• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    An object of the present invention is to provide a chromate treatment solution for a galvanized steel sheet which is excellent in resistance to deformation and corrosion resistance and does not deteriorate the surface appearance of the galvanized steel sheet. The present invention relates to a chromium-free chromic acid solution having a chromium concentration of 3 to 10 g / l in terms of chromium 6, and a phosphoric acid of 0.5 to 1 g / l and a molybdate of 20 to 40 g / This chromate treatment solution for a zinc-plated steel sheet is an important point.
    公开号:KR19980046359A
    申请号:KR1019960064682
    申请日:1996-12-12
    公开日:1998-09-15
    发明作者:이석규；최영민
    申请人:김종진；포항종합제철 주식회사；
    IPC主号:
    专利说明:

    Chromate solution for hot-dip galvanized steel sheet excellent in corrosion resistance and reduction resistance
    The present invention relates to a chromate treatment solution for a galvanized steel sheet, and more particularly to a chromate treatment solution for a galvanized steel sheet which does not deteriorate the surface appearance of the galvanized steel sheet,
    The zinc-coated steel sheet is a steel sheet coated with zinc on the surface of the steel sheet, which is widely used for automobiles, household electrical appliances, and building materials because of its excellent corrosion resistance due to the excellent corrosion resistance and sacrificial effect of the zinc itself. However, over time, corrosion products of zinc, called white rust, are formed on the surface of the galvanized steel sheet, causing the surface of the steel sheet to discolor white, thereby deteriorating the surface appearance.
    In order to prevent this, a chromate treatment is performed as a post-treatment during the manufacturing process of the galvanized steel sheet. Chromate treatment is a process in which a chromium oxide is formed on the surface of a steel sheet by reducing the chromium hexavalent chromium (VI) to 3, thereby causing a passive exposure to the atmosphere on the metal surface. ≪ / RTI > to form a hexa-valent compound that causes a < RTI ID = 0.0 > This hexavalent compound is known to be Cr (OH) 3 Cr (OH) CrO 4 .
    As a method of using the chromate solution, there is known a reaction type method in which a chromate film is formed on the surface of a steel sheet with chromium ion as a main component and sulfuric acid ions are added, and the solution remaining on the surface is removed by washing with water and then dried. Since this method sensitively changes the effect of increasing the film adhesion amount depending on the concentration of the sulfate ion, the variation of the film adhesion amount also becomes large due to the change of the trace amount of the sulfate ion in the solution, which causes the uniformity of the product quality. There is a risk of loss of gloss. In order to prevent this, a fluorine compound may be used. In this case, the fluorine ion (F - ) component in the solution forms a uniform coating, activates the surface and stabilizes the coating, and distributes the solution evenly on the surface of the plating to tighten the coating. However, when F - ion is added to the chromate solution, it is necessary to pay close attention to the handling of the drug due to the toxicity of hydrofluoric acid when it is dissolved in hydrofluoric acid (FH). In addition, when it is added to a chromate solution containing chromium 6 as a main component, the solubility is limited and it is not very effective for improving the corrosion resistance. Therefore, the use of an aluminum fluoride compound in Japanese Patent Application Laid-open No. 57-58554, A technique for improving the corrosion resistance by means of the above method is known. In addition, zirconium fluoride compounds are also used in the chromate powders that are commercially available in the domestic market.
    However, since the fluorine compound only has a limitation in improving the corrosion resistance and surface appearance, a method of forming a dense film by adding a compound such as titanium (Ti), arsenic (As) or vanadium (V) to the chromate solution has been proposed. However, It is difficult to manage the solution since it exists as an oxide in the solution and precipitation occurs. In order to solve this problem, there is a method for improving the corrosion resistance of a steel sheet by adding a reducing agent to chromic acid to reduce chromium (VI) in the form of Cr 3 and doping a chromate treatment solution containing phosphoric acid and a hydrofluoric acid compound ) 57-35685, (cat.) 57-29681.
    However, this method has a problem in that phosphoric acid and chromium trivalent components in the solution cause black stain which damages the gloss of the galvanized steel sheet after chromate treatment.
    It is an object of the present invention to provide a chromate treatment solution for a galvanized steel sheet which is excellent in resistance to aging and corrosion by adding molybdate to a chromate solution in order to solve the above-mentioned conventional problems.
    Hereinafter, the present invention will be described.
    The present invention relates to a chromate-free chromic acid solution having a chromium concentration of 3 to 10 g / l in terms of chromium 6 and having a composition obtained by adding 0.5 to 1 g / l of phosphoric acid and 20 to 40 g / l of molybdate, And a chromate treatment solution for a galvanized steel sheet.
