EP0545908A2 - Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet - Google Patents

Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet Download PDF

Info

Publication number
EP0545908A2
EP0545908A2 EP93102764A EP93102764A EP0545908A2 EP 0545908 A2 EP0545908 A2 EP 0545908A2 EP 93102764 A EP93102764 A EP 93102764A EP 93102764 A EP93102764 A EP 93102764A EP 0545908 A2 EP0545908 A2 EP 0545908A2
Authority
EP
European Patent Office
Prior art keywords
galvanizing
coating
hot
galvanized
post
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.)
Granted
Application number
EP93102764A
Other languages
German (de)
English (en)
Other versions
EP0545908B1 (fr
EP0545908A3 (fr
Inventor
Kazuhide Oshima
Hisakazu Morino
Tomio Kondo
Yasuo Shimada
Tadashi Nonaka
Hiroshi Oishi
Yoshikazu Yamanaka
Yoshihiko Hoboh
Atsuhisa Yakawa
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.)
Nippon Steel Corp
Original Assignee
Sumitomo Metal Industries 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 Sumitomo Metal Industries Ltd filed Critical Sumitomo Metal Industries Ltd
Priority claimed from EP90401217A external-priority patent/EP0397555B1/fr
Publication of EP0545908A2 publication Critical patent/EP0545908A2/fr
Publication of EP0545908A3 publication Critical patent/EP0545908A3/xx
Application granted granted Critical
Publication of EP0545908B1 publication Critical patent/EP0545908B1/fr
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
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel

