DE2053407A1 - Method for covering a substrate with aluminum - Google Patents

Description

PATENTAN WÄLl E Dr. D. Thomsen Dipi.-ing. H. Tiedtke Dipl.-Chem. G. BUhHnQ Dipl.-Ing. R. ΚίΠΠΘ W.Weinkauff

MUNICH 15 KAISER-LUDWIG-PLATZ β

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8000 Munich 15 October 30, 1970 T 3892 / case 23592 Sumitomo

Sumitomo Chemical Company, Limited Osaka (Japan)

Method for covering a substrate with aluminum

This invention relates to a method for depositing aluminum, more particularly to a method for Generating an excellent aluminum coating on one Substrate, by contacting a heated substrate with an alkyl aluminum compound, these being alkyl aluminum thermally decomposes.

The expression "a substrate covered with aluminum" is to be understood here as meaning a substrate covered with aluminum, wherein the aluminum was produced by thermal decomposition of an alkyl aluminum compound and the decomposition by Contacting the heated substrate with the alkyl aluminum precondition was caused, but the covered substrate is still

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has not been carried into the air.

It has been proposed by K.Ziegler and co-workers to coat a substrate with aluminum by bringing a heated substrate into contact with a liquid alkylaluminum compound or with the vapor of an alkylaluminum compound, so that thermal decomposition of the alkyl-P aluminum is brought about (see Japanese patent specification 234 069).

However, such a method of occupying one brings one Substrates with aluminum entail serious inconveniences, which are mentioned below.

This is because there are cracks and gas pores on the aluminum-covered surface, which cause deterioration the corrosion resistance, the oxidation resistance at high temperature and the electrical properties of the substrate bring about. Furthermore, the thickness of the aluminum film is not uniform, and the gloss of the surface is extremely poor and the aluminum film tends to pop off when bent.

It has now been found, surprisingly, that these deficiencies can be completely eliminated.

According to the invention is to a covered with aluminum Sub-

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strat at a temperature not lower than 400 C, but heat-treated below the melting point of the aluminum in an inert atmosphere and then the so treated Substrate to be discharged into the air.

Further, an aluminum covered substrate should contain a very small amount of a surface treating agent from the class of active hydrogen-containing compounds, oxygen and halogens, brought into contact, then at a temperature not lower than 400 C but below the melting point of aluminum in an inert atmosphere heat treated and then discharged into the air; or it should be an aluminum covered substrate at a Temperature not lower than 400 ° C but below the melting point of the aluminum heat treated, then with a very small amount of a surface treatment agent from the class of active hydrogen-containing compounds, brought into contact with oxygen and halogens and then discharged into the air.

Accordingly, the invention involves depositing aluminum with the formed aluminum film free from cracks and Has gas pores on its surface, has a uniform thickness and excellent gloss, and adheres to the substrate firmly bound is what is achieved by one with

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Aluminum covered substrate at 400 C to the melting point of the aluminum, 10 seconds to 30 minutes in an inert The atmosphere is heat-treated and then the substrate treated in this way is discharged into the air.

According to the method according to the invention, an aluminum film can be obtained which has no cracks and gas pores on its surface, has a uniform thickness, ei " shows excellent surface gloss and is firmly bonded to the substrate and does not peel off from it.

Other features emerge from the description below.

The alky / aluminum compounds used according to the invention include any alky / aluminum compounds which are in the P are able to deposit aluminum through thermal decomposition. Of these compounds, the following are preferred because they are Easily thermally decomposable and economical are: Dialkylaluminum hydride or trialkylaluminum with alkyl groups, which Contains 2 to 20 carbon atoms such as triethylaluminum, diethylaluminum hydride, tri-n-propylaluminum, trisopropylaluminum, tri-n-butylaluminum, di-n-butylaluminum hydride, Triisobutyl aluminum, diisobutyl aluminum hydride, tri-n-benzyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum, tri-2-ethylhexyl aluminum, di-2-ethylhexyl aluminum hydride, trldecyla aluminum

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or their mixtures.

Furthermore, the alkylaluminum compound can be used together with a compound which is capable of with to enter into a complex compound of the alkylaluminum compound, for example with an alkali metal compound, an ether, a tertiary amine, a quaternary ammonium salt, etc. which are mentioned in U.S. Patents 3,454,407 and 3,373,996, so that an aluminum covering of high purity is achieved. In addition, the alkyl aluminum compound can be mixed with a use inert organic solvents such as hexane, heptane, octane, cyclopentane, cyclohexane, benzene, toluene, xylene, petroleum, Paraffins, alkylbenzene, diphenyl, etc.

