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
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/06—Zinc or cadmium or alloys based thereon

Definitions

• the present invention relates to a method of galvanizing by dipping a series of individual steel objects, according to which a zinc bath containing silicon is used at a concentration which may go as far as saturation.
• a zinc bath containing silicon, preferably saturated with silicon is used, not only when all the objects to be galvanized have a silicon content of more than 0.02%, but also when at least one objects to be galvanized with such a silicon content, that is to say when it is not excluded that among the objects to be galvanized there is ⁇ * na whose silicon content does not exceed 0.02%, because it has been found that galvanizing in such a bath, steels whose silicon content does not exceed 0.02%, leads to very good results which are quite comparable to those obtained with these types.
• * _ in a classic bath is used, not only when all the objects to be galvanized have a silicon content of more than 0.02%, but also when at least one objects to be galvanized with such a silicon content, that is to say when it is not excluded that among the objects to be galvanized there is ⁇ * na whose silicon content does not exceed 0.02%, because it has been found that galvanizing in such a bath, steels whose silicon content does not
• the object of the present invention is to provide a process as defined above, which avoids this drawback.
• the said series is constituted so that all the objects are made of a steel containing at most 0.04% silidum and the bath contains in this first case at least 0.005 % silidum; (b) or the said series is constituted so that at least one of the objects is in an ader containing more than 0.04% of silidum and the bath contains in this second case at least 0.005% of silidum as well as either 0, 02-0.06% aluminum and 0.002-0.1% calcium, i.e. 0.05-0.12% nickel.
• the coating formed on an adder without silidum immersed for 5 minutes in a Georgia-solution at 450 ° C. has a "dassic" thickness of 66 / ⁇ m, while one obtains on the same ader and in the same conditions a coating with a thickness of only 37 ⁇ m after adding 0.03% silidum to the bath.
• zinc consumption decreases to the same extent as the thickness of the coating.
• the reduction in thickness is already substantial when 0.005% silidum is added to the bath.
• a "dassique" thickness that is to say a thickness of about 70 ⁇ m
• a coating thickness of only about 40 ⁇ m Part (a) of the process of the present invention is therefore particularly advantageous when it is necessary to galvanize a series of ader objects with or without a low silidum content (up to 0.04%) and we want to obtain a thickness of coating lower than the base thickness, more particularly a lower thickness
• the minimum silidum content (0.005%) is necessary on the one hand to reinforce the inhibitory effect of aluminum and nickel on the growth of the coating, in particular when the ader to be galvanized contains up to 0.20% of silidum, and secondly to avoid the formation in the bath of nickel-iron mattes.
• the minimum calrium content (0.002%) is necessary to obtain a coating which is free or practically free from defects in the continuity of the coating. B has proven difficult to avoid these defects, even in the presence of caldum, when the aluminum content is greater than 0.06%.
• a nickel content greater than 0.12% leads to the formation of interfering Ni-Zn compounds.
• the caldum added above 0.1% plays no role.
• the galvanizing bath according to part (b) of the process of the present invention is particularly advantageous, not only when one has to galvanize a series of ader objects which all have a silidum content of more than 0.04%, but also when a mixed series must be galvanized consisting partly of free or low silidum objects (up to 0.04%) and partially of objects with higher content silidum, and therefore, when a series of ader objects whose composition is unknown is to be galvanized, which is generally the case in custom galvanizing.
• the bath contains in both cases at least 0.01% of silidum, on the one hand to obtain a considerable reduction in the thickness of coating, more particularly on aders at 0-0.20% silidum, and secondly to avoid the formation in the bath of bottom mattes. It is also desirable that the bath contains in both cases lead at a concentration which can go as far as saturation, for example 0.1 to 1.2, this in order to reduce the surface tension of the bath. It is further desirable that the bath contains in the first case 0.001-0.015% aluminum and / or 0.002-0.1% caldum, ced to protect the donkey against oxidation; otherwise a yellowish film forms on the surface of the bath, which dirty galvanized objects. For the same reason it is advantageous that the nickel bath used in the second case also contains 0.001-0.015% aluminum and / or 0.002-0.1% caldum.