Definitions

  • This invention relates to a plating method for steel sheet. More particularly, it relates to an electroplating method of hot-galvanized steel sheet. It also relates to a plating line in which a steel sheet is continuously subjected to hot-galvanizing and then electroplating. The resulting plated steel sheet has an electroplated top coating with excellent covering power and adhesion to the underlying hot-galvanized coating.
  • Multi-layer plated steel sheet Steel sheet with a plurality of layers of plated coating (hereinafter referred to as multi-layer plated steel sheet) is highly suitable for use in automobiles and as a construction material not only on account of its coatability but also because of its excellent press forming characteristics (sliding properties), weldability, and various other properties.
  • the multi-layer electroplating that have been proposed in the prior art include a Zn-Ni/Fe or Fe-Zn coating (Japanese published Examined Patent Application No. 60-57518), a Zn-Ni/Zn or Zn-Ni or Zn-Fe/Cr(Cr-oxide) coating (Japanese Published Unexamined Patent Application No. 60-197893), a Zn-Mn/Zn-Fe coating (Japanese Publised Unexamined Patent Application No. 58-42787), and a Zn or Zn alloy/minute particle-dispersed Zn or Zn alloy coating (Japanese Publised Unexamined Patent Application No. 62-230999).
  • a Zn-Ni/Fe or Fe-Zn coating Japanese Unexamined Patent Application No. 60-57518
  • a Zn-Ni/Zn or Zn-Ni or Zn-Fe/Cr(Cr-oxide) coating Japanese Unexamined Patent Application
  • plating baths for different types of coatings are arranged in series along the line.
  • Equipment for dip water rinsing and, if necessary, equipment for rinsing with hot water or with brushes is installed between successive baths.
  • no treatment other than rinsing or scrubbing is performed on the steel sheet as it is passed from one bath to another.
  • Japanese Published Unexamined Patent Application No. 60-224791 discloses a continuous plating apparatus in which a pretreatment apparatus, a hot-galvanizing bath, an alloying furnace, and an electroplating apparatus are connected in series.
  • a skin-pass rolling mill and, if necessary, a water rinse tank may be disposed between the hot-galvanizing bath and the electroplating apparatus.
  • Japanese Published Unexamined Patent Application No. 62-17200 discloses a continuous one-sided plating apparatus in which a pretreatment apparatus, a hot-galvanizing bath for plating one side of a steel sheet, an alloying furnace, a cleaning apparatus for cleaning the unplated side of the sheet, and an electroplating apparatus are connected in series.
  • the electroplated coating is one such as an Fe coating which is intended to increase the coatability of the plated steel sheet by cationic electrodeposition, the electroplated coating cannot adequately perform its intended function.
  • the covering power of an electroplated coating with respect to microscopic irregularities will hereunder be referred to as its microcovering power.
  • a hot-galvanized steel sheet is subjected to post-galvanizing surface treatment prior to electroplating in order to remove oxide and other surface contaminants (hereinafter collectively referred to as surface oxide contaminants) and activate the surface of the galvanized coating.
  • the post-galvanizing surface treatment employed in the present invention greatly increases the adhesion and covering power of an electroplated coating.
  • the reasons for these improvements are not yet clear.
  • the surface treatment improves properties by dissolving away aluminum oxide and an Zn-containing aluminum oxide which are formed on the surface of a galvanized coating of a steel sheet by the heat applied by hot-galvanizing or alloying and which have poor electrical conductivity.
  • it can remove Al and other metallic contaminants which segregates on the surface and which are thought to influence electro-deposition of an electroplated coating.
  • the post-galvanizing surface treatment can be any form of treatment which can remove surface oxide contaminants which adversely affect the microcovering power of an electroplated coating.
  • the surface treatment may be carried out by applying a strong alkali solution or an acid which can dissolve aluminum oxide to the surface of the galvanized coating. Alternatively, it can be performed by electrolysis such as cathodic or anodic electrolysis in an alkaline solution (alkali electrolysis) or cathodic electrolysis in a neutral solution.
  • the post-galvanizing surface treatment can also be performed by skin-pass rolling using a strong alkali solution or an acid which can dissolve aluminum oxide as a skin-pass rolling liquid or by cooling a hot galvanized or alloyed steel sheet with an alkali solution as a cooling medium before skin-pass rolling.
  • a continuous plating line comprises a continuous hot-galvanizing apparatus for forming a galvanized coating on a steel strip which is optionally equipped with an alloying apparatus, a continuous electroplating apparatus connected in series with the hot-galvanizing apparatus for forming an electroplated coating on the galvanized coating, and at least one post-galvanizing surface treatment apparatus disposed between the hot-galvanizing apparatus and the electroplating apparatus for removing surface oxide contaminants and activating the surface of the galvanized coating.
  • the post-galvanizing surface treatment apparatus can be a device for spraying a steel strip with a surface treatment solution such as a strong alkali solution or an acid which can dissolve aluminum oxide, an immersion bath using such a surface treatment solution, an electrolytic cell, a cooling tank using an alkali solution as a cooling medium which is disposed before a skin-pass rolling mill, or a skin-pass rolling mill employing a strong alkali solution or an acid which can dissolve aluminum oxide as a skin-pass rolling liquid.
