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
  • C23C22/23—Condensed 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
  • C23C22/07—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
• • 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
  • C23C22/46—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 oxalates
  • C23C22/47—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 oxalates containing also phosphates

Definitions

• the invention relates to a phosphate containing composition (often de ⁇ noted hereinafter as a "bath" for brevity) for treating the surface of tinplate (i.e., tin-plated steel) and to a treatment process for tinplate. More specifically, the present invention relates to an improvement of a treatment that is already used, prior to the painting or printing of surfaces of tinplate sheet, strip, and formed objects, e.g., cans and the like, to provide such surfaces with an excellent cor ⁇ rosion resistance and paint adherence.
• a phosphate containing composition for treating the surface of tinplate (i.e., tin-plated steel) and to a treatment process for tinplate. More specifically, the present invention relates to an improvement of a treatment that is already used, prior to the painting or printing of surfaces of tinplate sheet, strip, and formed objects, e.g., cans and the like, to provide such surfaces with an excellent cor ⁇ rosion resistance and paint
• the treatment bath and treatment process of the present invention are well adapted for treating sur- faces of tinplate that has been formed by Dl (i.e., drawing-and-ironing) process ⁇ ing.
• the present invention concerns a novel technology for treating tin- plate surfaces, a technology that may be used to provide tinplate surfaces with an excellent corrosion resistance and paint adherence, but which is free or very nearly free of the insoluble salts (hereinafter referred to as "sludge") that are produced by the tin ions and iron ions that elute into the bath during treatment. This sludge reduces the productivity of tinplate surface treatment lines.
• the surface treatment equipment for tinplate Dl can is generally called a washer. Molded Dl can is inverted and continuous ⁇ ly treated in the washer with a cleaning bath and a surface treatment bath. Ex ⁇ isting washers normally use 6 steps (pre-cleaning, cleaning, water wash, sur ⁇ face treatment, water wash, and wash with de-ionized water), and treatment is conducted entirely by spraying.
• Compositions of phosphate ion, tin ion, and oxidizing agent are already known as surface treatment baths for tinplate Dl can.
• the mechanism of conversion film formation by these components consists of tin and iron elu- tion reactions (anodic reactions) and the precipitation of insoluble phosphate salts (cathodic reaction).
• This bath has a pH of 2 to 6 and con ⁇ tains 1 to 50 grams per liter (hereinafter often abbreviated "g/L") of phosphate ions, 0.2 to 20.0 g/L of oxyacid ions, 0.01 to 2.0 g/L of tin ion, and 0.01 to 5.0 g/L of condensed phosphate ions.
• Treatment with this conversion treatment bath forms a highly corrosion-resistant, highly paint-adherent phosphate film on the surface of tinplate Dl can.
• the oxyacid ion is an oxidizing agent that func ⁇ tions to oxidatively remove the hydrogen that is produced by the anodic reac ⁇ tions.
• the referenced invention When the aforesaid invention is practiced on a continuous basis, it is in fact capable of initially providing an excellent surface treatment.
• the referenced invention gradually generates a phosphate salt sludge, which is produced by the reaction of the phosphate ions present in the bath with the tin ions and iron ions that elute from the tinplate. It has also been determined that iron ions elute from the tinplate in the divalent state; that gradual oxidation by the oxidizing agent (oxyacid ion, etc.) produces the trivalent state in the surface treatment bath at a level of approximately 0.05 g/L; and that this is the cause of sludge production.
• This sludge can cause problems by adhering to the tinplate surface and degrading the paint adherence.
• the sludge can clog the piping and nozzles of the spray equipment and can thereby prevent a high quality surface treatment. This has necessitated the implementation of periodic maintenance in order to clean the piping and nozzles of the spray equipment and has result ⁇ ed in unstable quality characteristics. Since productivity enhancements and im- provements in quality stability have recently become critical issues, a surface treatment bath is desired that carries a reduced cleaning burden and that offers stable quality characteristics, i.e., that is free of sludge production in the bath even during continuous service. Disclosure of the Invention
• the present invention takes as its object the introduction of a bath and process for treating tinplate surfaces that solves the problems de ⁇ scribed above and that enhances quality stability and leads to improvements in productivity (easy maintenance and the like).
