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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
• • 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
• • 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
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
• • 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
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
  • C23C2/29—Cooling or quenching
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
  • C23C4/08—Metallic material containing only metal elements

Definitions

• This invention relates to a colored zinc coating tech­nique applied onto the surface of an iron or steel material, and particularly to a colored zinc coating method with the use of Mn-Zn, Mn-Cu-Zn, Mn-Ti-Zn system alloys by which the development of new colors not obtained by conventional tech­niques and clearer color developments compared to conven­tional ones are permitted.
• this invention the developments of gold, olive gray and iridescent colors which could not have yet obtained are permitted and simultaneously blue color, purple color etc. may be more clearly developed.
• this invention provides colored zinc coated materials which are applicable to wider variety of fields and have coloring more suitable to the environment where they are placed.
• Hot-dip galvanized iron and steel materials, coated by dipping in molten zinc, are used for corrosion protection purposes in a wide range of application, forming parts and facilities in the fields of building and construction, civil engineering, agriculture, fisheries, chemical plants, electric power supply and communications, and so forth.
• Coloration of hot-dip galvanized steels has usually been by the application of paints.
• the method has the disadvantage of the paint film eventually coming off the coated surface. This results from the activity of Zn in the coating of the hot-dip galvanized steel that causes gradual alkali decomposition of the fatty acid constituting the oily matter in the paint, leading to the formation of zinc soap that hampers the adhesion of the paint film to the under­lying surface.
• a steel article is first galvanized by dipping in a molten zinc bath.
• the coated steel is exposed to the air for one to three weeks so that corrosion products such as Zn(OH)2, ZnO, ZnCO3, ZnCl2 and the like deposit on the coated steel surface.
• the surface is then cleaned and colored.
• Patent Application Publication No. 42007/1971 discloses a coloring treatment that uses a coating bath prepared by adding at least one element selected from titanium, manganese, vanadium and the like to a hot-dip galvanizing bath.
• the hot-dip galvanized coatings obtained by the disclosed technique have been found to be generally very thin and light, with tendencies of rapid color fading and film separation with time. The desired color development is difficult to control precisely, often bringing out dim, indefinite hues.
• the object of this invention is to establish colored zinc coating technique by which the above mentioned improvements may be attained using Mn system zinc alloys.
• This invention also found that colored zing coating may be applied by spraying method.
• the change of the colored zinc coating with the lapse of time may be suppressed by painting thereon.
• Zinc alloy hot dipping is carried out by melting a zinc alloy in a coating bath and immersing a member to be coated thereinto.
• a zinc alloy for hot dipping to form on a base surface an olive gray colored coating of a composition composed of 0.2 - 0.8 wt % Mn - bal. Zn
• it is possible to form a colored coating with an olive gray hue on a base metal of iron or steel by plating the base metal using a bath of a the above zinc alloy for hot dipping at a bath temperature of 490 - 530°C, heating the plated work in an atmosphere at 500 - 520°C for 50 - 150 seconds, and there­after either cooling it with warm water or first forcibly air-cooling and then cooling it with warm water.
• the plating is carried out using a bath of molten zinc alloy made by adding 0.2 - 0.8 wt % Mn to a purest metallic zinc bullion (at least 99.995 % pure) or special zinc bullion (at least 99.99 % pure) conforming to JIS H2107 and used primarily as molten zinc alloy.
• the metallic zinc bullion for use in making the molten zinc alloy is desired to have a Pb content of 0.005 wt % or less.
• an iron or steel material as the base metal is immersed in the plating bath at 490 - 530°C for at least one minute.
• the base metal is pulled out of the bath and heated in an atmosphere at 500 - 520°C for 50 - 150 seconds, and then is either cooled with warm water or first air-cooled forcibly in air and then is cooled with warm water.
• the resulting colored coating can become uneven in hue or lose its hue, or the colored oxide film formed by the plating tends to come off, rendering it impossible to obtain the desired olive gray colored coating.
• a colored coating with a uniform orange gray hue can be formed on an iron or steel material by plating it under the specific conditions using the molten zinc alloy bath of the specific composition, heating the plated metal, and then either cooling it with warm water or first air-cooling forcibly and then cooling it with warm water. It thus provides a corrosion-resistant material for the components and facilities for uses where they are required to be olive gray in color from the aethetic viewpoint. Since the color-coated metal thus obtained is highly corrosion-resistant, the iron and steel products with such colored coatings according to the invention can be effectively used in a wide range of applications.