  • a surface treatment solution such as a strong alkali solution or an acid which can dissolve aluminum oxide
  • an immersion bath using such a surface treatment solution an electrolytic cell
  • a cooling tank using an alkali solution as a cooling medium which is disposed before a skin-pass rolling mill
  • a skin-pass rolling mill employing a strong alkali solution or an acid which can dissolve aluminum oxide as a skin-pass rolling liquid.
  • Figure 1 schematically illustrates a continuous plating line according to the present invention.
  • a steel strip 2 is unwound from a pay-off reel 1 and passed through a prewashing apparatus 3 and then through a pretreatment apparatus comprising a rapid heating furnace 4, a reduction furnace 5, and a cooling furnace 6 in which the surface of the steel strip is cleaned. If necessary, the strip 2 can be annealed. It is then passed through a hot-galvanizing bath 7 where hot galvanizing is carried out and a galvanizing coating is formed on one side or both sides of the strip. Then, if necessary, the strip 2 is passed through an alloying furnace 8 in which Fe in the steel strip 2 and Zn in the hot-galvanized coating are alloyed.
  • the hot-galvanizing bath 7 can be a bath of either zinc or a zinc alloy such as GALFAN [5% Al, 0.1% (La + Ce), the remainder Zn], GALVALUME (55% Al, 1.5% Si, the remainder Zn), or the like.
  • the optionally alloyed galvanized steel strip 2 is then passed through a post-galvanizing surface treatment apparatus 9, which removes surface oxide contaminants and activates the surface of the galvanized coating.
  • the surface treatment apparatus comprises a tank containing a strong alkali solution (pH at least 12) in which the strip 2 is immersed.
  • the strip 2 is then washed with a water scrubber 10 or similar water rinsing apparatus and passed through bridle rolls 19, a skin-pass rolling mill 11, and a leveller 12 to flatten the surface and remove strains.
  • the strip 2 is then passed through a pretreatment tank 13 and an electroplating cell 14, in which electroplating is performed on the galvanized coating.
  • finishing treatment such as chromate treatment can be performed in a finishing surface treatment apparatus 17, and the treated steel strip 2 is wound onto a tension roll 18.
  • the location of the post-galvanizing surface treatment apparatus 9 (and the water scrubber 10) in the plating line is not critical.
  • it can be disposed between the leveller 12 and the bridle rolls 19, in which case the post-galvanizing surface treatment is performed after skin-pass rolling instead of before.
  • post-galvanizing surface treatment apparatus 9 can be employed.
  • an additional post-galvanizing surface treatment apparatus 9 and water scrubber 10 can be disposed between the leveller 12 and the bridle rolls 19, in which case the post-galvanizing surface treatment is performed both before and after skin pass rolling.
  • the position of the skin-pass rolling mill 11 is also not critical.
  • the skin-pass rolling mill 11 and the leveller 12 can be disposed between the drier 16 and the surface treatment apparatus 17, in which case skin-pass rolling is performed subsequent to electroplating.
  • the post-galvanizing surface treatment apparatus 9 is not limited to an immersion tank, and it can be any device which is capable of removing oxide contaminants from the surface of the galvanized coating of the steel strip 2 and improving the adhesion of an electroplated coating deposited thereon.
  • it can be a spraying apparatus, an electrolytic cell, or a skin-pass rolling mill using a suitable post-galvanizing surface treatment solution as a skin-pass rolling liquid.
  • a steel strip 2 is washed in the prewashing apparatus 3 using an alkali solution or other suitable rinse solution. It is then subjected to surface cleaning and, if necessary, annealing in the pretreatment apparatus which consists of the rapid heating furnace 4, the reduction furnace 5, and the cooling furnace 6.
  • the temperature of the cleaned and optionally annealed steel strip 2 is adjusted to a level suitable for hot-galvanizing, after which one or both sides of the strip 2 are galvanized in a hot-galvanizing bath 7 containing molten Zn or a molten Zn alloy to form a galvanized coating.
  • the coating weight is adjusted to a prescribed level by a gas wiping device disposed directly above the galvanizing bath 7.
  • the galvanized coating is then alloyed by heating in the alloying furnace 8.
  • Any type of alloying furnace 8 can be employed, such as a gas-heated furnace, an electromagnetic induction furnace, or a laser heating furnace. The degree of alloying is controlled by adjusting the temperature and the heating time.
  • the galvanized coating typically has a Zn coating weight of 30 - 80 g/m2 and it can be alloyed into a Zn-Fe alloy containing 7 - 12% Fe.
  • the steel strip 2 can be simply passed through the alloying furnace without alloying treatment.
  • the surface of the resulting galvanized steel strip 2 is then subjected to post-galvanizing surface treatment in the treatment apparatus 9.
  • the post-galvanizing surface treatment is performed with a strong alkali solution by immersion or spraying.
  • Useful alkali solutions include sodium hydroxide, sodium silicate (ortho or meta), sodium phosphate, and sodium bicarbonate solutions.
  • Post-galvanizing surface treatment can also be performed by electrolysis.
