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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/364—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
  • C23C22/188—Orthophosphates containing manganese cations containing also magnesium cations
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/368—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing magnesium cations

Definitions

• the present invention relates to a conversion treating method for forming a zinc phosphate coating film on a metal surface.
• the invention relates to a treating method for forming a zinc phosphate coating film which does not contain any nickel ions, because of its recent trend in use to be limited according to environmental regulation, and which is suitable for cationic electrodeposition coating and superior in coating film adhesion and corrosion resistance, especially warm brine resistance and a property to prevent rust of a scab type (scab corrosion) (hereinafter, this property is referred to as "scab resistance”) on a metal surface simultaneously having an iron-based, a zinc-based and an aluminum-based surface.
• Metal materials have been used in various fields such as automobile bodies and other attachments, building materials, furniture, and the like.
• Metal is treated with zinc phosphate as coating pretreatment in order to prevent the metal from corrosion caused by oxygen or sulfur oxides in the air, rainwater, seawater, and so forth.
• a zinc phosphate coating film formed by this treatment is required to be superior in adhesion to a metal surface substrate, and also, to be superior in adhesion to a coating film further formed on the zinc phosphate coating film (secondary adhesion) and also, the zinc phosphate coating film is required to have sufficient rust preventability even if it is under corrosive environment.
• the scab resistance, a high order of warm brine resistance and so on are desired since the body is repeatedly subjected to permeation of salt water or variation of dry and wet atmospheric conditions from a scar of the external plate part.
• a zinc phosphate coating film formed on a metal surface does not consist of only zinc phosphate, but contains various kinds of metal components besides zinc to elevate corrosion resistance. Especially, to obtain a zinc phosphate coating film superior in scab resistance and warm brine resistance, the zinc phosphate coating film has contained nickel as an essential component.
• a method for forming a zinc phosphate coating film suitable for cationic electrodeposition coating on a surface of a metal material having two or more kinds of metal surfaces for example, a metal surface simultaneously having both of an iron-based surface such as a steel sheet as well as a zinc-based surface such as a material made by plating a surface of a steel sheet with zinc or a zinc alloy) by zinc phosphating the metal surfaces using an acidic zinc phosphating solution which does not contain nickel as an essential component.
• an acidic zinc-phosphating solution containing 0.5 to 1.5 g/l of a zinc ion, 5 to 30 g/l of a phosphate ion, 0.6 to 3 g/l of a manganese ion, 0.05 g/l or more of a fluorine ion, and a coating film-converting accelerator as main components is used in order to form a further superior coating film on a metal surface simultaneously having both of an iron-based and a zinc-based surface and to lower a treating temperature.
• the two kinds of phosphating solutions cited here contains 0.1 to 4 g/l of a nickel ion to elevate further the secondary adhesion and corrosion resistance compared with the case of using a manganese ion alone.
• a material made by combining an aluminum material with at least one of an iron material and a zinc material also has been practically used in various fields such as automobiles, building materials and so forth. It is desired to form a coating film having superior adhesion and high corrosion resistance on these metal surfaces by conversion treatment of the surfaces with the same zinc phosphating solution.
• the present invention provides a method for zinc-phosphating a metal surface to be treated by the cationic electrodeposition coating, which comprises bringing a metal surface having all of an iron-based, a zinc-based and an aluminum-based surface in contact with an acidic zinc-phosphating solution to make a zinc phosphate coating film; said method is characterized in that the acidic zinc phosphate solution does not contain a nickel ion, but 0.1 to 4 g/liter of a cobalt ion, 0.1 to 3 g/liter of a manganese ion, a coating film-converting accelerator ( a ), 200 to 500 mg/liter of a simple fluoride compound in terms of HF concentration, and a complex fluoride in a mole ratio of 0.01 to 0.5 relative to the simple fluoride compound.
• the acidic zinc phosphate solution does not contain a nickel ion, but 0.1 to 4 g/liter of a cobalt ion, 0.1 to 3 g/liter of a manganese
• a metal material to be treated with the zinc-phosphating method of this invention is a metal surface simultaneously having an iron-based, a zinc based and an aluminum-based surfaces.
• the cobalt ion concentration of the acidic zinc phosphating solution is in a range of from 0.1 to 4 g/l and preferably in a range of from 0.3 to 3 g/l. If the cobalt ion concentration is less than 0.1 g/l, an elevating effect on the corrosion resistance becomes insufficient. If it exceeds 4 g/l, an elevating effect on the corrosion resistance decreases.
• the manganese ion concentration is in a range of from 0.1 to 3 g/l and preferably in a range of from 0.3 to 3 g/l. If it is less than 0.1 g/l, the adhesion a zinc-based surface and an elevating effect on the warm brine resistance become insufficient. If it exceeds 3 g/l, further increased effect than that in this invention be expected and it is economically disadvantageous.
