US3558460A - Process for surface treatment of steel strip - Google Patents

Process for surface treatment of steel strip Download PDF

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Publication number
US3558460A
US3558460A US611064A US3558460DA US3558460A US 3558460 A US3558460 A US 3558460A US 611064 A US611064 A US 611064A US 3558460D A US3558460D A US 3558460DA US 3558460 A US3558460 A US 3558460A
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United States
Prior art keywords
strip
coating
electrodeposition
steel strip
film
Prior art date
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Expired - Lifetime
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US611064A
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English (en)
Inventor
Hiromu Uchida
Hideshi Sato
Takashi Ihara
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Nippon Steel Corp
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Nippon Steel Corp
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Publication date
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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
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
    • C25D13/16—Wires; Strips; Foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/20—Pretreatment

Definitions

  • This invention concerns a special treatment method applied on steel strip surface, in which cold rolled steel strip, after being cathodically treated in an electrolytic solution for a short period of time chiefly composed of chromic acid, can be advantageously treated by an electrodeposition coating method used in formation of thin organic coating at a high speed on its surface, to obtain steel strip characterized by improved anticorrosiveness, workability, lacquer adhesion, etc.
  • the electrolytic solution having chromic acid as a major component used for the purpose of applying cathodic treatment on cold rolled strip corresponds to one of the solutions disclosed in US. Pat. No. 3,113,- 845, Canadian Pat. No. 710,309, French Pat. No. 1,365,- 368 and the other solutions for the same purpose; namely, an electrolytic solution for electrodeposition of chromium coating film and/or chromate film on the steel strip.
  • Chromium-plated steel strip and chromate coated steel strip obtained from the cathodically treated strip by means of these electrolytic soltuions are widely being used in many ways as an excellent substitute for tin plate which has hitherto been favoured as typical can-material.
  • lacquering on such chromium-plated steel strip and chromate coated steel strip are generally done, as in case of tin plate which has hitherto been used as typical can-material, mostly on cut-off sheet and partially in a coiled condition at low temperature and low speed with lacquer diluted in organic solvent; quite separate and independent coating processes from that of electrolytic treatment.
  • roller coating method hitherto used was unable to provide a thin and uniform coating at a high speed and the other reason is that it was impossible to dry and cure coating film at high temperature and by direct firing because of organic solvent used.
  • a further reason is that in the case of tin plate, the typical can-material low melting point (232 C.) of tin coating has made drying and curing the coating film at high temperature and high speed impossible; therefore, even though this coating metal is replaced by other materials, the disadvantantages associated with prior art procedures still have to be overcome.
  • One of the objects of this invention is that it provides a high temperature and high speed process for lacquering thin steel strip.
  • Another object of this invention is to provide a special surface treatment method in which a high temperature and high speed lacquering process chromium plating and/ or chromate treatment can be jointly and continuously followed by lacquering process.
  • Another object of this invention is to provide a surface treatment method which can product satisfactory corrosion resistance, fabrication characteristics and lacquerability to a can, even if the time of cathodic treatment in an electrolytic solution chiefly composed of chromic acid is shortened, that is, even if chromium plate and/or chromate film on the strip surface is made thinner than the film which has been currently used.
  • Another object of this invention is to provide a special surface treatment method in which an excellent product can be obtained characterized by improved lacquer adhesion, workability and anti-corrosiveness in comparison with the ordinary product which is provided by a coating material having conventional organic solvent obtained by a roller coating process after a cold rolled strip is cathodically treated in the electrolytic solution chiefly composed of chromic acid.
  • the invention lies in application of an electrodeposition lacquering step to a cold rolled strip which was treated cathodically in an electrolytic solution chiefly composed of chromic acid.
  • the first feature of this invention is that an electrodeposition coating is applied on a strip surface on which chromium plate and/or chromate film were formed by cathodic treatment in an electrolytic solution chiefly composed of chromic acid as mentioned above.
  • FIG. 1 indicates the relation between electrodeposition time and electrodeposited film weight in the application of electrodeposition coating on various base materials.
  • FIG. 2 indicates the relation between electrodeposition time and electrodeposition velocity in case of electrodeposition coating on strip material.
  • FIG. 3 indicates the apparatus used in employing the present process.
  • the present invention provides, for the first time, a combined electrolytic process and electrodeposition step, which originates from the fact that strip with chromium plate and/or chromate film has been found to be lacquered more efficiently as compared with steel, zinc, nickel, copper, aluminum, and phosphated materials (refer to FIGS. 1 and 2).
  • Coating of chromium plate and/or chromate film has much higher melting point than plated tin and in consequence, it is possible to dry and cure electrodeposited lacquer film on the chromium plate and/or chromate film at a considerably higher temperature than that on tin coating.
  • Electrodeposition coating has so far been adopted chief- 3 ly in the motorcar industry; electrodeposition time in this case being 1-10 minutes, moving the speed of the material to be coated in the electrodeposition tank averages 0.1- meters/min. with a dry film weight of 200-400 mg./dm.
  • the material to be coated is generally phosphated steel or phosphated galvanized steel.
