Metal Plating Of Substrates

Abstract

Substrates, particularly plastics, are plated with metals by pretreatment of the substrate with phosphorus sesquisulfide in an organic solvent to deposit phosphorus sesquisulfide at the surface, followed by containing the treated surface with a metal salt or complex thereof, to form a metal-phosphorus-sulfur compound. The resulting treated surface is either conductive or is capable of catalyzing the reduction of a metal salt to produce a conductive surface. Such conductive surfaces are readily electroplated by conventional techniques.

Parent Case Text

REFERENCE TO PRIOR APPLICATION

This is a continuation-in-part of application Ser. No. 855,037, filed Sept. 3, 1969, and now abandoned.

Description

BACKGROUND OF THE INVENTION

There is a rapidly increasing demand for metal plated articles, for example, in the production of low cost plastic articles that have a simulated metal appearance. Such articles are in demand in such industries as automotive, home appliance, radio and television and for use in decorative containers and the like. Heretofore, the metal plating of plastics and the like has required many process steps, and generally such processes have been applicable to only one or a few related substrates. It was particularly surprising to find that plastics and the like could be plated with metal through the use of phosphorus sesquisulfide.

It is an object of this invention to provide a simple process for the metal plating of plastics. Another object of the invention is to provide a process that is applicable to the plating of many different substrates. A further object of the invention is to provide articles having an adherent metal coating that is resistant to peeling, temperature cycling and corrosion. Such coatings are electrically conductive whereby static charges may be readily dissipated from the surfaces. The metal coatings further serve to protect the articles from abrasion, scratching and marring, reduce their porosity and improve their thermal conductivity. The process of this invention can be used for unidirectional mirrors and the like; water and liquid collecting devices and the like; protective coatings on houses, cars, boats, power line poles, street lights and the like; and in thermal control of clothing, houses and the like; and the like.

SUMMARY OF THE INVENTION

This invention provides a process which comprises forming a metal-phosphorus-sulfur compound at the surface of a substrate to render the surface susceptible to conventional electroless plating and/or electrolytic plating. More particularly, this invention provides a process which comprises subjecting a substrate to phosphorus sesquisulfide so as to deposit phosphorus sesquisulfide at the surface and thereafter contacting the thus-treated surface with a solution of a metal salt or complex thereof to form a metal-phosphorus-sulfur compound. In one aspect of the invention, the treated surface is subjected to electroless metal plating to deposit an electroless conductive coating on the surface. Thereafter, the article is electroplated so as to deposit an adherent metal coating of the desired thickness on the electroless conductive coating.

Also in accordance with the invention, there is provided an article having a metal-phosphorus-sulfur compound adherently formed at the surface of the substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The process of this invention is applicable to substrates, such as plastics and to other substantially nonmetallic substrates. Suitable substrates include, but are not limited to, cellulosic and ceramic materials such as cloth, paper, wood, cork, cardboard, clay, porcelain, leather, porous glass, asbestos, cement, and the like.

