JPS60177187A - Fe-p plated steel sheet with superior suitability to phosphating - Google Patents

Abstract

PURPOSE:To obtain an Fe-P plated steel sheet with superior suitability to phosphating by forming an Fe-P layer contg. a specified amount of P by plating on the surface of a steel sheet having a Zn layer formed by plating. CONSTITUTION:An Fe-P layer contg. >0.5-15.0wt% P is formed by plating as an outer layer by >=0.5g/m<2> on at least one side of a steel sheet having a Zn or Zn alloy layer formed by plating as an inner layer. The suitability of the steel sheet to phosphating and coating by cationic electrodeposition is improved by the Fe-P layer. Ni, Zn, Mn or Ti may be deposited on the Fe-P layer by 5- 50mg/m<2> so as to improve the suitability to phosphating further.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly corrosion-resistant surface-treated steel sheet for use in automobiles, which is excellent in phosphate chemical conversion treatment properties, cationic electrodeposition coating properties, and the like.

Electrodeposition coating is often used as a primer coating for automobiles.
At the same time as the cationic paint particles are deposited on the surface of the object to be coated during electrodeposition, H2 gas is likely to be generated along with it due to the electrolysis of water, which is the medium. , causing coating defects. This coating film defect (referred to as a crater) phenomenon is particularly observed in steel sheets coated with zinc or zinc-based alloys mainly containing zinc.

In addition, steel sheets plated with zinc or zinc-based alloys mainly containing zinc have poor secondary adhesion of the coating after three coats of cationic electrodeposition coating, intermediate coating, and top coating.

Secondary electrodeposition of a paint film is the adhesion after the paint film has been deteriorated by some method.
There is a method of immersing the material in warm water at 40° C. for 10 days, and immediately after pulling it out, the adhesion is determined by a cross-cut peel test.

The secondary adhesion of the paint film and the crater during cationic coating
As a method to prevent this occurrence, Fe plating treatment methods (Japanese Patent Applications No. 55-141773, No. 56-82179, No. 56) have already been proposed.
131757), but phosphate chemical conversion treatment is poor in pure Fe plating treatment. On a pure Fe-plated surface, the number of phosphate nuclei generated is small, and coarse phosphate crystals are formed. Furthermore, depending on the phosphate treatment solution, scattering may occur in the phosphate film, and secondary adhesion may not be improved. In particular, no improvement effect is often seen in spray-type phosphate treatment.

Therefore, in order to solve the above-mentioned drawbacks of the prior art, the present invention provides Fe plating with improved phosphatide conversion treatment properties and cationic electrodeposition coating properties by incorporating an appropriate amount of P into the Fe plating. -The aim is to provide a P-plated steel sheet.

The present invention has a P content of 0.5w on at least one surface.
Provided is an Fe--P plated steel sheet in which an Fe--P plating layer of 15.0 wt % or less of O, O or more is formed.

The present invention has a P content of 0.5w on at least one surface.
More than t%15. The Fe-P plating layer is 0.0% or less.
01g102 or more is formed, and this c7) Ni, Zn, Mn, Ti on the Fe-P plating layer.
Fe made by adhering 5 to 50 mg/m2 of either
-Providing a P-plated steel sheet.

The present invention also provides a Zn or Zn-based alloy plating layer as an inner layer and a P content of more than 0.5 vt% as an outer layer. Ow
t% or less, the adhesion amount is 0, 5 g/m or less.
- Fe formed with a P plating layer formed on at least one surface
-Providing a P-plated steel sheet.

The present invention further provides a Zn or Zn-based alloy plating layer as an inner layer and a P content of more than 0.5 t% as an outer layer. o
wt% or less, +1. ? A Fe--P plating layer with an i=0.5 g/m2 or more is formed on at least one surface, and Ni is formed on this Fe--P plating layer.

Zn, Mn, Ti 5 to 50II18/I1
A Fe--P plated steel sheet is provided.

Hereinafter, the Fe-P plated steel sheet of the present invention will be explained in detail.

