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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/02—Pretreatment of the material 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
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/56—After-treatment

Definitions

• ABSTRACT Aluminum plating according to which aluminum film formed has no cracks and pin-holes on its surface, a uniform thickness, excellent luster and is strongly bonded to the substrate can be attained by heat treating a substrate covered with aluminum at 400 C the melting point of aluminum for 10 seconds 30 minutes in an inert atmosphere said heat treatment being preceded by or followed by treating of the covered substrate with a surface treating agentcomprising active hydrogencontaining compound, oxygen or halogen and thereafter taking out thus treated substrate into the air.
• This invention relates to an aluminum plating process and more particularly it concerns a process for effecting excellent aluminum plating on a substrate by contacting a heated substrate with an alkyl aluminum compound to cause thermal decomposition of said alkyl aluminum.
• a substrate covered with aluminum is meant a substrate which has been covered with aluminum produced by thermal decomposition of an alkyl aluminum compound which is caused by contact of the heated substrate with the alkyl aluminum compound, but which has not yet been taken out into the air.
• the aluminum film plated on the substrate has cracks and pin-holes which cause deterioration of the corrosion resistance, the oxidation resistance at a high temperature and the electric characteristics. Furthermore, the thickness of aluminum film is not uniform, luster of the surface is extremely poor and the aluminum film tends to peel off when bended.
• One object of this invention is that a substrate covered with aluminum is heat treated at a temperature of not lower than 400C, but below the melting point of aluminum in an inert atmosphere and thereafter the thus treated substrate is taken out into the air
• a substrate covered with aluminum is contacted with a very small amount of a surface treating agent selected from active hydrogencontaining compounds, oxygen and halogens, then is heat treated at a temperature of not lower than 400 C, but below the melting point of aluminum in an inert atmosphere and thereafter is taken out into the air or that a substrate covered with aluminum is heat treated at a temperature of not lower than 400 C, but below the melting point of aluminum, then is contacted with a very small amount of a surface treating agent selected from active hydrogen-containing compound, oxygen and halogen and thereafter is taken out into theair.
• the aluminum film which has no cracks and pin-holes on its surface has uniform thickness, exhibits excellent surface luster and is bonded strongly to the substrate and is not peeled off therefrom can be obtained.
• Alkyl aluminum compounds used in this invention include any alkyl aluminu compounds capable of depositing aluminum by thermal decomposition. Among them, the following are preferable because they are easily thermally decomposed and are economical. That is, dialkyl aluminum hydride or trialkyl aluminum having alkyl groups of two 20 carbon atoms such as triethyl aluminum, diethyl aluminum hydride, trinormal propyl aluminum, triisopropyl aluminum, trinormalbutyl aluminum, dinorrnalbutyl aluminum hydride, triisobutyl aluminum, diisobutyl aluminum hydride, trinormalbenzyl aluminum, trinormalhexyl aluminum, trinormaloctyl aluminum, tri-2-ethylhexyl aluminum, di-2- ethylhexyl aluminum hydride, and tridecyl aluminum, or mixtures thereof.
• dialkyl aluminum hydride or trialkyl aluminum having alkyl groups of two 20 carbon atoms such as triethyl aluminum,
• the alkyl aluminum compound may be used together with a compound capable of producing a complex compound with the alkyl aluminum compound such as an alkali metal compound, an ether, a tertiary amine, a quaternary ammonium salt, etc., which are mentioned in U.S. Pat. Nos. 3,154,407 and 3,273,996 to attain plating of aluminum in high purity.
• a compound capable of producing a complex compound with the alkyl aluminum compound such as an alkali metal compound, an ether, a tertiary amine, a quaternary ammonium salt, etc., which are mentioned in U.S. Pat. Nos. 3,154,407 and 3,273,996 to attain plating of aluminum in high purity.
• alkyl aluminum compound may beused in admixture with an inert organic solvent such as hexane, heptane, octane, cyclopentane, cyclohexane, benzene, toluene, xylene, petroleum, paraffins, alkyl benzene, diphenyl, etc.
• an inert organic solvent such as hexane, heptane, octane, cyclopentane, cyclohexane, benzene, toluene, xylene, petroleum, paraffins, alkyl benzene, diphenyl, etc.
• Substrates to be plated include, for example, metals such as iron, steel, aluminum, copper, brass pottery, glass, organic and inorganic resins, etc.
• the substrate is preferably cleaned prior to plating.
• the substrate is heated to a temperature higher than thermal decomposition temperature of alkyl aluminum compound, preferably of 300 600 C and is contacted with plating solution or plating vapor.
• the substrate may be heated by known heating methods and e.g., resistance heating, induction heating, etc., may be employed depending upon kind or shape of the substrate.
• the induction heating is preferable for continuous heating of especially thin metal sheet.
