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
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/02—Coating starting from inorganic powder by application of pressure only
  • C23C24/04—Impact or kinetic deposition of particles
  • C23C24/045—Impact or kinetic deposition of particles by trembling using impacting inert media

Definitions

• This invention relates to a process for mechanically plating a metal on a substrate by application of mechanical forces to particulate malleable metals and mixtures and alloys thereof, typically termed "mechanical plating".
• promoter chemicals typically comprise unsaturated fatty acids and the like, film-forming materials and surfactants.
• the metallic coating may not be deposited in a controlled fashion since the proper chemical'environment would not be continually present during the entire plating cycle. Consequently, the conditions necessary to apply successive layers of well consolidated, adherent particles could not be uniformly maintained.
• Patent No. 3,531,315 While it has been desirable to utilize the processing techniques of Patent No. 3,531,315 because such are typically based on a non-chelating and more economical acid system, such has not heretofore been available for the production of heavy, dense coatings.
• a chemical promoter system capable of being used in conjunction with finely divided mechanical plating metal, water, and impact media in a mechanical plating process to provide heavy dense metallic coatings on articles.
• the promoter system comprises a flash promoter which comprises, per 9.29 m 2 (100 square feet) of plating surface area, up to about 400 grams of a strong acid or salt thereof, from about 20 to about 80 grams of a soluble salt of a metal which is more noble than the plating metal, an effective amount of a dispersant capable of dispersing the plating metal, and an effective amount of an inhibitor capable of inhibiting corrosion of the plating metal, together with a continuing promoter which comprises, per pound of finely divided mechanical plating metal, from about 60 to about 150 grams of a strong acid or salt thereof, from about 5 to about 20 grams of a soluble salt of a metal which is more noble than the plating metal, an effective amount of a dispersant capable of dispersing the plating metal, and an effective amount of an inhibitor capable of inhibiting
• the flash promoter during the mechanical plating process, provides a thin adherent flash coating on the articles to be plated, following which the continuing promoter is incrementally added to the process in conjunction with incremental additions of the finely divided mechanical plating metal until a heavy dense metallic coating is built up on the articles to be plated.
• the invention provides a process for mechanically plating a metal upon a substrate by applying to such plating metal in particulate form, mechanical force to produce adhesion of said plating metal to said substrate in the presence of one or more promoter chemicals comprising one or more acids and one or more surfactants, said plating metal being supplied in increments, said process being characterised by the following steps:
• the continuing promoter's function is to provide a proper chemical environment for the mechanical plating process to occur.
• The includes a proper pH such that the surfaces of the finely divided mechanical plating metal is clean, but there is insubstantial dissolution of the metal in the plating solution, to prevent agglomeration of the finely divided metal to insure a proper plating rate and uniform coating thicknesses. Therefore, the concentration of components in this promoter is dependent upon the quantity of finely divided mechanical plating metal to be deposited.
• Exemplary soluble salts of metals more noble than the finely divided plating metal include cadmium, lead, and preferably, tin, e.g., stannous chloride, stannous sulfate, stannous fluoborate, etc.
• this salt should be included at a concentration level of from about 20 to about 80 grams per 9.29 m 2 (100 square feet) of surface area to be plated, with about 30 grams being preferred.
• the concentration thereof should be from about 5 to about 20 grams per 453 g (pound) of finely divided plating metal charged during the incremental steps of the plating cycle, with about 10 grams being preferred.
• concentration of adhesion of the metallic plating is exhibited.
• the upper concentration limit is maintained in terms of economics, as opposed to functionality, the cost thereof becoming excessive relative to additional benefit provided thereby.
• the next component which is useful in this mechanical plating process is a strong acid or saltthereof.
• This acidity is typically utilized in the processing to remove metal oxides contained on the finely divided mechanical plating metal and the articles to be plated.
• Typical strong acid salts include potassium or ammonium bisulfate, sulfamic acid, etc., with the preferred being sodium bisulfate.
• the concentration of the acid salt or acid component can be included therein up to about 400 grams per 9.29 m 2 (100 square feet) of plating surface charged.
