US3833483A - Process for pre-treating can materials for lacquering - Google Patents

Process for pre-treating can materials for lacquering Download PDF

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Publication number
US3833483A
US3833483A US00338957A US33895773A US3833483A US 3833483 A US3833483 A US 3833483A US 00338957 A US00338957 A US 00338957A US 33895773 A US33895773 A US 33895773A US 3833483 A US3833483 A US 3833483A
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chromium
lacquering
steel strip
lacquered
treating
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US00338957A
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English (en)
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R Wake
A Umezono
T Saito
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/38—Chromatising

Definitions

  • the present invention comprises a process for pretreating a steel strip intended for can making in the lacquring line in an electrolysis tank containing as the treating solution more than 50g/l of anhydrous chromic acid and sulfate ions in the amount of 2 to 5% of the anhydrous chromic acid, electrolytically treating the steel strip less than 0.2 sec. at a current density of 50 A/dm on the downward path in the tank, then dissovling the excessive part of attached hydrated oxide of chromium on the upward path and immediately applying lacquer.
  • the chemical treatment process of the present invention is very easily connected to the lacquring line for steel strips, and thereby lacquered can materials possessing excellent anti-under-film corrosion and suitable for cans for carbonated beverages are supplied with decreased cost.
  • the present invention relates to a process for producing lacquered steel strip for can materials on a lacquering line comprising placing an electrolytic treating tank before the lacquering section and applying a simple but effective chemical treatment in the tank followed by immediate lacquering.
  • the primary object of the present invention is to provide can materials, especially those suitable for containing carbonated beverages which avoid the underfilm corrosion which is often present with cans for carbonated beverages.
  • the second object of this invention is to provide cheap can materials especially suitable for cans for carbonated beverages by applying to steel strip materials, a chemical treatment which is effective especially against under-film corrosion in an electrolysis tank prior to lacquering and by then lacquering immediately thereafter.
  • Another object of this invention is to provide a process in which a chemical treatment is inexpensively and easily combined with the lacquering line of steel strip materials.
  • a further object of the present invention is to provide a process of chemical treatment which is very suitable to pre-treatment for high speed lacquermg.
  • Tin plates are extensively used as the base material for making food containers because tin reacts as an effective anode to prevent the corrosion of the steel substrate of the containers which is in contact with various foods.
  • tin reacts as an effective anode to prevent the corrosion of the steel substrate of the containers which is in contact with various foods.
  • tin is normally cathodic to the exposed steel base and is unable to prevent the local corrosion or perforations of the steel substrate, so that cans lacquered on the inside are used to prevent corrosion of the steel substrate for containers of such foods.
  • the can material called TFS which has been practically used as a can material mostly for carbonated beverages has two coating layers on the surface of the base steel, namely, a lower layer of metallic chromium and an upper layer of hydrated oxide of chromium.
  • Related patents include Japanese Patent No. 308,065, Patent Publication Sho 43-2768 (US. Pat. No. 3,296,100), Patent Publication Sho 46-6323 and Patent Publication Sho 46-19522. This material has been known for its excellent lacquer adhesion of paint and corrosion resistance of the lacquered surface.
  • can materials have been lacquered in a lacquering line for individual sheets, wherein each lacquered sheet is cured on a chain conveyor with wickets in an oven.
  • the production speed is low owing to the limitation of the equipment, the process is suitable to production of small quantities of diverse can materials, that is, for example, containers of different design for different use; Consequently the lacquering costs are high and as the demand of cans for carbonated beverages has increased in recent years, cheaper materials for lacquered cans are needed.
  • the present invention is based on the technical thought that the steel strip is submitted to continuous chemical treatment as a pre-treatment in the lacquering line followed by continuous lacquering of the steel strip coil to improve the production speed and thereby to permit cheap and large scale supply of lacquered can materials. Moreover, if the abovementioned pre-treatment is adopted in the lacquering line, it is not necessary to produce the anti-rusting property of the steel surface before the lacquering step, though the anti-underfilm corrosion property of the lacquered surface is obtained after the lacquering.
  • the present invention comprises providing an electrolysis tank for pre-treating the steel strip in the lacquering line, the tank containing as a treating solution, more than SOg/l of anhydrous chromic acid and sulfate ions in an amount of 2 to 5% of the anhydrous chromic acid, electrolytically treating the steel strip for less than 0.2 sec. at a current density of 50 A/dm on the downward path in the tank, then dissolving the excessive part of the attached hydrated oxide of chromium on the upward path and immediately applying lacquer.
  • the chemical treatment process is very easily connected to the lacquering. line for steel strip, and thereby lacquered can materials excellent in the anti-under-film corrosion and suitable to cans for carbonated beverages can be supplied with less cost.
  • FIG. 1 illustrates the operation line to be used in the process of this invention. However, the invention should not be limited by what is shown in the figures.
  • FIG. 1 explains an example of the process employed in the present invention.
  • FIG. 2 shows the relation between the time of electrolysis and the efficiency of deposition of metallic chromium and
  • FIG. 3 shows the relation between the extent of under-film corrosion and the amount of metallic chromium.
  • (l) is a pay-off reel of cold reduced steel strip (black plate coil), (2) is the uncoiled steel strip and (3) shows the accumulator on the inlet side.
  • (4) is an electrolysis tank where a pair of anodes (5) are installed on the downward path on the inlet side.
  • (6) isan apparatus for removing the electrolysis solution attached on the strip surface, such as, asqueezing roller and air wipers installed on the upward path above the electrolysis tank.
  • the steel strip is dried in the dryer (7) and is lacquered with the coaters (8) while the surface retains activity.
  • (9) is a curing oven, (10) is cooling equipment,.(1l) is an accumulator on the outlet side and the lacquered steel strip is recoiled on a recoiler (12) and is supplied as material for making cans.
  • the de-greasing and the acid pickling of the steel strip prior to the electrolysis are not necessary for a steel strip which has been processed in the ordinary process.
  • steel strip the surface of which is dirty with rolling oil used during the tempering, it is preferably submitted to the de-greasing and the pickling before electrolysis. These treatments do not limit the use of thepresent invention.