  • the electrolysis may be either in the form of cathodic or anodic electrolysis in a strong alkali solution or a weak alkali solution (such as a sodium phosphate or sodium bicarbonate solution), or cathodic electrolysis in a neutral solution (such as a sodium sulfate solution).
  • a current can be directly applied between an electrode and the strip, or an alternating current can be indirectly applied to the strip.
  • the temperature of the electrolytic solution is preferably at least 40 °C and more preferably at least 50°C.
  • Post-galvanizing surface treatment of the galvanized steel strip can also be performed by immersion or spraying with an acid which can dissolve aluminum oxide.
  • useful acids include hydrofluoric acid, phosphoric acid, and oxalic acid.
  • Sulfuric acid, hydrochloric acid, nitric acid, and the like have little ability to dissolve aluminum oxide, while they can dissolve the galvanized coating on the steel strip very rapidly, so they are not suitable.
  • the acid preferably has a pH of 1 - 4 and a temperature of at least 40 °C and more preferalby at least 50°C . If the pH is greater than 4, treatment requires a long time, while if the pH is less than 1, the dissolution of the galvanized coating is promoted, which is not desirable.
  • the steel strip is rinsed with hot or cold water in a rinse tank 10 which may be a water scrubber or a dip tank.
  • a rinse tank 10 which may be a water scrubber or a dip tank.
  • the remaining water can be removed from the surface of the strip using a ringer roll or an air blower.
  • the galvanized steel strip can then be subjected to coventional skin-pass rolling by passing through a skin-pass rolling mill 11 and a leveller 12.
  • Temper rolling prevents buckling of a hot-galvanized steel strip and removes strains caused by heating in the hot-galvanizing and alloying steps, and it flattens the surface of the galvanized coating. It can be performed with a reduction of 0.1 - 2.0%, for example.
  • skin-pass rolling is not mandatory, and it can be omitted with certain types of steel strips, such as with Ti-containing steel strip. With normal steel strip, it is also possible to perform skin-pass rolling before the post-galvanizing surface treatment or subsequent to electroplating, as described above.
  • the post-galvanizing surface treatment can be performed during the water cooling stage prior to skin-pass rolling using an alkali solution as a cooling medium.
  • a steel strip After a steel strip is hot-galvanized and optionally alloyed, it is at a high temperature. On the other hand, from the standpoint of the mechanical properties of the steel strip, it is desirable that skin-pass rolling be performed in the vicinity of room temperature. Therefore, the galvanized steel strip is normally cooled to room temperature by water cooling prior to skin-pass rolling.
  • an alkali solution is used as a cooling medium to perform cooling prior to skin-pass rolling, whereby the galvanized steel strip is cooled and simultaneously surface cleaning and activation of the galvanized coating can be performed.
  • at least two cooling tanks are disposed before the skin-pass rolling mill.
  • the cooling medium used in the last tank is water, but in at least one of the other tanks an alkaline solution is employed as a cooling medium and the galvanized steel strip is treated with the solution in that tank, thereby improving the microcovering power of the subsequent electroplating.
  • FIG. 5 illustrates an embodiment of a continuous plating line according to this form of the present invention in which the post-galvanizing surface treatment apparatus comprises an alkali solution cooling tank 9' which is followed by a water cooling tank 10'.
  • the structure of the plating line of this embodiment is otherwise the same as that of the embodiment of Figure 1.
  • a steel strip 2 which has been hot-galvanized and optionally alloyed and which is still hot is passed through the alkali solution cooling tank 9' in which the surface of the galvanized coating of the strip 2 is cooled and simultaneously cleaned and activated by immersing in or spraying with an alkali solution.
  • the strip 2 is then passed through the water cooling tank 10' for rinsing and further cooling.
  • the water rinsing in the final cooling tank 10' has no effect on the microcovering power of an electroplated coating, but it is merely to remove the alkali component adhering to the steel strip, thereby preventing the rolls and other equipment downstream of this tank from contamination and corrosion.
  • the alkali solution is typically formed from sodium hydroxide or potassium hydroxide, but other alkali compounds such as sodium carbonate, sodium bicarbonate, and sodium orthosilicate can also be employed.
  • the alkali solution may also contain a surfactant.
  • the pH of the alkali cooling solution is at least 10 in order to achieve the desired effect.
  • the temperature of the steel strip 2 at the entrance to the alkali solution cooling tank 9' is preferably at least 80 °C. If the strip temperature falls below 80°C , it is necessary for the pH of the solution to be 12 or higher. Thus, by performing the post-galvanizing surface treatment during cooling of a hot alloyed or galvanized steel strip, the surface cleaning and activation of a galvanized coating is promoted due to the heat of the steel strip and can be accomplished in a short period with an alkali solution of a lower pH.
  • Figure 4 shows the microcovering power of an electroplated coating when a hot-galvanized steel strip is treated with a sodium hydroxide solution of pH 10 for 1 second with different temperatures of the steel strip and the alkali solution.
