JP2782451B2 - High corrosion resistance superimposed plated steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plated steel sheet having excellent corrosion resistance for use in automobile bodies, building materials and home appliances.

(Prior Art) In applications using steel sheets, there is a great need for surface-treated steel sheets having excellent corrosion resistance, and galvanized steel sheets and zinc alloy-plated steel sheets are widely used from the viewpoint of sacrificial corrosion protection of iron. The present invention relates to a more excellent zinc-based plated steel sheet, and an object of the present invention is to provide a superposed plated steel sheet in which a coating having excellent corrosion resistance is overcoated on the surface of an existing zinc-based plated coating.

Prior art related to the present invention includes silica (SiO ₂ ).
Japanese Patent Publication No. 60-9590 for zinc or zinc alloy coated steel sheet coated with zinc and zinc (Zn) composite coating film
No. 61-190450, U.S. Pat. No. 3,438,754 for a two-layer vapor-deposited plated steel sheet of aluminum and zinc, and German Patent No. 1905908 for a steel sheet coated with two-layer vapor-deposited magnesium zinc (or white 781868-Q 1974-4-15: BEKAERT) BA N
V) there. These galvanized steel sheets have better corrosion resistance than galvanized steel alone, but there is a drawback of lap plating: corrosion is likely to progress at the interface due to the potential difference between the upper and lower plating layers, and blistering and poor adhesion are likely to occur. Was not converted.

(Problems to be Solved by the Invention) With respect to the sacrificial corrosion protection of iron, zinc is the most practical and excellent metal, and the relatively thick galvanized steel is used for corrosion protection of damaged parts such as pinholes, cut surfaces and scratches. Requires a coating.

However, since zinc is active, it generates white rust and is consumed. An ideal plating film desirably has a plating composition in which the minimum corrosion required for sacrificial corrosion protection of iron proceeds. In the case of overplating for this purpose, when a noble metal such as Ni, Cr, Fe or the like is coated on the galvanized film, a local battery is formed due to contact with a dissimilar metal, and the underlying zinc is selectively corroded. An extremely stable oxide film is formed even on metals such as Ti and Al, and the underlying zinc is selectively corroded. Superimposed plating shows very good corrosion resistance as long as it is a defect-free coating having no damaged portion.

As described above, when the plating is thin, the pitting corrosion of the lower plating from the defective portion easily proceeds in the superimposed steel sheet in which the zinc plating film is further superimposed on the upper layer. When the plating is made thick, in an environment including poor plating adhesion and electrolytic negative such as salt water, there is a problem that the film is peeled off at the interface between the upper layer and the lower layer due to corrosion from a defective portion, and that the cost is increased.

The present invention has solved these drawbacks in the development of a zinc-based alloy-plated steel sheet having a thin high-corrosion-resistant film as an upper layer.

(Means for Solving the Problems) The gist of the present invention is as follows. (1) A galvanized film has a composite film composed of one or more metals of Ti, Si, Al, Mg, and B, and an oxide thereof. High corrosion resistance superimposed plated steel sheet characterized by the following.

(2) A highly corrosion-resistant superimposed plated steel sheet comprising a zinc alloy plating film and a composite film made of one or more of Ti, Si, Al, Mg, and B, and an oxide thereof.

(3) One or more metals of Ti, Si, Al, Mg, and B, and the composition of the oxide on the galvanized film are composed of a metal element (MO) as an oxide and a metal element (M
A high corrosion resistant superimposed plated steel sheet characterized by having an atomic percentage ratio (MO / MM) of 0.1 to 1.0 and a coating thickness of 0.2 to 5.0 microns.

(4) One or two or more metals of Ti, Si, Al, Mg, and B, and the composition of the oxide on the zinc alloy plating film are composed of a metal element (MO) as an oxide and a metal element as a metal ( A high corrosion resistant superimposed plated steel sheet characterized by having an atomic% ratio (MO / MM) of 0.1 to 1.0 and a coating thickness of 0.2 to 5.0 microns.

(5) High corrosion resistance superimposition characterized by having a post-treatment film on the surface of a composite film composed of one or more metals of Ti, Si, Al, Mg, B and its oxide on the galvanized film Plated steel sheet.

(6) High corrosion resistance characterized by having a post-treatment coating on the surface of a composite coating consisting of one or more metals of Ti, Si, Al, Mg, B, and its oxide on the zinc alloy plating coating It is a superposed plated steel sheet.