Niha, 0, 5 wt% Jll 15, 0 wt% or less (7) in Fe-P plating applied in the four embodiments of the present invention
It is characterized by containing P. Since the oxide film formed on the surface of pure Fe plating is stable, the initial reaction of the phosphate chemical treatment is delayed and the crystals become rough.

However, when a small amount of P is contained, the initial reaction is significantly accelerated and the number of initial crystal nuclei increases.

As an example, Japanese Patent Application No. 58-84585 lists Fe-P plating with a P content of 0, 0003-0, 5wt% (1), and with this P content, the initial number of crystal nuclei after 5 seconds is extremely large. It shows that there will be more.

During phosphate treatment, even if the initial number of crystal nuclei after 5 seconds of phosphate chemical conversion treatment is small, crystal nuclei continue to be generated, and it is too difficult to evaluate based on the initial number of crystal nuclei after 5 seconds. There are many cases where it is inappropriate.

Chemical conversion properties are generally determined by the phosphorus 1 produced after 120 seconds of treatment.
It is a g-salt crystal with a 3f value, and normally the formed film is important.

In the present invention, the properties of the final film are evaluated by the P ratio and crystal size, which are most important to those skilled in the art.

Fe-P plating with a P content of more than 0.5 wt% may have a small initial number of crystal nuclei 5 seconds after chemical conversion treatment, but after that the number of crystal nuclei is generated, and eventually high quality crystals are formed. The present invention provides a film that is small in size, dense, and free of porosity.

As the P content increases, the cathodic deposition efficiency of Fe--P plating gradually decreases, resulting in poor economic efficiency. In addition, Fe--P plating with an excessively high P content tends to be non-inky, and the reactivity during phosphorus salt treatment may decrease.

Therefore, the upper limit of the P content is limited to 15 wt% or less, preferably 10 wt% or less, more preferably 5 wt% or less.
It is preferably less than wt%.

When applying such Fe-P plating directly onto a steel plate, the amount of Fe-P plating deposited is required to be 0.018/f112 or more. If this is less than 0.01 g/m2, the surface of the steel plate cannot be uniformly coated with Fe--P plating, so the effect is small. The method that is effective at a coating weight of 0.01 g/m' or more is when the phosphate film is coated with Z n2 Fe (PO4) 2 4 during phosphate chemical conversion treatment.
This is because Fe is supplied from the base steel when reforming to H20 (phosphophyllite).

In addition, when phosphate chemical conversion treatment is applied to zinc or zinc-based alloy coated steel sheets mainly containing zinc, the phosphate film formed is Zn3 (PO4)2.4 H20 (Hopeit
e), and it is a well-known fact that the water-resistant secondary adhesion of the paint film after three coats including cationic electrodeposition is poor, and the crater resistance during cationic electrodeposition is poor.

Therefore, if the Fe-P plating of the present invention is applied to the surface of a steel sheet plated with zinc or a zinc-based alloy mainly containing zinc, the phosphate film formed during phosphate chemical conversion treatment can be replaced with Zn2.
F e (PO4) 2 * 4H20 (Phosph
ophyllite), which is effective in improving crater resistance during cationic electrodeposition coating and water-resistant secondary adhesion of the coating film.

The amount of Fe--P plating to be applied to zinc or a zinc-based alloy plated steel sheet mainly composed of zinc is preferably 0.5 g/w2 or more, and the reason for this limitation is as follows. In order to improve the water resistant secondary adhesion of the coating film and the crater resistance during cationic electrodeposition coating, the phosphate chemical conversion coating should be treated with Zn2.
Fe' (PO4) Nu-4 H20 (Pho, 5pho
phyllite) is important. F
If the amount of e-P plating is less than 0.5 g/m2, Pho
Spophyllite (7) The amount formed is small and has no effect.

In addition, 5 to 50 mg of any one of IAN i , Z n , Mn , and Ti was applied directly to the steel sheet or to the Fe-P plating layer applied to the zinc or zinc-based alloy-plated steel sheet mainly composed of zinc. When a+2 is attached, fine microcells are formed on the surface and the phosphate chemical conversion properties are further improved. If the surface adhesion amount is less than 5 mg/m2, it has no effect, and if it exceeds 50 mg/m2, it will cover the surface uniformly and not only will it not form microcells, but it will also remain as phosphate in the phosphate conversion coating. The amount remaining increases, and Phosphophyllite /
(Phosphophyllite + Hopeit
e) It is not preferable because it lowers the ratio. In addition, Fe-P
In plating, instead of P, As, Sb, and B, which are similar to P, are used.
A similar effect can be achieved by adding i.

