US3822118A - Acid zinc-electroplating process and product thereof - Google Patents

Acid zinc-electroplating process and product thereof Download PDF

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Publication number
US3822118A
US3822118A US00331597A US33159773A US3822118A US 3822118 A US3822118 A US 3822118A US 00331597 A US00331597 A US 00331597A US 33159773 A US33159773 A US 33159773A US 3822118 A US3822118 A US 3822118A
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United States
Prior art keywords
zinc
layer
plated
electroplating
bath
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Expired - Lifetime
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US00331597A
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English (en)
Inventor
T Fukuzuka
H Sakai
T Furuya
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Kobe Steel Ltd
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Kobe Steel Ltd
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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
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/22—Electroplating: Baths therefor from solutions of zinc
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/923—Physical dimension
    • Y10S428/924—Composite
    • Y10S428/926—Thickness of individual layer specified
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9335—Product by special process
    • Y10S428/934—Electrical process
    • Y10S428/935—Electroplating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12639—Adjacent, identical composition, components
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12785—Group IIB metal-base component
    • Y10T428/12792—Zn-base component
    • Y10T428/12799—Next to Fe-base component [e.g., galvanized]

Definitions

  • the steel may have an initial plate of zinc in a thickness of at least 1 X 10' y, prior to said electrolysis treatment.
  • This invention relates to an acid zinc-electroplating process for use on steel plates or the like, which gives plated zinc layers which have excellent corrosion resistance properties and which have surfaces suitably adapted for painting.
  • the electroplating baths used for the plating of steel sheets usually contain therem a basic agent containing zinc ions, electro-conductive salts, to improve the electrical conductivity of the bath, and a buffer agent, to maintain the pH of the plating medium at a predetermined value. Since an electroplated layer or film, which is obtained from such a bath is usually pure 21110, the plated layer obtained is initially a uniform gray-white color. This layer, however, takes on the undesirable ap pearance of white rust in an extremely short period of time after the plated sheet is stored in an atmosphere with a high level of humidity.
  • the plates eventually develop rust.
  • the time it takes for the initial appearance of rust on the steel plates in a salt spray test is proportional to the thickness of the plated layer, that is, it takes an additional 6 to'8 hours for rust to appear for each additional micron of the plated layer.
  • An additional disadvantage of conventional zinc-plating procedures is that the plated layer does not have a surface suitable for painting because of the poor adhesion of the paint to the surface of the layer. This results in peeling of the paint from the layer.
  • the surface of the exposed layer must be further treated, such as by chromating or phosphating treatments to improve the corrosion resistance and to improve the ability of paint to adhere to the layer.
  • blisters will often develop in the baking process in the interface between the surface of the base metal and the electroplated layer. This results in critical defects in the metal.
  • the blisters are believed to be caused by the presence a very small amount of hydrogen formed during the electroplating process which becomes occluded or otherwise contained on the surface of the base metal.
  • one object of this invention is to provide an improved acid zinc-electroplating process.
  • Another object of the invention is to provide an improved acid zinc-electroplating process which yields a metal product having highly improved corrosion resistance and an improved 'bondability to paint coatings.
  • an acid zinc-electroplating process for use on steel plates or the like which comprises the electrolysis of a metal sheet in an acid zinc-electroplating bath containing 0.05 to 0.3 g./l. of Cr.
  • an acid zinc electroplating process wherein zinc is plated in a thickness of 1X10 ,u. onto the surface of base metal and then said plated metal is further subjected to electrolysis in an acid-zinc electroplating bath containing 0.05 to 0.3 g./l. of Cr+ ions.
  • the electroplated steel plates thus produced are characterized by excellent corrosion resistance and highly improved adhesive properties for paint films applied thereon.
  • FIG. 1 is an X-ray diffraction diagram of the plated layers produced by the process of this invention (1) and by conventional acid zinc-electroplating procedures (2);
  • FIG. 2 shows infrared spectra of a layer (3) produced by the acid zinc-electroplating process of this invention, a layer (4) obtained from conventional acid zinc-electroplating procedures, and a layer (5) on a steel plate which has been subjected to an electrolytic chromating process;
  • FIG. 3 is a plot obtained by an electron probe microanalyzer showing the chromium distribution throughout an electroplated layer produced by the process of this invention
  • FIG. 4 is a plot showing the relationship between the electrode potential and the current density for Zn-Cr electroplating a mild steel plate
  • FIG. 5 is a plot showing the relationship between the electrode potential and the current density for Zn-Cr electroplating a pure zinc layer 0.1, thick;
  • FIG. 6a shows the development of blisters throughout the surface of a sample having both surfaces electroplated
  • FIG. 6b shows no development of blisters on the surface of a sample having one surface electroplated
  • FIG. 60 shows no development of blisters on the surface of a sample which has been subjected to the acid zinc-electroplating process of the present invention
  • FIG. 7 is a plot showing the relationship between electrode potential and the thickness of a plated zinc layer
  • FIG. '8 is a perspective view of a tester used in testing the present invention.
  • FIG. 9 is a photograph showing the results of peeling tests conducted on plated metal sheets which have had patterns described on their surfaces with the describing tester of FIG. 8.
  • a small amount of Cr+ ions is added to an acid zinc-electroplating bath.
  • the amount of ions added is in the range of 0.05 to 0.3 g./l. If Cr ions are present in concentrations of less than 0.05 g./ 1., no appreciable improvements are notic-able in the corrosion resistance of the electroplated steel plates. If Cr+ ions are present in concentrations of greater than 0.3 g./l. the final appearance of the electroplated steel plates will be appreciably spoiled.
  • the chromium ions can be added to the bath in the form of compounds of Cr+ such as CrO K Cr O and/or (NH Cr O
  • the pH of the bath should preferably be adjusted to the range from 2.5 to 4.5. If the pH is less than 2.5, poor effects are noted because of the presence of Cr+ ions, while if the pH is greater than 4.5, zinc hydroxide could precipitate from the bath.
  • the concentration of zinc ions in the electroplating bath is in the range of 30 to 150 g./l., preferably 40 to 110 g./l.
  • Suitable zinc salts which are added to the electroplating bath include ZnSO -7H O, ZnCl Zn(B'F Zn P O; and the like.
  • the thickness of the zinc layer on the plated metal sheets obtained from the acid zincelectroplating bath is ten microns or less.
  • the salt spray test reveals, according to the present invention, that the corrosion resistance of the plated layer on a steel plate is three times greater than a layer obtained by conventional processes which do not contain Cr+ in the electroplating baths.