  • the microcovering power greatly depends on the strip temperature rather than the solution temperature. Accordingly, when the post-galvanizing surface treatment is performed in the cooling stage by using an alkali solution as a cooling medium immediately after the hot-galvanizing or alloying, the steel strip is still hot, usually at a temperature above 80 °C , and the microcoverig power of an electroplated coating can be improved by treatment with an alkali solution having a lower pH of 10 or above.
  • the post-galvanizing treatment with an alkali solution is performed after the galvanized steel strip has been cooled, it is undesirable to reheat the galvanized steel strip, particularly after skin-pass rolling, from the standpoint of maintaining the mechanical properties of the steel strip. Therefore, the alkali solution instead of the steel strip is heated.
  • the rise in solution temperature is less effective than that in strip temperature and it is preferable to use an alkali solution having a higher pH of at least 12.
  • the post-galvanizing surface treatment is performed during skin-pass rolling, using a strong alkali solution with a pH of at least 12 or an acid which can dissolve aluminum oxide as a skin-pass rolling liquid (lubricant).
  • Figure 3 schematically illustrates an embodiment of a continuous plating line according to this form of the present invention in which the post-galvanizing surface treatment apparatus is in the form of a skin-pass rolling mill 11. If necessary, this embodiment can be further equipped with a water cooling tank (not shown) for cooling the steel strip 2 to a suitable temperature for skin-pass rolling.
  • a water cooling tank not shown
  • An example of a strong alkali solution which can be used as a skin-pass rolling liquid is a 1M sodium hydroxide solution.
  • any alkali solution can be used which does not adversely affect the subsequent electroplating when a minor amount thereof is introduced into the electroplating solution.
  • a pH of at least 12 is effective, but when performing mass production, the pH is preferably at least 12.5.
  • acids which can dissolve aluminum oxide and which can be used as a skin-pass rolling liquid are as mentioned above and include hydrofluoric acid, phosphoric acid, and oxalic acid having a pH of 1 - 4.
  • the skin-pass rolling liquid formed from a strong alkali solution or an acid can be used by spraying onto the strip 2 or the work rolls of the skin-pass rolling mill.
  • the treating time may be varied by the distance between the skin-pass rolling mill 11 and ringer rolls (not shown) downstream of the mill.
  • the effectiveness of post-galvanizing surface treatment during skin-pass rolling is not significantly affected by manufacturing conditions such as the travelling speed of the steel strip or the roughness of skin-pass rolls.
  • the temperature of the skin-pass rolling liquid is preferably at least 50 °C .
  • an inhibitor may be added to water which is used as a skin-pass rolling liquid during temper rollling after hot galvanizing of a steel strip.
  • the addition of an inhibitor is performed for the purpose of removing greases from the steel strip and for preventing corrosion. It has no effect on the microcovering power of an electroplated coating, and is thus totally different from the skin-pass rolling liquid which can be employed in the present invention.
  • the steel strip 2 is passed through an electroplating apparatus to deposite an electroplated coating on the galvanized coating.
  • electroplating can be applied to either one or both sides.
  • galvanizing is performed on one side of the strip, usually electroplating is applied to the same side, i.e., on the galvanized coating, although there is no limitation in this respect.
  • the electroplating apparatus includes the pretreatment tank 13, the electroplating cell 14, and the washing tank 15 (a water scrubber).
  • the pretreatment tank 13 the galvanized steel strip 2 is washed with water which may contain a certain additive which improves the surface condition of the steel strip.
  • the electroplating cell 14 various types of electroplating can be performed.
  • the washing tank 15 the electroplated steel strip is rinsed with water. If necessary, the steel strip 2 can be dried with hot air or by electric heating in the drier 16.
  • the electroplated coating is not restricted to any particular type.
  • it can be one which improves coatability of the galvanized coating by cationic electrodeposition overlaid thereon such as a pure Fe or Fe-X coating (wherein X is Zn, P, Ni, B, Sn, Ti or the like), a coating which improves the sliding properties of the galvanized coating such as a Cr (Cr-oxide), Ni, Ni-Zn coating, or various dispersion-type coatings such as a Ni-SiC, Zn-SiO2, Ni-Zn-SiO2, or a Zn-Al2O3 coating.
  • a plurality of electroplating cells can be used.
  • finishing surface treatment such as chromate treatment, zinc phosphate treatment, or resin coating using a roll coater can be performed in the finishing surface treatment apparatus 17 to obtain a finished product.
  • an alkali degreasing apparatus is installed as a pre-treatment apparatus.
  • Such an apparatus is used merely for the purpose of removing dirt and grease (oil and fat) adhering to the steel strip, and its operation and effects are totally different from those of The post-galvanizing surface treatment employed in the present. invention.
  • a hot-galvanized coating sometimes contains elements such as Al, Mg, and Mn.
  • the post-galvanizing surface treatment of the present invention activates only the surface of the galvanized coating and does not reach the inside of the coating, so there is no adverse effect on these elements.
