US3679554A - Method for electrolytic treatment of steel surface in a chromate solution - Google Patents

Method for electrolytic treatment of steel surface in a chromate solution Download PDF

Info

Publication number
US3679554A
US3679554A US99A US3679554DA US3679554A US 3679554 A US3679554 A US 3679554A US 99 A US99 A US 99A US 3679554D A US3679554D A US 3679554DA US 3679554 A US3679554 A US 3679554A
Authority
US
United States
Prior art keywords
electrolyte
steel plate
acid
chromate
agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US99A
Other languages
English (en)
Inventor
Hidehisa Yamagishi
Hiroshi Takano
Masao Takeuchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Engineering Corp
Original Assignee
Nippon Kokan Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Kokan Ltd filed Critical Nippon Kokan Ltd
Application granted granted Critical
Publication of US3679554A publication Critical patent/US3679554A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
    • C25D9/10—Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel
    • 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

  • Japanese Pat. No. 269,930 proposes aromatic sulfonic acids or salts thereof
  • the Japanese Pat. No, 524,872 (US. Pat. 3,484,347) proposes thiocyanic acid or salts thereof
  • Japanese patent application publication No. 2,768/ 1968 proposes sulfuric acid or salts thereof.
  • a steel plate whose surface is electrolytically treated with a chromate solution by these prior art methods indeed has an excellent appearance and corrosion resistance, but still are handicapped by their somewhat poor paint adhesion. Where high grade deep drawing is applied on such steel plate after its surface is coated with a paint, part of the coated layer unavoidably comes off.
  • the process (1) leads to decrease the cathode current efliciency for deposited metallic chromium, and to decrease the corrosion resistance of said hydrated chromium oxide layer due to its greater porosity.
  • the process (II) presents difficulties in obtaining a homogeneous and beautiful surface as the concentration of a promoter rises.
  • the process (III) does not allow the entire cathode surface to be kept in a homogeneous and stable condition simply by mechanical agitation.
  • This promoter is an indispensable catalyst for electrolytically reducing hexavalent chromium ions in the bath.
  • the present inventors have found that part of said promoter is adsorbed to the layer of hydrated chromium oxide. As electrolysis proceeds, therefore, the concentration of the promoter gradually decreases until the treated surface of a steel plate cannot maintain prescribed appearance and other properties as desired. To assume the stable condition of said treated surface, there must be taken minute care and complicated operation in controlling the concentration of the promoter to a constant level. However, this is a very troublesome and time-consuming process unsuitable for practical work.
  • An object of the present invention is to coat the surface of steel plate with an extremely thin duplex layer which is excellent in visual appeal, corrosion resistance and paint adhesion.
  • Another object of the invention is to permit high grade deep drawing for an electrolytically treated steel plate without causing a paint layer coated on its surface to peel off during operation.
  • the method of the present invention can attain these objects by immersing a steel plate as a cathode in an electrolyte containing chromic acid or chromate as a main agent, inorganic sulfur compounds as a first promotive agent and inorganic fluorine compounds as a second promotive agent, and coating the surface of said steel plate with an extremely thin duplex layer, the upper portion of which consists of hydrated chromium oxide and the lower portion of which consists of metallic chromium.
  • FIG. 1 is a chart showing the relationship of the various concentrations of fluorine compounds in an electrolyte and the corresponding contents of chromium in the hydrated chromium oxide deposited on the surface of a steel plate;
  • FIG. 2. is another chart showing the relationship of the various concentrations of borofluoric acid in the same electrolyte and the corresponding rating of paint adhesion.
  • An electrolyte used in the method of the present invention contains chromic acid or a chromate dissolved as a main agent, such as chromium trioxide or sodium dichromate consisting of hexavalent chromium.
  • concentration of said main agent is of the order of 10 to g. CrO per liter.
  • a first promotive agent including inorganic sulfur compounds such as thiocyanic acid, thiosulfuric acid, dithionous acid, sulfurous acid, thiosulfurous acid, pyrosulfurous acid, a salt thereof or a sulfide.
  • Said first promotive agent is used at a proportion equal to l/500 to l/25 by weight of chromate ion the agent solution.
  • These two agents play a very important role in connection with the mechanism whereby there is deposited a duplex layer of metallic chromium and hydrated chromium oxide in one step. Electrolysis of an electrolyte containing these two agents results in the partial formation of trivalent chromium ions and further complex salts consisting of said trivalent chromium ion and originally contained hexavalent chromium ion, thereby promoting electrolytic deposition.
  • the technology up to this point is already known (cf. French Pat. 1,168,685).
  • the method of the present invention is characterized in that the electrolyte further contains a second promotive agent including inorganic fluorine compounds, such as hydrofluoric acid, hydrosilicofluoric acid, borofluoric acid, and salts thereof.
  • Said second promotive agent is used at a proportion corresponding to l/500 to l/25 by weight of chromate ion in the solution. It has been disclosed herein that addition of these fluorine compounds enables the hydrated chromium oxide layer to be deposited to a uniformly minute thickness and that adjustment of the concentration of said compounds allows the thickness of said hydrated chromium oxide layer to be controlled to any desired extent, namely the more concentrated said compounds, the thinner will become the hydrated chromiumn oxide layer produced.
