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
  • C23C18/1601—Process or apparatus
  • C23C18/1619—Apparatus for electroless plating
  • C23C18/1628—Specific elements or parts of the apparatus
  • C23C18/163—Supporting devices for articles to be coated
• • 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
  • C23C18/1601—Process or apparatus
  • C23C18/1619—Apparatus for electroless plating
  • C23C18/1621—Protection of inner surfaces of the apparatus
  • C23C18/1625—Protection of inner surfaces of the apparatus through chemical processes
• • 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
  • C23C18/1601—Process or apparatus
  • C23C18/1619—Apparatus for electroless plating
  • C23C18/1632—Features specific for the apparatus, e.g. layout of cells and of its equipment, multiple cells
• • 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
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1646—Characteristics of the product obtained
  • C23C18/165—Multilayered product
  • C23C18/1653—Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2046—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by chemical pretreatment
  • C23C18/2073—Multistep pretreatment
  • C23C18/2086—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/06—Suspending or supporting devices for articles to be coated
  • C25D17/08—Supporting racks, i.e. not for suspending

Definitions

• the art of metallizing plastics both for decorative and functional applications is undergoing rapid growth.
• the general method employed consists of chemically depositing on the plastic object a preliminary or initial conductive metallic coating, Whereafter it can be electroplated by known electro-chemical techniques as if the objects were made of metal.
• the successful application of the initial conductive metallic layer is of crucial importance for the subsequent successful electroplating of one or more layers of the same or different metal to build up a total metallic deposit of desired thickness and finish characteristics. Copper, nickel, chromium and sometimes cobalt are the metals most commonly applied to commercial articles in the automotive appliance, plumbing and related industries today.
• Step 1 Hang plastic articles to be plated on conveyor-carried plating racks and immerse articles and racks in organic solvent pretreatment 0 ution.
• Step A l Same as Step A. i
• Step 3 i Immerse racked articles in chromic-sulfuric acid etch solution.
• Step 4 Immerse racked articles in water and/or chrome reducing rinse.
• Step 5 Immerse racked articles in stannous chloridehydroehloric acid sensitizing solution.
• Step 6 Water rinse.
• Step 7 Immerse racked articles in palladium-ehloritie-hydrochloric acid activating solution.
• Step 9 Immerse activated plastic articles while still on rack in chemical plating solution containing a reducible salt of the metal to be initially deposited on the articles.
• Step 11 Immerse chemically plated articles while still on same racks in conventional electroplating solutions to electrodeposit one or more layers of the same or different plating metals to provide the final desired total thickness and external finish.
• compositions employed in the prior art cycle of operations are well known in the industry, including the chromic-sulfuric acid etch of Step 3, and the sensitizing, activating and chemical plating solutions of Steps 5, 7 and 9. See for example, US. Pat Nos. 2,430,- 581; 2,702,253; 2,766,138; 2,871,142 and 3,075,855. Further details of the organic solvent pretreatment, Step 1, are disclosed in copending U.S. appln. Ser. Nos. 654,901 now Pat. No. 3,486,361 and 717,006.
• Step 4 involves the removal of excess hexavalent chromium from the parts, following the etch treatment in Step 3, and depending on the plastic being plated and particulars of the subsequent plating procedures selected, may be simply a thorough water rinse or a chrome-kill solution of phosphoric acid or a surfactant solution of the type disclosed in copending appln. Ser. No. 758,589. In some instances the separate sensitizing and activating operations of Steps 5 and 7 are replaced by a colloidal palladium-tin chloride activator solution of the type disclosed in copending US.
• the principal object of this invention to provide a method of so treating the racks that the plastic sheathed portion does not become plated, yet plating of the articles themselves is in no Way adversely affected.
• a further object of the invention is to provide a method which may be incorporated directly in the normal plating cycle and be compatible with such cycle.
• the invention here disclosed provides a method that permits a continuous plating operation to be employed for both chemical and electrodeposition portions of the overall plating cycle without reracking of the articles at any time throughout the cycle.
• Such continuous uninterpreted sequence of process operations, from the initial step of mounting the parts on the rack to the final step of unloading the finished plated parts from the rack, is especially important in high speed automated plating operations.
• hexavalent chromium ions -i.e. Cr
• inclusion of chromium ions in the plastic surface may be accomplished in numerous ways, this can be simply accomplished by soaking the racks in an acidic aqueous solution rich in chromic oxide, thereby diifusing hexavalent chromium from solution into the plastic sheathing of the rack.
• Such an operation can be readily incorporated directly in the sequence of steps through which a rack is advanced by the conventional conveyor in traversing a complete cycle of operations in the plating system.