Substrates that can be covered include, for example, metals such as iron, steel, aluminum, copper, brass, Earthenware, glass, organic and inorganic resins, etc.

The substrate is preferably cleaned before covering.

The substrate is heated to a temperature which is higher than the thermal decomposition temperature of the alkylaluminum compound, preferably 300 to 600 ° C., and is brought into contact with the deposition solution or the deposition vapor. The substrate can be heated by known heating methods, for example by resistance heating, induction

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tion heating, depending on the type and shape of the substrate. That Induction heating is preferred for continuous heating of particularly thin sheet metal.

As a method for obtaining an aluminum covered substrate according to the invention, any method can be used

. be, according to which a heated substrate with a liquid Alkylaluminum compound is brought into contact, as well as the method according to which a heated substrate is contacted with the vapor an alkyl aluminum compound is brought into contact. The choice of the method in question depends on the type and shape depends on the substrate to be covered. The substrate can be mixed with the aluminum by thermal decomposition of an alkyl aluminum compound be covered on the substrate by heating once or by two or more times, intermittent Heat. The latter is particularly preferred. Furthermore,

"The latter method doesn't change the heat treating one with Aluminum covered substrate.

The thermal decomposition can be carried out in the presence of a compound which is capable of the accelerate thermal decomposition such as titanium chloride, titanium bromide, vanadium chloride, iron chloride, copper chloride etc. which are mentioned in U.S. Patent 3,306,732.

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The addition of this compound is particularly useful in covering a substrate of poor thermal stability.

The thermal decomposition is required to be carried out in an inert atmosphere, but there is still a problem the pressure under which to work is not a critical limit.

The substrate covered with aluminum as mentioned above is then fed to the heat treatment step or it is first brought into contact with a very small amount of a surface treatment agent, which is selected from the group of the active Hydrogen-containing compounds, oxygen and halogens is selected, and then the heat treatment step fed. The heat treatment is carried out according to the invention by the substrate at a temperature of not lower than 400 ° C, but below the melting point of the aluminum, preferably to 450 to 600 C, heated and held.

If the heat treatment temperature is lower than 400 ° C, good surface properties cannot be obtained and, moreover, a long treatment time is required for the heat treatment. For example, a reaction between iron and aluminum takes place when the substrate is iron, and the aluminum film tends to peel off.

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According to the invention, the heat treatment is carried out in the presence of a gas inert to aluminum or a molten one Salt. Usually nitrogen, argon and helium are used effectively, but it should be noted that this invention is not limited to the use of these substances.

The heat treatment time varies somewhat depending on the The kind and shape of the substrate, the thickness of the aluminum film and the heating temperature, but it is generally 10 seconds to 30 minutes. However, in the case of a substrate made of iron, too long a treatment time causes a reaction between the aluminum and the iron, whereby the applied surface is deteriorated; hence the substrate preferably commercial 20 seconds to 15 minutes of heat treatment held. ,

ψ After the heat treatment has been completed, the substrate is in

discharged into the air or first brought into contact with a small amount of a surface treatment agent selected from the group of active hydrogen-containing compounds, oxygen and halogens, and then discharged into the air. '

Contact of the substrate with a surface treatment agent from the group of compounds containing active hydrogen, ie oxygen and halogens, can occur

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the heat treatment can be carried out. As mentioned above, results in the contact of the substrate with a very small amount of a surface treatment agent from the group of the active Hydrogen-containing compounds, oxygen and halogen before or after the heat treatment, to one more excellent aluminum covering than that which is obtained only by heat treatment.

Illustrative of the active hydrogen containing compounds covered with the aluminum Are brought into contact with the substrate: Compounds with at least one substitutable hydrogen such as water, ammonia, primary or secondary amine compounds, for example Dimethylamine, monobutylamine, etc .; Sulfides, for example Hydrogen sulfide, ethylthioalcohol, dodecylthioalcohol, etc .; monohydric or polyhydric alcohols, for example methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, propylene glycol, Glycerin, etc .; Carboxylic acids, for example acetic acid, naphthenic acid, stearic acid, adipic acid, maleic acid, phthalic acid etc.; and inorganic acids such as hydrochloric acid, hydrofluoric acid, hydrobromic acid, nitric acid etc.

