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
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
  • C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
  • C23C22/184—Orthophosphates containing manganese cations containing also zinc cations containing also nickel 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
  • C23C22/182—Orthophosphates containing manganese cations containing also zinc cations

Definitions

• This invention relates to phosphating metal surfaces.
• Japanese Patent Publications (unexamined) No. 107784/1980 and No. 152183/1980 (both in the name Nippon Paint Co. Ltd.) disclose phosphating methods for treating iron-based metal surfaces which are particularly suitable for treating manufactured products having complicated surfaces, such as automobile bodies.
• the phosphating methods are in use commercially in the automotive industry for pre-treating automobile bodies prior to cationic electrocoating, which is a coating process now used extensively in this industry.
• 107784/1980 is carried out by first subjecting the metal surface to a dipping treatment with an acidic aqueous solution containing 0.5 to 1.5 g/l of zinc ion, 5 to 30 g/1 of phosphate ion, and 0.01 to 0.2 g/1 of nitrite ion and/or 0.05 to 2 g/1 of m-nitrobenzene--sulfonate ion at a bath temperature of 40° to 70°C for 15 seconds or more, followed by spraying with the above--mentioned solution for 2 seconds or more.
• 152183/1980 comprises spraying onto the metal surface an acidic aqueous solution containing 0.4 to 1.0 g/l of zinc ion, 5 to 40 g/1 of phosphate ion, 0.01 to 0.2 g/l of nitrite ion and 2.0 to 5.0 g/1 of chlorate ion at 40° to 70 ⁇ C for 40 seconds or more.
• German Patent 29 31 693 discloses a phosphating process using a solution containing zinc, manganese, phosphate, nitrate, and chlorate ions in stated gram-atom relationships.
• Japanese Patent J50139-039 discloses a conversion coating solution containing manganese ions for the treatment of zinc surfaces.
• this prior art solution contains from 3 to 20 g/l of zinc ions, which results in a conversion coating having leaf-like crystals on iron-based surfaces. Such leaf--like crystals are unsuitable as a substrate for cationic electrocoating.
• the solutions of this patent are unsuitable for treating both zinc-based and iron-based surfaces.
• the present inventors have suprisingly found that by the inclusion of defined auantities of manganese ion in certain acidic aqueous phosphating solutions, very satisfactory results can be attained, and that the resulting solutions can be applied by dipping, spraying, or a combination thereof.
• the inventors have further found that while chlorate ion can also be present, it is not an essential component of the treating solution especially for spray applications, provided the defined amounts of manganese ion are present, and that even when chlorate ion is added, as is preferred, the amounts of chlorate ion can be markedly lower than those of known compositions.
• the present invention provides an improved phosphating method for metal surfaces, which is particularly suitable for treating metal surfaces, such as those of car bodies, which have both iron-based surfaces and zinc-based surfaces.
• the invention also provides the aqueous treating compositions involved, concentrates useful in their preparation, and the phosphate coating films resulting from their use.
• the method is especially advantageous for forming phosphate coating films suitable for electrocoating, particularly cationic electrocoating.
• the invention provides a process for phosphating an iron- or zinc-based metal surface comprising contacting the metal surface with an acidic aqueous solution containing:
• the invention also provides an acidic aqueous composition for phosphating an iron- or zinc-based metal surface, which composition is this solution.
• the invention provides also an aqueous concentrate which upon dilution with water forms a solution for use in the application of a conversion coating to iron- or zinc-based metal surfaces, which concentrate comprises:
• the invention provides also a metal substrate having an iron- or zinc-based surface, which surface is coated with a zinc phosphate conversion coating which contains from 1 to 20%, preferably 2 to 15%, especially 2 to 7%, by weight of manganese, and which coating has a non-leaf-like crystal structure on iron-based surfaces.
• the metal surface can be contacted with the acidic aqueous solution by spraying the solution onto the surface of the metal, by dipping the metal surface into the solution, or by a combination of dipping and spraying steps.
• the solution contains 0.1 to 0.4 g/1 of zinc ion. In another particular, preferred, embodiment, the solution contains 1.6 to 2.0 g/l of zinc ion. In another particular, preferred, embodiment, the solution contains 0.2 to 0.5 g/l of manganese ion.