• either one of the method according to which a heated substrate is contacted with a liquid alkyl aluminum compound and the method according to which a heated substrate is contacted with vapor of an alkyl aluminum compound may be used.
• Election of either one of these methods depends upon kind and shape of the substrate to be plated.
• the substrate may be covered with aluminum by thermal decomposition of an alkyl aluminum compound on a substrate by one time heating or by intermittent two or more heatings. The latter is especially preferable. Further, there is the case that the latter method does not necessitate heat-treating of a substrate covered with aluminum.
• the thermal decomposition may be carried out in the presence of a compound capable: of accelerating the thermal decomposition such as titanium chloride, titanium bromide, vanadium chloride, iron chloride, copper chloride, etc. which are mentioned in U.S. Pat. No. 3,306,732. Addition of said compound is useful especially for plating a substrate of low heat stability.
• a compound capable: of accelerating the thermal decomposition such as titanium chloride, titanium bromide, vanadium chloride, iron chloride, copper chloride, etc. which are mentioned in U.S. Pat. No. 3,306,732. Addition of said compound is useful especially for plating a substrate of low heat stability.
• the thermal decomposition is required to be carried out in an inert atmosphere, but no critical limitation is present in pressure for operation.
• the substrate covered with aluminum as mentioned above is then fed to a heat treatment step or is firstly contacted with a very small amount of a surface treating agent selected from the group consisting of active hydrogen-containing compounds, oxygen and halogen, and thereafter fed to the heat treatment step.
• the heat treatment in this invention is carried out by heating and keeping the substrate at a temperature of not lower than 400 C, but below the melting point of aluminum, preferably of 450 600 C.
• the heat treating temperature is lower than 400 C, good surface properties cannot be obtained and furthermore a long period of time is required for heat treatment. For example, with a substrate of iron, a reaction occurs between iron and aluminum and the aluminum film is apt to peel off.
• the aluminum heat treatment is effected in the presence of an inert gas or a molten salt.
• an inert gas or a molten salt usually, nitrogen, argon and helium are effectively used, but it should be noted that this invention is not limited to the use thereof.
• the heat treating time somewhat varies depending upon kind and shape of the substrate, thickness of aluminum film and heating temperature, but generally is seconds 30 minutes. However, with a substrate of iron, too long treating time causes a reaction between aluminum and iron to deteriorate the plate surface and hence industrially, the substrate is preferably kept for 20 seconds minutes.
• the substrate After completion of the heat treatment, the substrate is taken out into the air or firstly is contacted with a small amount of a surface treating agent selected from the group consisting of active hydrogen-containing compound, oxygen and halogen and thereafter taken out into the air.
• a surface treating agent selected from the group consisting of active hydrogen-containing compound, oxygen and halogen
• the contact of the substrate with a surface treating selected from the active hydrogen-containing compound, oxygen and halogen may be carried out before said heat treatment.
• a surface treating agent selected from active hydrogencontaining compound, oxygen and halogen before or after the heat treatment results in more excellent aluminum plating than that attained only by heat treatment.
• Illustrative of the active hydrogen-containing compounds to be contacted with the substrate covered with aluminum are compounds containing at least one substitutable hydrogen such as water, ammonia primary or secondary amine compounds, e.g., dimethyl amine, monobutyl amine, etc.; sulfides, e.g., hydrogen sulfide, ethyl thioalcohol, dodecyl thioalcohol, etc.; monoor poly-hydric alcohols, e.g., methanol, ethanol, isopropylalcohol, butanol, ethylene glycol, propylene glycol, glycerine, etc.; carboxylic acids, e.g., acetic acid, naphthenic acid, stearic acid, adipic acid, maleic acid, phthalic acid, etc.; and inorganic acids, e.g., hydrogen chloride, hydrogen fluoride, hydrogen bromide, nitric acid, etc.
• substitutable hydrogen such
• active hydrogen-containing compounds are used as a solution which contains 10 10,000 ppm, preferably 100 1,000 ppm (weight basis) of said compound dissolved in aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, alkyl benzene, etc., aliphatic hydrocarbons such as pentane, hexane, octane, decene, etc., and mixtures thereof or as an atmosphere of the active hydrogen-containing compound of 0.1 mmHg, preferably 0.1 10 mml-lg.
• aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, alkyl benzene, etc.
• aliphatic hydrocarbons such as pentane, hexane, octane, decene, etc.
• the substrate is contacted with said aromatic or aliphatic hydrocarbon containing 10 10,000 ppm, preferably 100 1,000 ppm (weight basis) of oxygen or is used as an oxygen atmosphere of 0.01 100 mmHg, preferably 0.1 80 mml-lg.
• halogens such as fluorine, chlorine, bromine, etc.
• they are used as a halogen atmosphere of 0.01 20 mmHg, preferably 0.1 10
• mmHg or as a solution containing 10 2,000 ppm of a halogen dissolved in a suitable solvent such as a paraffin.