These active hydrogen containing compounds are used as a solution containing 10 to 10,000 parts per million, preferably 100 to 1,000 parts per million (to the

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Based on weight) of this compound in aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, alkylbenzene, etc., dissolved in aliphatic hydrocarbons such as pentane, hexane, octane, decane, etc. and mixtures thereof, or used as an atmosphere of the active hydrogen-containing compound of 0.1 to 20 mmHg, preferably 0.1 to 10 mm Ed.

In the case of treatment with oxygen, the substrate is made with the aromatic or aliphatic hydrocarbon brought into contact, which contains 10 to 10000 parts per million, preferably 100 to 1000 parts per million (by weight) of oxygen, or the oxygen is applied as an oxygen atmosphere at 0.01 to 100 mm Hg, preferably 0, 1 to 80 mm Hg.

Further, when halogens such as fluorine, bromine, etc. are used, they are used as a halogen atmosphere of 0.01 to 20 mm Hg, preferably 0.1 to 10 mm Hg, or as a solution containing 10 to 2000 parts per million of a halogen dissolved in a suitable solvent such as paraffin. When the halogen is brought into contact in a vapor phase, so it is not the steam alone that is brought into contact, but the steam is diluted with an inert gas and the treatment is carried out under normal pressure or under increased pressure.

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This treatment is carried out at from ⁰ to 300.degree. C., preferably from 15 to 200.degree.

As mentioned above, the method of the invention provides the following advantages compared with the conventional method in which the substrate covered with aluminum is discharged without further treatment: The aluminum film on the substrate has no cracks and gas pores on its Surface, has a uniform thickness, exhibits excellent surface gloss and is firmly bonded to the substrate .

The substrate covered with aluminum according to the invention has a high resistance to corrosion and oxidation at high temperature as well as excellent electrical properties.- Furthermore, the coated substrate of the metal ! surface treatment, for example the well-known sealing treatment, the stabilization treatment and the alumid surface finishing are subjected. As a result of this having excellent properties, the commercial value of the invention is extremely great.

The following embodiments are provided to the invention merely to illustrate without defining their framework.

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example 1

A 50 mm 50 mm 0.6 nm steel sheet is washed with water and then washed with alcohol and then dried. The steel sheet thus treated is used as a sample.

All process steps from the heat treatment of the sample to its discharge into the air are carried out in one Carried out in an argon atmosphere.

This sample is heated to 400 ° C. in an argon atmosphere and then in 500 cm of an alkyl aluminum solution of Submerged at 20 ° C, which contains 81% by weight of diisobutyl aluminum hydride, 11% by weight diethyl aluminum hydride, 5% by weight triisobutyl aluminum and 3% by weight of triethylaluminum.

After 1 minute has elapsed, the sample is withdrawn from the solution and the deposited alkylaluminum is kept at 100 ° C. in an argon atmosphere and washed off. Furthermore, the same, above-mentioned operation is repeated again in order to effect the covering with aluminum. The sample covered with aluminum is then heated to 450 ° C. in an argon atmosphere. After the sample 1st been held at this temperature for 5 minutes, it is cooled in argon gas to room temperature and then discharged into the air.

The ώ-t aluminum-coated substrate obtained in this way has 109822/1170

a film of a thickness of 1.1 µm and has an excellent silver-white sheen.

An acid resistance test is also carried out by immersing this coated substrate, which has been covered by solid paraffin for a width of 10 mm around the substrate, in 500 cm ^{3 of} a 25% strength by weight aqueous nitric acid solution at 20 ° C. Even after 30 minutes have passed, no bubbles develop and no change is observed on the covered surface.

For comparison, another sample of the same type, coated with aluminum in the same manner as mentioned above, is discharged into the air without the heat treatment. The substrate covered with aluminum has a film thickness of 1.1 μ and its surface is silver-white. The same acid resistance test is carried out on this substrate. After a lapse of 11 minutes, bubbles develop, and after a lapse of 20 minutes, the aluminum film on the substrate is almost peeled off.

From the foregoing results, it can be seen that in the substrates coated with aluminum of the same thickness, the properties of the surface subjected to the heat treatment are extremely superior to the properties of the surface which has not been subjected to the heat treatment.

