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
  • 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
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/40—Oxides
  • C23C16/403—Oxides of aluminium, magnesium or beryllium

Definitions

• Coatings of this kind which even today are still commonplace, are applied by electrochemical deposition, in particular by electroplating. Although they are satisfactory in regard to their protective effect, they do have the disadvantage of necessitating one or more relatively delicate treatments of the machined articles in baths of which some are toxic and require skilled personnel, resulting in an increase in price in relation to unprotected articles.
• coatings of this kind have eliminated the appearance of the basic material, namely, copper, brass or any other copper alloy. This accounts for the advantage there would be in any method of protection which, without in any way losing its effectiveness, would leave the appearance of the underlying metal intact, i.e., would cover the underlying metal with a transparent protective layer.
• cases of this type have to be subjected to surface treatment(s) designed to protect them against corrosion (i.e., chemical protection) against wear (i.e., mechanical protection) or against both.
• surface treatment(s) designed to protect them against corrosion (i.e., chemical protection) against wear (i.e., mechanical protection) or against both.
• the various known treatments which are applied even today are, for the most part, electroplating treatments which cover the surface of the cases with a protective layer obtained electrochemically.
• this protective layer changes the surface appearance of the underlying metal.
• a protective layer is deposited by the technique of chemical vapour deposition rather than by electrochemical treatment.
• this process can only be used for articles made of steel, and is not suitable for metals of Group [B of the Periodic System or their alloys.
• the protective substances used in this process apparently do not form a transparent layer.
• the present invention which is concerned with protecting articles whose surface at least is made of a metal of Group IB or of an alloy containing at least one metal of this group, especially the alloy Cu-Ni (20%)-Mn (20), relates to a process which is distinguished by the fact that the surface of this article is coated with a layer of amorphous, transparent aluminium oxide obtained by chemical vapour deposition.
• the protective layer is made of amorphous alumina A1 0
• amorphous means that the Xray diffractogram of this layer does not show the known lines which characterise the various well-crystallised forms of alumina A1 0
• this layer is transparent so that the appearance of the underlying metal is in no way affected.
• the process of the invention is intended in particular for articles of small dimensions whose surface is re? quired to retain a durable, attractive and aesthetic appearance despite frequent handling, or to have a long service life. This is the case, for example, with cocks and valves so far as the first category is concerned, and with clocks and watches especially watch cases, even jewellery, so far as the second category is concerned.
• the process according to the invention comprises using the technique of chemical vapour deposition to obtain the formation, over the surface of the article, of an adherent, transparent layer of amorphous alumina A1 0 which, by virtue of its chemical inertia and its physical hardness, provides the required protection.
• a volatile compound of aluminium for example aluminium chloride AlCl is preferably subjected to hydrolysis under heat (pyrohydrolysis) in the presence of steam.
• the article to be treated is placed in a chamber in which the air has been replaced by an inert gas (hydrogen H or argon A).
• the pressure in this chamber is reduced to a value between 0.1 and Torr, after which the article is heated to a temperature in the range from 300 to 800C either by placing the chamber itself in a radiation furnace or by subjecting the article to highfrequency induction heating, whilst at the same time passing through the chamber a gas mixture of a selected volatile aluminium compound and steam, each of these components being introduced by a so-called carrier gas with which it is mixed before being introduced into the chamber.
• the carrier gas has to be inert.
• EXAMPLE 1 EXAMPLE [1 Article of Cu-Ni (20%)-Mn (20%) alloy Temperature: 600C Pressure in the chamber: 4 Torr Active components and carrier gases:
• the protective A1 0 layer was perfectly transparent and in no way affected the appearance of the underlying metal. Resistance to corrosion was excellent. In particular, there was no evidence of corrosion after exposure for 24 hours to an atmosphere containing ammonia gas NH;,.
• a process for protecting against corrosion and wear a metallic surface consisting essentially of at least one element belonging to Group IB of the Periodic Classification of Elements in pure or alloyed form, which process comprises forming on said surface by chemical vapor deposition a layer of amorphous and transparent aluminium oxide.

Landscapes

• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Inorganic Chemistry (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Vapour Deposition (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Physical Vapour Deposition (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

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Publications (1)

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Cited By (12)

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Citations (5)

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• 1973
  • 1973-06-15 CH CH870573A patent/CH566398A5/xx not_active IP Right Cessation
• 1974
  • 1974-06-12 DD DD179113A patent/DD112292A5/xx unknown
  • 1974-06-13 JP JP49066640A patent/JPS5036324A/ja active Pending
  • 1974-06-13 GB GB2636174A patent/GB1432107A/en not_active Expired
  • 1974-06-13 DE DE19742428530 patent/DE2428530A1/de not_active Withdrawn
  • 1974-06-14 FR FR7420756A patent/FR2233415B1/fr not_active Expired
  • 1974-06-14 IT IT51517/74A patent/IT1013465B/it active
  • 1974-06-14 AT AT490474A patent/ATA490474A/de not_active Application Discontinuation
  • 1974-06-17 US US480152A patent/US3885063A/en not_active Expired - Lifetime

Patent Citations (5)

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