  • Figures 2a and 2b schematically illustrate the structure of a multi-layer coating according to the present invention and the prior art, respectively.
  • minute irregularities 24 and 26 can be observed in the alloyed hot-galvanized coating layer 22 formed on a steel strip 20, but an electroplated coating 28 is uniformly formed over the irregularities. Surface contaminants which obstruct electrodeposition are previously removed.
  • the electroplated coating layer 28 is able to cover the protrusions of the underlying alloyed galvanized coating 22, but the coating 22 is exposed where it contains depressions. Therefore, the coatability and workability of the resulting steel strip are not adequately improved by the electroplated coating.
  • Continuous hot-galvanizing and electroplating were carried out using a continuous plating line like that illustrated in Figure 1.
  • the plating line was equipped with an additional post-galvanizing surface treatment apparatus between the leveller 12 and the bridle rolls 19 such that post-galvanizing surface treatment could be performed either before or after skin-pass rolling.
  • Both sides of a steel strip were hot-galvanized with a coating weight of 45 g/m2 for each side and then alloyed.
  • Post-galvanizing surface treatment was performed under the conditions given in Table 1 and after or before that the galvanized strip was temper-rolled using water which might contain a conventional inhibitor as a skin-pass rolling liquid.
  • Electroplating was performed on both sides of the galvanized coating with a coating weight of 4 g/m2 for each side. The plating conditions were otherwise normal ones.
  • adhesion of the electroplated coating was measured by an adhesive tape peel test after the test piece was subjected to 0T 180° bending.
  • the microcovering power of the electroplated coating was evaluated by microscopic observation of a cross section and an EPMA (electron probe microanalyzer). The rating in these tests are as follows: adhesion microcovering power ⁇ (good) no peeling complete covering over irregular surfaces ⁇ (fair) slight peeling small uncovered areas X (poor) peeling large uncovered areas
  • the electroplated coating of the resulting multi-layer plated steel strip according to the present invention had excellent adhesion and microcovering power.
  • the microcovering power in particular was far superior to that of a conventional coating.
  • a 0.8 mm-thick GA (alloyed galvanized) steel strip having a galvanized coating of 45 g/m2 on both sides which was manufactured by a commercial galvanizing line and which had not been treated with an oil or a chromate or other surface treatment solution was subjected to post-galvanizing surface treatment by immersion in various solutions shown in Table 2. Thereafter, Fe-Zn electroplating was performed on both sides under the following conditions. The microcovering power of the resulting electroplated coating was evaluated by microscopic observation of a cross section and an EPMA. The results are shown in Table 2. In Table 2, an ⁇ indicates that the plating was able to cover the irregularities in the GA layer as shown in Figure 2a, while an X indicates that the electroplated layer was discontinuous as shown in Figure 2b.
  • Sulfate bath Total Fe 80 g/l, current density: 60 A/dm2 Fe3+ 1000 ppm, plating weight: 5 g/m2 Zn2+ 2 g/l, pH: 1.6 Na+ 25 g/l Temperature: 50°C TABLE 2 No. Immersion solution pH Temp.
  • samples No. 4 and No. 5 the weak alkali treatment was carried out with a pH of less than 12, and samples No. 9 and 10 used an acid which could not dissolve aluminum oxide.
  • Samples Nos. 11 - 13 illustrate conventional methods. In each of these samples, the aluminum oxide on the surface of the GA layer could not be dissolved and therefore the microcovering power was poor.
  • post-galvanizing surface treatment was able to dissolve the aluminum oxide on the surface of the GA coating without dissolving the GA coating itself, so the microcovering power was excellent.
  • Hot-galvanizing followed by electroplating was performed on both sides of a steel strip using an apparatus like that illustrated in Figure 3.
  • the coating weight of the galvanized Zn layer was 45 g/m2 for each side.
  • a 1M NaOH solution at a temperature of 50 °C with a pH of 13.5 was used as a skin-pass rolling liquid during skin-pass rolling of the alloyed galvanized strip which was performed with a reduction of 0.6%.
  • Continuous electroplating was carried out under the same conditions as for Example 2. The resulting plating had good microcovering power.
  • the electroplated layer of the resulting multi-layer plated steel strip obtained by the method of the present invention had excellent microcovering power.
  • an alloyed hot-galvanized steel strip was subjected to cooling using a NaOH solution with a pH of 10.0 as a cooling medium in an alkali solution cooling tank 9' and then washed with water in a water cooling tank 10'. It was then electroplated under the same conditions as in Example 4.
  • the alkali solution cooling conditions were as follows: Strip temperature upon entry: 90 °C Alkali solution temperature: 85 °C Treatment time: 0.6 seconds
  • the electroplated layer of the resulting multi-layer plated steel strip had good microcovering power.
  • Example 2 The procedure described in Example 2 was repeated except that the post-galvanizing surface treatment of a GA steel strip was performed by cathodic or anodic electrolysis under the conditions shown in Table 4.
  • the electrolytic solutions used were a 1M sodium sulfate solution, a 1M ammonium chloride solution, both neutral, and a 1M sodium sulfate solution which had been adjusted to pH 11. The results are shown in Table 4.