The lower zinc-based plating film used in the present invention includes electroplating, physical vapor deposition plating, and hot-dip plating film.

(Operation) In the present invention, the upper layer is composed of metals of Ti, Si, Al, Mg, and B (metal elements as metals are abbreviated as MM) and oxides thereof (metal elements as oxides are abbreviated as MO). It is characterized by having a composite coating.

Item 1 of the present invention has a zinc plating film as a lower layer.

The metals Ti, Si, Al, Mg, and B are more active metals than zinc, but their oxides are stable compounds. When these metals are directly coated on zinc plating by a vapor phase plating method such as vacuum vapor deposition, a film having many defects is formed in a thin film.

In the present invention, a part of Ti, Si, Al, and Mg is deposited so as to form an oxide, and the thin film has few defects, and the insulating property of the upper plating is provided, so that a local battery with the lower zinc is formed. It is possible to obtain a high corrosion resistant superimposed plated steel sheet which is hard to generate and hardly causes pitting corrosion. It is presumed that the mechanism of defect-free due to the eutectoid of the oxide is that in the case of vacuum deposition, the oxide acts as a suppressing film and the film is formed in the horizontal direction with respect to the growth of the crystal of the deposited metal.

The second aspect of the present invention is an invention using zinc alloy plating as the lower plating. When zinc alloy plating is used as the lower layer compared to zinc, a more uniform upper layer plating is formed, and there is an advantage that the allowable amount of the oxide to metal ratio (MO / MM ratio) with respect to pitting corrosion is increased. It is significantly improved compared to the case of zinc plating.

Although the composition of the upper layer plating of the present invention is included in a wide range, a composite having the following composition is preferable. The upper layer film is composed of at least one metal of Ti, Si, Al, Mg and its metal oxide. The metal element (M
According to the relationship between M) and the metal element (MO) as an oxide, the MO / MM ratio is desirably 0.1 to 1.0 in atomic% ratio. There are various ways to determine this ratio, and for example, the ratio is measured as follows.

In recent years, the development of surface analysis devices has been remarkable, and Auger electron spectroscopy (AES), which measures the concentration of elemental components in the extremely surface layer, has been put to practical use as a device capable of quantitatively measuring. Normally, the intensity is measured using Ag as a standard substance, multiplied by the relative sensitivity coefficient of each element, the intensity is corrected, and the relative concentration is calculated as the atomic% ratio (Re
lative concentration%). For example, in the case of 0, the strength is obtained by using SiO ₂ as a standard, and the above-mentioned correction is applied to obtain the atomic ratio of Si: O as 1: 2.

Using this AES, the upper plating of the present invention is analyzed (depth-o-profile) in the depth direction to determine the atomic% ratio. As an example of the present invention, FIG. 1 shows a composite plating composed of Si and an oxide of Si (assumed as SiO ₂ ) of about 1.0 μm on a zinc alloy plating film 10 μm (abbreviated as SZ) containing 5% Al. The results obtained by analyzing each element while sputtering the upper layer coating film of the present invention, which was subjected to vacuum evaporation plating in the depth direction, are shown.

Si is atomic% of silicon (a), O is atomic% of oxygen
3B shows a concentration curve in the depth direction. The method of calculating MO and the method of calculating MM are calculated as follows. In the case of silicon, oxide
Assuming SiO ₂ , the ratio of Si to O is 1/2 of Si / O ₂ (denoted by f),
0.5. Therefore, MO is b (27%) × 0.5 or 14 which is 0.5 times atomic% (b) of O. MM is a (54) -MO (1
4) That is, it can be calculated as 40. Therefore, the MO / MM ratio is 0.35. In the case of this example of the present invention, the salt water spray test (abbreviated as SST) specified in JIS Z2371 does not generate white rust at the time of 1000 hours (the lower plating is not corroded). Indicated. SZ without upper plating of the present invention
In the same test, 5% of red rust (rust generation area ratio) was generated.

Similarly, FIG. 2 shows a zinc alloy plating film 3 containing 12% Ni.
This shows an example of the present invention in which composite plating of Ti and Ti oxide is plated on μ (abbreviated as ZL) by vacuum evaporation. Ti is atomic% of Ti
(A), O indicates the atomic% ratio of oxygen (b). By the same calculation as in FIG. 1, the MO / MM ratio can be calculated as 0.4. In the case of this example of the present invention, white rust was not generated in 1000 hours of SST, and when no upper layer plating was applied, red rust was generated by 50% (area ratio), and the steel sheet of the present invention showed extremely excellent corrosion resistance.