  • Electrolysis according to the method of the present invention is generally conducted under the following conditions:
  • the concentration of said second promotive agent varies very little. For instance, where electrolysis was conducted by continuously introducing a 4000 111. sheet of stripped steel through 1400 liters of electrolyte, said second promotive agent did not substantially vary in concentration, though the concentration of the first promotive agent changed slightly. However, the effect that the varied concentration of said first promotive agent exerted on the properties of a chromium layer formed was not so prominent as in the case of the prior art binary electrolyte. Accordingly, the method of the present invention permits the concentration of electrolyte components to be controlled with far greater ease than is possible with the prior art.
  • a thin steel plate whose surface is treated with the chromate solution by the method of the present invention displays excellent formability after painting, and, in the case of can making, fully withstands deep drawing. Further, as the outer portion of the closely deposited layer which consists of hydrated chromium oxide has very excellent corrosion resistance, the surface of the steel plate is free from rusting when the steel plate is left long in the open air until it is painted.
  • the inner portion of the deposited layer be formed of 0.8 to 1.5 mg./dm. of metallic chromium and the outer portion consists of hydrated chromium oxide containing 0.2 to 0.4 mg./dm. of chromium. Adjustment of the concentration of the second promotive agent enables the deposited layer to be varied in thickness within the aforementioned range according to the application in which said steel plate is to be used.
  • FIG. 1 gives the relationship of the concentrations of various fluorine compounds dissolved as a second promotive agent in an electrolyte and the chromium content of the hydrated chromium oxide which constitutes the outer portion of the deposit layer.
  • the curves A, B and C of the chart represent the case where there were used in a static state bath sodium silicofluoride Na SiF borofluoric acid HBF, and sodium borofluoride NaBF respectively, as a second promotive agent.
  • the curve D denotes the case where there was added borofluoric acid HBFI, to a flowing state bath.
  • the electrolysis in a static state bath represented by the curves A, B and C was conducted under the following conditions.
  • Bath composition 50 g./l. of chromium trioxide, 0.5 g./l. of sodium thiocyanate and 0 to 1.5 g./l. of the various fluorine compounds
  • Current density of cathode 30 a./dm.
  • Treating time 3 seconds Electrolysis in a flowing state bath associated with the curve D was performed under the same conditions as described above excepting that the current density was changed to 20 arnp./dm. and the treating time was increased to 4 seconds.
  • the second promotive agent consisted of borofluoric acid
  • the thinner became the hydrated chromium oxide which formed to outer portion of the deposit layer.
  • the thickness of said hydrated chromium oxide was generally more reduced when electrolysis was conducted in a flowing state bath than in a static state bath.
  • FIG. 2 is a chart showing the relationship of the concentration borofluoric acid corresponding to the curve B of FIG. 1 and the formability after painting of a steel plate treated with chromate solution.
  • the surface of steel plate treated electrolytically in chromate solution was coated with phenol-epoxy resin uniformly at the rate of 50 mg./dm. respectively. Painting of said surface was completed by baking 10 minutes at a temperature of 205 C.
  • the paint adhesion was evaluated in the following manner. In the square can forming test, there was allotted a maximum of 10 points to the case where the paint did not come off from any of the four corners of the square can. Namely, the greater the paint adhesion, there were allotted larger points. Where there occurred peel-offs starting with those portions which had a small radius of curvature, the rating was decreased by 2 for each such peel-off. Again where the peel-off extended up to a portion corresponding to one-fourth or one-third of the entire length of each sample can as measured from its top, the rating was further de-, creased by 1. Where there even appeared a peel-01f at the bottom of the can, there was allotted a zero point.
  • the curve E denotes the degree of paint adhesion as determined by the aforesaid forming test, where there was applied painting on the outside of the can
  • the curve F the degree of such formability where the inside of the can was painted
  • the curve G the formability of a screw-cap whose inside was painted as determined by the screwcap forming test
  • the curve H the formability of a screw-cap whose outside was painted, as determined by said screw-cap forming test.
  • Example 1 A cold stripped steel plate 0.23 mm. thick was electrolytically degreased in a solution of sodium silicate, and also electrolytically washed in a dilute sulfuric acid solution and finally subjected to a chromate treatment in an electrolyte having the following composition and under the following treating conditions.
  • composition of electrolyte g./l.:
  • Chromium trioxide 50 Sodium thiocyanate 0.5 Borofiuoric acid 1.0 Bath temperature, C. 50 Current density of cathode, amp./dm. 20 Treating time, seconds 4
  • the cathode used in this example consisted of a lead plate whose surface was coated with lead peroxide.
  • the inner portion of a deposited layer on the treated surface of said steel plate contained 1.0 to 1.1 mg./dm. of metallic chromium, and the outer portion consisted of hydrated chromium oxide contained 0.25 to 0.30 mg./dm. of chromium.
  • This steel plate displayed good paint adhesion for paints containing phenol resin, phenolepoxy resin or phenol-urea resin, respectively.
  • Example 3 Steel plates of the same type as used in Example 1 were treated with an electrolyte having the following composition and under the following treating conditions.
  • composition of electrolyte g./l.:
  • Example 5 Tests were made in the same manner as in Example 1, excepting that there was used an electrolyte composed as follows:

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Electroplating Methods And Accessories (AREA)
US99A 1969-01-13 1970-01-02 Method for electrolytic treatment of steel surface in a chromate solution Expired - Lifetime US3679554A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP206669 1969-01-13

Publications (1)

Publication Number Publication Date
US3679554A true US3679554A (en) 1972-07-25

Family

ID=11518954

Family Applications (1)

Application Number Title Priority Date Filing Date
US99A Expired - Lifetime US3679554A (en) 1969-01-13 1970-01-02 Method for electrolytic treatment of steel surface in a chromate solution

Country Status (4)

Country Link
US (1) US3679554A (de)
DE (1) DE2001274C3 (de)
FR (1) FR2028235B1 (de)
GB (1) GB1258021A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3986940A (en) * 1975-02-04 1976-10-19 Nippon Kokan Kabushiki Kaisha Process for manufacturing electrolytically chromated steel sheet
US4421828A (en) * 1979-09-06 1983-12-20 Carnaud S.A. Steel sheet carrying a protective layer and process for producing such a sheet
US4432842A (en) * 1979-03-30 1984-02-21 Toyo Kohan Co., Ltd. Process for producing tin-free steel
US4437944A (en) 1980-07-28 1984-03-20 Zincroksid S.P.A. Process of making long-life thin metal plate for automobile bodies
EP0132722A1 (de) * 1983-07-20 1985-02-13 Kawasaki Steel Corporation Verfahren zur Herstellung zinnfreier Stahlbänder mit verbessertem Haftvermögen für Lacke
EP2922983B1 (de) * 2012-11-21 2019-02-20 Tata Steel IJmuiden BV Auf stahlsubstrate für verpackungsanwendungen angewandte chrom-chromoxid-beschichtungen und verfahren zur herstellung besagter beschichtungen