    The molybdate that can be used in the present invention is a metal salt form of molybdic acid (MMoO 4 wherein M represents a metal element), such as zinc molybdate, sodium molybdate, potassium molybdate, And can be selected from among various metal salts in consideration of easiness of availability and economy.
    Hereinafter, the reason for limiting the component range in the chromate treatment solution of the present invention will be described.
    When the concentration of chromium 6 is less than 3 g / l in the solution, the thickness of the chromate film is too thin and deteriorates in terms of corrosion resistance. When the concentration is more than 10 g / l, the corrosion resistance is increased but yellow coloration may occur on the surface, It is preferable that the concentration of chromium hexavalent chromium is limited to 3 to 10 g / l.
    When phosphoric acid is added in an amount of 0.5 g / l or less, the surface of the phosphoric acid is colored yellow. When the amount of phosphoric acid is 1.0 g / l or more, Is generated and the surface becomes poor and the adhesion between the roughened layers is deteriorated. Therefore, it is preferable to limit it to 0.5 to 1.0 g / l.
    The molybdate is a component for improving the corrosion resistance and resistance to degeneration by densifying the film. When the amount is less than 20 g / l, the effect is not added. When the amount is 40 g / l or more, precipitation may occur in the solution. The amount of the solution is preferably limited to 20 to 40 g / l.
    Hereinafter, the present invention will be described in detail by way of examples.
    [Example]
    The specimens obtained from the hot-dip galvanized steel sheets were immersed in a chromate treatment solution at 70 ° C. for 10 seconds, and then pressed with rubber roll to adjust the applied amount to 20 to 30 mg / m 2 , And dried by hot air to perform a chromate treatment.
    In this embodiment, Na 2 MoO 4 .2H 2 O was used as the molybdate.
    The specimens subjected to the chromate treatment as described above were evaluated for corrosion resistance, harsh degeneration and surface appearance, and the evaluation results are shown in Table 1 below.
    Test methods and evaluation methods for the corrosion resistance, harshness and surface appearance conditions in the following Table 1 are as follows.
    1) Corrosion resistance
    The corrosion resistance of the chromate-treated specimens was evaluated by observing JIS Z-2371 in accordance with JIS Z-2371 and observing the specimens every 12 hours.
    2) Degeneration
    After the sample was stored for 140 hours in a high temperature and high humidity environment with a relative humidity of 90% or more and a temperature of 50 ° C, the occurrence of blackening was assessed through visual observation.
    ○: No blackening occurred
    : Black shade
    X: Severe blackening
    3) Surface appearance
    The outer surface of the chromate-treated specimen was visually observed and evaluated according to the following criteria.
    Good: good (no coloring)
    : Gloss loss, slight discoloration
    X: Severely colored
    As shown in the following Table 1, it can be seen that the compositions (A to H) of the chromate treatment solution of the present invention are excellent in corrosion resistance and also in harsh degeneration and surface appearance.
    On the other hand, when the amount of phosphoric acid added was less than the range of the present invention (Comparative Examples 1, 3 and 5), the surface appearance was not good (surface coloring was observed) (Comparative Examples 2, 4, 6, 7, 8), it can be understood that the degree of overturning is not good.
    When the amount of molybdate to be added is less than the range of the present invention (Comparative Examples 1 and 2), the corrosion resistance is weakened, and in many cases (Comparative Examples 7 and 8), precipitation occurs in the solution.
    In addition, it can be seen that when the chromium 6 content is less than the range of the present invention (Comparative Examples 1, 2, 3 and 4), the corrosion resistance is chlorinated, and when the chromium 6 content is smaller (Comparative Examples 7 and 8)
    [Table 1]
    INDUSTRIAL APPLICABILITY As described above, the present invention has an effect of producing a zinc-plated steel sheet which is excellent in resistance to chromatic deformation and corrosion resistance in a chromate treatment method of a galvanized steel sheet, and which does not deteriorate the luster specific to the galvanized steel sheet.
    权利要求:
    Claims (1)
    [1" claim-type="Currently amended] Characterized in that the composition is formed by adding 0.5 to 1 g / l of phosphoric acid and 20 to 40 g / l of molybdate to a chromic anhydride solution having a chromium concentration of 3 to 10 g / l in terms of chromium 6 in terms of transversal conversion, Chromate treatment solution for plated steel sheet.
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    同族专利:
    公开号 | 公开日
    KR100296687B1|2001-10-24|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1996-12-12|Application filed by 김종진, 포항종합제철 주식회사
    1996-12-12|Priority to KR1019960064682A
    1998-09-15|Publication of KR19980046359A
    2001-10-24|Application granted
    2001-10-24|Publication of KR100296687B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019960064682A|KR100296687B1|1996-12-12|1996-12-12|Chromate solution with superior corrosion/blackening resistance for hot dipped galvanized steel sheet|
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