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
  • C23C22/07—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
• • 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
  • C23C22/365—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 containing also zinc and nickel cations

Definitions

• the present invention relates to a phosphate conver ⁇ sion treatment aqueous liquid composition (also called a “bath” below) which will form strongly paint-adherent phos- phate films with excellent post-painting corrosion resist ⁇ ance on the surfaces of iron, zinc, and aluminum metal structures, particularly sheet metal structures such as automobile bodies, household electrical appliances, and the like.
• a phosphate conversion treatment composition ac- cording to this invention is very well suited to be a pretreatment for cationic electrodeposition painting operations.
• compositions and processes according to this in ⁇ vention are particularly well suited for treating a sheet metal structure which is made up of at least one type of ferrous metal containing material, such as steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, galvannealed steel sheet, or the like, and an aluminum material selected from aluminum sheet and aluminum alloy sheet.
• ferrous metal containing material such as steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, galvannealed steel sheet, or the like
• aluminum material selected from aluminum sheet and aluminum alloy sheet such as steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, galvannealed steel sheet, or the like
• aluminum material selected from aluminum sheet and aluminum alloy sheet such as steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, galvannealed steel sheet, or the like
• aluminum material selected from aluminum sheet and aluminum alloy sheet such as steel sheet, galvanized steel sheet, zinc alloy plated steel sheet, galvannealed steel sheet, or the like
• the aluminum ion present in a phosphate conversion treatment composition typically acts as an interfering ion for the conversion reactions.
• the aluminum ion concentration in the treatment composition must be suppressed below a particular prescribed concen ⁇ tration.
• the afore ⁇ said invention (1) comprises a method for the precipita- tive removal of the aluminum ion which, however, requires removal of the sludge component precipitated as the fluor- ide. A substantial filtration plant is required for the elimination of this sludge, and this method suffers from, problems with both equipment and production technology, i.e., an unavoidable expansion of the installation and treatment of the discharged sludge industrial waste.
• the aforesaid invention (2) comprises a method in which the proportions for both the free acidity and free fluorine are restricted.
• the present invention aims to provide a satisfactory phosphate conversion coating treatment for surfaces in ⁇ cluding aluminum, without requiring as large a sludge re ⁇ moval volume and/or suffering the low limitations on ac ⁇ ceptable levels of aluminum ions in the composition as were observed in the prior art. Summary of the Invention
• the present invention introduces a phosphate conver ⁇ sion treatment composition, particularly for iron-aluminum sheet metal structures, that characteristically comprises, preferably consists essentially of, or most preferably con ⁇ sists of: (A) a source of zinc ions to provide from 0.4 to 2.5 grams per liter (hereinafter "g/L") of zinc(II) ions,
• (C) a source of manganese ions to provide from 0.4 to 2.0 g/L manganese(II) ions
• the free acidity of the composition is in the range from to 0.1 to 1.5 points.
• This invention makes possible a substantial increase in the permissible aluminum ion content of phosphating con ⁇ version treatment composition over previous values. This in turn makes possible the execution of a satisfactory phosphate conversion treatment on any material, such as aluminum material, cold rolled steel sheet, and zinc and/or zinc alloy plated steel sheet, without resorting to pre- cipitative removal of the aluminum ion. Furthermore, a completely satisfactory post-painting corrosion resistance and paint film adherence are also achieved, in particular when the invention is applied as a pretreatment for cat ⁇ ionic electrodeposition painting.
• the zinc ion and phosphate ion are film source mater ⁇ ials for formation of the phosphate film.
• the presence of zinc ion in excess of 2.5 g/L precludes the formation of a good, strongly corrosion-resistant film.
• a uniform, fine, and dense film cannot be obtained at less than 0.4 g/L zinc ion.
• the phosphate ion should be present within the range of 8 to 30 g/L. Good films cannot be obtained below this lower limit, while exceeding the upper limit is uneconomical since no further improve ⁇ ment in performance is obtained thereby.
• the fluorine component is preferably added in the form ' of one or more selections from among the fluoride ion and complex fluoride ions, and a total fluorine of 10 to 3,500 ppm as F is required. A satisfactory conversion process will not normally be achieved on the treatment substrate when either the upper or lower limit value is violated.
• Aluminum ion concentrations in excess of 1,000 ppm prevent a satisfactory conversion process on the treatment substrate. From a practical standpoint, the concentration level cannot usually be reduced to below 1 ppm during actual operation when there is aluminum in the workpieces to be treated. Moreover, the total fluorine/aluminum ion molar ratio must be at least 5; lower values preclude a satisfactory film formation just as does an impermissible total fluorine concentration.