• the concentration of a simple fluoride compound in the acidic zinc-phosphating solution in this invention should be adjusted in a range of 200 to 500 mg/l in terms of HF and preferably in a range of from 250 to 500 mg/l. If it is less than 200 mg/l, the aluminum ion concentration in the treating solution increases due to formation of a water-soluble complex fluoride compound, and deterioration of the conversion treating occurs. If it exceeds 500 mg/l, zinc phosphate coating film formed on an aluminum-based surface is contaminated with Na3AlF3 and warm brine resistance of the cationic electrodeposition coating film deteriorates.
• a complex fluoride compound contained in the acidic zinc-phosphating solution must be adjusted so that the mole ratio relative to simple fluoride concentration in terms of HF is satisfactory for the following equation (1). 0.01 ⁇ (complex compound)/(simple compound) ⁇ 0.5
• the amount of the complex fluoride compound in the equation 1 does not comprise the complex fluoride containing aluminum. If the mole ratio of complex fluoride to simple fluoride exceeds 0.5, eluted aluminum ions form a water-soluble complex and the aluminum ion concentration in the treating solution increases and, accompanying with these, deterioration of conversion occurs. Also, even if a water-insoluble complex is formed, because of its having floating and suspending characters, the removal by filtration of precipitate becomes difficult, and it makes a reason of inferior electrodeposition coating (for example, uniformity lack in the coating film and deterioration in the corrosion resistance of a coating film ) by its attaching with a matter to be treated. If the above molar ratio is less than 0.01, Na3AlF3 is mingled in a zinc phosphate coating film formed on an aluminum-based surface and the warm brine resistance of the coating film formed by the cationic electrodeposition coating decreases.
• the concentration of a simple fluoride compound in terms of HF in an acidic zinc-phosphating solution can be measured by a commercially available silicon electrode meter or fluorine ion meter, it is preferable to control the concentration by measuring the active fluorine concentration using a silicon electrode meter.
• the concentration is preferably controlled so as to be in a range of from 15 to 130 ⁇ A in a value indicated by the silicon electrode meter, more preferably in a range of 40 to 140 ⁇ A.
• the silicon electrode meter shows high sensitivity in the pH region of an acidic zinc-phosphating solution used in this invention ( an acidic region, preferably pH ⁇ 4 ) and has such advantage as the indicated value becomes large in proportion to the active fluorine concentration.
• an uniform zinc phosphate coating film is not formed on an aluminum-based surface and also, because aluminum ions dissolved into a treating solution form a water-soluble fluoride complex, the aluminum ion concentration in the treating solution increased and, accompanying with this, the conversion deterioration occurs. If the indicated value exceeds 130 ⁇ A, the zinc phosphate coating film formed on an aluminum-based surface is contaminated with Na3AlF3 componet and the warm brine resistance of the electrocoating film decreases.
• a silicon electrode meter described above is, for example, the one disclosed in Japanese Official Patent Gazette, showa 42-17632, but not limited to this type.
• the silicon electrode meter is commercially available with the trade name of product of Surfproguard 101N made by Nippon Paint Co., Ltd. and easily obtainable.
• a silicon electrode meter is generally arranged so as to read an electric current value by bringing a p-type silicon electrode and an inactive electrode made of platinum in contact with a solution to be measured under a condition where the solution is not in light and by connecting a direct current source between both of these electrodes.
• the solution to be measured is arranged so as to be at a stationary state or to be in a constant current. Then, under these conditions a direct current is impressed between both the electrodes, so that the active fluorine concentration is known by reading an electric current when it becomes a steady state.
• a simple fluoride for example, HF, NaF, KF, NH4F, NaHF2, KHF2 and NH4HF2 and so on are used.
• a fluoride complex for example, H2SiF6, HBF4, and these metal salts such as a nickel salt and a zinc salt and so on are used.
• components other than a cobalt ion, a manganese ion, a simple fluoride compound and a complex fluoride compound are, for example, a zinc ion, a phosphate ion and the accelerator for converting a coating film.
• the accelerator for converting a coating film (a) is used at least one kind selected from a nitrite ion, a meta-nitrobenzensulfonate ion, and hydrogen peroxide.
• Their preferable concentrations are as follows: 0.1 to 2.0 (0.3 to 1.5) g/l for a zinc ion, 5 to 40 (10 to 30) g/l for a phosphate ion, 0.01 to 0.5 (0.01 to 0.4) g/l for a nitrite ion, 0.05 to 5 (0.1 to 4) g/l for a m-nitrobenzensulfonate ion, and 0.5 to 10 g/l for hydrogen peroxide on a basis converted into 100 % H2O2. Values in parentheses are more preferable concentrations.