• a bath for treating tinplate surfaces that comprises, preferably consists essentially of, or more preferably consists of, water, acidity, phosphate ions, chelating agent, and tin ions
• an excellent corrosion resistance and paint adherence could be ob ⁇ tained without sludge production — even during continuous treatment — by such a bath for treating tinplate surfaces that has a pH in the range of 2.0 to 4.5 and a concentration of chelating agent in the range of 0.1 to 5.0 g/L and that essentially does not contain ferric iron or an oxidizing agent sufficiently strong to oxidize ferrous to ferric ions.
• the present invention was achieved based on these findings.
• the iron ions eluting from tinplate often undergo spontaneous oxidation to the trivalent state when the surface treatment process employs the surface treatment bath on a continuous basis.
• the use of the oxidation-reduction potential to monitor the oxidation state of the iron ions was therefore examined.
• Phosphoric acid H 3 PO 4
• sodium phosphate Na 3 P0 4
• the like can be used to provide the phosphate ion, and this component should be used in quantities sufficient to bring about tin phosphate precipitation.
• the reactivity is low when phosphate ion is present at less than 1 g/L, and this prevents satis ⁇ factory formation of the coating under ordinary treatment conditions. While a good quality coating is formed at values in excess of 30 g/L, the corresponding high cost of the treatment bath becomes economically disadvantageous.
• the phosphate ion is present preferably in the range of 1 to 30 g/L and more preferably in the range of 4 to 8 g/L.
• the present invention requires that the bath contain chelating agent in a quantity sufficient to bring about a satisfactory etching, selective conversion film formation on exposed iron regions, and a satisfactory tin ion stabilization.
• Preferred chelating agents that meet these requirements are exemplified by condensed phosphate ions, tartaric acid, oxalic acid, and citric acid.
• Particularly preferred chelating agents comprise at least one selection from the condensed phosphate ions. This is because the condensed phosphate ions gradually de ⁇ compose to phosphoric acid and therefore have little to no adverse effect on waste water treatment.
• the acid or salt can be used to provide condensed phosphate ion.
• pyrophosphoric acid H 4 P 2 O 7
• sodium pyrophos- phate Na 4 P 2 O 7
• so forth can be used to provide pyrophosphate ion.
• the etching activity is weak and film formation is unsatisfactory at a chelating agent concentration of less than 0.1 g/L.
• the etching activity is too strong and the film-formation reactions are inhibited at more than 5 g/L of che ⁇ lating agent.
• the chelating agent content therefore preferably falls in the range of 0.1 to 5 g/L and particularly preferably falls in the range of 0.2 to 1.0 g/L.
• the surface treat ⁇ ment bath of the present invention contains a chelating agent, it is able to se- 5 lectively and uniformly cover the exposed iron regions with a conversion coat ⁇ ing, whereas a very poor conversion is produced at these exposed iron regions in the absence of chelating agent. This makes possible the production of a highly corrosion-resistant conversion film.
• the chelating agent and particularly the condensed phosphates function to stabilize the eluted tin ions 0 in the bath and therefore also act to inhibit sludge production.
• the tin ions can be supplied by tin metal or a tin salt, for example, tin chloride, but the tin source is not specifically restricted. In the case of continu ⁇ ous treatment, supplemental additions are not specifically required due to elu- tion of tin ion from the tinplate.
• the tin ion content should be selected so as s to yield the formation of a satisfactory tin phosphate coating, and preferably falls into the range of 0.01 to 2.0 g/L, more preferably into the range of 0.1 to 1.0 g/L, and particularly preferably into the range of 0.2 to 0.6 g/L.
• the range of 0.01 to 2.0 g/L yields a highly corrosion resistant film and avoids the precipi ⁇ tation of sludge.
• the pH of the treatment bath should be maintained at 2.0 to 4.5. Strong etching and an inhibition of film formation are obtained at below 2.0.
• the anod ⁇ ic reaction conditions suffer from substantial deterioration when the pH exceeds 4.5 because the development of the anodic reactions is inhibited due to the es ⁇ sential absence of oxidizing agent from the treatment bath in accordance with 5 the present invention. Accordingly, the pH must be held in the range of 2.0 to 4.5, and is preferably held in the range of 2.5 to 3.5 and more preferably in the range of 2.7 to 3.3.