Typical plastics to which the process of this invention is applicable include the homopolymers and copolymers of ethylenically unsaturated aliphatic, alicyclic and aromatic hydrocarbons such as polyethylene, polypropylene, polybutene, ethylenepropylene copolymers; copolymers of ethylene or propylene with other olefins, polybutadiene; polymers of butadiene, polyisoprene, both natural and synthetic, polystyrene and polymers of pentene, hexene, heptene, octene, 2-methyl-propene, 4-methyl-hexene-1, bicyclo (2.2.1.)-2-heptene, pentadiene, hexadiene, 2,3-dimethylbutadiene-1,3,4-vinylcyclohexene, cyclopentadiene, methylstyrene, and the like. Other polymers useful in the invention include polyidene, indenecoumarone resins; polymers of acrylate esters and polymers of methacrylate esters, acrylate and methacrylate resins such as ethyl acrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl methacrylate and methyl methacrylate; alkyd resins; cellulose derivatives such as cellulose acetate, cellulose acetate butyrate, cellulose nitrate, ethyl cellulose, hydroxyethyl cellulose, methyl cellulose and sodium carboxymethyl cellulose; epoxy resins; furan resins (furfuryl alcohol or furfural ketone); hydrocarbon resins from petroleum; isobutylene resins (polyisobutylene); isocyanate resins (polyurethanes); melamine resins such as melamine-formaldehyde and melamine-urea-formaldehyde; oleoresins; phenolic resins such as formaldehyde, phenolic-elastomer, phenolic-epoxy, phenolic-polyamide, and phenolic-vinyl acetals; polyamide polymers, such as polyamides, polyamide-epoxy and particularly long chain synthetic polymeric amides containing recurring carbonamide groups as an integral part of the main polymer chain; polyester resins such as unsaturated polyesters of dibasic acids and dihyroxy compounds, and polyester elastomer and resorcinol resins such as resorcinol-formaldehyde, resorcinol-furfural, resorcinol-phenol-formaldehyde, resorcinal-polyamide and resorcinol-urea; rubbers such as natural rubber, synthetic polyisoprene, reclaimed rubber, chlorinated rubber, polybutadiene, cyclized rubber, butadiene-acrylonitrile rubber, butadiene-styrene rubber, and butyl rubber; neoprene rubber (polychloroprene); polysulfides (Thiokol); terpene resins; urea resins; vinyl resins such as polymers of vinyl acetal, vinyl acetate or vinyl alcohol-acetate copolymer, vinyl alcohol, vinyl chloride, vinyl butryal, vinyl chloride-acetate copolymer, vinyl pyrrolidone and vinylidene chloride copolymer; polyformaldehyde; polyphenylene oxide; polymers of diallyl phthalates and phthalates; polycarbonates of phosgene or thiophosgene and dihydroxy compounds such as bisphenols, thermoplastic polymers of bisphenols and epichlorohydrin (trade named Phenoxy polymers); graft copolymers and polymers of unsaturated hydrocarbons and an unsaturated monomer, such as graft copolymers of polybutadiene, styrene, and acrylonitrile, commonly called ABS resins, ABS-polyvinyl chloride polymers, recently introduced under the trade name of Cycovin; and acrylic polyvinyl chloride polymers, known by the trade name of Kydex 100.

The polymers of the invention can be used in the unfilled condition, or with fillers such as glass fiber, glass powder, glass beads, asbestos, talc and other mineral fillers, wood flour and other vegetable fillers, carbon it its various forms, dyes, pigments, waxes and the like.

The substrates of the invention can be in various physical forms, such as shaped articles, for example, moldings, sheets, rods, and the like; fibers, films and fabrics, and the like.

In the first step of the preferred process of the invention, the substrate is treated with phosphorus sesquisulfide. The phosphorous sesquisulfide can be utilized as a liquid or dissolved in a solvent. Suitable solvents or diluents for the phosphorus sesquisuflide are solvents that dissolve the phosphorus sesquisulfide and which preferably swell the surface of a plastic without detrimentally affecting the surface of the plastic. Such solvents include the halogenated hydrocarbons and halocarbons such as chloroform, methyl chloroform, phenyl chloroform, dichloroethylene, trichloroethylene, perchloroethylene, trichloroethane, dichloropropane, ethyl dibromide, ethyl chlorobromide, propylene dibromide, monochlorobenzene, monochlorotoluene and the like; aromatic hydrocarbons such as benzene, toluene, xylene, ethyl benzene, naphthalene and the like; ketones such as acetone, methyl ethyl ketone, and the like; acetic acid; acetic acid-trichloroethylene mixtures; carbon disulfide; and the like.

When a solution of phosphorus sesquisulfide is employed in the process, the solution concentration is generally in the range from about 0.0001 weight percent of phosphorus sesquisulfide based on the weight of the solution up to a saturated solution, and preferably from about 0.5 to about 2.5 percent. Prior to contacting the substrate with the phosphorus sesquisulfide, liquid or solution, the surface of the substrate should be clean. When a solution is used, the solvent generally serves to clean the surface. A solvent wash may be desirable when liquid phosphorus sesquisulfide is employed. The phosphorus sesquisulfide treatment is generally conducted at a temperature below the softening point of the substrate, and below the boiling point of the solvent, if the solvent is used. Generally, the temperature is in the range of about 0.degree. to 135.degree. Centigrade, but preferably in the range of about 15.degree. to 75.degree. Centigrade. The contact time varies depending on the nature of the substrate, the solvent and temperature, but is generally in the range of about 1 second to 1 hour or more, preferably in the range of about 1 to 20 minutes.