As described above, the MO / MM ratio in the present invention is ideally 0.1 to 1.0. If it is less than 0.1, a plating film having many defects is formed as described above, and pitting corrosion is easily generated from a damaged portion. or,
If it exceeds 1.0, the adhesion processing performance of the plating deteriorates, which is not preferable.

The plating thickness of the upper plating is preferably from 0.2 to 5.0 μm. 0.
If it is less than 2 μm, the plating thickness is insufficient, and the function as the upper plating is not sufficiently exhibited, so that the corrosion resistance is insufficient. 5.0
Above μ, the adhesion processability of plating deteriorates,
It is not preferable because it is peeled off by pressing. But,
When used in a flat plate, it exhibits high corrosion resistance.

As a method for obtaining the upper layer plating of the present invention, any method may be used, but vapor phase plating such as vacuum deposition plating and ion plating is preferable. To obtain an MO / MM ratio, a weakly oxidizing atmosphere such as O ₂ gas, O ₂ + N ₂ , Ar + O ₂ , O ₂ + H ₂ O, H ₂ O, CO ₂ + O ₂ , CO + C
A method of evaporating the metal of Ti, Si, Al, Mg, and B and depositing it on a plated steel plate (substrate) while supplying a simple substance such as O ₂ , H ₂ O + H ₂ or a mixed gas near the substrate, or depositing Ti, S
It is obtained by co-evaporating the metals i, Al, Mg, B and these oxygen-containing compounds. The plating thickness can be detected by a quartz crystal monitor and controlled by controlling the shutter, the heating temperature of the evaporation source, the substrate temperature, and the vacuum conditions.

Higher corrosion resistance and other performances, such as paints, by treating a post-treatment coating on a composite plating coating comprising one or more metals of Ti, Si, Al, Mg, B and their oxides of the present invention and their oxides Adhesion, corrosion resistance after painting, coloring, lubricity, etc. can be imparted or improved. As a post-treatment coating,
Chemical conversion treatment such as chromate treatment, phosphate treatment, anodic oxidation, etc., and treatment of organic coatings are included.

Among these post-treatments, the chromate treatment is particularly effective in sealing or passivating the pinholes of the upper plating film and improving the corrosion resistance. Examples of the chromate include a baking chromate of an anhydrous washing coating type, a post-washing type chromate of an etching property, and an electrolytic chromating treatment of reducing and depositing by electrolysis. Cr adhesion amount is 10 to 200G in terms of T and Cr
m / m ² is preferred. If it is less than 10 mg / m ² , the effect of chromate is insufficient, and if it is more than 200 mg / m ² , the workability of the chromate film itself deteriorates, which is not preferable.

The pinhole is sealed by forming an oxide film on the surface layer by anodizing treatment, and a colored appearance is obtained depending on conditions. The organic coating is solvent-based or clear resin or C aqueous, preferably a resin film complexed with particles of SiO ₂ or the like, in combination with the chromate is improved performance such as corrosion resistance.

Example 1 Ti, Si, Al, Mg and B were deposited on the various types of galvanized steel sheets prepared by the existing methods shown in Table 1 under the following conditions, and the plated surface was subjected to Auger electron spectroscopy. The MO / MM ratio was determined by elemental analysis in the depth direction. The amount of plating was measured and controlled by a quartz crystal monitor at the time of vapor deposition. In addition, a calibration curve was separately prepared using a steel sheet based on the plated steel sheet, and measured by fluorescent X-ray analysis. A corrosion resistance test and an adhesion test were performed as the quality of the obtained superposed plated steel sheet. The former is JI
Observation is performed at regular intervals in the salt spray test (SST) specified by S-Z2371 to determine the area ratio of white rust (corrosion product of zinc: symbol WR) and red rust (corrosion product of iron: symbol RR) ( %). For the latter, 180 ° bending press (2T-bending) with a gap of two sheet thicknesses, peeling with cellophane tape, dissolving the cellophane tape with mixed acid, measuring metal elements by atomic absorption, and measuring all metal elements The sum was evaluated as the amount of peeling (g / m ² ).