• the pH may be adjusted through the use of an acid such as phosphoric acid, sulfuric acid, and the like or through the use of an alkali such as sodium hydroxide, sodium carbonate, ammonium hydroxide, and the o like.
• a characteristic feature of the treatment bath in accordance with the present invention is that essentially it contains neither ferric iron ions nor any oxidizing agent that will oxidize any substantial amount of ferrous iron ions to ferric iron ions.
• the concentration of ferric ions in any surface treat ⁇ ment bath according to this invention is not greater than 7 mg/L, more prefer ⁇ ably not greater than 3 mg/L, still more preferably not greater than 2.0 mg/L, or most preferably not greater than 1.1 mg/L
• the surface treatment bath in accordance with the present invention essentially does not contain an oxidizing agent such as oxyacid ion or the like, that is, does not contain oxidizing agent which substantially removes the hydrogen pro- **d by anodic reactions.
• an oxidizing agent such as oxyacid ion or the like
• oxidizing agent which substantially removes the hydrogen pro- **d by anodic reactions.
• trivalent iron ion facilitates the occur ⁇ rence of sludge precipitation
• the reason for omitting the oxidizing agent is that the presence of oxidizing agent leads to a condition in which both divalent and trivalent iron ions are present.
• the oxidation-reduction potential of the treatment bath is to be controlled to ⁇ 450 mV during treatment.
• the poten ⁇ tials provided in the present invention were obtained using a platinum electrode as the oxidation- reduction electrode and a silver-saturated silver chloride elec ⁇ trode as the reference electrode.
• the oxidation-reduction potential is ⁇ 450 mV during this measurement, the iron ion is present almost entirely in the divalent state and the production of sludge is inhibited.
• atmospheric oxygen al ⁇ so can oxidize the divalent iron ions in the treatment bath.
• the tendency for the divalent iron ions to be oxidized by atmospheric oxygen varies as a function of the precise nature of the equipment, the spray conditions, and the like.
• the oxidation-reduction potential may in some cases exceed 450 mV when the present invention is implemented on a continuous basis under conditions in which air tends to be taken up and the difficult-to-avoid removal of bath by the treatment substrate requires only minor renewal of the surface treatment bath.
• reducing agent must be added on a preliminary basis or when the oxidation-reduction potential becomes elevated in order thereby to maintain the oxidation-reduction potential at ⁇ 450 mV. No specific restrictions apply to this reducing agent, but sub ⁇ stances that inhibit conversion film formation on the tinplate by the surface treatment bath should be avoided.
• phosphorous acid and hypophosphorous acid are preferred as reducing agents, because the main component of the surface treatment bath is phosphate ion and both phos ⁇ phorous acid and hypophosphorous acid are converted into phosphate ion in fulfilling their function as reducing agent.
• adverse effects due to an ac ⁇ cumulation of their decomposition product are completely avoided.
• Phosphorous acid and hypophosphorous acid can be added as the acid or salt.
• the quantity of addition will vary as a function of the treatment condi ⁇ tions, but is preferably as small as possible from the standpoint of economics. Thus, the presence or addition of the minimum quantity that maintains the oxi ⁇ dation-reduction potential at ⁇ 450 mV is sufficient. In other words, the quantity of addition of the reducing agent can be regulated based on the oxidation-re- duction potential.
• the conversion film that is formed will now be briefly considered.
• the conversion film that is formed by a phosphate surface treatment bath for tin- plate is generally a phosphate salt whose principal component is tin phosphate, and the basic mechanism for its formation is believed to be the same even for the present invention.
• the tinplate substrate is etched by the phosphate ions and chelating agent (particularly condensed phosphate ions); a local in ⁇ crease in the pH at the interface occurs at this time; and a phosphate conver- sion film (principally of tin phosphate) precipitates on the surface.
• the phosphate film formed on tin-plated steel sheet in the case of tinplate Dl can is usually extremely thin, approximately 10 to 20 Angstroms, in both the tin-plated regions and the exposed iron regions, the sludge skin is not suscept ⁇ ible in this case to visual evaluation, in contrast to ordinary zinc phosphate films, for which the areal density is approximately 1 to 10 g/m 2 and the corre- sponding thickness from 1 ,000 to 8,000 Angstroms. The exact situation has therefore yet to be elucidated.