• the present process consists essentially of contacting the metal surface with the solution by spraying the metal surface with the solution by optionally after spraying dipping the metal surface in the solution.
• a contacting which consists of dipping or dipping followed by spraying.
• the contacting can be by spraying more than once optionally interrupted by dipping.
• the present acidic aqueous solution may also contain one or more of the following:
• the present process is carried out preferably at a temperature of from about 40° to about 70°C, especially about 45° to about 60°C, and preferably for a contact time of at least 5 seconds, more preferably at least 15 seconds, especially about 30 to about 180 seconds, and most preferably about 30 to about 120 seconds, as hereinafter discussed.
• the period of treatment is generally at least about 15 seconds for dipping and at least about 5 seconds for spraying. It should be noted that at temperatures below about 40 0 C coatings can be formed, but the coating is sparse, coating formation is relatively slow and longer times are required to form satisfactory coatings.
• the conversion coating accelerators begin to decompose at an unacceptable rate, changing the composition of the solution and resulting in an unacceptable conversion coating; also, precipitates begin to form in the bath.
• the phosphated metal surface(s) are then usually coated with a siccative coating by a known electrocoating process, preferably by the cationic electrocoating process.
• iron- or zinc-based metal surface means iron-based surfaces, iron alloy-based surfaces, zinc-based surfaces, and zinc alloy-based surfaces.
• Zinc-based and zinc alloy-based surfaces include, for example, zinc plated steel plate formed by hot dipping, alloyed zinc plated steel plate formed by hot dipping, zinc plated steel plate formed by electroplating, and alloyed zinc plated steel plate formed by electroplating.
• An important advantage of the present invention is that surfaces of metal components, such as car bodies, that contain both iron-based surfaces and zinc-based surfaces can be treated by the process of the invention with excellent results.
• the process of the invention produces better conversion coatings than are obtainable with conventional dip or spray treating processes, and the amount of etching of the metal surfaces during the present process is only 2/3 to 4/5 that of conventional processes, so that both the quantity of chemicals used in the process as well as sludge formation is only from 2/3 to 4/5 that of conventional processes.
• the present process is equally applicable to the treatment of a single metal surface of a type described above.
• the metal surface to be phosphated is preferably first degreased by dipping in and/or spraying with a known alkaline degreasing agent at 50° to 60°C for a few minutes; washed with tap water; dipped in and/or sprayed with a known surface conditioner at room temperature for 10 to 30 seconds; and the thus treated metal surface then contacted with the acidic aqueous solution of the invention at about 40° to about 70 ⁇ C for at least 5 seconds. Finally, the thus treated metal surface is preferably washed with tap water and then with deionized water. An acidic final chromate rinse can be employed before the rinse with deionized water.
• the acidic aqueous solution preferably contains
• the conversion coating accelerator when the amount of these accelerators is less than the lower amounts given above, the conversion coating on iron-based surfaces is inadequate, forming yellow rust, etc. When the amount of accelerator exceeds the higher amounts given above, a blue-coloured uneven film is formed on iron-based surfaces.
• the acidic aqueous solution desirably contains
• the coating composition can be applied by these methods without a loss in coating formation.
• the coating solution can be applied by intermittent spray, where the metal substrate is sprayed for about 5 to about 30 seconds, then allowed to stand without any coating application for about 5 to about 30 seconds, and then sprayed for at least 5 seconds, with a total spray time of at least 40 seconds. This cycle can be carried out once, twice or three times.
• the components can be subjected first to dipping treatments for about 15 seconds or more, preferably about 30 to about 90 seconds, and then to spray treatment with the solution for about 2 seconds or more, preferably for about 5 to about 45 seconds.
• the spray treatment is preferably carried out for as long a period within the above range as the speed of the production line will permit. Dipping treatment is preferred to spray treatment, but dipping followed by spraying is more preferred.
• the coating can be applied by first spraying the metal surface for from about 2 to aboutl 5 seconds, and then dipping the metal surface into the coating solution for at least about 15 seconds, preferably from about 90 to about 120 seconds.