The deposition conditions were as follows. Incidentally, O ₂ partial pressure from the outside
O ₂ washing → Ar sputtering (1 min) at existing plated steel → organic solvent → vacuum evaporation [O ₂ partial pressure of 10 ^-3 torr (O ₂ gas introduction) electron beam heating evaporation, sheet temperature 50-70 ° C. (water cooling A1 to A5 are the superposed plated steel sheets of the present invention obtained by subjecting 5% Al-containing hot-dip zinc alloy plating as the lower layer plating, and then evaporating Ti, Si, Al, Mg, and B individually with an electron beam. The MO / MM ratio is 0.3 for Ti, Si, and B, which have high affinity for oxygen.
It is as high as 5 to 0.42, and Al and Mg are 0.22 to 0.25. Appearance is Si
In the case of, it was colored slightly blue. Corrosion resistance was good with no occurrence of red rust as compared with the untreated control material (A6). Adhesion was also in a range that could be used practically. For A2 and A3, the first analysis result in the depth direction by Auger electron spectroscopy
This is shown in FIG. (A2) and FIG. 3 (A3). N1 to N5 are obtained by plating an electric zinc alloy containing 12% of Ni as a lower layer plating and then evaporating the corresponding metal alone. T
N1 and N2 from which i and Si were evaporated showed very high corrosion resistance with little generation of white rust. FIG. 2 shows the results of Auger electron spectroscopy for N1. Al (N3 and Fig. 6), Mg (N
4) Also for B (N5), a superimposed plated steel sheet of the present invention having excellent corrosion resistance and adhesion as compared with untreated N6 as a comparative material was obtained. Z1 to Z5 are examples of the present invention using a plating containing 0.2% of Al of a normal hot-dip galvanized steel sheet as a lower layer plating. Under the untreated (Z6) high vacuum conditions (O ₂ partial pressure 10 ⁻⁵ Torr) of the comparative material, the results obtained were superior in corrosion resistance and adhesion workability as compared with Z7 and Z8 in which Al and Mg were plated on the upper layer. The results of Auger electron spectroscopy are shown in Z1 (FIG. 5) and Z3 (FIG. 4).

Example 2 According to the method of Example 1, Si was evaporated on a 5% Al molten zinc alloy plating film, and plating was performed while introducing O ₂ with a target of MO / MM ratio of 0.4. The plating thickness is monitored and controlled with a crystal monitor.
The superimposed plated steel sheet of the present invention was prepared aiming at 2 to 5.0. Table 2 shows the results. The corrosion resistance was improved in proportion to the thickness of the upper composite plating, but the opposite tendency was observed in the adhesion workability. No.T-5 had a relatively large amount of peeling.

S-1 and S-2, whose MO / MM ratio was increased to 1.0 and 2.0 by increasing the O ₂ gas to be introduced, have a slightly large amount of peeling due to 2-T bending. Especially, S-2 is difficult to process and practical. The level has been reduced to a level that can only be used as a flat plate. The corrosion resistance improved in proportion to the thickness of the upper plating, but all showed good results.

Example 3 A 5% Al-containing hot-dip zinc alloy plating was performed on the surface of a cold-rolled steel sheet according to the procedure of Example 1, and Ti, Si, Al, Mg,
After evaporating B individually, the chromic anhydride was reduced by 30%, and a dilute aqueous solution composed of a 5 g / aqueous solution of chromic acid and 10 g / a silica sol was used as a Cr adhesion amount.
mg / m ^{2 was} applied and hot-air dried at a sheet temperature of 80 ° C. to prepare a coated chromate-coated superimposed plated steel sheet (C1 to C5). Electrolysis (5A / dm ² , 12c / dm ² ) in a chromic anhydride (50 g /) and trace amount of sulfuric acid (0.5 g /) aqueous solution using a superposed plated steel sheet as a cathode
Then, it was washed with water and dried to prepare an electrolytic chromate-treated superposed plated steel sheet having a Cr adhesion amount of 60 mg / m ² (P1 to P4). The superposed plated steel sheets of the present invention shown in Table 3 were prepared.

An emulsion containing acrylic resin as a main component was further applied to a thickness of 0.5 μm on a plated steel sheet subjected to electrolytic chromate treatment, and baked at a sheet temperature of 120 ° C. to prepare a post-treated steel sheet (R1 to R).
Five). C6, P5 and R6 are comparative examples in which no upper layer plating was performed.

Compared with the comparative material C6, the present invention example in which the coating chromate treatment of C1 to C5 was applied was particularly effective for the generation of white rust, and the corrosion resistance was remarkably improved. In the case of electrolytic chromates P1 to P5, the corrosion resistance is slightly lower than that of the coated chromate.
It showed better white rust properties than those without A1-A5 chromate. For R1 to R5, a post-treated coated super-coated steel sheet having extremely excellent corrosion resistance without white rust in 1000 hours of SST was obtained. Comparative Example R6 showed an effect of improving white rust, but was inferior to the present invention.