• the preferred caldum content is 0.005-0.05%.
• the preferential zinc content is at least 98%.
• composition of the bath will change during the operations, the consumption rates, by oxidation and other reactions, of the components, zinc and additives, at the temperature of use (normally close to 450 ° C) and in the presence of flux (ZnC-2 and NH4CI) being different, and practically all the higher as the metal is oxidizable.
• Additive deficits as a result of oxidation relate mainly to silidum and caldum as well as aluminum when the caldum is absent.
• the Applicant has found that it is possible to maintain the composition of the bath during the galvanizing operations by compensating for the consumption of bath by adding a zinc-based alloy containing to the bath.
• the zinc-based alloy to be used may contain, depending on the case, either 0.1-1.5% of Si; or 0.1-1.5% of Si and 0.01-0.8% of A_; or 0.1-1.5% of Si and 0.1-1.2% ofPb; or 0.1-1.5% of S and 0.02-1% of Ca; or 0.1-1.5% of S; , 0.01-0.8% Al and 0.02-1% Ca; or 0.1-1.5% of S:, 0.01-0.8% of Al and 0.1-1.2% ofPb; or 0.1-1.5% of S:, 0.02-1% of Ca and 0.1-1.2% ofPb; or 0.1-1.5% of Si, 0.01-0.8% of Al, 0.02-1% of CaetO, M, 2% of Pb; or 0.1-1.5% of Si, 0.1-0.8% of Al and 0.02-1% of Ca; or 0.1-1.5% of S, 0.1-0.8% of Al, 0.02-1% of Ca and 0.1-1.-1-1-1-1-1-1-1-1-1-1-1-1.2% of
• the alloy contains, in addition to the zmc, only the elements mentioned with the mentioned contents and unavoidable impurities. It is obvious that the equivalent of zmc can be substituted for an equivalent in the form of at least one master alloy and of zinc or in the form of at least one master alloy and of a less alloy. loaded with additives as the alloy to be replaced.
• first case i.e. 10 kg of mother alloy with 10% Si and 1% Al (prepared by powder metallurgy) and 90 kg of Zn, i.e. 10 kg of mother alloy to 10% Si (ex powder metallurgy), 1 kg of alloy- mother with 10% Al and 89 kg of Zn, i.e. 1 kg of alloy-mother with 10% of Al and 99 kg of alloy with 1.01% of Si.
• the zinc-based alloy defined above can be used for other applications than that described above.
• REPLACEMENT SHEET A variant of the process of the invention consists in constituting said series in the first case so that all the objects are in an ader containing at most 0.02% silidum (instead of 0.04%), and in the second case so that at least one of the objects is in an ader containing more than 0.02% of silidum (instead of 0.04%).
• This example concerns the galvanization of an ader having the following composition, in% by weight: 0.050 C, 0.28 Mn, 0.012 Si, 0.009 S, 0.014 P, 0.020 Al, 0.020 Ni, 0.020 Cr and 0.025 Cu.
• a zinc bath is used and in a second test a zinc bath with 0.029% Si. In both cases the temperature of the bath is 450 ° C and the immersion time 5 minutes. In the first test a coating with a thickness of 66 ⁇ m is obtained and in the second test a coating with a thickness of only 39 ⁇ m.
• This example concerns the galvanization of an ader having the following composition, in% by weight: 0.144 C, 0.920 Mn, 0.092 Si, 0.010 S, 0.014 P, 0.048 Al, 0.020 Ni, 0.020
• a zinc bath with 0.029% Si is used, in a second test a zinc bath with 0.10% Ni and in a third test a zinc bath with
• a thickness of more than 200 ⁇ m is obtained, in the second test a thickness of 69 ⁇ m and in the third test a thickness of only

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating With Molten Metal (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Citations (3)

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• 1991
  • 1991-04-12 FR FR9104501A patent/FR2675159B1/fr not_active Expired - Fee Related
• 1992
  • 1992-03-26 IL IL101384A patent/IL101384A0/xx unknown
  • 1992-04-02 CA CA002106763A patent/CA2106763A1/en not_active Abandoned
  • 1992-04-02 WO PCT/EP1992/000740 patent/WO1992018662A1/fr active IP Right Grant
  • 1992-04-02 AU AU14476/92A patent/AU1447692A/en not_active Abandoned
  • 1992-04-02 EP EP92907556A patent/EP0579642B1/fr not_active Expired - Lifetime
  • 1992-04-02 DE DE69203231T patent/DE69203231T2/de not_active Expired - Fee Related
  • 1992-04-07 TW TW081102658A patent/TW206262B/zh active
  • 1992-04-10 PT PT100376A patent/PT100376B/pt not_active IP Right Cessation
• 1993
  • 1993-10-11 NO NO933666A patent/NO933666L/no unknown
  • 1993-10-11 FI FI934469A patent/FI98468C/fi active

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