Landscapes

  • 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)
  • Coating With Molten Metal (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
EP93102764A 1989-05-08 1990-05-07 Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet Expired - Lifetime EP0545908B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP11479189 1989-05-08
JP114791/89 1989-05-08
JP1302562A JPH0375384A (ja) 1989-05-08 1989-11-21 溶融亜鉛系メッキ鋼板の電気メッキ方法および亜鉛系連続メッキ製造設備列
JP302562/89 1989-11-21
EP90401217A EP0397555B1 (fr) 1989-05-08 1990-05-07 Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
EP90401217.6 Division 1990-05-07

Publications (3)

Publication Number Publication Date
EP0545908A2 true EP0545908A2 (fr) 1993-06-09
EP0545908A3 EP0545908A3 (fr) 1994-01-12
EP0545908B1 EP0545908B1 (fr) 1997-07-30

Family

ID=14646777

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93102764A Expired - Lifetime EP0545908B1 (fr) 1989-05-08 1990-05-07 Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet

Country Status (3)

Country Link
EP (1) EP0545908B1 (fr)
JP (1) JPH0375384A (fr)
KR (1) KR940004103B1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113061890A (zh) * 2021-03-19 2021-07-02 中山大学 一种铝合金表面恒压电沉积Ni-SiC复合镀层的方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB417411A (en) * 1933-08-25 1934-10-04 Duncan James Macnaughtan Improvements in the production of adherent metal coatings upon iron, steel or other metal
DE937209C (de) * 1952-04-10 1955-12-29 Richard Dr Springer Verfahren zum elektrolytischen Entrosten, Entzundern und Bruenieren von Metallen in alkalischen Loesungen
JPS5378937A (en) * 1976-12-23 1978-07-12 Nippon Steel Corp Surface treatment method of zinc plated steel plate or zinc alloy plated steel plate