  • Analysis of the chromium content in the plated layer obtained by the process of the present invention indicates that from 0.05 to 0.6% chromium is contained in the plated zinc layer depending on the electroplating conditions.
  • X-ray diffraction tests of placed layers which reveals the condition of the co-deposits of chromium and zinc contained in the plated layers
  • infrared spectra of the plated layers and
  • electron probe micronanalyzer tests which analyze for chromium in the plated layer have been used.
  • the X-ray diffraction tests show that the layer obtained by the process of the present invention presents a diffraction image (1) of metallic zinc, similar to the diffraction image 2) of the plated layer obtained from a conventional acid zinc-electroplating bath.
  • the infrared spectrum (3) (FIG. 2) of the plated layer produced by a bath containing Cr+ ions has absorption bands in the neighborhood of 5 90 and 1130 cm.- These absorption bands are considered to correspond to the absorption bands at 610 and 1130 cmf which are obtained from an infrared spectrum of the chromate film on a steel plate which has been subjected to electrolytic chromating. It is felt that these absortion paterns suggest the existence of chromium hydrate. Thus, it can be considered that in the process of zinc electroplating in the presence of Cr+ ions, chromium c0- deposits as chromium hydrate simultaneously with the precipitation of zinc.
  • the deformation, and stretching vibration of OH are responsible for the absorption patterns at 1600 and 3200 cm.
  • the plated layer obtained from a conventional acid zinc-electroplating bath indicates (4) that the stretching vibration of OH only is in the neighborhood of 3200 cm.
  • the results of a chromium analysis of the cross section of a plated layer obtained from a bath of the present invention, as determined by an electron probe microanalyzer, are shown in FIG. 3.
  • the spectrum indicates a uniform distribution of chromium depthwise in the plated layer (10) as compared to the spectrum of a base steel sheet (11).
  • chromium is distributed throughout the depth of the layer which results in increased corrosion resistance.
  • the as-plated condition of the layer obtained by the process of the present invention can present the same effect as is obtained from electrolytic chromating, thus providing improved corrosion resistance for the zinc plated steel plate.
  • electrolysis of a sheet of metal in an acid zinc-electroplating bath containing a specific amount of Cr ions therein affords a plated layer which offers substantial improvements in corrosion resistance as compared with the plated layers obtained from conventional acid zinc-electroplating baths.
  • plates A, B, and C three samples of a mild steel plate 0.8 mm. thick, which were identified as plates A, B, and C were prepared.
  • Plate A was electroplated on both surfaces in an acid zinc-electroplating bath containing Cr ions therein to produce layers 10a thick.
  • Plate B was electroplated on one of its surfaces to produce a layer 10p. thick.
  • Plate C was first plated with pure or normal zinc to produce a layer 01;; thick followed by an electroplating step in the acid zinc-electroplating bath containing Cr ions therein to produce an additional layer 10p. thick.
  • the samples were then subjected to a boiling water immersion test.
  • FIG. 7 is a plot of the potential of an electrode versus the thickness of a plated zinc layer in microns. The plot shows the change in the electrical potential from a base sheet (40) at a potential of -720 mv. vs. SCE to that of zinc plated sheet (41) at a potential of 1020 mv. vs.
  • Example 1 shows a conventional art process for electroplating a metal sheet.
  • Examples 2-8 represent the first embodiment of the electroplating process of this invention.
  • Examples 9-11 represent the second embodiment of the electroplating process of this invention.
  • EXAMPLE 1 A mild steel sheet was electroplated under the following conditions to achieve plated layers of a thickness of 4;/..
  • One coating of an acrylic base paint was applied on the surface of the layer obtained under a baking temperature of 180 C. for 30' minutes.
  • the final coat was 20 thick.
  • Electroplating time 42 sec. (corresponding to a layer 4n thick).
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • Electroplating time 28 sec. (corresponding to a layer 4, thick).
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • Electroplating time 28 sec. (corresponding to a layer 4 thick).
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • Electroplating time 42 sec. (corresponding to a layer 4 4 thick).
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • Electroplating time 28 sec. (corresponding to a layer 4n thick).
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • the metal sheet was covered with a coating of paint similar to that of Example 1.
  • EXAMPLE 9 A mild steel sheet was electroplated on its surfaces under the conditions below in which (i) pure zinc layers 1Xl0 ,u thick were first electroplated followed by (ii) a second electroplating step using an electroplating bath containing Cr ions to give a layer 4;]. thick.
  • the metal sheet was covered with a coating of paint similar to that of Example 9.
  • Table 1 gives the results from the corrosion resistance tests and the adhesion to paint film tests of the plated layers which have been obtained in Examples 1-11.
  • One coating of an acrylic paint was applied on the surface of the plated layers to give a layer 20 1. thick after baking at a temperature of 180 C. for 30 minutes.
  • the helical pattern describing adhesion test is a test made by the tester 50 shown in FIG. 8, wherein a needle 51 is mounted on the lower tip of the shaft 52 which extends vertically and is adapted to rotate. The needle is designed so that it may describe a helical pattern on a painted surface as shown in FIG. 9. Mounted on the top of the shaft 52 is a loading dish 53 on which is placed a weight 54 weighing 300:1 g. The diameter 9 of the helical pattern described is limited to 10 mm. while the length thereof is over 30 mm.
  • a piece of adhesive tape (such as Scotch tape) is placed on the sheet over the helical pattern.
  • the tape is suddenly peeled from the sheet to observe how much of the paint film is removed from the metal sheet.
  • FIG. 9 shows the inspection criteria.
  • the cross-cut adhesion test is a test in which the film of paint on a sample metal sheet is cut into a grid pattern with a blade such as a safety razor to a depth which reaches the electroplated surface of the metal sheet.
  • the spacing between adjacent lines of the grid pattern is 1 mm., with eleven lines, longitudinal and lateral, being described so as to intersect each other at right angles. This provides 100 sections 1 mm. in area.
  • a strip of adhesive tape is placed on the grid pattern and is suddenly peeled from the sample. The paintability or the adhesiveness of the paint coating on the plated layer is determined by the amount of paint removed.
  • the layer is graded as 10 on a scale of 0 to 10. If paint is removed from all of the sections, the layer receives a grade of 0.
  • the paintability test in the table indicates that the best results are achieved when metal sheets are plated by the process of the second embodiment (Examples 9 10 to 11) when compared to the data of Examples 1 to 8.
  • a process for improving the corrosion resistance and paintability of steel plate which comprises electroplating a pure zinc layer of at least 1X10- p. onto said steel plate and then subjecting said zinc-coated steel plate to electrolysis as cathode in an aqueous acidic zinc electroplating bath containing 0.05 to 0.3 g./l. Cr+ therein to deposit an additional layer of zinc thereon.