  • the reasons why motorcar industry utilizes electrodeposition coating are due to the fact that electrodeposition coating is quite free from the danger of fire because of the use of an aqueous solution, that the coating material penetrates well into the seams of joints and that throwing power in electrodeposition is very good.
  • the coating material is of water base which is different from ordinary coating material which is of organic solvent base.
  • the solid content in a wet coating film after electrodeposition is so high, i.e., it is up to about 90% and it is not necessary to expect a levelling effect of coating film in the course of drying.
  • epoxy-based, acrylic-based, phenol-based, alkydbased coatings, etc. are employed making use of each special property.
  • Epoxy coating weight 20 mg./dm. This epoxy coating can hardly be removed by acetone, although some electrodeposited coating on tin plate is easily removed by acetone.
  • the purpose of adopting electrodeposition as coating process in this invention is to unify the lacquering process with previous washing process, to obtain uniform Wet resulted inorganic surface film is less than 0.01 micron in thickness (chromium content: 0.5 mg./dm.
  • chromium content 0.5 mg./dm.
  • applying an electrodeposition coating for 0.5-5 seconds and obtaining an organic film of 5-100 mg./dm. it is possible to obtain a product satisfactory for various uses, even if the inorganic film be less than 0.01 micron in thickness.
  • the method of this invention is intended to draw out the electrodeposited strip vertically and to dry, cure and cool the strip during the process in which it reaches so far as deflector roll installed almost directly above the electroplating tank so that the coating film cannot be scratched by deflector roll.
  • the deflector roll can draw the strip out of the tank so that there is no fear of having scratches by the rolls over coating film on the strip in the course of its movement.
  • the strip applied with chromium plate and/or chromate treatment only as well as the surface treated strip obtained through the method of this invention is used in the manufacture of food cans, crown caps, miscellaneous cans, etc. as in the case of tin plate, but the surface treated strip obtained through the method of this invention is superior to the conventionally treated products. Since prior products often oiled at the final step, there is a fear of having eye-holes in the following lacquering strip.
  • the product obtained by the process of this invention avoids this problem. Further, using conventional procedures it is also diflicult to avoid scratches on the surface during the can making process, especially in case of some work done on it like drawing where it is hardly subject to scars in the course of working. Using the present process, products are obtained having superior anticorrosiveness in the air, corrosion resistance against water, salt spray and chemicals are as compared with products obtained by the use of conventional pro cedures.
  • the product obtained by the process of this invention is superior in properties to the product obtained by a roller coating process in a separate line from electrolytic treatment.
  • a cold rolled steel strip uncoiled from uncoiler 1 goes through pinch roll 2, tension bridle 3, electrolytic cleaner 4, washer 5, pickling tank 6, washer 7, brushing and washer for surface cleaning 8, cathodic treatment tank 9, in which chromium plate and/ or chromate film of 0.00l0.1 micron in thickness are formed on the strip surface, washer and then the strip is conducted on to electrodeposition tank 11 in which coating material is electrodeposited, taken out vertically to deflector roll directly above, and surplus aqueous solution is pushed downward back by air knife 12. Baking is done in the drying and curing furnace 13 and at point 14 the strip is compulsively cooled by air in the course of the strips movement toward deflector roll 15. The strip finally passes through tension roll 16 to be coiled up by recoiler 17.
  • EXAMPLE 1 In such continuous treatment line as shown in FIG. 3, continuous surface treatment was applied on cold rolled steel strip 0.22 mm. thick and 150 mm. wide. In this case, chromium plate (0.02 micron thick) was applied in cathodic treatment tank 9 and directly after washing at the final stage 10 of plating process, the strip in wet condition was conducted consecutively to electrodeposition tank 11 at a temperature of C. in which 8% aqueous coating solution of epoxy type is kept and organic film was electrodeposited on the anodic strip for 1.5 seconds.
  • the strip was taken out upward vertically and at the same time surplus aqueous solution was pushed back downward to the electrodeposition tank.
  • the strip went through the drying and curing furnace 13 for 3.5 seconds at a temperature of 800 C. and directly after passage through this furnace, the strip was subjected to air cooling at room temperature resulting in the formation of a coating film of about 2 microns.
  • the strip was coiled up on recoiler 17. The line speed was about 120 mm./ min. throughout the line. No visual defect was noted on the coating film of the product.
  • test specimens A were manufactured according to Example 1, test specimens B manufactured w1th chrom1um plating process only of Example 1, test specimens C manufactured with test specimens B coated additionally by roller coating.
  • a styrene alkyd lacquer was applied and baked for 10 mlnutes at 170 C., the dry film weight being 20 mg./dm.
  • Test pieces (a) are pushed out 5 mm. in center by the Erichsen Testing Machine, and test pieces (b) are lids of food can of 301 diameter. Scratch test results are shown with a number of rubbing time so that the abrasive defect becomes visible by rubbing test pieces with chromium coated plate which is 10 cm. long, 5 cm. wide and 200 g. in weight.
  • Test plece (a) Test piece (a) Test piece (b) 1% citric acid test, 0., 5 hours:
  • the test results shown above indicate that test specimens A are superior to test specimens B with chromium coating only and superior to test specimens C. Specimen A is superior to specimen B especially in the outdoor exposure test and the scratch test.
  • EXAMPLE 2 EXAMPLE 3
  • a cathodic treatment tank 9 at a temperature of 30 C. was filled with a electroytic solution lncluding chromic acid 35 g./l. and sulphuric acid 0.4 g./l., and the strip was cathodically treated for 4 seconds at the current density of 15 a./dm.
  • the strip was electrocoated for 3 seconds in the electrodeposition tank filled with 5% aqueous solution of the alkyd type and passed through the drying and curing furnace for 6 seconds at 600 C. with a line speed of m./min.
  • This strip was characterized by the same results seen in Example 1.