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113061890A (zh) * 2021-03-19 2021-07-02 中山大学 一种铝合金表面恒压电沉积Ni-SiC复合镀层的方法

Also Published As

Publication number Publication date
KR940004103B1 (ko) 1994-05-13
EP0545908B1 (fr) 1997-07-30
KR900018420A (ko) 1990-12-21
JPH0375384A (ja) 1991-03-29
EP0545908A3 (fr) 1994-01-12

Similar Documents

Publication Publication Date Title
US5236574A (en) Electroplating of hot-galvanized steel sheet and continuous plating line therefor
CN102625863A (zh) 设有金属的防腐镀层的钢部件的制造方法和钢部件
JP2922926B2 (ja) 合金化亜鉛めっき帯鋼の製法
JPS6056418B2 (ja) 溶融亜鉛メツキ鋼板の製造法
JP3307312B2 (ja) 耐低温チッピング性、加工性に優れた合金化溶融亜鉛めっき鋼板の製造方法
EP0545908A2 (fr) Electroplacage de bandes d'acier galvanisées à chaud et installation en continu à cet effet
JPH07126863A (ja) 金属板およびメッキ金属板のフレキシブル生産設備
KR890004047B1 (ko) 화성처리가 대단히 용이한 냉간압연 강스트립의 제조방법
US3523067A (en) Selective galvanizing of steel strip
JP3426408B2 (ja) 潤滑性に優れた電気亜鉛系めっき冷延鋼板の製造設備
EP0324116B1 (fr) Procédé et dispositif de fabrication de bandes d'acier revêtues sur une seule face par électroplacage et présentant une meilleure aptitude à la phosphatation
JP2952612B2 (ja) 溶融亜鉛めっきステンレス鋼材の製造方法
JP2947633B2 (ja) 塗装下地用ニッケル・クロム含有亜鉛めっき鋼板・鋼材並びにその製造法
JP2013136825A (ja) 外観の優れた化成処理電気亜鉛系めっき鋼板の製造方法
JP2827709B2 (ja) 複数のめっき層を有する、耐糸状錆び性、耐食性および溶接性に優れた表面処理鋼板
JP2980990B2 (ja) 合金化溶融亜鉛めっき鋼板の冷却方法および冷却設備
JP3191660B2 (ja) 亜鉛系メッキ鋼板およびその製造方法
JP3643473B2 (ja) 高速シーム溶接性、密着性、耐食性に優れた表面処理鋼板およびその製造方法
JP2000080498A (ja) 錫系めっき鋼板の化学処理法
JP2726144B2 (ja) 被覆性と密着性に優れた高耐食性Ｐｂ‐Ｓｎ合金めっきＣｒ含有鋼板の製造法
JP3670845B2 (ja) ニッケル系めっき鋼板の化学処理法
JPH09324250A (ja) 溶融金属めっき熱間圧延鋼板およびその製造方法
JP2000008194A (ja) 錫系めっき鋼板の化学処理法
JPS59129794A (ja) Ｚｎ−Ｆｅ合金電気メツキ鋼板の製造方法
JPH04224666A (ja) めっき密着性及び耐食性に優れた溶融亜鉛めっきステンレス鋼帯の製造方法

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AC Divisional application: reference to earlier application

Ref document number: 397555

Country of ref document: EP

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): BE DE FR GB

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): BE DE FR GB

17P Request for examination filed

Effective date: 19940530

17Q First examination report despatched

Effective date: 19960221

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AC Divisional application: reference to earlier application

Ref document number: 397555

Country of ref document: EP

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): BE DE FR GB

REF Corresponds to:

Ref document number: 69031174

Country of ref document: DE

Date of ref document: 19970904

ET Fr: translation filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19980326

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19980501

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19980603

Year of fee payment: 9

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19980722

Year of fee payment: 9

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19990507

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19990531

BERE Be: lapsed

Owner name: SUMITOMO METAL INDUSTRIES LTD

Effective date: 19990531

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19990507

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000131

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000301

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST