Classifications

• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47K—SANITARY EQUIPMENT NOT OTHERWISE PROVIDED FOR; TOILET ACCESSORIES
  • A47K13/00—Seats or covers for all kinds of closets
  • A47K13/02—Seats or covers for all kinds of closets of plastic materials
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/06—Other polishing compositions
  • C09G1/08—Other polishing compositions based on wax
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated

Definitions

• the method of this invention for electrodepositing a corrosion-resistant chromium plate on the surface of a metal may comprise forming on the surface of said metal an adherent thin film of a preferably organic, hydrogen-acceptor, film-forming composition, and electroplating a chromium plate onto said metal bearing said film.
• This invention relates to chromium plating. More specifically it relates to a novel process for obtaining deposits particularly characterized by their high resistance to corrosion.
• decorative chromium plating may be effected by various techniques. Although the prior art processes and the decorative plate produced thereby may be satisfactory for many purposes, platers have long appreciated that they were less than fully satisfactory. Specifically although it has long been desired to quickly produce decorative plate possessing a microcrack structure, it has not heretofore been possible to accomplish this in less than 12-16 minutes. Furthermore the prior art processes have not permitted attainment at low current density of thin chromium plate characterized by its microcrack or microporous structure and resulting high resistance to corrosion.
• the method of this invention for electrodepositing a corrosion-resistant chromium plate on the surface of a metal may comprise forming on the surface of said metal an adherent thin film of a preferably organic, hydrogen-acceptor, film-forming composition, and electroplating a chromium plate onto said metal bearing said film.
• the basis metals which may be treated by the process of this invention may include metals such as iron, steel, brass, bronze, copper, zinc, aluminum, magnesium, nickel, etc.
• the preferred basis metal which may be plated may be steel, zinc, or brass, and preferably steel, zinc, or brass which has been plated with a plate of nickel, typically preceded by a first plate of copper.
• the basis metal preferably bearing a nickel plate, may be cleaned as by cathodically treating in an alkaline cleaner and rinsing in water prior to further treatment.
• the sotreatment metal may be dried or it may be further treated as 1s.
• the sotreated metal may be treated with an organic, hydrogen- 3,464,899 Patented Sept. 2, 1969 acceptor, film-forming composition.
• organic, hydrogen-acceptor, film-forming compositions permit attainment of the novel results hereinafter set forth.
• These compositions may be characterized by their ability to readily accept, i.e., to react with, hydrogen (particularly in the form of nascent hydrogen) in the presence of activated metal catalyst. They may be characteristically considered as hydrogen overvoltage poisons, i.e., when they are added to a system evolving hydrogen at a cathode, a higher potential is necessary to continue the hydrogen evolution at the same rate.
• They may be particularly characterized by their ability to raise the hydrogen overvoltage of a standard hydrogen electrode typically by at least about 0.20 volt. This may be observed by electrolyzing a solution which is one molar in acetic acid and one molar in sodium acetate at a current of 30 milliamps over an 8.25 cm. steel cathode. It will be found that the hydrogen overvoltage may be raised by at least about 020- volt when the composition is added in amount of saturation up to 0.0232 molar, q.v. Duwell, E.J., Jour. Electrochem. Soc., vol. 109, pp. 1013-1017 (1962).
• compositions used in practice of the process of this invention may be found to possess a high degree of adherence to and/ or adsorption on the basis metal cathode, particularly during the initial period (i.e., the first few seconds) of chromium plating.
• the preferred composition may be formed from at least one material selected from the polymer-forming group consisting of acrylate, acrylonitrile, butadiene and styrene. These compositions may be used in the form of monomers or preferably in the form of polymers. Typical compositions may be formed from inertly substituted materials including isoprene, i.e., 2-methylbutadiene, etc. Preferred compositions may include polymers and derivatives of acrylonitrile such as polyacrylonitrile and acrylic rubber, polymers of butadiene'including natural rubber (i.e., poly-Z methylbutadiene), and polymers of styrene including polystyrene.
• Copolymers such as butadienestyrene, butadiene-acrylonitrile, or acrylonitrile-butadienestyrene may be used.
• Modified polymers including modi fied butadieue-acrylonitrile may be employed wherein the acrylouitrile residue in the molecule may have been hydrolyzed to the acrylic acid or salt, i.e., the --CN groups may have been hydrolyzed to the -COOH group.