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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 And Plating Baths Therefor (AREA)
  • Electroplating Methods And Accessories (AREA)
US00331597A 1972-02-12 1973-02-12 Acid zinc-electroplating process and product thereof Expired - Lifetime US3822118A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3986843A (en) * 1975-01-22 1976-10-19 Nippon Kokan Kabushiki Kaisha Process for manufacturing chromated electro-galvanized steel sheet and sheet made thereby
US4036600A (en) * 1975-06-05 1977-07-19 Kawasaki Steel Corporation Steel substrate electroplated with Al powder dispersed in Zn
US4048381A (en) * 1975-01-22 1977-09-13 Nippon Kokan Kabushiki Kaisha Method for manufacturing an electro-galvanized steel sheet excellent in bare corrosion resistance and adaptability to chromating, and product thereof
US4064320A (en) * 1975-03-26 1977-12-20 Nippon Kokan Kabushiki Kaisha Chromated electro-galvanized steel sheet excellent in corrosion resistance and process for manufacturing same
US4957594A (en) * 1988-02-19 1990-09-18 Nippon Steel Corporation Process for producing a zinc or zinc alloy coated steel sheet having excellent spot weldability
US5510196A (en) * 1992-07-10 1996-04-23 Kawasaki Steel Corporation Corrosion resistant steel sheets improved in corrosion resistance and other characteristics
DE102016225681A1 (de) * 2016-12-20 2018-06-21 Thyssenkrupp Ag Vergraute Oberfläche zum Zwecke einer verkürzten Aufheizung