It has been found that subjection of the substrate to the solvent hereinbefore disclosed prior to subjection to the phosphorus sesquisulfide has a very marked effect on the adhesion of the final metal plated article. The temperature of the solvent is directly related to the adhesion realized. Generally, the temperature is in the range of about 30.degree. Centigrade to the boiling point of the solvent, preferably about 50.degree. to 100.degree. and higher than the temperature of the solution of phosphorus sesquisulfide, if a solution is used. The contact time varies depending on the nature of the substrate, solvent and temperature but preferably is 1 to 15 minutes.

As a result of the first treatment step, the phosphorus sesquisulfide is deposited at the surface of the substrate. By this is meant that the phosphorus sequisulfide can be located on the surface, embedded in the surface and embedded beneath the surface of the substrate. The location of the phosphorus sesquisulfide is somewhat dependent on the action of the solvent on the surface if one is used.

Following the first treatment step, the substrate can be rinsed with a solvent, and then can be dried by merely exposing the substrate to the atmosphere or to inert atmospheres such as nitrogen, carbon dioxide, and the like, or by drying the surface with radiant heaters or in a conventional oven. Drying times can vary considerably, for example, from 1 second to 30 minutes or more, preferably 5 seconds to 10 minutes, more preferably 5 to 120 seconds. The rinsing and drying steps are optional.

In the second treatment step of the process of the invention, the phosphorus sesquisulfide treated substrate is contacted with a solution of a metal salt or a complex of a metal salt, which is capable of reacting with the phosphorus to form a metal-phosphorus-sulfur compound. The term metal-phosphorus-sulfur compound used herein, means the metal-phosphorus-sulfur coating which is formed at the surface of the substrate. Without being limited to theory, the metal-phosphorus-sulfur compound may be an ionic compound or a solution (alloy). The metals generally employed are those of Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table. The preferred metals are copper, silver, gold, chromium, vanadium, tantalum, cadmium, tungsten, molybdenum, and the like.

The metal salts that are used in the invention can contain a wide variety of anions. Suitable anions include the anions of mineral acids such as sulfate, chloride, bromide, iodide, fluoride, nitrate, phosphate, chlorate, perchlorate, borate, carbonate, cyanide, and the like. Also useful are the anions of organic acids such as formate, acetate, citrate, butyrate, valerate, caproate, stearate, oleate, palmitate, dimethylglyoxime, and the like. Generally, the anions of organic acids contain one to 18 carbon atoms.

Some useful metal salts include copper sulfate, copper chloride, silver nitrate, nickel chloride and nickel sulfate.

The metal salts can be complexed with a complexing agent that produces a solution having the basic pH (>7). Particularly useful are the ammonical complexes of the metal salts, in which one to six ammonia molecules are complexed with the foregoing metal salts. Typical examples include NiSO.sub.4 .sup.. 6NH.sub.3, Ni(C.sub.2 H.sub.3 OO).sub.2.sup. . 6NH.sub.3, CuSO.sub.4.sup. . 6NH.sub.3, CuCl.sub.2.sup. . 6NH.sub.3, AgNO.sub.3.sup. . 6NH.sub.3, NiSO.sub.4.sup. . 3NH.sub.3, CuSO.sub.4.sup. . 4NH.sub.3, NiCl.sup.. 6NH.sub.3 Ni(NO.sub.3).sub.2.sup. . 4NH.sub.3, and the like. Other useful complexing agents include quinoline, amines and pyridine. Useful complexes include compounds of the formula MX.sub.2 Q.sub.2 wherein M is the metal ion, X is chlorine or bromine and Q is quinoline. Typical examples include: CoCl.sub.2 Q.sub.2, CoBr.sub.2 Q.sub.2, NiCl.sub.2 Q.sub.2, NiBr.sub.2 Q.sub.2, CuCl.sub.2 Q.sub.2, CuBr.sub.2 Q.sub.2 and ZnCl.sub.2 Q.sub.2. Useful amine complexes include the mono-(ethylenediamine). bis-(ethylenedamine)-, tris(ethylenediamine)-, bis(1,2-propane diamine)-, and bis-(1,3-propanediamine)-complexes of salts such as copper sulfate. Typical pyridine complexes include NiCl.sub.2 (py).sub.2 and CuCl.sub.2 (py).sub.2 where py is pyridine.