• a suitable solvent such as a paraffin.
• Said treatment is carried out at 0 300 C, preferably 15 200 C.
• the method of this invention provides the following advantages as compared with the conventional method in which the substrate covered with aluminum is taken out without further treatments.
• the aluminum film on the substrate has no cracks and pin-holes on its surface, has a uniform thickness, exhibits excellent surface luster and is bonded strongly to the substrate.
• the substrate plated with aluminum in accordance with this invention has high corrosion resistance and oxidation resistance at a high temperature and excellent electric characteristics. Furthermore, the substrate plated can be subjected to metal surface treatment, such as known sealing treatment, stabilizaton treatment and alumite finishing. Due to these excellent characteristics the industrial value of this invention is extremely great.
• EXAMPLE 1 A steel sheet of 50 mm X 50 mm X 0.6 mm was washed with water and subsequently with alcohols and then dried. Thus treated steel sheet was used as a specimen.
• Said specimen was heated to 400 C in argon atmosphere and thereafter was dipped in 500 cc of an alkyl aluminum solution which comprises 81 percent by weight of diisobutyl aluminum hydride, 11 percent by weight of diethyl aluminum hydride, 5 percent by weight of triisobutyl aluminum, and 3 percent by weightpf triethyl aluminum at 20 C.
• an alkyl aluminum solution which comprises 81 percent by weight of diisobutyl aluminum hydride, 11 percent by weight of diethyl aluminum hydride, 5 percent by weight of triisobutyl aluminum, and 3 percent by weightpf triethyl aluminum at 20 C.
• the same procedure as mentioned above was repeated once more to effect aluminum plating. Subsequently, the specimen thus plated with aluminum was heated to 450 C in argon atmosphere. After the specimen was kept at that temperature for 5 minutes, it was cooled to room temperature in argon gas and then taken out into the air.
• substrate plated with aluminum has a film of 1.1 p. in thickness and has excellent luster of silver white.
• an acid resistance test was made by dipping in 500 cc of 25 weight percent aqueous nitric acid solution at 20 C said plated substrate which was covered by solid paraffin in a width of 10 mm around said substrate.
• substrate plated with aluminum has a film of 1.1 p. in thickness and its surface showed silver white.
• the same acid resistance test was made with this substrate. After lapse of 11 minutes, bubbles were generated and after lapse of 20 minutes the aluminum film on the substrate was nearly peeled off.
• EXAMPLE 2 The same specimen as in Example 1 and which was cleaned in the same manner as in Example 1 was employed in this Example. The treatment was carried out in argon atmosphere as in Example I. The specimen was pre-heated to 500C and was dipped in an alkyl aluminum solution having the same compositions as in Example 1, heated to 200 C.
• the steel sheet thus plated with aluminum had excellent luster of silver white and had'excellent surface properties.
• the average thickness of the aluminum film was 2.1 .u. determined by weight increased.
• the specimen was also subjected to the acid resistance test in the same manner as in Example 1. Even after lapse of 30 minutes, no bubbles were generated.
• the specimen prior to said heat treatment was cooled in argon and then taken out into the air.
• the steel sheet thus plated with aluminum had a grey color and little luster.
• the same acid resistance test as mentioned above was given to the specimen. After lapse of 5 minutes, generation of bubbles was observed.
• the specimen was similarly heated to 300 C in argon atmosphere and kept at that temperature for 5 minutes. Then, it was cooled in argon and taken out into the air. Thus obtained steel sheet plated with aluminumshowed grey color and had little luster. The specimen was subjected to the same acid resistance test as mentioned above. After lapse of 7 minutes, generation of bubbles was observed.
• EXAMPLE 3 A substrate covered with aluminum treated in the same manner as in Example 1 until the heat treatment step was contacted with 500 cc of hexane containing 0.01 percent by weight of water at 20 C for one minute and then taken out into the air.
• Said steel sheet was subjected to the same acid resistance test as in Example 1. Even after lapse of 50 minutes, generation of bubbles was not observed.
• the steel sheets were treated with 500 cc of hexane containing 0.01 percent by weight of ethanol, 500 cc of hexane containing 0.01 percent by weight of oxygen and argon atmosphere containing chlorine gas of 1 mmHg, respectively and they were taken out into the air.
• 500 cc of hexane containing 0.01 percent by weight of ethanol 500 cc of hexane containing 0.01 percent by weight of oxygen and argon atmosphere containing chlorine gas of 1 mmHg, respectively and they were taken out into the air.
• steel sheets plated with aluminum showed excellent luster of silver white and had extremely excellent surface properties.
• EXAMPLE 4 A substrate covered with aluminum in the same manner as in Example 1 was contacted with 500 cc of hexane containing 0.01 percent by weight of water at 20 C for one minute. Thereafter, it was heated to 500 C in argon atmosphere for 5 minutes and kept at that temperature. Then, the substrate was cooled to room temperature in argon gas and taken out into the air. Thus obtained steel sheet plated with aluminum showed excellent luster of silver white and had extremely excellent surface properties.
• This steel sheet was subjected to the same acid resistance test as in Example I to find no generation of bubbles even after lapse of 40 minutes.
• steel sheets were treated with 500 cc of hexane containing 0.01 percent by weight of ethanol, 500 cc of hexane containing 0.01 percent by weight of oxygen and argon atmosphere containing chlorine gas of 1 mmHg, respectively. Thereafter, they were heat treated as mentioned above, cooled and then taken out into the air. They had excellent surface properties as in the case of the water treatment.
• a method for aluminum plating of a substrate by contacting a heated substrate with an alkyl aluminum compound to cause thermal decomposition of said alkyl aluminum compound an improvement which comprises heat treating said substrate covered with aluminum at a temperature of not lower than 400 C, but below the melting point of aluminum for 10 seconds 30 minutes in an inert atmosphere, then contacting thus treated substrate with a small amount of a surface treating agent selected from active hydrogencontaining compound, oxygen and halogen, and thereafter taking out the substrate into the air.
• alkyl aluminum compound is selected from dialkyl aluminum hydride, trialkyl aluminum having alkyl groups of two-20 carbon atoms and a mixture thereof.
• the active-hydrogen containing compound is selected from the group consisting of water, ammonia, primary and secondary amine compounds, sulfides, monoand polyhydric alcohols, carboxylic acids, and inorganic acids.
• sultide is selected from the group consisting of hydrogen sulfide, ethyl thioalcohol, dodecyl thioalcohol.
• a method according to claim 6, wherein the monoand poly-hydric alcohols are methanol, ethanol, isopropyl-alcohol, butanol, ethylene glycol, propylene glycol and glycerine.
• carboxylic acid is selected from the group consisting of acetic acid, naphthenic acid, stearic acid, adipic acid, maleic acid and phthalic acid.
• a method according to claim 6, wherein the inorganic acid is selected from the group consisting of hydrogen chloride, hydrogen fluoride, hydrogen bromide and nitric acid.
• halogen is selected from chlroine, fluorine and bromine.
• a method for aluminum plating a substrate by contacting a heat substrate with an alkyl aluminum compound to cause thermal decomposition of said alkyl aluminum compound an improvement which comprises contacting said substrate covered with aluminum with a small amount of a surface treating agent selected from active hydrogen-containing compound, oxygen and halogens, then heat treating the substrate at a temperature of not lower than 400 C, but below the melting point of aluminum for seconds 30 minutes and thereafter taking out thus treated substrate into the air.
• a surface treating agent selected from active hydrogen-containing compound, oxygen and halogens
• alkyl aluminum compound is selected from dialkyl aluminum hydride, trialkyl aluminum having alkyl groups of two-20 carbon atoms and a mixture thereof.
• the active-hydrogen containing compound is selected from the group consisting of water, ammonia, primary and secondary amine compounds, sulfides, monoand polyhydric alcohols, carboxylic acids, and inorganic acids.
• a method according to claim 24, wherein the primary and secondary amine compounds are selected from the group consisting of dimethyl amine, and monobutyl amine.
• sultide is selected from the group consisting of hydrogen sulfide, ethyl thioalcohol, dodecyl thioalcohol.
• a method according to claim 24, wherein the monoand poly-hydric alcohols are methanol, ethanol, isopropyl-alcohol, butanol, ethylene glycol, propylene glycol and glycerine.
• a method according to claim 24, whrein the carobxylic acid is selected from the group consisting of acetic acid, naphthenic acid, stearic acid, adipic acid, maleic acid and phthalic acid.
• a method according to claim 1, wherein the inorganic acid is selected from the group consisting of hydrogen chloride, hydrogen fluoride, hydrogen bromide and nitric acid.
• halogen is selected from chlorine, fluorine and bromine.

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• Organic Chemistry (AREA)
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Citations (7)

• 0
  • BE BE758258D patent/BE758258A/xx unknown
• 1969
  • 1969-11-01 JP JP44087965A patent/JPS4819057B1/ja active Pending
• 1970
  • 1970-10-28 FR FR7038912A patent/FR2066672A5/fr not_active Expired
  • 1970-10-28 GB GB5128170A patent/GB1320383A/en not_active Expired
  • 1970-10-29 NL NL707015888A patent/NL143625B/xx unknown
  • 1970-10-30 CA CA096,976A patent/CA944634A/en not_active Expired
  • 1970-10-30 US US00085823A patent/US3753768A/en not_active Expired - Lifetime
  • 1970-10-30 SE SE14702/70A patent/SE363356B/xx unknown

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