• the acid salt or strong acid should be utilized in a range of from about 60 to about 150 grams per 453 g (pound) of finely divided plating metal charged to the plating operation. While an acid salt is preferred, because same can act as a carrier for the other components of the promoter chemistry, sulfuric acid or other strong acids can also be utilized to provide acidity, as necessary, as mechanical plating occurs.
• the next component having utility in my invention is a dispersant, same being typically utilized to disperse the metal particles charged to the plating run to prevent their premature agglomeration.
• Materials capable of functioning effectively for dispersing the plating metal powders include polyoxyethylene glycols having a cloud point in a 1 percent aqueous solution below 100°C, such as "Carbowax” 20M (available from the Union Carbide Chemicals Company), or “Polyglycol E50,000” (available from the Dow Chemical Company); quaternary aliphatic ammonium salts such as "Arquad” S-2C (available from the Armour Industrial Chemical Company; proteinaceous materials such as "Technical Protein Colloids” No. 185,169, or 70 (available from Swift & Company); among other materials which are disclosed in U.S. Patent No. 3,531,315.
• additives which function as dispersants are typically related to both the specific acid and the specific finely divided plating metal involved.
• effective dispersants for zinc powder in sulfuric acid include “Carbowax” 20M and “Orzan” AH-3, which is a salt of a polymerized alkyl aryl sulfonic acid, commercially available from the Crown Zellerbach Company;
• dispersants for zinc or tin particles in hydrochloric acid include "Nalquat” G-8-11 (which is a hydrophilic heterocyclic adduct of a hydrophilic alkyl compound containing nitrogen groups, commercially available from Nalco Chemical Company).
• Many other examples could, of course, be cited.
• Whether a given component will function satisfactorily for dispersing specific plating metal particles in a specific acid can be determined by adding from about 0.25 to about 0.5 grams of the material to 250 milliliters of the acid plating solution in a 400 milliliter beaker, adding 10 grams of finely divided plating metal, stirring vigorously, and allowing the beaker and its contents to stand for 5 minutes. An effective dispersant will keep the plating metal in suspension, thereby rendering the acid plating solution opaque.
• the flash promoter can contain up to about 40 grams per 9.29 m 2 (100 square feet) of plating charge, with about 20 grams being preferred, while the continuing promoter can contain up to about 8 grams per 453 g (pound) of metal powder charged with about 3.5 grams being preferred.
• the next component having utility in my invention is an inhibitor, same being typically utilized to inhibit corrosion of the plating metal by the acidic component, thereby preventing undesirable gassing and allowing the plating metal to perform its intended function.
• the inhibitor component is capable of functioning itself as a dispersant, and the aforementioned dispersant is not necessary.
• optimum benefits have been found to be achieved by utilizing a dispersant in conjunction with an inhibitor.
• materials capable of functioning as an effective means for inhibiting the corrosion of at least some plating metal in at least some acid plating solutions are compounded cationic amine inhibitors, such as "Armohib” 25 (available from the Armour Industrial Chemical Company); cationic inhibitors such as Inhibitor GC (available from the Sinclair Mineral and Chemical Company); and other materials as are described in U.S. Patent No. 3,531,315.
• a preferred inhibitor is designated Additive "R”.
• Additive "R” is a product made as follows: to 23.4 grams of dehydroabietyl amine (Amine D, available from Hercules Chemical Company) was slowly added 7.5 grams of acetophenone, with stirring; 10 grams of 20 Be HCI solution in water was added slowly in the same manner. Next, 9.7 grams of 37% formaldehyde was added in small increments and the mixture refluxed intermittently at 80°C over a period of 3 days. At this point, 25.0 grams of acetone was added directly and 9.5 grams of 37% formaldehyde added incrementally, continuing to reflux for an additional 24 hours.
• a test to ascertain the effective inhibitor for a particular system can be undertaken utilizing the test indicated above relative to a dispersant.
• An effective corrosion inhibitor utilizing this test, will essentially prevent both gassing and clumping of the plating metal powder into tough balls.
• Additive "R” up to about 12 grams per 9.29 m 2 (100 square feet) of plating charge can be included in the flash promoter, with about 8 grams being preferred, and up to about 1.0 gram per pound of plating metal charged, with about 0.35 gram being preferred, has been found to provide satisfactory results in the continuing promoter.
• the optimum amount of a given dispersant or inhibitor is, of course, related to the specific system in which it is used. In general, however, large volumes of liquid, open barrels, or highly acidic conditions, typically require more inhibitor than small volumes of liquid, closed barrels, or less acidic conditions. Similarly, the optimum concentration of dispersant decreases as the pH rises or as the weight of plating metal particles decreases.
• the promoter chemistry as well as the plating metal additions are added at appropriate intervals during the plating cycle.