• a zinc alloy for hot dipping to form on a base surface an olive gray colored coating of a composition comprising 0.2 - 0.8 wt % Mn - 0.05 - 1.0 wt % Cu - bal. Zn, it is possible to form a colored coating with an olive gray hue on a base metal of iron or steel by plating the base metal using a bath of a the above zinc alloy for hot dipping at a bath temperature of 490 - 530°C, heating the plated work in an atmosphere at 500 - 520°C for 50 - 150 seconds, and thereafter either cooling it with warm water or first forcibly air-cooling and then cooling it with warm water.
• the zinc to be used in making the molten zinc alloy is according to 1).
• the base metal is immersed in the plating bath of the molten zinc alloy of the above zinc containing 0.2 - 0.8 wt % Mn and 0.05 - 1.0 wt % Cu at 490 - ­530°C for at least one minute.
• the metal is pulled out of the bath and heated in an atmosphere at 500 - 520°C for 50 - ­150 seconds, and then is either cooled with warm water or first air-cooled forcibly in air and then is cooled with warm water. In this way a colored coating of oxide film olive gray in hue is formed on the iron or steel surface.
• the resulting colored coating can mix with some other hue or lose its hue, or the colored oxide film tends to come off, rendering it impossi­ble to obtain the desired olive gray hue.
• the colored zinc coated steel obtained is excellent in its corrosion resistance.
• Iridescent, multicolored coating which exhibits a blend of golden, purple, blue, and green colors was found in an epochal way of color development that is not mere coloration of the ordinary metallic-colored hot-dip galvanized articles but a breakthrough in the traditional concept of hues with ordinarily colored galvanized products.
• This is accom­plised, under the use of a zinc alloy comprising either 0.1 - 0.8 wt % Mn alone or 0.1 - 0.8 wt % Mn and 0.05 - 1.0 wt % Cu and the balance Zn and inevitable impurities, by hot-­dipping a base metal of iron or steel into a bath at a temperature of 450 - 550°C, and then cooling the galvanized metal with warm water.
• the zinc alloy is made by adding a specific alloying additive or additives to metallic zinc bullion.
• the metallic zinc bullion to be used in making the molten zinc alloy under the invention is typically one of the grades conforming to JIS H2107, for example, distilled zinc 1st grade (at least 98.5 % pure), purest zinc (at least 99.99 % pure), and special zinc grades.
• the impurities inevitably contained in these zinc materials are, for example in the distilled zinc 1st grade, all up to 1.2 wt % Pb, 0.1 wt % Cd, and 0.020 wt % Fe.
• a metallic zinc with a total impurity content below 1.5 wt % is desirable.
• Hot dipping is effected by the use if the above molten zinc alloy bath at a bath temperature of 450 - 550°C.
• the immersion time is about 1 to 3 minutes.
• After the immersion the coated work is cooled with warm water.
• the cooling is done by dipping the work in warm water at 40 - 60°C for 3 - ­30 seconds. If the bath composition and treating conditions are outside the specified ranges, the desired iridescent color development will not be attained.
• the workpieces to be galvanized are desired to be 1.6 mm or more in thickness.
• the work Before being galvanized, the work is pretreated in the usual way. It is degreased, for example by the use of an alkaline bath, descaled by pickling or other treatment, and then fluxed by a quick dip in a flux solution such as ZnCl2-KF solution or ZnCl2-NH4Cl solution.
• a flux solution such as ZnCl2-KF solution or ZnCl2-NH4Cl solution.
• the metallic zinc bullion to be used in making the zinc alloy of the invention must be such that its impurity Pb content is limited to 0.005 wt % or less. For this reason the use of the purest zinc bullion (at least 99.995 wt % pure) defined in JIS H2107 is desirable. Special zinc bullion (at least 99.99 wt % pure) may also be used provided its Pb content is confined within the limited 0.005 wt % or below. If more than 0.005 wt % lead is present in the coating bath, the colors of the golden-purple-red series will not develop within short periods of time.
• 0.2 - 0.8 wt % Mn and 0.01- 0.1 wt % Ti are added to the metallic zinc of high purity. These ranges of additions are based on the fact that a relatively small amout of Ti and a relatively large amount of Mn in the zinc alloy have been found helpful in shortening the period of time for which the galvanized work is held in the heating atmosphere. Thus, the upper limit of Ti is fixed to be 0.1 wt %. If the Ti content is less than 0.01 wt %, there is no beneficial effect of the Ti addition and coloring in desired hues becomes impossible. A large Mn content of 0.2 wt % or above is necessary to obtain desired hues rapidly, but if the content exceeds 0.8 wt % the adjustment of hues becomes difficult and the work is not adequately wetted with the bath.