• the nickel and manganese ions function to provide minute, fine film crystals.
• the post-painting corrosion resistance and the paint film adherence are also improved as a result of the improvement in the film crystals deriv ⁇ ing from the uptake of these metal components into the film.
• the manganese ions must be added at 0.4 to 2.0 g/L.
• the aforementioned benefits do not manifest to a satisfac- tory degree when this lower limit is not met, while exceed ⁇ ing this upper limit in fact adversely affects the post painting corrosion resistance.
• the nickel ion is a par- ticularly crucial metal additive component from the stand ⁇ point of the painting performance, and it should be added at 0.5 to 3.5 g/L.
• the manganese ion the afore ⁇ mentioned activities do not manifest to a satisfactory de- gree when the lower limit is not met, while exceeding the given upper limit degrades the conversion process.
• the nickel ion/aluminum ion molar ratio must be at least 1.6, and the nickel ion/ total fluorine molar ratio must be at least 0.3.
• the painting performance of the treatment workpiece will de- teriorate when either of the prescribed molar ratios (con ⁇ centration balances) is violated.
• nitrate ion it may be added as a nitrate salt at the same time as addition of the metal ion, but the nitrate ion concentration should be 2.0 - 20 g/L.
• the treatment composition will not be stable when this low ⁇ er limit is not met, while the corrosion resistance deter ⁇ iorates when the given upper limit is exceeded.
• nitrite ion to provide at least 10 ppm as a film formation accelerator is necessary in order to increase the initial conversion reaction rate in treatment by the present invention's treatment composition and bring about the rapid formation of a uniform film. A uniform film will not be formed when this quantity of addition falls below the lower limit.
• Exceeding 250 ppm of nitrite is economically disadvantageous since no further incremen ⁇ tal effect is obtained for aluminum materials and zinc plated steel sheet. With regard to cold-rolled steel sheet, a satisfactory film weight is not obtained when the given upper limit is exceeded, and the painting performance is therefore degraded.
• the free acidity of the treatment composition prefer ⁇ ably should also be controlled. At less than 0.1 points, not only can a stable treatment composition not usually be obtained, but an inferior conversion tends to occur, in particular in the case of cold-rolled steel sheet. A uni ⁇ form, dense, and fine film will not usually be obtained on the sheet metal structure under consideration when 1.5 points is exceeded.
• the total acidity is governed by the phosphoric acid concentration and metal ion concentration in the treatment composition, and, given that these concen ⁇ trations fall within the specified ranges, is not specif- ically limited.
• the treatment composition according to the present invention is preferably applied within the temperature range of 25 to 55 ° C. While the preferred treatment meth ⁇ od is immersion, the benefits associated with the present invention are not compromised even by spray treatment, or by any other method of contacting the composition with the workpieces for an adequate time to produce a conversion coating thereon.
• Aluminum sheet (according to Japanese Industrial Standard ⁇ "JIS" ⁇ 5052, abbreviated below as Al sheet)
• a 10 milliliter (“mL”) sample of the treatment compo ⁇ sition was titrated to neutrality with 0.1 N aqueous NaOH solution using bromophenol blue as the indicator.
• the "point" (pt) value is the number of milliliters of 0.1 N aqueous NaOH solution required for the color change from yellow to blue.
• the tricoated sheet was immersed in deionized water at 40° C for 240 hours.
• a checkerboard-like pattern of one hundred (100) squares 2.0 mm on each side was then scribed, deeply enough to reach the substrate, on the sample using a sharp cutter. This was followed by peeling with cello ⁇ phane tape pressed against the scribed area, and the number of peeled squares was counted and reported in the tables. The best score is zero and the worst is 100 for this test.
• a cross was scribed into the tricoated sheet using a sharp cutter so as to reach the substrate, and the sheet was then subjected to 5 cycles, wherein each cycle con ⁇ sisted of salt spray testing according to JIS-Z 2371 for 24 hours followed by exposure to air at 50° C with 70 % relative humidity for 144 hours. After five cycles, the maximum single-side blister width from the cross cut was measured and reported according to the criteria shown in Table 1.
• Table 2 reports the quantitative characteristics of the treatment compositions used in each example and com ⁇ parison example and also reports the results for the paint ⁇ ing performance testing. The results in Table 2 make it clear that an excellent paint performance was obtained in each of Examples 1 through 7 according to the invention while a satisfactory paint performance was not obtained in the case of Comparison Examples 1 through 4.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Publications (1)

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Cited By (4)

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Citations (4)

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• 1990
  • 1990-10-24 JP JP2286266A patent/JP2794013B2/ja not_active Expired - Lifetime
• 1991
  • 1991-10-16 AU AU89598/91A patent/AU8959891A/en not_active Abandoned
  • 1991-10-16 WO PCT/US1991/007668 patent/WO1992007974A1/en active Application Filing
  • 1991-10-23 KR KR1019910018660A patent/KR100234498B1/ko not_active IP Right Cessation

Patent Citations (4)

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