• the amount of plating metal added and the frequency of such additions are dependent upon the ultimate coating thickness desired and the size, weight, and geometry of the articles to be plated. Additionally, the ratio of articles to impact media, the size of the plating barrel, and rotational speed thereof can have an affect upon the number and frequency of such addition.
• the initial chemistry be provided in the flash promoter with subsequent chemical additions added as the continuing promoter along with the plating metal addition.
• the flash promoter is added to the plating mixture subsequent the preferred conventional deposition of copper on the articles to be plated. Then, a small amount of finely divided plating metal is introduced to provide a galvanomechanical deposit upon the articles, as is discussed in U.S. Patent No. 3,400,012.
• a sufficient quantity of plating metal to provide a predetermined thickness can be added to the plating mixture.
• the introduction rate of the metal powder to the plating mixture which is again dependent upon the aforementioned factors, will typically be 1/30 of the total plating metal quantity required, with an addition being every 1 to 1.5 minutes. With each addition of metal, the appropriate quantity of continuing promoter is added simultaneously therewith.
• the quantity of plating metal can be increased to about 1/12 the total amount thereof required, and each increment can be added at approximately 3 to 4 minute intervals, again with the corresponding quantity of necessary chemistry.
• the plating cycle can be continued for an additional 3 to 5 minutes at which time the plated articles can be rinsed, separated from the impact media and dried.
• lighter part types to be plated require fewer additions, over longer time periods, while heavier part types require increased additions ar more frequent intervals.
• a 525-kg (1,160-pound) load of 1.9 x 6.4 cm (4 by 2) inch) bolts having 21.6 m 2 (232 square feet) of plating surface was precleaned in an inhibited sulfuric acid-based cleaner containing surfactants and placed in a 1698-liter (60-cubic foot) multi-sided barrel having an angle of approximately 20° above horizontal rotating at 10 RPM's, together with an equal volume of glass beads of various sizes (4 parts 3.5 to 5 mesh, 2 parts 8-10 mesh, 1 part 14-30 mesh, and 1 part 40-70 mesh), the glass beads functioning as impact media.
• sufficient 24°C (75°F) water was added such that a puddle was formed having a width of 15 to 30 cm (6 to 12 inches) while the barrel was rotating, thereby providing a free flowing mixture.
• the metallic coating was found to have a uniform thickness by magnetic thickness testing, good appearance and excellent adhesion by conventional tape peel testing.
• the thickness was from 2.4 to 2.6 mils (60 to 65 ⁇ ).
• Example 1 was duplicated with the exception that the following mixture was added incrementally with the zinc powder:
• the thickness was measured and determined to be from 2.9 to 3.1 mils (72 to 78p).
• Example 1 was duplicated with the exception that the following mixture was utilized in incremental addition with the metallic zinc powder:
• the resultant coating exhibited excellent adhesion and uniform appearance.
• the thickness, as measured, was found to be 2.8 to 3.3 mils (70 to 82 ⁇ ).
• Example 1 A precleaned, as in Example 1, 200 pound load of 1.9 x 6.4 cm (i by 2 inch) bolts having 3.72 m 2 (40 square feet) of plating surface was placed in a 340 liter (12 cubic foot) multi-sided barrel having an angle of approximately 30° above horizontal rotating at 12 RPM's, together with an equal volume of glass beads of various sizes, as in Example 1.
• the resultant coating was found to have uniform appearance and excellent adhesion.
• the thickness as measured was 2.5 mils (62 ⁇ ).
• Example 1 A precleaned, as in Example 1, 6-pound load of 0.8 x 1.9 cm (5/16 by 3/4) inch bolts having 3225 cm 2 (500 square inches) of plating surface was placed in a 8.5-liter (0.3 cubic foot) open end multi-sided barrel having an angle of approximately 20° above horizontal rotating at 60 RPM's, together with an equal volume of glass beads of various sizes, as in Example 1. Then 24°C water was added to the mixture with 30 grams of an inhibited acid solution containing 99.7 parts 66° Be sulfuric acid and 0.3 part Additive "R" and allowed to mix for two minutes. To the barrel contents, 12.9 grams of a mixture containing 43.9 parts 66° Be sulfuric acid, 23.1 parts cupric sulfate pentahydrate, and 33.0 parts sodium chloride, were added to promote a copper deposit.
• the resultant coating was found to be uniform in appearance and had excellent adhesion.
• the thickness was determined to be 2.8 mils (70p).

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Chemically Coating (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=22527104

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (4)

Citations (1)

Family Cites Families (10)

• 1981
  • 1981-05-08 JP JP56501797A patent/JPS57500568A/ja active Pending
  • 1981-05-08 WO PCT/US1981/000642 patent/WO1981003292A1/en unknown
  • 1981-05-11 DE DE8181302092T patent/DE3172411D1/de not_active Expired
  • 1981-05-11 EP EP81302092A patent/EP0040090B1/en not_active Expired
  • 1981-05-12 CA CA000377432A patent/CA1171605A/en not_active Expired
  • 1981-05-12 ZA ZA00813160A patent/ZA813160B/xx unknown

Patent Citations (1)

Also Published As

Similar Documents

Legal Events