• the treatment of tinplate using the surface treatment bath of the present invention is briefly explained below.
• the treatment bath of the present in ⁇ vention is used, preferably as part of the following sequence, which is provided as a preferred example:
• Tinplate cleaning degreasing (a weakly alkaline degreaser is typically used) Water wash
• Treatment temperature 30° C to 70° C
• Treatment technique spray or immersion
• Treatment time 2 to 40 seconds
• the treatment temperature with the surface treatment bath of the present invention is preferably 30° C to 70° C, and heating the bath generally to 40° C to 60° C for use is particularly preferred.
• the preferred treatment time is 2 to 40 seconds. At below 2 seconds, the reaction is inadequate and a highly corro ⁇ sion-resistant film will not normally be formed.
• the perform ⁇ ance does not improve at treatment times in excess of 40 seconds, and there ⁇ fore optimal treatment times fall in the range of 2 to 40 seconds.
• the treatment technique can be either immersion or spray, as dis ⁇ cussed above the present invention gives particularly good effects when used with spray equipment.
• iron ions are be- lieved to elute from the tinplate as divalent ferrous ions.
• the iron ions are typically present as ferrous ions at a concentration of about 0.005 to about 0.025 g/L when the line is running, while ferric ions are essentially not present.
• the ferrous ions are almost entirely oxidized in prior art treatment baths to yield ferric ions or colloid in a concentration typically on the level of 0.05 g/L.
• Sludge is produced because this ferric ion and the phosphate ion form an insoluble salt that also traps the tin and phosphate ions that are present.
• sludge production in the surface treatment bath can be suppressed by maintain ⁇ ing the iron ion eluted from the tinplate in the divalent state.
• the iron ions in the present invention consist almost completely of divalent iron ions. It is thought that this occurs because both divalent tin ions and tetravalent tin ions are present and the divalent tin ions rapidly reduce tri ⁇ valent iron ions to divalent iron ions.
• the oxidation- reduction potential of a composition is measured by the equilibrium electrode potential of an inert oxidation-reduction electrode in contact with the composition, and it represents the magnitude of the oxidizing power or reducing power of the composition.
• the following equation gives the oxidation-reduction potential E e for the half-reaction oxidation of ferrous ion to ferric ion according to the chemical equation Fe 2+ ⁇ Fe 3+ + e " .
• the utility of the surface treatment bath of the present invention is ex ⁇ plained below through a comparison of several working examples with compari- son examples.
• the tinplate substrates consisted of tinplate Dl cans fabricated by the Dl processing of tin-plated steel sheet.
• the corrosion resistance after surface treatment was evaluated using the iron exposure value ("IEV").
• the IEV was measured in accordance with United States Patent Num ⁇ ber 4,332,646. Lower IEV values correspond to a better corrosion resistance, and values ⁇ 150 generally correspond to an excellent corrosion resistance.
• a bath that was transparent and free of precipitate or the like was judged as essentially free of ferric ion.
• the oxidation-reduction potential was measured after standing using a platinum electrode as the oxidation-reduction electrode and a silver-saturated silver chloride electrode as the reference electrode.
• a bath that was transparent and free of precipitate or the like was judged to be essentially free of ferric ion.
• the iron ion concentration in the treatment bath after continuous treatment was measured by atomic absorption.
• analysis was run by dissolving the pre ⁇ cipitate by the addition of hydrochloric acid.
• Example 1 Tinplate Dl cans (fabricated by the Dl processing of tin-plated steel sheet) were (1) thoroughly cleaned using a hot 1 % aqueous solution of a weakly alkaline degreaser (FINECLEANERTM 4488 from Nihon Parkerizing Company, Limited); (2) sprayed for 20 seconds with surface treatment bath 1 heated to 60° C; (3) washed with tap water; (4) sprayed with deionized water (with a specific resistance > 3 Mohm-cm) for 10 seconds; and (5) dried in a hot-air drying oven for 3 minutes at 180° C.
• the treated cans were evaluated for corrosion resistance and paint adherence, and surface treatment bath 1 was evaluated for sludge production.
