• the activation can be achieved, for example, in the manner set forth in German Patent 1,182,015.
• the process of the present invention can be used for the nickel plating of non-metallic substances or articles, such as polypropylene or glass or Bakelite or plastics obtained by the graft-polymerization of acrylonitrile, butadiene and styrene. 7
• the bath of the present invention offers the following advantages:
• nitrilo-trismethylene-phosphonic acid means high precipitation velocity for the nickel at temperatures of the nickel-plating bath between 30 and 70 (3., so that non-metallic articles pretreated in convenient fashion, can be metallized more rapidly than heretofore.
• the bath used in carrying out the nickel-plating can be regenerated in customary manner by means of hypophosphite and nickel ions, for example by the process disclosed in German Patent 1,107,045.
• the regeneration is very easy to achieve as there is no need for cooling the bath liquid prior to the addition of the regenerating agent.
• Shaped plastics obtained by the graft polymerization of acrylonitrile, butadiene and styrene were chemically nickel-plated. Prior to being nickel-plated, they had been purified and degreased by means of an aqueous solution of a commercial wash-active substance, chemically roughened at 60 C. for 15 minutes with the use of chromo sulfuric acid and ultimately sensitized with an aqueous tin chloride solution in hydrochloric acid. Thereafter, the surface of the shapes had been activated by means of a PdCl solution in hydrochloric acid.
• the shaped plastics were nickel-plated by means of a nickel-plating bath prepared in accordance with the present invention, the bath containing:
• the bath was adjusted by means of sodium hydroxide solution to have a pH-value of 5.5, and heated to 55 C.
• a continuous, welladhering nickel plating was found to have precipitated on the shapes within a period of 15 seconds, which, after a further 3 minutes, was found to have a thickness of 3.5,.
• nickel-plating bath contains the hypophosphite ions in a concentration of about 0.25 to 1 mol per litter.

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=7229389

Family Applications (1)

Country Status (6)

Cited By (8)

Citations (7)

• 1966
  • 1966-08-06 DE DE1521350A patent/DE1521350C3/de not_active Expired
• 1967
  • 1967-07-10 CH CH978967A patent/CH480447A/de not_active IP Right Cessation
  • 1967-07-10 US US651968A patent/US3484282A/en not_active Expired - Lifetime
  • 1967-07-24 GB GB33958/67A patent/GB1131030A/en not_active Expired
  • 1967-07-27 NL NL6710406A patent/NL6710406A/xx unknown
  • 1967-08-04 BE BE702339D patent/BE702339A/xx unknown

Patent Citations (7)

Also Published As

Similar Documents