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
  • C23C22/12—Orthophosphates containing zinc cations
  • C23C22/16—Orthophosphates containing zinc cations containing also peroxy-compounds

Definitions

• an adherent zinc phosphate coating may be formed on ferrous metal surfaces by immersing the surfaces in a nitrite-containing aqueous zinc phosphate solution, at temperatures up to about 50 degrees C.
• the nitrite which is generally added in the form of the alkali nitrite, serves to accelerate the rate at which the zinc phosphate coating layers are formed on the metal and, further, oxidizes the dissolved iron in the solution from ferrous to the ferrite state, thus effecting the precipitation of the iron from the solution in the form of the substantially insoluble ferric phosphate.
• a further object of the present invention is to provide an improved process for forming zinc phosphate coatings on ferrous metal surfaces wherein the formation of ferro-nitroso complexes in the coating bath is substantially reduced.
• a still further object of the present invention is to provide an improved nitrite accelerated zinc phosphate coating process which may be operated at substantially room temperature With high metal throughput rates without the undesirable formation of ferro-nitroso complexes.
• the present invention includes a composition for the treatment of ferrous metal surfaces which comprises an aqueous acidic zinc phosphate solution, which solution contains nitrite ions and peroxide, and wherein the peroxide content of the solution is provided by including in the solution at least one soluble sulfur-oxygen compound containing peroxogroups.
• the phosphating solutions of the present invention are aqueous acidic zinc phosphate solutions which contain an accelerating amount of nitrite ions.
• the nitrite content of these phosphatizing solutions are within the range of about 0.1 to 2 grams per liter, calculated as NaNO Amounts of nitrite outside of this preferred range may, of course, be used, depending upon the particular zinc phosphate solution and process operating conditions which are employed, so long as the amount of nitrite present is sufficient to effect the desired acceleration of the coating action and oxidation of the ferrous irons in the coating bath.
• the phosphating solutions of the present invention also contain peroxide, in the form of one or more sulfur-oxygen compounds which contain peroxo-groups. These compounds will be present in the solution in amounts which will be effective in maintaining the solution substantially free from ferro-nitroso complexes, with amounts within the range of about 0.01 to 0.2 gram per liter, calculated as H 0 being preferred.
• sulfur-oxygen compounds containing a peroxo group may be used.
• suitable compounds of this type are peroxo-monosulfates, peroxo-disulfates, as well as the corresponding acids of these materials, such as the meta sulfuric acids, (Caros acid), as well as mixtures of these, and the like.
• the preferred compounds have been found to be the alkali metal, and particularly the sodium peroxy disulfates (Na S O and the meta sulfuric acids (H 80 Accordingly, hereinafter particular reference will be made to these sulfur-oxygen compounds although, it is to be understood, that these are merely exemplary of similar materials which may be used.
• the phosphating solutions of the present invention may also contain other layer-forming cations, such as manganese, calcium, and the like. Additionally, other oxidizing or accelerating agents, such as nitrate ions, copper ions, nickel ions, simple and/or complex fluorides, and the like, may also be present. Moreover, the solution may also contain one or more suitable wetting agents which will help promote the penetration of the phosphatizing solution into tightly packed workpieces, such as for example, wire coils. Additionally, the solutions may also contain lead ions, which materials have been found, in some instances, to be effective in promoting the generation of nitrite from nitrates in the solution.
• the metal throughput rate was increased to about 0.6 square meter per liter in 24 hours, under the same operating conditions, solution temperatures had to be raised to 55 degrees C to maintain the solution free of the ferro-nitroso complexes.
• This method of operation obviously, is an expensive way, in terms of heating costs, to maintain these solutions free of these ferro-nitroso complexes.
• the phosphating solutions of the present invention are utilized in immersion processes, at temperatures which are not substantially in excess of about 50 degrees C.
• the sulfur-oxygen compounds may be used either in new phosphating baths or in solutions which are already in operation, and are effective in both in substantially minimizing the formation of the stable ferro-nitroso complexes.
• the bath is made up in the conventional maner so as to contain the desired concentration of zinc, phosphate, as well as other components which may be required.
• sodium nitrite is added to the bath, preferably in amounts within the range of about 0.3 to 0.7 gram per liter, along with the sulfur-oxygen compound, preferably in amounts within the range of about 0.03 to 0.06 gram per liter, calculated on the basis of H 0
• the zinc phosphate may be replenished in the conventional manner, using a replenishing concentrate containing the zinc and phosphate in amounts which will maintain the solution at a constant point level.
• the concentrate containing the zinc and phosphate ions which is used to make up the initial solution may also be used as the replenishing concentrate.
• the nitrite ions which are consumed during operation may be replenished by adding to the solution amounts of sodium nitrite such that when a sample of the bath is titrated against a KMNO solution, the reducing effect will remain substantially constant.
• the process of the present invention may also be utilized with solutions which are already in operation and which already contain substantial quantities of the ferro-nitroso complexes. In this type of operation, a determination is first made as to whether the solution still contains suflicient quantities of nitrite to oxidize all of the ferrous iron to ferric iron.