• the work to be galvanized is degreased, for example by the use of an alkaline bath, descaled by pickling or the like, and then treated with a flux to be ready for galvanizing.
• the flux treatment is effected, for example, by a dip for a short time in a ZnCl2-KF solution, ZnCl2-NH4Cl solution, or other known flux solution.
• the work is immersed in a coating bath at a specific controlled temperature for 1 to 3 minutes.
• the coated metal is pulled out of the bath and, through proper control of the degree of oxidation of the coating film, a golden, purple, or blue color is selectiveivelyly obtained at will. As the degree of oxidation increases, golden, purple, and blue colors are brought out successively in the order of mention.
• the galvanizing bath temperature is generally 480 - ­550°C, preferably 490 - 520°C, or lower than the usual bath temperatures. This means a substantial reducation of energy cost in the case of mass treatment.
• the coated work After the coated work has been taken out of the bath, its degree of oxidation is changed through control of the cooling rate by cooling the work in a variety of ways, including natural cooling in the air, cooling with cold or warm water, forcible cooling, and slow cooling in an oven.
• a desirable practice consists in holding the galvanized metal in an atmosphere at 450 - 550°C for a predetermined period of time and changing the rate of subsequent cooling so as to control the degree of oxidation. If the alloy layer comes up to the surface no color will develop, and therefore it is important to thicken the oxide film in preference to the growth of the alloy layer.
• the holding temperature, holding time, or cooling rate is so chosen as to cause appropriate color development. Under the invention the heating time can be shortened.
• the colored oxide film formed on the colored, hot-dip galvanized material tends to discolor or fade with time, with changes in hue due to the progress of deterioration, depending on the environmental conditions including the sunlight, temperature, and humidity.
• the deterio­ration of the colored oxide film does not adversely affect the corrosion resistance of the hot-dip galvanized steel itself, the original beautiful appearance is unavoidably marred.
• this product acts to decompose the resinous content (oily fatty acid) of an oily paint or long oil alkyd resin paint, causing the decomposition product to react with the zinc to produce zinc soap along the interface between the zinc surface and the paint film, thereby substantially reducing the adhesion of the paint.
• the colored oxide film layer formed on the surface of the colored hot-dip galvanized steel does not provide an adequate barrier between the zinc surface and the surrounding air.
• the pessimistic view that painting over the oxide film would, after all, be the same as direct paint application to the galvanized surface has been predominant. Contrary to these predictions, it has now been found that the colored oxide film has good affinity for and adhesion to paints, allowing the applied paint to permeate through the film to show high separation resistance, and is sufficiently capable of preventing water permeation to inhibit the reaction of the zinc layer with water and therefore the formation of zinc soap.
• the hot-dip galvanized materials thus colored may be coated with a paint having excellent adhesion, weather resistance, durability, and environmental barrier properties.
• pretreatment is essential and the types of paints that may be employed are limited.
• paints that may be employed are limited.
• With colored, hot-dip galvanized steels by contrast, there is no need of pretreatment and various paints may be used. Since the heating for oxidation that follows the galvanized step produces a film of oxide such as TiO2 or MnO on the galvanized surface, the coating on the galvanized steel is so clean that there is no necessity of treating the surface before painting.
• the paint to be used may be any type which does not unfavorably affect, but protect, the colored oxide film layer to be painted.
• a synthetic resin paint is used.
• synthetic resin paints those superior in pro­tective effects are polyurethane resin, acrylic resin, epoxy resin, and chlorinated rubber paints. The paint is properly chosen in consideration of the price, environments to be encountered, ease of application, and other factors.
• the color of the colored oxide film is to be shown as it is, a clear paint is the best choice, and where the color tone is to be modified, an aqueous paint is the easiest to handle.
• the paint can be applied by brushing, spraying, or dipping.
• multicoating is not impractical. For instance, where the environments are very severe or adverse, multiple painting may be taken into account.
• An example is the application of an aqueous paint as the base coat and a clear paint as the intermediate and top coats.
• an epoxy resin paint durable against the alkali attacks that result from zinc elution may form the undercoat and a chlorinated rubber or polyurethane paint excellently resistant to water, chemicals, and weather may form the intermediate and surface coats.
• the colored zinc coating by metal spraying basically involves spraying a zinc alloy, which is otherwise used for a coating bath, in the form of wire, rod, or powder, over the object. Surprisingly, the oxidation reaction of the additional element had been found to proceed more favorably than expected during the spraying process, achieving at least as satisfactory effects as the colored hot-dip galvanizing.
• a colored zinc coating may be attained by spraying a coloring, oxidizing zinc alloy over a base surface by a metal spraying process, whereby a colored oxide film is formed on the base surface. After the spraying, the color development of the colored oxide film may be controlled by cooling and/or heating.
