US2028312A - Electroplating of aluminium - Google Patents

Electroplating of aluminium Download PDF

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Publication number
US2028312A
US2028312A US682706A US68270633A US2028312A US 2028312 A US2028312 A US 2028312A US 682706 A US682706 A US 682706A US 68270633 A US68270633 A US 68270633A US 2028312 A US2028312 A US 2028312A
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US
United States
Prior art keywords
aluminium
hydride
article
metal
oxide
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US682706A
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English (en)
Inventor
Bornhauser Oscar
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Societe dElectro Chimie dElectro Metallurgie et des Acieries Electriques Dugine SA SECEMAU
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Individual
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Publication date
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Publication of US2028312A publication Critical patent/US2028312A/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals
    • C25D5/44—Aluminium

Definitions

  • This invention relates to improvements in the electro-plating of aluminium with other metals.
  • Remedies for this difficulty have already been sought, either by modifying suitably the oxidized surface of the aluminium in such a manner that it permits, in spite of the presence of oxide, of the galvanic deposit of other metals, or by causing the layer of oxide to disappear, by preliminary treatment in cleaning baths or by electrical or thermal treatment, for a time at least sufllcient in order that the surface of the aluminium can become covered in the plating bath with the metal intended to constitute the coating.
  • the present invention permits on the contrary of the complete removal of the layer of oxide from the surface of the articles to be treated, for a time sufi'icient to allow the galvanic deposit of metal on metal.
  • the process which forms the object of the invention consists essentially in replacing at the surface of the aluminium the layer of oxide by a film of aluminium hydride, that is to say the hydrogenated compound of aluminium which presents characteristics permitting it to be ranged in the electromotive series approxi-- mately in the same place as hydrogen.
  • aluminium in the very active state that is to say absolutely white, is capable of reacting on the hydrate of its own oxide by removing water therefrom and by reacting with this water oxide is reformed in such a violent manner that its molecular structure is modified, the valencies thus liberated are saturated by the hydrogen produced during the reaction.
  • This hydride presents an appearance which recalls graphite and has a remarkable resistance to the oxygen of the atmosphere and to water; its
  • electrical conductivity is that of a metal; its characteristics are those of an alloy, for example similar to those of the hydride of nickel. In the is-sufliciently resistant up to temperatures in the neighborhood of 300 C. but at incipient redness it burns or decomposes leaving a white residue of aluminium oxide.
  • the position of this aluminium hydride in the electromotive series which position is referred to above and corresponds to that of hydrogen, can be determined by its reactions towards solutions of metallic salts, in fact the hydride is indiiferent to solutions of salts of metals below lead but reacts with those of metals above lead with exchange of its hydrogen for the metal.
  • this film of aluminium hydride in accordance with the invention, this article is heated strongly at a temperatureexceeding 100 C. and it is subjected in the presence of small quantities of water to the action of violent reagents capable of'attacking aluminium.
  • reagents of this nature can be utilized hydrochloric acid in the liquid or gaseous state, the salts of metals of a position superior to or equal to aluminium and so on.
  • the salt dissociates giving aluminium hydroxide with the small quantity of water present.
  • the aluminium of the article in the very active state owing to the attack of the reagent employed, reacts very violently in order to give rise according to the reaction set out above to the oxide A1203, while the-hydrogen liberated gives rise to aluminium hydride of which one portion remains in the powder form mixed with the oxide A120: on the surface of the article while the other portion forms directly at the surface of the aluminium metal of the article the very adherent film of aluminium hydride desired.
  • the film of aluminium hydride formed on the surface of the article protects this latter for a sufiiciently long time from the reformation of hydroxide.
  • any object thus coated can be metallized directly in any neutral or acid plating bath.
  • the coatings by means of metals lower 1 than hydrogen can be eflfected directly without difiiculty while the production of coatings of metals above hydrogen requires the known precautions at present employed in the art for plating in cases of this type that is to say, high initial intensity or strong simultaneous evolution of hydrogen.
  • the metals of the coating which are distinguished by a particularly firm connection with the metal of the base are chiefly those having a strong tendency to displace hydrogen such as nickel, iron and chromium and also brass andplatinum. It appears probable that the metal of the coating removes the hydrogen of the aluminium hydride and itself occupies the place thus liberated in the molecular structure. This is the more probable since these metals are of the same type as aluminium from the point of view of structure.
  • reaction must be carried out as indicated above in the presence of small quantities of water, sufiiciently small in order not to permit of the dilution of all the salt formed at the time of the attack on the aluminium by the reagent employed.
  • the characteristic of the present invention resides in the formation of this adherent film of aluminium hydride directly on the surface of the metal, which film is formed at the expense of the hydroxide produced by the dissociation, under the effect of the heat, of the salts of aluminium formed under the action of reagents and remaining on the surface of the article.
  • the essential reaction that is to say the formation of hydride always takes place when the aluminium constitutes the major portion of the alloy. Even when the alloy contains copper the aluminium hydride is formed with certainty but the formation of hydride only lasts for a short time on account of the catalyticcarrying of oxygen. On account of this fact alloys of this type, for example duralumin, must as rapidly as possible after the hydrogenation, be introduced into the plating bath. For the same reason direct chroming in baths containing chromic acid is difiicult when the alloy contains copper whereas alloys free from copper and also pure aluminium can be chromed directly and without difliculty in baths of this type.
  • the article to be prepared is heated to a temperature above 100 C., plunged into a concentrated bath of basic aluminium chloride brought to the same temperature, then withdrawn from the bath when the violent reaction with attack of the metal is produced, the formation of hydride then takes place, a large increase of temperature and with rapid consumption of the small quantities of water.
  • a very interesting application of this process consists in producing at the surface of an article of aluminium coated with a galvanic deposit of another metal, a superficial alloy of this metal and aluminium without risk of deformation or injury of the article.
  • the article of aluminium by a preliminary process according to the present invention with the superficial production of hydride before covering it with an electrolytic deposit of another metal it will sumce to heat the article to a temperature much lower than the point of fusion of the aluminium (or of the metal of the coating) in order to obtain without deformation of the article an alloy of aluminium and of the metal of the coating at the surface of the article.
  • the preliminary treatment which comprises heating thearticle to a temperature above 100 6., plunging it into a concentrated bath of basic aluminium chloride brought to the same temperature and then withdrawing from the bath when a violent reaction with attack of 10 the metal is produced.