The foregoing metal salts and their alcohol, are used in ionic media, preferably in aqueous solutions. However, nonaqueous media can be employed such as alcohols, for example, methyl alcohol, ethyl alcohol, butyl alcohol, heptyl alcohol, decyl alcohol and the like. Mixtures of alcohol and water can be used. Also useful are ionic mixtures of alcohol with other miscible solvents of the types disclosed hereinbefore. The solution concentration is generally in the range from about 0.1 weight percent metal salt or complex based on the total weight of the solution up to a saturated solution, preferably from about 1 to about 10 weight percent metal salt or complex. The pH of the metal salt or complex solution can range from about 4 to 14, but is generally maintained in the basic range, i.e., greater than 7, and preferably from about 10 to about 13.

The step of contacting the phosphorus sesquisulfide treated substrate with the solution of metal salt is generally conducted at a temperature below the softening point of the substrate, and below the boiling point of the solvent, if one is used. Generally, the temperature is in the range of about 30.degree. to 110.degree. Centigrade, preferably from about 50.degree. to 100.degree. Centigrade. The time of contact can vary considerably, depending on the nature of the substrate, the characteristics of the metal salts employed and the contact temperature. However, the time of contact is generally in the range of about 0.1 to 30 minutes, preferably about 5 to 10 minutes.

Depending on the conditions employed in the two treatment steps, the duration of the treatments, and the nature of the substrate treated, the resulting treated surface may be either (1) conductive, such that the surface can be readily electroplated by conventional techniques, or (2) non conductive. In the latter instance the treated surface contains active or catalytic sites that render the surface susceptible to further treatment by electroless plating process that produce a conductive coating on the plastic surface. Such a conductive coating is then capable of being plated by conventional electrolytic processes.

The treated substrates that result from contacting the phosphorus-sesquisulfide treated surface with a metal salt solution can be subjected to a process that has become known in the art as electroless plating or chemical plating. In a typical electroless plating process, a catalytic surface is contacted with a solution of metal salt under conditions in which the metallic ion of the metal salt is reduced to the metallic state and deposited on the catalytic surface. The use of this process with the products of this invention relies upon the catalytic metal sites deposited on the surface as a result of the treatment with the solution of metal salt or complex of this invention. A suitable chemical treating bath for the deposition of a nickel coating on the catalytic surface produced in accordance with the process of the invention can comprise, for example, a solution of nickel salt in an aqueous hypophosphite solution. Suitable hypophosphites include the alkali metal hypophosphites such as sodium hypophosphite and potassium hypophosphite, and the alkaline earth metal hypophosphites such as calcium hypophosphite and barium hypophosphite. Other suitable metal salts for use in the chemical treating bath include the metal salts described hereinbefore with respect to the metal salt treatment of the phosphorus-treated substrate of the invention. Other reducing media include formaldehyde, hydroquinone and hydrazine. Other agents, such as buffering agents, complexing agents, and other additives are included in the chemical plating solutions or baths.

The treated substrate of the invention that are conductive can be electroplated by the processes known in the art. The article is generally used as the cathode. The metal desired to be plated is generally dissolved in an aqueous plating bath, although other media can be employed. Generally, a soluble metal anode of the metal to be plated can be employed. In some instances, however, a carbon anode or other inert anode is used. Suitable metals, solutions and condition for electroplating are described in Metal Finishing Guidebook Directory for 1967, published by Metals and Plastics Publications, Inc. Westwood, N. J.