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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)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Chemical Treatment Of Metals (AREA)
US611064A 1966-01-26 1967-01-23 Process for surface treatment of steel strip Expired - Lifetime US3558460A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP448866 1966-01-26

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US (1) US3558460A (nl)
DE (1) DE1621898B2 (nl)
FR (1) FR1508914A (nl)
GB (1) GB1165805A (nl)
NL (1) NL140903B (nl)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928157A (en) * 1972-05-15 1975-12-23 Shinto Paint Co Ltd Cathodic treatment of chromium-plated surfaces
GB2266895B (en) * 1992-05-15 1996-12-04 Wednesbury Diecasting And Meta Improvements relating to electrophoretic coatings
US5584984A (en) * 1994-07-07 1996-12-17 Mannesmann Aktiengesellschaft Method and apparatus for electrolytic treatment of a surface
US5707505A (en) * 1988-09-29 1998-01-13 Gesellschaft fur Technische Studien Entwicklung Planung mbH Method for the electrophoretic dip coating of chromatizable metal surfaces
US20030111350A1 (en) * 2001-12-07 2003-06-19 United States Steel Corporation Electrocoating chrome-plated steel
US20060219334A1 (en) * 2003-07-22 2006-10-05 Daimlerchrysler Ag Press-hardened component and associated production method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA707917B (en) * 1969-12-11 1971-08-25 M & T Chemicals Inc Novel electrocoated product and process

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928157A (en) * 1972-05-15 1975-12-23 Shinto Paint Co Ltd Cathodic treatment of chromium-plated surfaces
US5707505A (en) * 1988-09-29 1998-01-13 Gesellschaft fur Technische Studien Entwicklung Planung mbH Method for the electrophoretic dip coating of chromatizable metal surfaces
GB2266895B (en) * 1992-05-15 1996-12-04 Wednesbury Diecasting And Meta Improvements relating to electrophoretic coatings
US5584984A (en) * 1994-07-07 1996-12-17 Mannesmann Aktiengesellschaft Method and apparatus for electrolytic treatment of a surface
US20030111350A1 (en) * 2001-12-07 2003-06-19 United States Steel Corporation Electrocoating chrome-plated steel
WO2003078697A1 (en) * 2001-12-07 2003-09-25 Uec Technologies Llc 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
US20060219334A1 (en) * 2003-07-22 2006-10-05 Daimlerchrysler Ag Press-hardened component and associated production method
US8141230B2 (en) * 2003-07-22 2012-03-27 Z.A.T. Zinc Anticorosion Technologies Sa Press-hardened component and process for producing a press-hardened component

Also Published As

Publication number Publication date
FR1508914A (fr) 1968-01-05
NL6701254A (nl) 1967-07-27
NL140903B (nl) 1974-01-15
GB1165805A (en) 1969-10-01
DE1621898B2 (de) 1978-06-01
DE1621898A1 (de) 1972-03-16

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