Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/42—Electroplating: Baths therefor from solutions of light metals
  • C25D3/44—Aluminium

Definitions

• This invention relates to the electroplating of aluminum on metallic substrates.
• electrolyte systems are aluminum organometallic complex compounds used in conjunction with onganoaluminum compounds; solutions of an aluminum salt in an organic solvent, such as ethyl ether; organic complexes of aluminum halohydrides; molten salt systems containing anhydrous aluminum halides; an alkali metal chloride and an alkali metal fluoride; and baths consisting essentially of an aluminum halide and the reaction product of benzene with an alkyl halide.
• organic solvent such as ethyl ether
• organic complexes of aluminum halohydrides such as ethyl ether
• molten salt systems containing anhydrous aluminum halides
• an alkali metal chloride and an alkali metal fluoride an alkali metal fluoride
• baths consisting essentially of an aluminum halide and the reaction product of benzene with an alkyl halide.
• the present invention provides an improved method for electroplating a metallic substrate with aluminum in which an electrically conductive organoaluminum complex is utilized as the electrolyte, and an alkyl halide compound is used as a deposit modifier.
• an electrically conductive organoaluminum complex is utilized as the electrolyte
• an alkyl halide compound is used as a deposit modifier.
• organoaluminum complexes can be utilized, and the alkyl halide compound utilized as a deposit modifier may be any compound of the formula RX, where R is an alkyl radical and X is selected from the group consisting of chloride, bromine, and iodine.
• the deposit modifier is included in the electrolyte system in an amount of from about 1 weight percent to about 10 weight percent.
• the electrolyte is maintained at a temperature of from about 0 C. to about 100 C. during the electroplating of the substrate, and current densities of from about 1 ma./cm. to about 1 ampere/cm. can be utilized.
• a high purity aluminum anode is preferably used.
• An object of the invention is to provide a smooth, shiny aluminum plating on a metallic substrate by an electroplating process.
• a more specific object of the invention is to provide a deposit modifier for use with organoaluminum complex 3,672,965 Patented June 27, 1972 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
• the metals plated with aluminum by the process of this invention can be substantially any dissimilar metal such as steel, copper, iron, lead, tin, zinc, brass or bronze.
• the metal is shaped to correspond to an article which it is desired to aluminum plate, and is made the cathode positioned within the cell for immersion in the electrolyte bath.
• the anode employed consists of aluminum which is preferably of relatively high purity to avoid undesirable alloying in the plate which is deposited, unless such alloying should be desired, in which event an aluminum alloy can be usefully employed as the anode.
• the electrolyte bath used in the invention consists essentially of an electrically conductive organoaluminum complex containing from about 1 weight percent to about 10 weight percent, based on the total weight of the electrolyte system, of a deposit modifier of the formula RX, where R is an alkyl radical, and X is selected from the group consisting of chloride, bromine and iodine.
• organoaluminum complexes which are electrically conductive and thus suitable for use in the invention are lower aluminum trialkyl metallic complexes of the formula MeX-2AlR where Me is a metal-preferably an alkali metal, X is halogen, and R is a lower alkyl radical containing from 1 to 5 carbon atoms; lower aluminum dialkyl metallic complexes of the formula MeX-AlR X', where Me, X and R have the meanings set forth above, and X is halogen which may be identical to, or different from, X; and complexes of the formula MeAlR X where Me, R and X have the meanings set forth above, and x is an integer of from 0 to, and including, 4.
• Etherate complexes of organoaluminum compounds are also electrically conductive and suitable.
• etherate complexes a wide variety of others may be utilized, such as ethyl ether, propyl ether, butyl ether, octyl ether, etc.
• alkali metal aluminum alkyl halide complexes are preferred. These compounds have the formula MeAlR X as defined above. Sodium aluminum ethyl trichloride functions especially well in conjunction with the alkyl halide deposit modifiers hereinafter described in greater detail.
• the deposit modifier utilized in the electrolyte system is selected from the group consisting of alkyl chlorides, alkyl bromides and alkyl iodides.
• the alkyl radical though not so limited, is preferably of straight chain configuration, and preferably contains from 2 to 8 carbon atoms.
• useful deposit modifiers include ethyl chloride, propyl bromide, octyl iodide, iso-butyl chloride, and tertiary amyl bromide.
• the modifier constitutes from about 1 wieght percent to about 10 weight percent of the total weight of the electrolyte system, and preferably from about 1 weight percent to about 5 3 weight percent is employed, and is distributed evenly throughout the organoaluminum complex.
• 6,13 dichlorethyl ether may be used in fgfigtfigfi f l small amounts to improve the smoothness and hardness 0 un pos Clancy, Remarks on plating of the plating.
• percent The electroplating bath is maintained at temperatures X 82 Very ssywhich are, in general, above that required to maintain 323%, ⁇ ? 3% i b the electrolyte in a molten, or relatively low viscosity x 98 3 state (where a diluent is used).
• the upper temperature 5 241x10 96 limit is dictated by the decomposition temperature of the Although certain preferred embodiments of the invem complex.
• organoalummum complex course widely variable, and their selection will be i containmg afiecnye amount of an alkyl dependent upon the electrolyte used, the amount, if any, deposlt having theflformula Where of diluent used, the temperature of the bath, the electrode R is an f i radlcal X 15 selected q spacing and the specific type of plating desired.
• grfmp conilstmg of q bromme Iodine considerations and their effect upon voltage and current said elefimcauy conductwe t, density requirements are well understood in the art.
• the 40 Flex bemg seleqed from the group consisting of current densities utilized should, in general, however, cmpunds,havmg the formula Mex'zAlks range from about 1 ma./cm. to about I ampere/0m Pounds having the formula MBX'AIRZX and It may also be stated as a general proposition that it is Pounds hav1ng,th formula M where desirable, in most instances, to use the highest current is a m t X halogen R is a lower alkyl radical densities possible for economic reasons. Fontammg from 1 to 5 carbon Fltoms, and x is an The following working examples will serve to further Integer of from!
• the first run is a control run since is maintained at a temperature of from about to the system did not include any deposit modifier in the about dul'iug the Passage of electric current electrolyte system.
• a Pyrex glass tween said electrodes. cell having a volume of 50 ml. was utilized, and a Aprocess as definedin claim 1 wherein said organemedium-grade, glass-fritted disk was used for separating aluminum eomPieX has the formula x (4x) the anode compartment from the cathode compartment.
• e is an alkali metal
• R is a loWer aikyl'radieal The distance of separation of the electrodes was 2 inches.
• a process as defined in claim 1 wherein the current terns, and with the imposed electrical conditions identidensity of the electric current passed between the electrodes is from about 1 ma./cm. to about 1 ampere/cm. at the cathode surface.
• alkyl halide modifier is present in the electrolyte in an amount of from about 1 weight percent to about 10 weight percent of the total weight of the electrolyte system.
• organealnminum complex is sodium aluminum ethyl trichloride.
• organoaluminum complex has the formula MeAlR X where Me is an alkali metal, R is a lower alkyl radical containing from 1 to 5 carbon atoms, X is halogen, and x is an integer of from 0 to, and including, 4.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electrolytic Production Of Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (3)

Cited By (7)

• 1970
  • 1970-06-29 US US50883A patent/US3672965A/en not_active Expired - Lifetime
• 1971
  • 1971-06-25 DE DE19712131672 patent/DE2131672A1/de active Pending
  • 1971-06-28 FR FR7123534A patent/FR2096567A1/fr not_active Withdrawn

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