• the zinc ion concentration is less than 0.1 g/l, an uniform zinc phosphate coating film does not form on a metal surface. Lack of hiding is much and, a coating film of a blue color type in part sometimes forms. Also, if the zinc ion concentration exceeds 2.0 g/l, an uniform zinc phosphate coating film is formed, but the coating film is apt to dissolve easily in an alkali and, especially under an alkali atmosphere where the film is exposed during a cationic electrodeposition process, the coating film sometimes easily dissolves. As a result, the warm brine resistance generally lowers and, especially in a case of treating an iron-based surface, the scab resistance deteriorates, and thus, desired properties are not obtained.
• the phosphate ion concentration is less than 5 g/l, a non-uniform coating film is apt to be formed. If it exceeds 40 g/l, elevation of effects can not be expected and the amount of using drugs becomes large leading to an economical disadvantage.
• concentration of an accelerator for converting a coating film (a) is lower than the forementioned range, sufficient coating film-conversion is not possible on an iron-based surface and yellow rust is easily formed. If the concentration exceeds the range, a non-uniform coating film of a blue color type is easily formed on an iron-based surface.
• the zinc-phosphating solution used in this invention is desired to contain one or more kinds selected from magnesium ion, calcium ion and copper ion in a specially defined concentration range besides the main components described above.
• a preferable range of the magnesium ion is from 0.01 to 3 g/l and a more preferable one is from 0.1 to 2.5 g/l. If the ion is less than 0.01 g/l, an effect upon elevating the corrosion resistance becomes insufficient and if it exceeds 3 g/l, there is a trend that the effect upon elevating the corrosion-resistance decreases.
• the calcium ion prefers to be in a range of from 0.01 to 3 g/l and more prefers to be in a range from 0.1 to 2.5 g/l.
• the copper ion prefers to be in a range from 0.005 to 0.2 g/l and more prefers to be in a range from 0.01 to 0.1 g/l. If it is less than 0.005 g/l, the effect upon elevating the corrosion-resistance becomes insufficient and if it exceeds 0.2 g/l, there is a trend that the scab resistance elevates, but the effect upon elevating the warm brine resistance decreases.
• the zinc-phosphate treating solution used in this invention prefers to contain a sulfuric acid ion. It is desirable to contain a sulfuric acid ion so that the mole ratio of a sulfuric acid ion to a cobalt ion is in the range from 0.1 to 2. If this ratio is less than 0.1, the effect on the improvement of scab resistance is insufficient and if exceeds 2, there is a trend that the effect on the improvement of scab resistance decreases.
• the zinc phosphating solution used in this invention may contain an accelerator for converting a coating film (b).
• an accelerator for converting a coating film (b) is cited, for example, a nitrate ion and a chlorate ion and so forth.
• the nitrate ion prefers to be in a range from 0.1 to 15 g/l and more prefers to be in a range from 2.0 to 10 g/l.
• the chlorate ion prefers to be in a range from 0.05 to 2.0 g/l and more prefers to be in a range from 0.2 to 1.5 g/l.
• These components may be contained alone or in combination of two or more kinds.
• the accelerator for converting a coating film (b) may be used in combination with the accelerator for converting a coating film (a) or without combination with this (a).
• Phosphoric acid zinc phosphate, manganese phosphate and cobalt phosphate, etc.
• Cobalt nitrate Cobalt sulfate, cobalt phosphate, cobalt hydroxide, cobalt chloride and cobalt fluoride, etc.
• Nitrous acid sodium nitrite, ammonium nitrite, sodium meta-nitrobenzensulfonate, and hydrogen peroxide, etc.
• temperature of the phosphating solution prefers to be in a range of from 20 to 70 °C and more prefers a range of from 35 to 60°C. If it is lower than 20 °C, the coating film-converting is insufficient and it consumes a long time to complete the processing. Also, if it is higher than 70°C, balance of the phosphating solution is easily broken due to the decomposition of an accelerator for converting a coating film and a precipitate formation in the phosphating solution, so that it is difficult to obtain a good coating film.
• a preferable time for treating with zinc phosphating solution is 15 seconds or more and a more preferable one is in a range of from 30 to 120 seconds. If it is less than 15 seconds, there is a case where a coating film having desired crystals is not sufficiently formed. Furthermore, in a case where an article having a complicate structure such as an automobile body is treated, it is practically preferred to combine the immersing treatment with the spraying treatment, and in this case, an article is at first subjected to the immersing treatment for 15 seconds or more, preferably, for a period of from 30 to 120 seconds and then to the spraying treatment for 2 seconds or more, preferably, for a period of from 5 to 45 seconds.