• the bath may be operated in the manner described above, with periodic replenishment of all of the bath components, including the nitrite and the sulfur-oxygen compounds, as is required to maintain the efficient operation of the solution.
• the total acidity of the solution was 30 points and the pH was adjusted with sodium hydroxide to 2.9. Steel sheets which had been pickled in sulfuric acid and rinsed with water were then immersed in the solution for minutes at 30 degrees C. The metal throughput in the solution was 0.04 square meter of steel surface per liter of solution. Following the removal of the sheets, the solution became completely light colored in less than one minute.
• This solution had a total acidity of 40 points.
• the solution was made up in three portions. To the first was added 0.07 gram per liter H 0 to the second 0.2 gram per liter NaBO .H O (corresponding to 0.07 gram per liter H 0 and to the third 0.5 gram per liter Na S O- (corresponding to 0.07 gram per liter H 0 Drawing lubricant was removed from steel wire segments by treatment in sulfuric acid, and after rinsing in water, the segments were immersed in the various solutions for 10 minutes at 30 degrees C. The metal throughput through each of the solutions was 0.04 square meter of steel surface per liter of solution.
• EXAMPLE 3 To show the effect of the addition of various amounts of hydrogen peroxide to these phosphating solutions, a phosphating solution was formulated as described in Example 2.*To different portions of this solution was added hydrogen peroxide (H 0 in amounts of 0.04, 0.07, 0.10, 0.16, 0.5, 1.0 and 3.0 grams per liter. Steel wire segments which had been pretreated in the manner described in Example 2 were then phosphated in accordance with the process set forth in this example. Following the removal of the wires from the various solutions it was found that the solutions which contained hydrogen peroxide additions in quantities up to and including 0.16 gram per liter were all brown colored and this brown coloration remained for over 30 minutes. In those solutions which had hydrogen peroxide additions of 0.5 gram per liter and higher were not brown colored but there was no phosphate coating formed on the wire segments treated in these solutions.
• EXAMPLE 4 By way of comparison, the procedure of Example 3 was repeated with the exception that instead of the hydrogen peroxide, Na S O was added to the various portions of the treating solution in amounts of 0.1, 0.03, 0.5, 0.7 and 1.3 grams per liter. These additions corresponded to 0.014, 0.043, 0.071, 0.10, and 0.16 gram per liter H 0
• the steel wire segments were then processed in the solutions in the same manner as in Example 3 and following the removal of the wires from the solution it was found that the time for reestablishment of the light color in the solution containing 0.1 gram per liter Na S O was 20 minutes while in all the other solutions became clear in less than one minute. Additionally, the phosphate coatings formed on the wires treated in each of the solutions were all found to provide uniform coverage with no visible difference in the coatings formed, the coating weights all being from about 10 to 11 grams per square meter.
• solution A This solution had a total acidity of 40 points.
• solution B a second portion of this solution was designated as solution B, was modified by the addition thereto of 0.2 gram per liter Na S O Steel wire segments were treated in sulfuric acid to remove any lubricant materials therefrom, rinsed with water and then phosphated by immersion for 10 minutes at 30 degrees C. in the two solutions, using a throughput frequency of 0.2 square meter per liter of solution for an hour.
• solution B was replenished with 0.2 gram per liter Na S O
• the phosphate coatings obtained from both solutions A and B were strongly adherent and quite satisfactory.
• solution A after a throughput of only 0.12 square meter of steel surface per liter of solution, a brown coloration developed in this solution, which coloration remained and was not disapated during the remainder of the run, despite replenishing of the solution with sodium nitrite.
• four square meters of steel surface per liter of solution were passed through solution B without any discoloration developing in the solution which lasted longer than about 1 minute.
• a composition suitable for treating ferrous metal surfaces which comprises an aqueous acidic zinc phosphate solution, which solution contains nitrite ions present in an amount within the range of 0.1 to 2 grams per liter calculated as NaNO and peroxide wherein the peroxide is incorporated in the solution by the addition of a peroxomonosulfur compound being present in an amount within a range of about 0.01 to 0.2 gram per liter, calculated as H 0 and is sufficient to minimize the formation of ferro-nitroso complexes during the use of the bath in the treatment of ferrous surfaces.
• composition of claim 1 wherein the peroxomonosulfur compound is selected from the group consisting of peroxo-monosulfates and peroxo-monosulfuric acid.
• a process for phosphating ferrous metal surfaces which comprises immersing the ferrous metal to be treated v in the phosphatizing solution as claimed in claim 1 and maintaining the ferrous metal in the solution for a period sufiicient to form a phosphate coating thereon.
• peroxo-monosulfur compound is selected from the group consisting of peroxo-monosulfates and peroxo-monosulfuric acid.

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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)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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• 1969
  • 1969-03-10 DE DE19691911972 patent/DE1911972A1/de active Pending
• 1970
  • 1970-01-22 FR FR7002233A patent/FR2033745A5/fr not_active Expired
  • 1970-01-26 BE BE744950D patent/BE744950A/xx unknown
  • 1970-02-11 ES ES376451A patent/ES376451A1/es not_active Expired
  • 1970-02-18 CH CH239270A patent/CH525289A/de not_active IP Right Cessation
  • 1970-02-20 NL NL7002422A patent/NL7002422A/xx unknown
  • 1970-02-26 AT AT180370A patent/AT290244B/de not_active IP Right Cessation
  • 1970-03-09 US US00018322A patent/US3723192A/en not_active Expired - Lifetime
  • 1970-03-10 BR BR217368/70A patent/BR7017368D0/pt unknown

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