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Example 2

The same sample as in Example 1, which was also purified in the same manner as in Example 1, is shown in applied to this example. As in Example 1, the treatment is carried out in an argon atmosphere. The sample is preheated to 500 ° C and in an alkyl aluminum solution the same composition as in Example 1 heated to 200 ° C. After the lapse of one minute the sample is taken and washed with 500 cm hexane. Then the sample is heated to 500 ° C in an argon atmosphere heated and held at this temperature for 5 minutes. The sample is then cooled and carried out into the air. The steel sheet covered with aluminum has an excellent silver-white gloss and has excellent surface properties on. The mean thickness of the aluminum "film is 2.1 yes, which was determined by weight gain.

The sample is also subjected to the acid resistance test in the same manner as in Example 1. Even after no bubbles develop for 30 minutes.

For comparison, the sample is cooled in argon before the heat treatment and then discharged into the air. That with Sheet steel covered with aluminum has a gray color with a low gloss. The same acid resistance test as above mentioned is carried out with the sample. After the

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After 5 minutes, the development of bubbles is observed .

For further comparison, instead of this heat treatment, the sample is similarly heated to 300 ° C. in an argon atmosphere heated and kept at this temperature for 5 minutes. Then it is cooled in argon and discharged into the air. That The aluminum-coated steel sheet obtained in this way shows a gray color Color and has a low gloss. The sample is subjected to the same acid resistance test mentioned above. After this The development of bubbles is observed after a lapse of 7 minutes.

From the above results it can be seen that in the steel sheets covered with aluminum in the same thickness, the gloss and the properties of the surface treated according to the invention are superior to those of the surface, which was not treated according to the invention.

Example 3

A substrate treated in the same way as in Example 1 up to the heat treatment is brought into contact for 1 minute with 500 cm of hexane at 20 ^° C., which contains 0.01 % by weight of Kasser. The Stahlblec thus obtained, coated with aluminum

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shows excellent silver-white gloss and has very excellent Surface properties. This sheet steel is the subjected to the same acid resistance test as in Example 1. Even after the lapse of 50 minutes, bubbling becomes not observed.

With this method, the steel sheets are used instead of the

™ Water treatment, treated with 500 cm of hexane, which contains 0.01% by weight Contains ethanol, furthermore with 500 cm hexane with 0.01 wt .-% oxygen, as well as with argon atmosphere, which chlorine gas from 1 mm Hg and the steel sheets are discharged into the air. The aluminum-coated steel sheets obtained in this way show an excellent silver-white gloss and have extremely excellent surface properties.

Every steel sheet is made of the same acid resistance-) test as in Example 1 subjected. The same results are obtained as is the case with water treatment.

Example 4

A substrate covered with aluminum in the same way as in Example 1 is ^{brought into contact for 1 minute with 50 cm 3 of} hexane at 20 ° C., which contains 0.01% by weight of water. Then it is heated to 500 ° C for 5 minutes in an argon atmosphere

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heated and kept at this temperature. The substrate is then cooled to room temperature in argon gas and worn in the air. The aluminum-covered steel sheet obtained in this way shows an excellent silver-white gloss and possesses extremely excellent surface properties.

This steel sheet is subjected to the same acid resistance test as in Example 1, and it is found by yourself no bubbling after the lapse of 40 minutes.

In this procedure, instead of the V7asSer treatment, the steel sheets are treated with: 500 cm ^{3 of} hexane with a content of 0.01% by weight of methanol; or with 500 cm of hexane containing 0.01% by weight of oxygen; or with an argon atmosphere containing chlorine gas of 1 mm Hg. Thereafter, as mentioned above, the sheets are heat-treated, cooled and then discharged into the air. They have excellent surface properties, as is the case with water treatment. Each steel sheet thus treated was subjected to the acid resistance test wb in Example 1, and the same results as in the water treatment were obtained.