• Metal spraying comprises heating a sprayable material to a half-molten state and spraying it over a base surface to form a coating tightly bonded to the surface.
• the sprayable material takes the form of a wire, rod, or powder, any of which may be employed under the invention.
• the sprayable material may be any of the zinc alloys in common use for colored hot-dip galvanizing. It may, for example, be a Mn-Zn, Mn-Cu-Zn or Mn-Ti-Zn alloy with or without the further addition of Cu, Ni and/or Cr.
• a work high in Ti, Mn or the like is not readily wetted when dipped in the bath, leaving holidays on the surface.
• the possibility of uncoating puts limitations to the amounts of the additive ingredients. Metal spraying is free from the wettability problem, and larger proportions of the additional elements can be used. Accordingly, the range of color development is wider and the hues have longer life.
• An example of desirable sprayable material is a zinc alloy containing 0.1 - 2.0 wt % Ti and optionally 0.01 - 4.0 wt % of at least one selected from Mn, Cu, Cr, and Ni. With good workability the zinc alloy can be easily made into a wire or rod or powdered by crushing or melt dropping.
• the sprayer that may usually be used is of the type known as a gas flame spray gun.
• An arc type spray gun may be employed as well.
• the sprayable material is melted by the sprayer and sprayed over the base surface to be coated.
• the corners and intricate portions of the work difficult to coat by hot dipping can be completely coated by aiming the spray gun to those portions. Localized coatability permits figures and other patterns to be made easily.
• Another major advantage of metal spraying is the ability of coating iron and steel structures or the like at the sites.
• the degree of surface oxidation is controlled so as to develop a desired color.
• a variety of colores e.g., yellow, dark red, green, golden, purple, and blue colors, can be selectively developed as desired, depending on the degree of oxidation.
• the cooling rate of the sprayed coat can be adjusted by the use of natural cooling in the air or forced cooling with water or air.
• the spray coat may be heated for a variable period with flame, infrared lamp, oven (where usable) or the like, and the subsequent cooling may be controlled. Proper combination of the sprayable material composition and surface oxidation conditions renders it possible to bring out a desired hue.
• the painting described above may be applied onto the sprayed coating.
• the Examples 1 to 4 correspond to the items 1 to 4 described in the detailed explanation.
• the steel sheet thus pretreated was plated by the use of a plating bath of the following composition under the following conditions:
• the plated steel sheet surface had a colored coating with a uniform olive gray hue.
• the steel sheet pretreated as previously described was plated by immersion in a plating bath of the following composition at 490 - 530°C for one minute. The sheet was then pulled out of the bath and held in an oven at 500 - ­520°C for 50 - 150 seconds. The plated sheet taken out of the oven was either cooled with warm water or forcibly air-cooled in air and then cooled with warm water.
• the plated steel sheet surface had a colored coating with a uniform olive gray hue.
• Example 3 development of iridescent color with Mn-Zn or Mn-Cu-Zn alloy
• Example 4 development of gold - purple - blue with Mn-Ti-Zn alloy
• Example 2 The steel pieces treated as described in Example 1 were immersed in a bath of molten zinc alloy containing 0.5 wt % Mn and 0.08 wt % Ti, with the Pb content restricted to 0.004 wt %, at 500°C for one minute. They were then held in a heating atmosphere at 500°C and cooled.
• the relations between the treating conditions and coloring are shown in the following Table 2. Golden and purple colors came out very rapidly and even blue color developed in 30 seconds. The galvanized surfaces were quite smooth and beautiful in appearance.
• Test pieces of steel sheet measuring 50 mm wide, 100 mm long, and 3.2 mm thick, were either conventionally hot-­dip galvanized or colored, hot-dip galvanized (with a Zn-Ti alloy).
• the coated pieces, together with uncoated ones, were subjected to outdoor weathering tests. The tests were conducted within a plant under the possession of the present appli­cant. The degrees of degradation after test periods of three months, six months, and one year were visually inspected. The results are tabulated below in Table 3.
• a rod of zinc alloy containing 0.3 wt % Mn was used as a sprayable material. It was sprayed over a steel material by means of an oxy-acetylene gas flame type spray gun. The sprayed surface was allowed to cool, heated to 500°C for 30 seconds, and again allowed to cool in the air.

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Cited By (17)

Citations (7)

• 1987
  • 1987-11-19 DE DE8787117098T patent/DE3781375T2/de not_active Expired - Fee Related
  • 1987-11-19 EP EP87117098A patent/EP0269006B1/fr not_active Expired - Lifetime

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