  • a treating solution containing more than 50 g/l of anhydrous chromic acid and 2 5% as much sulfate ions as anhydrous chromic acid is placed in the tank (4).
  • the steel strip (2) is treated as cathode on the downward path at the current density larger than 50 A/dm for less than 0.2 sec., and then non-electrolytically treated on the upward path to remove, by dissolution, the excessive amount of hydrated oxide of chromium over the controlled amount.
  • a base layer with a thickness of 0.05 0.5 mgldm of metallic chromium and an upper layer of a verysmall amount of hydrous chromiumthat is" below 0.05 mg/dm as chromium are formed on the steel strip (2).
  • the treating solution of the present invention belongs to those solutionswhich employ highconcentration anhydrous chromic acid and sulfate ions.
  • concentration of anhydrous chromic acid is limited to above 50 g/! is asfollows:
  • Patent Publication Sho 43-2768 (U.S. Pat. No. 3,296,100), referred, to above, usesless than 50 g/l of anhydrous chromic acid and thereby has an'object to produce an amount of hydrated oxide of chromium sufficient to secure the rust resistance by covering pin holes on the metallic chromium layer with the said oxide. Therefore, this invention is entirely different from the present invention with respect to the amount of anhydrous chromic acid.
  • the concentration may be as high as 100 g/l.
  • the amount of sulfate ions is limited to 2 5% of anhydrous chromic acid. For a concentration below 2%, more hydrated oxide of chromium is formed and the dissolving rate on the upward path is decreased, and therefore it is difiicult to control hydrated oxide of chromium to the pre-determined amount. For a concentration exceeding 5%, it is difficult to produce the pre-determined amount of metallic chromium on the downward path of the electrolysis.
  • the current density should be 50 A/dm or more, be-
  • Patent Publication Sho 46-2768 (US. Pat. No. 3,296,100) referred to above andPatent Publication Sho 46-19522 adopted more than about 3 sec. and more than about 0.5 sec., respectively.
  • a considerably shorter time of electrolysis is adopted in the present invention and a high efficiency of deposition of metallic chromium is obtained.
  • the steel strip electrolytically treated in the electrolysis tank (4) is submitted to the dissolution treatment on the upward path of the electrolysis tank and then the electrolysis solution attached on the surface is removed by the electrolysis solution remover (6) installed on the upward path above the tank.
  • the electrolysis solution remover contains pairs of squeezing rollers, air wipers or a combination thereof.
  • Squeezing rollers are apt to produce irregularity in squeezing, which spoils surface tone after lacquering and deteriorates the quality especially at those areas where a large amount of, chromic acid remains. If the removing is doneonly with squeezing rollers, those provided with convex crowns of hard rubber should be used and pressure as high as 5 kg/em should be applied to remove the electrolysis solution.
  • the most desirable device for removing the electrolysis solution is a combination of squeezing rollers and air wipers. Most of i the solution is removed with the squeezing rollers from the surface of the steel strip, and
  • the steel strip when it leaves the dryer (7), is coated with two layers on the surface, a base layer of metallic chromium as thick as 0.05 0.5 mg/d m and an upper layer of hydrated oxide of chromium'thinner than 0.05 mg/dm.
  • the amount of hydrated oxide of chromium, which is controlled on the upward path by the nonelectrolytic treatment in the specified treating solution, is restricted in the range described above for the following reason:
  • the electrolytic treatment as the pretreatment before lacquering is immediately followed by lacquering, so that the electrolytically treated steel strip is required-to have little rust resistance and such an amount of hydratedoxide of chromium is considered sufficient as to secure the lacquerability.
  • Investigations of the present inventors on this subject revealed that hydrated oxide of chromium below 0.05 mg/dm (as Cr) issufficient to meet the mentioned purpose.
  • the surface of the specimen was squeezed with rollers under applied pressure of 8 kg/cm to remove the solution on the surface.
  • the electrolysis solution was removed first by roll squeezing then with air wipers.
  • the steel strip (2) thus treated electrolytically and dried, is then lacquered immediately in the coater-(l0) while the surface still retains activity.
  • the process that follows to obtain the product is shown in the drawings.
  • the present invention does not intend to produce better workability as a result of electrodeposition lacquering, but to provide a method for combining the processes of electrolytical treatment and lacquering using an inexpensive and simple installation by specifying the composition of the electrolytic treatment solution and condition of the electrolysis, and further to provide cheap lacquered steel plates for making cans by specifying each process incorporated in the lacquering line.
  • the elelctrolysis solution was removed by roll squeezing followed by applying air wipers.
  • epoxyphenol lacquers DIC 83-088, DIC 5 l-O55
  • Table 1 shows the amounts of metallic chromium, amounts of chromium in the hydrated oxide of chromium and amounts of applied lacquer of the materials obtained in Examples 1 to 3.
  • Table 2 shows results of tests specified in the following (1) through (4) applied to lacquered materials of which had been treated in Examples 1 through 3.
  • Table 1 Metallic Chromium Lacguer coating weight chromium in hyd- 1 (mg/dm) rated -Outside Inside oxide of (DlC 50 (DIC 83 chromium 055) 088) (mgldm (mg/dm) (mg/dm Black plate (no chemical treatment 45 45 applied) Specimen in Example I 0.20 0.02l 45 45 Specimen in Example 2 0.29 0.036 45 45 Specimen in Example 3 0.18 0.030 45 45
  • Table 2 Draw test Steam Under-film Immersion into caps retort corrosion test in test test citric acid Black plate Slight Slight Whole Whole (no chemical peeling swelling lacquer lacquer 8 treatment at the of lacqfilm film applied) processed I uer film peeled peeled part at the fabricated part Specimen in No peeling No peeling No peeling No peeling No peeling Example I at all at all at all at all Specimen in Example 2 do. do. do. do. Specimen in Example
  • the improvement which comprises electrolytically treating the strip prior to lacquering by passing it through an electrolytic treating tank in first a downward path and then an upward path, said tank containing an electrolytic treating solution of at least 50 g/l anhydrous chromic acid and 2 to 5% sulfate ions based on the amount of anhydrous chromic acid, the strip being treated as a cathode on the downward path at a current density of more than 50 A/dm for a time of less than 0.2 sec.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Electrochemical Coating By Surface Reaction (AREA)
US00338957A 1972-03-10 1973-03-07 Process for pre-treating can materials for lacquering Expired - Lifetime US3833483A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0330921A3 (en) * 1988-02-27 1990-02-07 Nkk Corporation Method for manufacturing electrolytically chromated steel sheet
US20030111350A1 (en) * 2001-12-07 2003-06-19 United States Steel Corporation Electrocoating chrome-plated steel
US20150329981A1 (en) * 2012-11-21 2015-11-19 Tata Steel Ijmuiden B.V. Chromium-chromium oxide coatings applied to steel substrates for packaging applications and a method for producing said coatings
US10000861B2 (en) 2012-03-30 2018-06-19 Tata Steel Ijmuiden Bv Coated substrate for packaging applications and a method for producing said coated substrate