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Claims (23)

Patent claims 1J method for allocating a substrate with aluminum by contacting a heated substrate with an alkyl aluminum compound under inducing thermal decomposition of the alkyl aluminum compound, characterized denotes ge _k, that the area covered by the thermal decomposition of the alkyl aluminum compound with an aluminum substrate in an inert atmosphere for 10 seconds to Subjecting it to heat treatment at a temperature not lower than 400 ° C. but below the melting point of aluminum for 30 minutes, and then discharging the thus treated substrate into the air. 2. The method according to claim 1, characterized in that the alkyl aluminum compound is dialkyl aluminum hydrides, "Trialkylaluminum containing 2 to 20 carbon atoms Alkyl groups, or mixtures thereof, are used. 3. The method according to claim 1, characterized in that the heated to a temperature of 300 to 600 ° C substrate with liquid or vaporous alkylaluminum compound brings in contact to cover the substrate with aluminum. 4. The method according to claim 1, characterized in that the heat treatment for 20 seconds to 15 minutes at 450 109822/1170 up to 600 ° C. 5. The method according to any one of the preceding claims, characterized in that, after the heat treatment lasting 10 seconds to 30 minutes in an inert atmosphere, the aluminum covered substrate is brought into contact with a small amount of a surface treatment agent which contains an active hydrogen-containing compound, oxygen , or
is a halogen, and that you then put the substrate in the air
unsubscribes. 6. The method according to claims 1 to 4, characterized in that the substrate covered with aluminum is brought into contact with a small amount of a surface treatment agent, which latter is active hydrogen-containing compound, oxygen or halogen, that the substrate is then 10 seconds to 30 Minutes at a temperature of not less than 40O ⁰ C, but below the melting point of the aluminum heat-treated, and that you then discharged the so treated substrate into the air. 7. A method according to claims 5 and 6, characterized in that aluminum hydride, Trialkylaluminiuia having 2 to 20 carbon atoms containing alkylene groups as alkyl aluminum dialkyl!, Or a mixture thereof used. 109822/1170 8. The method according to claims 5 and 6, characterized. that the heated to 300 to 600 C substrate for the purpose of covering the substrate with aluminum with liquid or vapor Brings alkyl aluminum compound into contact. * 9. The method according to claims 5 and 6 _r, characterized in that the heat treatment is carried out for 20 seconds to 15 minutes at 450 to 600 ° C. 10. The method according to claims 5 and 6, characterized in that that the active hydrogen-containing compound is water, ammonia, primary and secondary amine compounds, sulfides, monohydric and polyhydric alcohols, carboxylic acids or inorganic acids are used. 11. The method according to claim 10, characterized in that ρ that the primary and secondary amine compounds are dimethylamine or monobutylamine is used. 12. The method according to claim 10, characterized in that the sulfide is hydrogen sulfide, ethylthioalcohol or Dodecylthio alcohol used. 13. The method according to claim 10, characterized gekennzeich- 'net that as monohydric or polyhydric alcohol is methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, propylene glycol or glycerol used. 109822/1170 14. The method according to claim 10, characterized in that that acetic acid, naphthenic acid, stearic acid, adipic acid, maleic acid or phthalic acid is used as the carboxylic acid. 15. The method according to claim 10, characterized in that the inorganic acid, hydrochloric acid, Hydrofluoric acid, hydrobromic acid or nitric acid used. 16. Process according to Claims 5 and 6, characterized in that the halogen used is chlorine, fluorine or bromine . 17. The method according to claim 5 and 6, characterized in that: net that the substrate coated with aluminum is brought into contact with a solution which contains active hydrogen Compound in an amount of 10 to 10,000 parts per million. 18. The method according to claims 5 and 6, characterized in that the substrate covered with aluminum with an atmosphere of active hydrogen-containing compound of 0.01 to 20 mm Hg. ■ 19. The method according to claims 5 and 6, characterized in that that the substrate covered with aluminum with 109822/1170 a solution containing 10 to 10,000 parts per million oxygen. 20. The method according to claims 5 and 6, characterized in that the coated with aluminum substrate with a gas atmosphere in contact, which oxygen ^ Contains from 0.01 to 100 mm Hg. 21. The method according to claims 5 and 6, characterized in that the substrate covered with aluminum with a solution containing 10 to 2000 parts per million halogen. 22. The method according to claims 5 and 6, characterized in that the coated with aluminum substrate with brings into contact with an oasis atmosphere which contains a halogen "contains from 0.01 to 20 mm Hg. 23. Process according to Claims 5 and 6, characterized in that the substrate covered with aluminum is in contact with the surface-active agent ^{at 0 to 300 0 C}
brings. 10SS22 / 117Q