• a preferred composition may include methyl acrylate or ethyl styreneacrylonitrile together with a fatty acid emulsifier having a pH of 9.5 and an average particle size of about 400 Angstrom units (such as that sold by B. F. Goodrich under the trademark Hycar 1577);
• a latex containing a carboxylated copolymer of acrylonitrile-butadienestyrene together with alkyl aryl sulfonate anionic detergent having a pH of 8.0 and an average particle size of about 1200 Angstrom units such as that sold by B. F. Goodrich under the trademark Hycar 1570-X20;
• a butadiene-styrene copolymer containing a fatty acid emulsifier having a pH of 10.0 and having an average particle size of 600 Angstrom units such as that sold under the trademark Naugatex 2006 by Naugatuck Chemical 00.
• a butadiene-acrylonitrile-carboxylic modifier latex i.e., a polymer wherein the CN groups of the nitrile have been hydrolyzed to COOH groups
• an anionic emulsifier having a pH of 8.5 and an average particle size of about 1800 Angstrom units (such as that sold under the trademark Chemigum 520 by Good year Co.);
• a latex of styrene-butadiene such as that sold under the trademark SBR-2000 by B. F. Goodrich C0.
• compositions may be in the form of a latex in aqueous medium having a concentration of 0.001%60%, say 0.05%.
• the preferred medium may be natural rubber latex which is an aqueous dispersion of 3% of rubber, i.e., predominantly Z-methylbutadiene.
• organic, hydrogen-acceptor, film-forming, monomeric compositions which may be employed may include acetylenic compounds, i.e., compounds containing a CEC group such as phenyl acetylene; heptyne-l; heptadiyne-1,7; hexyne-3; 2,S-dimethyl-3-hexyne-2,5-diol; propargyl malondiamide; hexyn-5-ol; hexyne-Z; etc.
• acetylenic compounds i.e., compounds containing a CEC group such as phenyl acetylene; heptyne-l; heptadiyne-1,7; hexyne-3; 2,S-dimethyl-3-hexyne-2,5-diol; propargyl malondiamide; hexyn-5-ol; hexyne-Z;
• Suitable hydrogen-acceptor, film-forming monomeric compositions which may be employed may include sulfur compounds including: sulfur; carbon disulfide; dicyclopentamethylene thiuram monosulfide; dicyclopentamethylene thiuram disulfide; dicyclopentamethylene thiuram tetrasulfide; 2,5 dimercapto-l,3,4-thiadiazole; phenyl-Z-mercaptobenzimidazol; piperidine pentamethylene dithiocarbamate; dibenzothiazyl dimethyl thiol urea; o-mercaptobenzoic acid; diethyldithiocarbamic acid (Na salt); tetramethyl thiuram disulfide; tetrabutyl thiuram disulfide; o-mercaptosuccinnic acid; 2 mercaptothiazoline; 2 mercaptoethanol; bis(2-hydroxyethyl)dithiocarbamic acid (K salt); bis
• illustrative hydrogen-acceptor, film-forming compositions which may be employed may include: 2- nitrobenzene arsonic acid; arsenous acid; p-(phenyl selenyl)aniline; ethylene dicyclohexanol; hippuric acid; perthiocyanic acid (as Na salt); antimony oxide Sb O and arsenic oxide AS203.
• the hydrogen-acceptor, monomeric, film-forming composition When employed in practice of this invention, it may preferably be employed in appropriate solution, typically of 0.005% in concentration up to saturation. Sulfur, if used, may be dissolved in isopropanol. Other compositions may be dissolved, suspended, etc., in appropriate medium typically water, alcohols such as methanol, ethanol, propanol, etc., hydrocarbons such as benzene, xylene, toluene, etc.
• the composition may be deposited onto the metal by cathodic treatment.
• arsenous acid, arsenic oxide, antimony oxide, etc. may be deposited by cathodizing the metal in a solution (e.g., of sulfuric acid) containing these materials.
• the organic, hydrogen-acceptor, film-forming composition is a latex of the polymer-forming group supra consisting of acrylate, acrylonitrile, butadiene, and styrene, by the use in the body of composition of a lyophilic protective colloid.
• Typical of such colloids may be gelatin, agar, gum tragacanth, karaya gum, ethyl cellulose, alginates, methyl ether of cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, pectin, etc. They may be added to the latex in amount of 0.005%10% or more.
• a typical composition may include methyl ether of cellulose (Methocel brand) in amount of 4 g./l. in an aqueous latex containing 7.5% ethyl acrylate polymer.
• Treatment of the basis metal may include dipping, spraying, electrolytically treating, swabbing, electrophoretically depositing, or dabbing the composition onto the basis metal.
• this may be effected by dipping the metal in a body of the latex.
• the metal surface may be maintained in contact with the composition at 10 C.50 0, say 20 C. for 1-60, say 5 seconds or longer and then withdrawn from contact.
• the time may be very short.
• the rate of introduction to the body should be less than about 10 centimeters per minute.
• the metal surfaces bearing the films formed from the composition in latex form may be rinsed with water. Rinsing may remove the excess of composition and leave a film on the surface. These films may be dried to a uniform layer (that may be a monomolecular film) prior to rinsing.
• compositions when applied to the metal surface, they may form a film.
• This film may be more-or-less continuous, i.e., substantially uniformly distributed on the entire surface of the metal.
• sulfur the sulfur may be uniformly but discontinuously distributed over the entire surface.