• a method for treating with zinc phosphate of this invention includes the immersing treatment and spraying treatment as well as treating embodiment made by combining those treatments.
• a zinc phosphate coating film is formed on a metal surface simultaneously having an iron-based, a zinc-based and an aluminum-based surface by bringing it in contact with an acidic zinc-phosphating solution containing 0.1 to 4 g/l of a cobalt ion, 0.1 to 3 g/l of a manganese ion, the phosphating accelerator ( a ), 200 to 500 mg/l of a simple fluoride compound in terms of HF concentration, and a fluoride complex compound in 0.01 to 0.5 mole ratio relative to the simple fluoride.
• the coating film with conversion superior in adhesiveness and corrosion resistance after the cationic electrodeposition coating is obtained even using the zinc-phosphating solution not containing a nickel ion.
• an identical zinc-phosphating solution not containing nickel use of which suffers limitation according to environmental regulation, can be applied to a metal surface simultaneously having an iron-based, a zinc-based and an aluminum-based surface, and a zinc phosphate coating film suitable for cationic electrodeposition coating and superior in film adhesiveness and corrosion resistance, especially in warm brine resistance and scab resistance can be formed.
• A Cold rolled steel sheet 20% (iron-based surface)
• B Alloyed melt zinc-plated steel sheet 50% (zinc-based surface)
• C Aluminum-magnesium alloy sheet 30% (aluminum-based surface) total area 0.07 m2 per treatment
• Coated metal sheets were obtained by treating three kinds of the above-described metal with the following processes, (a)degreasing, (b)rinsing, (c)surface-conditioning, (d)phosphating (dipping process) (e)rinsing, (f)rinsing with pure water, (g)drying and (h)coating in this sequence.
• a metal to be treated was immersed at 40 °C for 2 minutes. Then the reaction in the bath was controlled by maintaining alkalinity at an initial value, which was shown a milliliter amount of a 0.1 N NaOH solution required for neutralizing a 10 ml of the bath using bromophenolblue as an indicator.
• Surf Cleaner SD 250 was used as a supplementary reagent.
• a metal to be treated was immersed at room temperature for 15 seconds in the solution.
• the bath control was performed by adding Surf Fine 5N-5 to maintain the alkalinity.
• a concentrated solution for supplement A which contains zinc oxide, phosphoric acid, cobalt nitrate, manganese carbonate, hydrosilicofluoric acid and nitric acid corresponding to each of the above ions was used.
• a concentrated solution for supplement B was used.
• Supplement C which contains sodium hydrogen fluoride (NaHF2) was used to control the simple fluoride concentration in terms of HF by an active fluorine concentration using a silicon electrode meter.
• a cationic electrodeposition coating reagent, Power Top U-1000 made by Nippon Paint Co., Ltd. was coated in film thickness of 30 ⁇ m by a cationic electrodeposition coating in the usual way.
• an intermediate coated film having 30 ⁇ m in film thickness was formed by coating an melamine alkyd intermediate coat made by Nippon Paint Co., Ltd. in the usual way.
• a top coat film was formed in film thickness of 40 ⁇ m on the intermediate coated film.
• an electrodeposition coated sheet was immersed in a 5 % sodium chloride solution for 480 hours at 55°C. Then an adhesive tape was pasted on the cut part and peeled off. A maximum peeled width (both sides of the cut part in mm) was measured.
• Corrosion tests one cycle of which consists of a 5 % brine spraying test ( based on JIS-Z-2371 and for 2 minutes ), drying at 60°C for 58 minutes and a wetting test at 50°C for 3 hours under an atmosphere of 95 % relative humidity, were repeated 200 cycles. After completing the cycle tests, a maximum width ( one side width from the cut part in mm ) of coating abnormality on the coated surface ( filament type rust and blister, etc. ) was examined.
• the conversion treatment in which the used zinc-phosphating solution does not contain a nickel ion resulted in an excellent adhesion and corrosion resistance for all the iron-based, zinc-based and aluminum-based surfaces, and the conversion was kept in excellent conditions.
• the results of comparative example 1 show that, because the solution did not contain a simple fluoride compound was used, aluminum ions accumulated in the phosphating solution and inferior phosphating occurs and that the phosphating can not be carried out continuously for a metal surface having all the iron-based, zinc-based and aluminum-based surfaces.
• the comparative example 5 corresponds to a case where the nickel ion was eliminated from a conventional zinc-phosphating solution, because the cobalt ion was not used, the corrosion resistance on the iron-based, zinc-based and aluminum-based surfaces was inferior.

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• 1992
  • 1992-04-03 JP JP8250992A patent/JPH05287549A/ja active Pending
• 1993
  • 1993-04-01 EP EP93302582A patent/EP0564287A2/fr not_active Withdrawn

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