Hereinafter, the present invention will be specifically explained with reference to examples.

A cold-rolled steel sheet that has been electrolytically degreased and pickled according to the conventional method is subjected to F under the following conditions.
e-P plating was applied. Regarding some of them, F
Ni and Zn are deposited on e-P plating by flash plating.
, Mn, or Ti.

The following various tests were conducted on the obtained Fe-P plated steel sheet. The results are shown in Table 1 and the photograph in FIG.

(1) Fe-P plating (1-1) Bath composition FeCl2 150g/JI KC text 200g/L;L Kuen dairy log/text NaH2PO20,001~ Log/text (1-2) Plating conditions pH=3.0+bath temperature 50°C9 Current density 10 N150A/dm2 NaH2PO2 concentration and current density in the bath Control the P content by changing the degree of I did a rule.

(2) Flash plating (2-1) Ni plating bath composition NiSO4250g/NiC2 45g/boric acid 30g/plating conditions pH=3.5 Bath temperature 60°C Anode Ni plate electricity amount 28 coulombs/, 32 (2-2) Zn plating bath composition Zn0 sentence 2210 glI KC sentence 360 g/fL Plating conditions pH = 5.0 Bath temperature 50°C Anode Zn plate electricity amount 60 coulombs/I112 (2-3) Mn plating bath Composition MnSO404H20 150g/text (NH4) 2 SO4100g/9°Na2so3
2g/l Glycine 15 glI Plating conditions pH=3.0 Bath temperature 20℃ Anode Insoluble carbon charge Iio coulomb/m2 (2-4) 3Ti03 for Ti plating 0. Plating was performed by immersing it in a bath containing 1 mol/u of OO for 5 seconds at room temperature.

Additionally, Zn was electroplated using conventional methods.

Fe--P plating was performed on Zn--Ni alloy and Zn--Fe composite plated steel sheets under the following conditions.

For some of them, any of Ni, Zn, Mn, or Ti is applied by flash plating on Fe-P plating.
I made him wear one. The following various tests were conducted on the obtained Fe-P plated steel sheet.

The results are shown in Table 2.

(1) Fe’-P plating (1-1) Bath composition FeC sentence 3 200 g/l KC Bun 200g/stand Tsucitric acid 20g/view NaH2PO20,001～ tOg/sentence (1-2) Plating conditions pH=3.0. Bath temperature: 50℃ Current density 10-60 A/do2 NaH2PO2 concentration and current density in / Control the P content by changing the degree of I did a rule.

(2) Flash plating This was done in the same manner as described above.

As is clear from Tables 1 and 2 showing these results and the photograph in Fig. 1, the Fe-P plated steel sheet according to the present invention has
More than 0.5 wt% but not more than 15.0 wt% of P during Fe plating
It can be seen that by containing Fe--P plating directly on steel or on Zn or Zn-based plated steel sheet, the phosphatide salt chemical conversion treatment properties are excellent.

(1) Phosphate chemical treatment After degreasing, washing with water, and surface conditioning under standard conditions suitable for each treatment solution,
Phosphate chemical conversion treatment was performed, followed by washing with water and drying. As the chemical conversion treatment liquid, Bonderite 3030 (1) dip type made by Parkerizing), Ponterite 3128
(spray type made by Nippon Parkerizing Acid) and Granozin SO'2000 (dip type made by E1 Paint) were used.

(2) Crystal size After normal chemical conversion treatment, SEM (Scanning)
'electron m1 microscope) observation was performed to measure the crystal size. Average maximum length of crystal 4f
I got i.

7. The present invention example and the comparative example are shown in FIG. 1a and FIG. 1b, respectively. ti < SEM photos are shown.

(3) Film amount It was measured by the dissolution method using a 5% chromic acid solution.

(4) P ratio It was determined by the above formula.