• Nylon parts are mounted on a vinyl plastic coated rack which has been previously soaked for 5 minutes in a solution containing 6 pounds of chromic acid per gallon equivalent to 45% by weight at 140 F. using a plating cycle as hereinabove described, with the exception of eliminating Step 3 and inserting the antiplate treatment of the racks, Step A, ahead of Step 1.
• Parts are successfully plated by first depositing an initial layer of copper or nickel in the electroless or chemical plating portion of the cycle, followed by nickel and/or chromium plating in the electroplating portion of the cycle, all without re-racking.
• Step A comprises immersing the rack and supported articles in an aqueous solution containing 4 pounds of chromic acid per gallon (approximately 33% by weight) for a period of 30 seconds at 120 F. No plating of the plastic coating of the racks occurs, while complete coverage of the ABS parts is accomplished.
• Step A involves the same type of anti-plate composition as Step A but in this particular example the solution contains 1.5 pounds of chromic acid per gallon (approximately 16% by weight), and the plastic coated rack and parts are immersed in it for 2 minutes at 110 F. Following this, the process is resumed at Step 3 and continues with the balance of the procedure as outlined. This results in complete electroplate coverage of the polypropylene parts with no plating on the plastic coated rack.
• the plastic coating employed commercially is commonly a PVC (polyvinyl chloride) base resin material which can be applied by dipping the racks in a solution of such material and either evaporating a solvent carrier if such is used or otherwise curing the polymer material to form an adherent film or coating on the rack.
• the method of the present invention is likewise applicable to plating racks coated with polypropylene sheathing, provided the articles to be plated are not also polypropylene, and when treated in accordance with the invention, such sheathing will not acquire a metal plate in traversing through the metallizing operations described.
• a polypropylene sheathed rack used in supporting nylon parts following the procedure of Example 1 results in complete plating of the parts with no plating of the rack.
• ABS parts are mounted on polypropylene sheathed racks and processed as in Example 2. Again complete metal coverage of the parts is obtained with no deposit of metal on the racks.
• EXAMPLE 7 Polysulfone parts supported on vinyl plastic coated racks are processed in the same manner as in Example 3 above, using the same chromic acid concentration, time and temperature conditions as in the aforesaid example. Complete plating of the parts is obtained with no rack plating.
• the treatment produces a distinctive green-brown coloration of the rack sheathing due apparently to adsorption of hexavalent chromium, and it is readily observed that the freedom from rack plating is strongly dependent on the degree of coloration.
• Step A comprises immersing the rack and supported articles in a mixed chromic-sulfuric acid solution having a high Baum in which the hexavalent chromium ion content is only about 1.4% by weight while the sulfuric acid is about Even when using an excessive processing time in Step A of several minutes and a temperature of around F., rack plating readily occurs. It is also noted that the characteristic deep green-brown coloration of the plastic coating, which results in each of the previous examples after processing in Step A or Step A, is not obtained in this case.
• EXAMPLE 9 A further modification of the procedure outlined in Example 8, in which the hexavalent chromium ion concentration in Step A is raised to 12-14% by weight, while the sulfate (sulfuric acid) concentration is reduced to 40-50%, produces a noticable decrease in rack plating and may in some cases provide acceptable operating conditions where the plating activator employed subsequently is reasonably selective, and/or where the plastic material of the parts being plated is of the relatively more easily platable type.
• the characteristic green-brown coloration of the plastic rack coating is observable, though substantially lighter in color than that obtained in Examples 1 through 6.
• the hexavalent chromium ion must be present in the anti-rack plating solution at a minimum concentration of about (by weight), but at this level, it will generally be necessary to employ longer treatment times and higher solution temperatures. Optimally it is in the range of 16%, as seen from Example 3, but may go as high as (Example 1) or even to saturation (about 52% by weight in straight aqueous solution).
• the straight aqueous chromic acid solution gives best results and is preferred in most instances, but sulfate ion can be present provided its concentration is not in excess of by weight and preferably this should be kept below 40%, as seen by Example 9.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• Inorganic Chemistry (AREA)
• Chemically Coating (AREA)
• Electroplating Methods And Accessories (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25119950

Family Applications (1)

Country Status (7)

Cited By (6)

• 1968
  • 1968-12-02 US US780567A patent/US3592744A/en not_active Expired - Lifetime
• 1969
  • 1969-08-19 GB GB41403/69A patent/GB1222046A/en not_active Expired
  • 1969-09-08 ES ES371593A patent/ES371593A1/es not_active Expired
  • 1969-10-07 FR FR6934194A patent/FR2024974A1/fr not_active Withdrawn
  • 1969-10-09 BE BE740018D patent/BE740018A/xx unknown
  • 1969-11-21 DE DE1958519A patent/DE1958519B2/de active Pending
  • 1969-11-28 NL NL6917886A patent/NL6917886A/xx unknown

Also Published As

Similar Documents