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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 Methods And Accessories (AREA)
  • Chemically Coating (AREA)
US682706A 1932-07-29 1933-07-28 Electroplating of aluminium Expired - Lifetime US2028312A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR753672T 1932-07-29

Publications (1)

Publication Number Publication Date
US2028312A true US2028312A (en) 1936-01-21

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ID=9163149

Family Applications (1)

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US682706A Expired - Lifetime US2028312A (en) 1932-07-29 1933-07-28 Electroplating of aluminium

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US (1) US2028312A (fr)
FR (1) FR753672A (fr)
GB (1) GB412430A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2491839A (en) * 1945-12-06 1949-12-20 Gen Electric Process for electroplating a sintered ferrous article
US2856333A (en) * 1955-06-28 1958-10-14 Tiarco Corp Electroplating
US2856334A (en) * 1955-11-01 1958-10-14 Tiarco Corp Chromium plating
US2862859A (en) * 1956-02-08 1958-12-02 Otto Heinrich Drager Dr Detecting impurities in gases
US2995479A (en) * 1961-08-08 Degassing aluminum articles
US3136709A (en) * 1959-07-14 1964-06-09 Nat Steel Corp Method of electroplating an aluminum containing coating

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2995479A (en) * 1961-08-08 Degassing aluminum articles
US2491839A (en) * 1945-12-06 1949-12-20 Gen Electric Process for electroplating a sintered ferrous article
US2856333A (en) * 1955-06-28 1958-10-14 Tiarco Corp Electroplating
US2856334A (en) * 1955-11-01 1958-10-14 Tiarco Corp Chromium plating
US2862859A (en) * 1956-02-08 1958-12-02 Otto Heinrich Drager Dr Detecting impurities in gases
US3136709A (en) * 1959-07-14 1964-06-09 Nat Steel Corp Method of electroplating an aluminum containing coating

Also Published As

Publication number Publication date
GB412430A (en) 1934-06-28
FR753672A (fr) 1933-10-21

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