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS50102538A (enExample) * 1974-01-18 1975-08-13
JPS51112436A (en) * 1975-03-28 1976-10-04 Nippon Kokan Kk Electrogalvanized steel plate having excellent net corrosion resistance and property to be treated and method of fabricating the same
JPS51110443A (en) * 1975-03-26 1976-09-30 Nippon Kokan Kk Kuromeetoshoriseino suguretadenkiaenmetsukikohan oyobi sonoseizoho

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3986843A (en) * 1975-01-22 1976-10-19 Nippon Kokan Kabushiki Kaisha Process for manufacturing chromated electro-galvanized steel sheet and sheet made thereby
US4048381A (en) * 1975-01-22 1977-09-13 Nippon Kokan Kabushiki Kaisha Method for manufacturing an electro-galvanized steel sheet excellent in bare corrosion resistance and adaptability to chromating, and product thereof
US4064320A (en) * 1975-03-26 1977-12-20 Nippon Kokan Kabushiki Kaisha Chromated electro-galvanized steel sheet excellent in corrosion resistance and process for manufacturing same
US4036600A (en) * 1975-06-05 1977-07-19 Kawasaki Steel Corporation Steel substrate electroplated with Al powder dispersed in Zn
US4957594A (en) * 1988-02-19 1990-09-18 Nippon Steel Corporation Process for producing a zinc or zinc alloy coated steel sheet having excellent spot weldability
US5510196A (en) * 1992-07-10 1996-04-23 Kawasaki Steel Corporation Corrosion resistant steel sheets improved in corrosion resistance and other characteristics
DE102016225681A1 (de) * 2016-12-20 2018-06-21 Thyssenkrupp Ag Vergraute Oberfläche zum Zwecke einer verkürzten Aufheizung

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JPS5617438B2 (enExample) 1981-04-22
JPS4884040A (enExample) 1973-11-08

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