(5) Water Resistance Secondary Adhesion After phosphate chemical conversion treatment, apply cationic electrodeposition coating at 20 lm, intermediate coat, and top coat to give a total coating thickness of 90 to 1100 pL, and after immersing in hot water at 40°C for 10 days, Immediately 2II1m
100 goblin lines reaching the L-square base steel plate were drawn and peeled off using cellophane tape, and the number of peels was calculated.

(6) Blister resistance Water resistance Secondary adhesion After painting at 90 to 100 lm, the same as during the secondary adhesion test, draw a cross cut that reaches the base steel plate to scratch the paint film, and then immerse it in 5% saline solution for 15 minutes. Soak 1 then at room temperature for 7
The sample was left to dry for 5 minutes, and then placed in a humid box at 49° C. and 85% relative humidity for 22.5 hours. This cycle was repeated 100 times, and the bulge width (arm) of the uneven portion was observed.

(7) After mixing the crater-resistant cationic electrodeposition paint U-30 (manufactured by Nippon Paint Co., Ltd.) and stirring for one week, the electrodeposition time was 180 seconds with a distance between electrodes of 4 cm, a voltage of 350 V, and no soft touch. I painted it. The evaluation is as shown in the table below.

Table 3

[Brief explanation of drawings]

Figures 1a and 1b show the steel sheets of the present invention (Fe-P plating with a P content of 41.5 wt% on a cold-rolled steel sheet).
．． 5g/m') and comparative example (SPCC) chemical conversion treatment (Granogin 5D-2000) 750 after 120 seconds
This is a double SEM photo. Figure 1a Figure ib Procedure No. 10 (spontaneous) July 13, 1980 Director General of the Patent Office Manabu Shiga 1, Indication of the case 1982 Patent Application No. 33305 2, Name of the invention Phosphate Chemical Fe-P plated steel sheet 3 with excellent processability,
Relationship with the case of the person making the amendment Patent applicant's office 1-1-28 Kitahonmachi-dori, Chuo-ku, Kobe, Hyogo Prefecture Name (125) Kawasaki Steel Co., Ltd. 4, Agent 101 Telephone 864-4498 Address
3-2-2 Iwamoto-cho, Chiyoda-ku, Tokyo The "Title of the Invention" column of the application, the "Brief Description of Drawings" column 4 of the specification, and the brief description of the drawings, Figures 1a and 1b, are as follows: These are electron micrographs showing the crystal structure of a chemical conversion coating formed on a steel plate, each showing a steel plate of the present invention (a cold-rolled steel plate with a P content of 1.5 wt).
% Fe-P plating of 2.5 g/m') and comparative example (SPCC) chemical conversion treatment (Granogin 5D-20
00) 7504@SEM photograph after 120 seconds.

Claims (4)

[Claims] (1) At least one side has a P content of 0.5 wt%
Super 15. Fe-P plating layer with Owt% or less of 0.01
An Fe-P plated steel sheet with excellent phosphate chemical conversion treatment properties, characterized by having a size of 7 m2 or more. (2) At least one side has a P content of 0.5 wt%
Super 15. Fe-P plating layer of 0.01% or less
Ni g/m2 or more is formed on this Fe-P plating layer.
, Z n , M n , T t to 5
An Fe-P plated steel sheet excellent in phosphate chemical conversion treatment characterized by being coated with ~50 mg/m2. (3) A Zn or Zn-based alloy plating layer is used as the inner layer, and the P content is more than 0.5 wt% as the outer layer.15. Fe-P plating excellent in phosphate chemical treatment, characterized by forming an Fe-P plating layer of 0.5 g/+a2 or more with an adhesion amount of 0.5 g/+a2 or more on at least one surface. steel plate. (4) Zn or Zn-based alloy plating layer as the inner layer and P content exceeding 0.5 wt% as the outer layer 15. A Fe-P plating layer with an adhesion amount of 0.5 g102 or more is formed on at least one surface, and 5 to 50 mg1 of any of Ni, Zn2Mn, or Ti is formed on this Fe-P plating layer.
An Fe-P plated steel sheet excellent in phosphate chemical conversion treatment, characterized in that it is coated with No. 112.