The following examples serve to illustrate the invention but are not intended to limit it. Unless specified otherwise, all temperatures are in degrees centigrade and parts are understood to be expressed in parts by weight.

EXAMPLE I

A sample of polypropylene sheet was immersed for 2 minutes in a solution containing 2 percent by weight phosphorus sesquisulfide in a mixture of 700 milliliters of trichloroethylene, 700 milliliters of perchloroethylene and 14 milliliters of ethanol at 70.degree. Centigrade. The sample was thereafter immersed for 10 minutes in a solution of copper pyrophosphate at 60.degree. Centigrade. The copper pyrophosphate solution was prepared by adding the following ingredients to water followed by dilution to 6 liters of solution and filtering: 223 grams copper oxide, 2,660 grams tetrapotassium pyrophosphate trihydrate, 123 grams oxalic acid, 40 grams of 30 volume percent aqueous ammonia, and 61.2 grams of 70 percent by volume aqueous nitric acid. A red conductive copper-phosphorus-sulfur coating was produced on the surface of the polypropylene. Thereafter, layers of nickel and chrome were adherently bound to the polypropylene by electrodeposition as follows: The article was plated in a bath of semi-bright nickel (Harshaw Co.) employed a current density of 50 amperes per square foot, followed by plating in a bath of bright nickel (Harshaw Co.) at 50 amperes per square foot current density and then plating in a chrome bath (Udylite Corp.) at 150 amperes per square foot current density.

EXAMPLES 2-14

Following the procedure of Example 1, a metal-phosphorus-sulfur coating was obtained on the following specified plastics by employing a 2 percent solution of phosphorus sesquisulfide in trichloroethylene and perchloroethylene followed by subjection of the thus-treated plastic to the specified metal salt baths. Table I specifies the plastic, metal salt bath and the appearance of the resulting metal-phosphorus-sulfur coating. ##SPC1##

EXAMPLE 15

A molded polypropylene plaque was immersed for 5 minutes in a 1 percent solution of phosphorus sesquisulfide in trichloroethylene at room temperature, rinsed with water and immediately subjected for 10 minutes in an aqueous solution containing nickel sulfate (0.063 mole per liter) and ammonia (2.5 moles per liter) maintained at 60.degree. Centigrade. After drying, the black plastic surface had a resistance of 10,000 ohms per centimeter.

EXAMPLE 16

A polypropylene plaque was immersed in a 50.degree. bath containing trichloroethylene for 15 minutes and then treated as in Example 15. The resistance of the resulting treated plastic surface was 3,000 ohms per centimeter. The sample was electroplated to give a 0.3-mil semi-bright nickel strike and 1.7-mil thickness of acid copper thereon. The adhesion was determined to be 10.0 pounds per inch.

EXAMPLE 17

An epoxy resin-glass fiber resin laminate was immersed for 5 minutes in a 1.3 percent solution of phosphorus sesquisulfide in methylene chloride at room temperature, dried in air for 10 seconds and then immersed for 10 minutes in an ammoniacal solution of nickel sulfate at 60.degree. Centigrade. The resistance of the black preplate was 5,000 ohms per centimeter. The laminate was thereafter electroplated.

EXAMPLES 18-26

A 2 percent solution of phosphorus sesquisulfide was prepared in the following specified solvents. Thereafter, samples of polypropylene, ABS, phenolic resin, epoxy resin, and polyvinyl chloride were immersed in the phosphorus sesquisulfide solution for 3 minutes at 50.degree. Centigrade and transferred to an ammoniacal nickel sulfate bath at 65.degree. Centigrade for 30 minutes. Each of the experiments were repeated replacing the nickel with a bath containing an ammoniacal solution of 5 percent of copper sulfate. In every instance, a metal-phosphorus-sulfur compound was formed.

Example Solvent __________________________________________________________________________ 18 Trichloromethane 19 Carbon tetrachloride 20 Trichloroethane 21 Benzene 22 Toluene 23 Turpentine 24 Decalin 25 Dimethylformamide 26 Dimethylsulfoxide __________________________________________________________________________

EXAMPLE 27

Following the procedure of Example 18, the following metal salts were employed in the metal salt bath to obtain a metal-phosphorus-sulfur compound: nickel chloride, nickel nitrate, nickel acetate, nickel formate, nickel citrate, silver nitrate, iron chloride and cobalt chloride.

EXAMPLE 28

Following the procedure of Example 18, the following substrates were provided with an adherent metal coating: novolac resin, cotton string, Teflon, cardboard, leather, rubber, masonite, ceramics, wood, Lexan (polycarbonate), nylon, polyacetyl, acrylics (plexiglass), and polystyrene.

EXAMPLE 29

An epoxy resin-glass fiber laminate was immersed for 5 minutes at room temperature in a 1 percent solution of phosphorus sesquisulfide dissolved in a 2:1 (by volume) solvent mixture of trichloroethylene and methylene chloride. After being rinsed in a water bath, the laminate was immersed for 15 minutes in an aqueous solution, at 65.degree. Centigrade, containing nickel sulfate (0.063 mole per liter) and ammonia (2.5 mole per liter). The sample was rinsed with water and then immersed in an aqueous electroless copper bath for 10 minutes at room temperature. The electroless copper bath had the following composition.

CuNO.sub.3 .sup.. 3H.sub.2 O 15 g. per liter NaHCO.sub.3 10 g. per liter Rochelle salt 30 g. per liter NaOH 20 g. per liter Formaldehyde (37%) 100 ml. per liter

After drying the sample was electroplated with 0.3-mil semi-bright nickel and 1.7 mil acid copper.

EXAMPLE 30

An epoxy resin-glass fiber laminate was treated as in Example 29 except that an electroless nickel bath instead of electroless copper was used. The electroless nickel bath had the following composition.

NiSO.sub.4 28.9 g. Sodium citrate 8.9 g. Sodium hypophosphite 12.0 g. Magnesium sulfate 7.8 g. Water 800 ml.

The sample was immersed in the bath at 85.degree. Centigrade for 10 minutes, and then electroplated as described in Example 29.

EXAMPLE 31

A set of four polypropylene discs were immersed in a 1 percent solution of phosphorus sesquisulfide in perchloroethylene for 15 minutes at about 32.5.degree. C. and then for 15 minutes in a 70.degree. C. aqueous copper chloride-ethylene diamine solution. A second set of four discs was subjected to the same procedure except that they were immersed for 2 minutes in perchloroethylene at 65.degree. C. before subjection to the phosphorus sesquisulfide. Both sets of treated discs were thereafter identically washed, dried and electroplated to provide 3 mils of Watt's nickel thereon. The average maximum adhesion of the first set of discs was determined to be 4.4 pounds per inch and the average maximum adhesion of the second set was found to be 32.8 pounds per inch.

Similar results are obtained when other solvents such as benzene, acetone and the like are employed as a treatment step prior to subjection to the phosphorus sesquisulfide,

EXAMPLE 32

Example 16 was repeated except that ABS was employed in place of the polypropylene and perchloroethylene was employed in place of the trichloroethylene.

Various changes and modifications can be made in the process and products of this invention without departing from the spirit and scope of the invention. Various embodiments of the invention disclosed herein serve to further illustrate the invention but are not intended to limit it.

Claims

I claim:

1. A process which comprises subjecting a substrate to phosphorus sesquisulfide to deposit phosphorus sesquisulfide at the surface of the substrate and thereafter subjecting the phosphorus sesquisulfide treated surface to a solution of a metal salt or complex thereof so as to form a metal-phosphorus-sulfur coating, wherein said metal is selected from the Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table.

2. A process wherein the treated substrate resulting from the process of claim 1 is subjected to electroless metal plating to deposit an electroless conductive coating on the treated substrate.

3. A process wherein the substrate resulting from the process of claim 2 is electroplated to deposit an adherent metal coating on the electroless conductive coating.

4. A process wherein the treated substrate resulting from the process of claim 1 is electroplated to deposit an adherent metal coating on the treated substrate.

5. A process which comprises subjecting a plastic to phosphorus sesquisulfide to deposit phosphorus sesquisulfide at the surface of the plastic and thereafter subjecting the phosphorus sesquisulfide treated substrate to a solution of metal salt or complex thereof which so as to form a metal-phosphorus-sulfur coating, wherein said metal is selected from Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table.

6. The process according to claim 5 wherein the plastic is subjected to a solution of phosphorus sesquisulfide dissolved in a solvent.

7. The process according to claim 6 wherein the solvent is a halogenated hydrocarbon.

8. The process according to claim 7 wherein the solvent is trichloroethylene.

9. The process according to claim 7 wherein the solvent is methylene chloride.

10. The process of claim 6 wherein the metal of said metal salt is selected from the group consisting of nickel and copper.

11. The process of claim 6 wherein the metal salt complex is a complex of ammonia, amines, quinolines or pyridines.

12. The process of claim 6 wherein the plastic is polypropylene, the phosphorus sesquisulfide is employed as a solution of phosphorus sesquisulfide dissolved in trichloroethylene, and the metal salt complex is a complex of nickel.

13. The process of claim 6 wherein the plastic is an epoxy resin, the phosphorus sesquisulfide is employed as a solution of phosphorus sesquisulfide dissolved in a mixture of trichloroethylene and methylene chloride, and the metal of the metal salt complex is nickel.

14. A process wherein the treated plastic surface resulting from the process of claim 6 is subjected to electroless metal plating to deposit an electroless conductive coating on the treated plastic surface.

15. A process wherein the plastic surface resulting from the process of claim 14 is electroplated to deposit an adherent metal coating on the electroless conductive coating.

16. A process wherein the treated plastic surface resulting from the process of claim 6 is electroplated to deposit an adherent metal coating on the treated plastic surface.

17. An article having a metal-phosphorus-sulfur coating adherently formed at the surface of a plastic, wherein said metal is selected from the Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table.

18. The plastic articles of claim 17 wherein at least one component of the plastic is a thermoplastic polymer.

19. The plastic article of claim 17 wherein at least one component of the plastic is polyproylene.

20. The plastic article of claim 17 wherein at least one component of the plastic is polyethylene.

21. The plastic article of claim 17 wherein at least one component of the plastic is polyvinyl chloride.

22. The plastic article of claim 17 wherein at least one component of the plastic is a graft copolymer of polybutadiene, styrene and acrylonitrile.

23. The article of claim 17 having an adherent electroless conductive coating deposited on the metal-phosphorus-sulfur coating.

24. The article of claim 23 having an adherent metal coating electrolytically deposited on the electroless conductive coating.

25. The plastic article of claim 24 wherein at least one component of the plastic is a thermoplastic polymer.

26. The plastic article of claim 24 wherein at least one component of the plastic is polypropylene.

27. The plastic article of claim 24 wherein at least one component of the plastic is polyethylene.

28. The plastic article of claim 24 wherein at least one component of the plastic is polyvinyl chloride.

29. The plastic article of claim 24 wherein at least one component of the plastic is a graft copolymer of polybutadiene, styrene and acrylonitrile.

30. The article of claim 17 having an adherent metal coating electrolytically deposited on the metal-phosphorus-sulfur coating.

31. The plastic article of claim 30 wherein at least one component of the plastic is a thermoplastic polymer.

32. The plastic article of claim 30 wherein at least one component of the plastic is polypropylene.

33. The plastic article of claim 30 wherein at least one component of the plastic is polyethylene.

34. The plastic article of claim 30 wherein at least one component of the plastic is polyvinyl chloride.

35. The plastic article of claim 30 wherein at least one component of the plastic is a graft copolymer of polybutadiene, styrene and acrylonitrile.

36. A process wherein a plastic is subjected to a solvent and thereafter treated by the process of claim 5.

37. The process of claim 36 wherein the solvent is trichloroethylene and the plastic is polypropylene.

38. The process of claim 36 wherein the solvent is perchloroethylene and the plastic is a graft copolymer of polybutadiene, styrene and acrylonitrile.

39. The process of claim 1 wherein the metal salt complex is an ethylene diamine complex of a copper salt.

40. The process of claim 5 wherein the metal salt complex is an ethylene diamine complex of a copper salt.