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112663104A (zh) * 2020-12-24 2021-04-16 重庆金美新材料科技有限公司 一种防止电镀设备挤液组件镀液结晶的装置及方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3113845A (en) * 1960-03-29 1963-12-10 Fuji Iron & Steel Co Ltd Chromium-plated steel
US3245577A (en) * 1962-12-12 1966-04-12 American Can Co Resin-coated tin plate container
US3296100A (en) * 1962-05-09 1967-01-03 Yawata Iron & Steel Co Process for producing anticorrosive surface treated steel sheets and product thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3113845A (en) * 1960-03-29 1963-12-10 Fuji Iron & Steel Co Ltd Chromium-plated steel
US3296100A (en) * 1962-05-09 1967-01-03 Yawata Iron & Steel Co Process for producing anticorrosive surface treated steel sheets and product thereof
US3245577A (en) * 1962-12-12 1966-04-12 American Can Co Resin-coated tin plate container

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0330921A3 (en) * 1988-02-27 1990-02-07 Nkk Corporation Method for manufacturing electrolytically chromated steel sheet
US20030111350A1 (en) * 2001-12-07 2003-06-19 United States Steel Corporation Electrocoating chrome-plated steel
US7291252B2 (en) * 2001-12-07 2007-11-06 United States Steel Corporation Electrocoating chrome-plated steel
US20080020226A1 (en) * 2001-12-07 2008-01-24 Li Jian X Electrocoating chrome-plated steel
US10000861B2 (en) 2012-03-30 2018-06-19 Tata Steel Ijmuiden Bv Coated substrate for packaging applications and a method for producing said coated substrate
US20150329981A1 (en) * 2012-11-21 2015-11-19 Tata Steel Ijmuiden B.V. Chromium-chromium oxide coatings applied to steel substrates for packaging applications and a method for producing said coatings

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