• This method of applying the coating composition helps to eliminate "hash” marks on the metal surface as the metal surface enters the dip coating solution.
• the "hash” marks result when the conveyor system fails to move the substrate at a constant velocity, or when the substrate "sways" in a direction perpendicular to the direction of conveyor movement.
• treating times and treating sequences can be changed according to the composition of the metal substrate to be treated and the treating solution and conditions to be used.
• the coating solution is conveniently applied at a spraying pressure of from about 0.5 to about 2 Kg/cm 2 .
• the resulting phosphate film present on the zinc-based surface should preferably contain from about 1.0 to about 20% by weight, more preferably from about 2 to about 18% by weight, and most preferably from about 5 to about about 18% by weight of manganese ion, which is very important for the subsequent cationic electrocoating.
• the zinc ion is usually present in from about 28 to about 45% by weight, preferably about 28 to about 40% by weight.
• nickel ion is used in the solution, then from about 0.3 to about 4% by weight, preferably about 0.5 to about 4% by weight of nickel is usually present in the coating.
• the remainder of the coating is usually phosphate and water, except for iquantities of other ions such as sodium, calcium and magnesium, which usually total less than 1% by weight. It has also been found that as the content of manganese in the bath increases, increased manganese coating results. However, increasing the manganese level of the coating above the ranges given above does not improve coating quality.
• sources of zinc ions for use in the invention one or more of the following can be employed: zinc oxide, zinc carbonate, and zinc nitrate.
• sources of phosphate ions one or more of the following can be used: sodium phosphate, zinc phosphate, and manganese phosphate.
• sources of manganese ions one or more of the following can be employed: manganese carbonate, manganese nitrate, manganese chloride, and manganese phosphate.
• sources of conversion coating accelerators sodium nitrite, ammonium nitrite, sodium m-nitrobenzene--sulfonate, and hydrogen peroxide can be employed.
• the addition of nickel ion to the manganese-containing composition results in further improvement in the performance of the phosphate conversion coating, so that the adhesion and the corrosion-resistance of the film produced by cationic electrocoating are also further improved.
• nickel carbonate, nickel nitrate, nickel chloride, nickel phosphate, etc. can be used for nickel ions; sodium nitrate, ammonium nitrate, zinc nitrate, manganese nitrate, nickel nitrate, etc. for nitrate ions; and chloric acid, sodium chlorate, ammonium chlorate, etc. for chlorate ions.
• the acidic aqueous treating solutions are conveniently prepared by diluting an aqueous concentrate which contains a number of the solution ingredients in proper weight ratios, and then adding other ingredients as needed to prepare the treating solutions.
• the concentrates are advantageously formulated to contain zinc ion, phosphate ion and manganese ion, and optionally nickel ion, in a weight proportion of
• the concentrates are preferably formulated to contain at least about 25 g/l, and more preferably from about 50 g/1 to 130 g/l, of zinc ion.
• the phosphated metal surface is preferably rinsed and electrocoated.
• Examples I to IX are Examples of the process and compositions of the invention.
• Examples X to XIV are Examples using known compositions, given for comparison purposes.
• the treating process used, which is common to all of Examples I - XIV, is given below, with the aqueous coating compositions of each Example being set forth in Table 1, while the metal treated and the test results obtained following the phosphate treatment are given in Table 2.
• Examples XV to XXV are Examples of the process and compositions of the invention.
• Examples XXVI to XXXI are Examples using known compositions, given for comparison purposes.

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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)
• Materials For Medical Uses (AREA)
• Chemically Coating (AREA)
• Dental Preparations (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (2)

Family

ID=8191259

Family Applications (1)

Country Status (7)

Cited By (7)

Citations (4)

• 1983
  • 1983-08-22 AT AT83304846T patent/ATE39134T1/de not_active IP Right Cessation
  • 1983-08-22 EP EP83304846A patent/EP0135622B1/fr not_active Expired
  • 1983-08-22 DE DE8383304846T patent/DE3378641D1/de not_active Expired
• 1984
  • 1984-01-13 MX MX200034A patent/MX161907A/es unknown
  • 1984-01-31 BR BR8400392A patent/BR8400392A/pt not_active IP Right Cessation
  • 1984-02-03 CA CA000446700A patent/CA1218284A/fr not_active Expired
  • 1984-08-21 ES ES535314A patent/ES8607423A1/es not_active Expired

Patent Citations (4)

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