Example 4 Composite plating with a MO / MM ratio of 0.3 by heating and evaporating silica and silicon with an electron beam on a zinc alloy electroplated steel sheet having a Ni content of 12% at an O ₂ partial pressure of 10 ⁻⁵ torr, respectively. After coating 0.5 μm of the coating by vapor deposition, the coated chromate (TCr10 mg / m ² ) was treated to prepare a superposed plated steel sheet of the present invention.

 No white rust was observed in the salt spray test for 1500 hours.

Example 5 After vacuuming, Ar gas was put into the chamber and plasma discharge was performed to evaporate silica and silicon on a zinc alloy electroplated steel sheet having a Ni content of 12%, and ion plating was performed to perform superposition plating of the present invention. A steel plate was created. The thickness of the composite plating was 0.5 μm. As for the corrosion resistance, no generation of white rust was observed in 1000 hours, and no peeling was observed in the adhesion workability.

(Effects of the Invention) The present invention has a composite plating containing a metal which is active in terms of potential as compared with the conventional alloy plating, and since the corrosion resistance is imparted by its insulating action, extremely excellent corrosion resistance is obtained. . Further, since the existing plating is coated on the base, for example, the thickness of the vapor deposition plating as the upper layer plating can be reduced, and the process can be simplified, so that an increase in equipment cost, which is a problem in practical use of the vapor deposition plating, can be suppressed.

In addition, from the viewpoint of composite plating containing an oxide, there is an advantage that it is excellent in corrosion resistance and can be colored by adding characteristics such as resistance to wear and abrasion and controlling the film thickness.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an analysis of the superposed plated steel sheet of the present invention having a molten aluminum zinc alloy plating on which Si and its oxides are deposited by Auger electron spectroscopy, and shows the depth direction of the upper plating (sputtering time). ) Are shown in relative electron%. Similarly, FIG. 2 shows an analysis result of the upper plating in which Ti and its oxide are deposited. FIGS. 3, 4 and 6 show the results of analysis of the plating of the upper layer of the plating film of the present invention on which Al and its oxide are deposited. FIG. 5 shows the result of Auger electron spectroscopy of the present invention in which Ti oxide was plated on the upper layer. In each case, the element “MM” as a metal and the element “M” as an oxide were determined from the relative atomic% ratio of Si and O using SiO ₂ as a standard substance.
The ratio MO / MM of O "was calculated.

──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hiroyuki Tachibana 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (56) References JP-A 64-11983 (JP, A) JP-A-63-297576 (JP, A) JP-A-63-153286 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 28/00-30/00 C23C 14/00-14 / 58 C23C 2/00-2/26 C25D 5/00-5/56

Claims (6)

(57) [Claims] 1. A high corrosion resistant superimposed plated steel sheet comprising a galvanized coating having a composite coating comprising one or more metals of Ti, Si, Al, Mg, and B, and an oxide thereof. 2. Ti, Si, Al, Mg,
A high corrosion resistant superimposed plated steel sheet having a composite coating comprising one or more metals of B and an oxide thereof. 3. A metal element (MO) as an oxide and a metal element as a metal, wherein one or two or more metals of Ti, Si, Al, Mg, and B are formed on a galvanized coating film. A high corrosion resistant superimposed plated steel sheet having an atomic percentage ratio (MO / MM) of (MM) of 0.1 to 1.0 and a coating thickness of 0.2 to 5.0 microns. 4. Ti, Si, Al, Mg,
The composition of one or more metals of B and the oxide thereof is such that the atomic% ratio (MO / MM) of the metal element (MO) as the oxide to the metal element (MM) as the metal is 0.1 to 1.0; A high corrosion resistant superimposed plated steel sheet having a coating thickness of 0.2 to 5.0 microns. 5. A method according to claim 1, wherein a post-treatment film is provided on the surface of the composite film comprising one or more metals of Ti, Si, Al, Mg, and B, and an oxide thereof on the galvanized film. Corrosion resistant superimposed plated steel sheet. 6. Ti, Si, Al, Mg,
A highly corrosion-resistant superimposed plated steel sheet having a post-treatment film on the surface of a composite film comprising one or more kinds of B metals and oxides thereof.