• other compositions e.g., a natural rubber latex
• the rubber may form a very thin and substantially continuous film.
• a film may have a thickness of -2000, say 400 Angstrom units and typically it may be a monomolecular film.
• the films, which may be invisible to the naked eye, remaining on the metal surface may be characterized by their high degree of adsorption and their adherence.
• the so-developed film may preferably be cathodically treated, i.e., maintained as cathode for 1-60 seconds, say 30 seconds preferably in acid solution, typically 0.5%- 10%, say 2% by weight aqueous solutions of sulfuric acid.
• the cathode current density may be 0.5-8 a.s.d., say 4 a.s.d.
• the metal surface bearing the film may then be placed in a chromium bath and chromium plating may be initiated.
• the film may gradually during 3-180 seconds, typically 5-10 seconds be dissolved, dissipated, or etched off the cathode.
• the dissolution of the film may initiate at selected spots more-or-less uniformly distributed over the surface of the cathode at which the initial deposit of chromium may form.
• Substantially the entire film may be removed from the metal surface by the action of the evolving hydrogen at the cathode, and reaction with the chromium plating solution.
• Chromium plating may be effected at temperatures of 30 C.-60 C., say 50 C., and 5-50, say'30 a.s.d. for 0.5-15, say 1-9 minutes from a bath containing 100-500 g./l., say 250 g./l. of chromic acid and 1-5 g./l., say 2.5 g./l. of sulfate ion, typically derived from sodium sulfate.
• Other components including other chromium plating catalysts, e.g., fluoride or silicofiuoride, self-regulating compositions, fume suppressants, etc., may be present.
• the chromium plate prepared by the process of this invention may be particularly characterized by its bright decorative appearance, its high corrosion resistance, and by its microcracked or microporous structure in a thin layer. When this plate is formed in decorative thickness, it may be found that it is characterized by unexpectedly superior properties.
• novel deposit It is a particular characteristic of the novel deposit that it does not, in contrast to prior art plate deposited directly on the basis metal, acquire the stress pattern of the basis metal. Rather it acquires a low stress which is characteristic of the novel deposited plate.
• the novel deposit is unexpectedly characterized by excellent corrosion resistance at very low thickness, typically as'low as 0.1 micron and simultaneously by a microcrack pattern attained at thickness as low as 0.25-0.75 micron, say 0.3 micron, not heretofore attainable.
• the unexpected ability of this novel process to permit attainment of the noted crack pattern at such low thickness is particularly outstanding.
• the plate is normally characterized by presence of fine cracks, typically in amount of 20- 800 or higher, say 400 per centimeter. Even at thicknesses below which a crack pattern is attained, the chromium possesses an unusual microporosity which during corrosion testing develops into a disconnected microcrack pattern in the forms of stars or crowfeet.
• This novel product when tested for corrosion as conducted under ASTM Specification B368-61T (CASS- Test) and B-117-62 (neutral salt spray) may be found to be substantially superior to a standard chromium plate of the same thickness when prepared by conventional methods.
• the novel chromium plate of this invention may be characterized by its unique combination of low thickness, as low as 0.1-0.75 micron, commonly 0.3 micron, and its fine crack pattern in thickness as low as 0.25 micron.
• the chromium deposit may be characterized by a plurality of holes each typically of diameter of 0.01-0.2 micron, say q 04 micron and spaced at a distance from each other of 50-200, say 100 microns.
• the plate may include (as demonstrated by testing in the CASS test followed by copper plating in the standard Dupernell test, to reveal crack structure) a plurality of nonconnected, nonintersecting, very fine attenuated crack lines, each 1-4 microns, say 2 microns long and radiating from the said holes.
• each hole may have less than about 5 crack lines radiating therefrom; most commonly 3 cracks may be present in the form of a star or a crowfoot.
• the number of holes present in this form may be 1000-4000, say 2000 per square centimeter.
• the crack pattern which develops may include a plurality of intersecting microcracks, typically in amount of 20-800 per centimeter or higher, say 400 per centimeter.
• the novel chromium plate of this invention which may be particularly characterized'by its crack pattern of typically 20-800 cracks per centimeter in decorative thickness of 0.25-0.75 micron, may be found to possess unexpectedly superior corrosion-resistant properties in these decorative thicknesses.
• a decorative thickness of, e.g., 0.25 micron the novel plate is completely satisfactory while a control plate of the same thickness produced by prior art techniques is totally unsatisfactory with respect both to appearance of the chromium plate and attack of the basis metal.
• novel chromium plate of this invention which also may be unexpected characterized by microporosity in thickness as low as 0.1 micron may be found to possess unexpectedly superior corrosion resistant properties in these decorative thicknesses.
• a decorative thickness of, e.g., 0.125 micron the novel plate is satisfactory while a control plate of the same thickness produced by prior art techniques is totally unsatisfactory with respect to appearance of the chromium plate and attack of the basis metal.
• this novel plate may possibly be related to the hydride content of the initial layer of chromium deposit.
• chromium hydride may be codeposited with chromium during electrodeposition, and the stress in the chromium deposit may arise from the conversion of this hydride to chromium metal and the simultaneous release of hydrogen. Cracking in chromium deposits may appear at this time because the newly formed chromium lattice is smaller than the lattice of the deposited chromium hydride.
• the novel process of this invention appears to permit increase in the hydrogen overvoltage during the initial stages of deposition so that a larger proportion of hydride is formed.
• the initial stress which causes cracking may occur sooner, i.e., when the deposited plate is thinner.
• the nickel plated basis metal was treated in manner generally similar to that set forth in the standard example except that in the step there designated as step (f), the lower portion of the panel was treated in the manner set forth in Table I.
• the number of cracks per centimeter was determined for the upper or control portion of the plate and for the lower or experimental portion of the plate.
• the number of cracks per centimeter for the control was determined by measuring across a line generally perpendicular to the plurality of parallel gross cracks which characterized the substrate on which the control is deposited. These Y- or grosscracks reflect the surface structure of the basis metal rather than that of the microcrack pattern; and in fact no microcrack pattern was observed in the control areas.
• the number of cracks for the experimental was determined by measuring along a randomly positioned line.
• synthetic polymer latex (B. F. Goodrich Co. SEE-2000 latex) formed from styrene-butadiene, ml. distilled water and ml. acetone.
• Hycar 1552 meduim acrylonitrile type latex
• a nickel plated panel was treated in the standard manner supra'through steps (e).
• step (f) the lower 25 mm. of the panel was dipped into-a 20% by volume solution of an acrylate (B. F. Goodrich Hycar 2600 X94). Then the panel was water rinsed andplated 'at 48 C.
• Samples of the control panel and the experimental panel were each independently chromium plated in a first chromium plating bath containing 190 g./l. CrO 1.03 g./l. SO and 1.64 g./l. SiF (from potassium silicofluoride) or in a second bath containing 240 g./l. CrO 0.9 g./l. SO and 1.9 g./l. SiF Plating in each case was effected at 43 C. and 15 a.s.d.
• Another set of parts were treated as before and plated in the second bath supra but with a higher current of 300 amperes for the nine minutes.
• the thickness range was from about 0.25 microns in the recesses to about 5 microns on the protuberances.
• the crack density was found to be about 1000 cracks per centimeter on the protuberances of the experimental part.
• the parts showed no corrosion (rating of 10) both in the recesses and where the thickness was greater, after 76 hours CASS testing.
• the novel product is characterized by the unique combination of microcrack pattern at the unusually low decorative thickness of less than about 1 micron. It is also apparent from Table V, and the example using parts, that at very low chromium thicknesses where continuous chromium cracking does not occur, outstanding corrosion protection is still attained. It will be further apparent that the novel plate of this invention may be deposited in greater thickness in the typical decorative range up to about 5 microns or more as illustrated by the parts plated at the greater chromium thicknesses, but that the advantages herein disclosed are peculiarly outstanding at lower thicknesses.
• said hydrogen-acceptor, film-forming composition is an acetylenic compound selected from the group consisting of heptyne-l; heptadiyne-1,7; hexyne-B; 2,5-dimethyl-3- hexyne-2,5-diol; propargyl malondiamide; hexyne-S-ol; and hexyne-Z.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Health & Medical Sciences (AREA)
• Public Health (AREA)
• Electroplating Methods And Accessories (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Laminated Bodies (AREA)

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Cited By (2)

Citations (9)

• 1964
  • 1964-04-24 US US362457A patent/US3464899A/en not_active Expired - Lifetime
• 1965
  • 1965-04-22 ES ES0312109A patent/ES312109A1/es not_active Expired
  • 1965-04-22 CH CH556765A patent/CH478920A/de not_active IP Right Cessation
  • 1965-04-22 GB GB17107/65A patent/GB1110412A/en not_active Expired
  • 1965-04-23 DE DE1965M0064991 patent/DE1496909A1/de active Pending
  • 1965-04-23 SE SE05332/65A patent/SE334274B/xx unknown
  • 1965-04-23 NL NL6505220A patent/NL6505220A/xx unknown

Patent Citations (9)

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