• Surface treatment bath 1 75% phosphoric acid (H 3 P0 4 ) 10.0 g/L (PO ⁇ : 7.2 g/L)
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 10 seconds with surface treatment bath 2 heated to 40° C, and then washed with water and dried under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 2 was evaluated for sludge production. Surface treatment bath 2
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 40 seconds with surface treatment bath 3 heated to 60° C, and then washed with water and dried under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 3 was evaluated for sludge production. Surface treatment bath 3
• Example 4 Tinplate Dl can was cleaned using the same conditions as in Example
• Example 1 sprayed for 10 seconds with surface treatment bath 4 heated to 40°C, and then washed with water and dried under the same conditions as in Example 1.
• the treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 4 was evaluated for sludge production.
• Hypophosphorous acid H 3 PO 2 0.01 g/L pH 3.0 (adjusted with sodium carbonate)
• Tinplate Dl can was cleaned using the same conditions as in Example
• Example 1 sprayed for 30 seconds with surface treatment bath 5 heated to 50° C, and then washed with water and dried under the same conditions as in Example 1.
• the treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 5 was evaluated for sludge production.
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 20 seconds with surface treatment bath 6 heated to 50°C, and then washed with water and dried under the same conditions as in Example 1.
• the treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 6 was evaluated for sludge production.
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 2 seconds with surface treatment bath 7 heated to 70° C, and then washed with water and dried under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 7 was evaluated for sludge production.
• Surface treatment bath 7 75 % Phosphoric acid (H 3 P0 4 ) 30.0 g/L (PO " : 21.6 g/L)
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 30 seconds with surface treatment bath 8 heated to 40° C, and then washed with water and dried under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 8 was evaluated for sludge production. Surface treatment bath 8
• Tinplate Dl can was cleaned using the same conditions as in Example 1 , sprayed for 30 seconds with surface treatment bath 9 heated to 50° C, and then washed with water and dried under the same conditions as in Example 1.
• the treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 9 was evaluated for sludge production.
• Tinplate Dl can was cleaned using the same conditions as in Example o 1 , sprayed for 30 seconds with surface treatment bath 10 heated to 50° C, and then washed with water and dried under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and surface treatment bath 10 was evaluated for sludge production. Surface treatment bath 10 5 75 % Phosphoric acid (H 3 PO 4 ) 1.33 g/L (PO " : 0.97 g/L)
• Tinplate Dl can was cleaned using the same conditions as in Example 1 and was then sprayed for 30 seconds with a 4 % aqueous solution (heated to 50° C) of a commercial tinplate Dl can surface treatment agent (PALFOSTM K3466 from Nihon Parkerizing Company, Limited). This was followed by wash- 5 ing with water and drying under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and the treatment bath was evaluated for sludge production. Comparison Example 5
• Tinplate Dl can was cleaned using the same conditions as in Example o 1 and was then sprayed for 30 seconds with a 4 % aqueous solution (heated to 50° C) of a commercial tinplate Dl can surface treatment agent (PALFOSTM K3482 from Nihon Parkerizing Company, Limited). This was followed by washing with water and drying under the same conditions as in Example 1. The treated can was evaluated for corrosion resistance and paint adherence, and the treatment bath was evaluated for sludge production.
• a commercial % aqueous solution heated to 50° C
• PAFOSTM K3482 from Nihon Parkerizing Company, Limited
• treating the surface of tinplate (tin-plated steel) sheet, strip, or shaped objects (cans or the like) with the surface treat ⁇ ment bath of the present invention accrues the highly desirable effects of imparting an excellent corrosion resistance and adherence to the tinplate sur- face and avoiding sludge production in the treatment bath when treatment is run on a continuous basis.

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• 1992
  • 1992-12-09 JP JP35151892A patent/JP3256009B2/ja not_active Expired - Fee Related
• 1993
  • 1993-12-01 DE DE69325035T patent/DE69325035T2/de not_active Expired - Fee Related
  • 1993-12-01 EP EP94902385A patent/EP0673445B1/fr not_active Expired - Lifetime
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  • 1993-12-01 WO PCT/US1993/011435 patent/WO1994013855A1/fr not_active Ceased
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