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4062737A (en) * 1974-12-11 1977-12-13 International Business Machines Corporation Electrodeposition of chromium
US4141803A (en) * 1975-12-03 1979-02-27 International Business Machines Corporation Method and composition for electroplating chromium and its alloys and the method of manufacture of the composition
US4161432A (en) * 1975-12-03 1979-07-17 International Business Machines Corporation Electroplating chromium and its alloys
JPS62124296A (ja) * 1985-11-25 1987-06-05 Toyo Kohan Co Ltd シ−ム溶接性，塗料密着性の優れた表面処理鋼板およびその製造方法
JP2541269B2 (ja) * 1987-08-27 1996-10-09 日本板硝子株式会社 酸化物薄膜の製造方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3296100A (en) * 1962-05-09 1967-01-03 Yawata Iron & Steel Co Process for producing anticorrosive surface treated steel sheets and product thereof
FR1382237A (fr) * 1963-10-30 1964-12-18 Toyo Kohan Co Ltd Perfectionnements apportés aux procédés pour la formation de revètement protecteur sur la surface de métaux, aux électrolytes utilisés à cette fin, et aux procédés pour la préparation de tels électrolytes
GB1099836A (en) * 1965-07-12 1968-01-17 Toyo Kohan Co Ltd Process for treating electrolytically chromated metal surfaces
FR1543364A (fr) * 1967-09-07 1968-10-25 Nippon Kokan Kk Traitement anti-corrosif des surfaces des matériaux en fer et acier

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3986940A (en) * 1975-02-04 1976-10-19 Nippon Kokan Kabushiki Kaisha Process for manufacturing electrolytically chromated steel sheet
US4432842A (en) * 1979-03-30 1984-02-21 Toyo Kohan Co., Ltd. Process for producing tin-free steel
US4455355A (en) * 1979-03-30 1984-06-19 Toyo Kohan Co., Ltd. Tin-free steel can body
US4421828A (en) * 1979-09-06 1983-12-20 Carnaud S.A. Steel sheet carrying a protective layer and process for producing such a sheet
US4437944A (en) 1980-07-28 1984-03-20 Zincroksid S.P.A. Process of making long-life thin metal plate for automobile bodies
EP0132722A1 (de) * 1983-07-20 1985-02-13 Kawasaki Steel Corporation Verfahren zur Herstellung zinnfreier Stahlbänder mit verbessertem Haftvermögen für Lacke
EP2922983B1 (de) * 2012-11-21 2019-02-20 Tata Steel IJmuiden BV Auf stahlsubstrate für verpackungsanwendungen angewandte chrom-chromoxid-beschichtungen und verfahren zur herstellung besagter beschichtungen

Also Published As

Publication number Publication date
DE2001274A1 (de) 1970-07-30
DE2001274C3 (de) 1981-06-04
FR2028235B1 (de) 1973-04-06
FR2028235A1 (de) 1970-10-09
DE2001274B2 (de) 1980-10-16
GB1258021A (de) 1971-12-22

Similar Documents

Publication Publication Date Title
US5032236A (en) Process for producing a surface-blackened steel sheet
US4861441A (en) Method of making a black surface treated steel sheet
US3679554A (en) Method for electrolytic treatment of steel surface in a chromate solution
US4902387A (en) Chromate-treated zinc-plated steel strip and method for making
KR910002103B1 (ko) 아연계 복합도금 금속재료와 그 도금방법
US3592747A (en) Method of forming a decorative and protective coating on a surface
US3799814A (en) Chromate treated metal sheet
US4935111A (en) Method for producing black colored steel strip
US4137132A (en) Chromite coatings, electrolytes, and electrolytic method of forming the coatings
US3895969A (en) Composition and process for inhibiting corrosion of non-ferrous metal surfaced articles and providing surface for synthetic resin coating compositions
US3421986A (en) Method of electroplating a bright adherent chromium coating onto cast-iron
US4591416A (en) Chromate composition and process for treating zinc-nickel alloys
US3785940A (en) Method for electrolytically treating the surface of a steel plate with a chromate solution
US3943040A (en) Microcracked chromium from a bath using an organic sulfur compound
US2380044A (en) Process for producing electrodeposits
US2985567A (en) Electrodeposition of black chromium coatings
US3713999A (en) Electrodeposition of chromium
GB2113721A (en) Chromate composition for treating electrodeposited zinc- nickel alloys
US2963784A (en) Base stock for vitreous enamel coatings
US3586612A (en) Anodic phosphating of metallic articles
JPS5928638B2 (ja) マグネシウム材表面に着色保護皮膜を形成する方法
US2080483A (en) Electrodeposition of zinc
US3755091A (en) Process for reducing discoloration of electrochemically treated chromium plated ferrous metal strip
JPS61291981A (ja) 黒色亜鉛合金メツキ鋼板の製造方法
US3346404A (en) Chemical plating process