JP3020579B2 - Phosphate treatment method for surface of zinc-based metal material having ground portion - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for treating a surface-treated steel sheet for cationic electrodeposition coating, particularly a method for treating a surface of a zinc-based metal material having a ground portion with a phosphate.

(Prior Art) In recent years, a material used for a vehicle body such as an automobile has been shifting from a general steel plate or pure iron to a surface-treated steel plate in order to improve its rust resistance.

On the other hand, the body of an automobile or the like is finally subjected to electrodeposition coating, but a chemical conversion treatment is performed prior to applying this coating. This chemical conversion treatment is a process necessary to form a chemical conversion coating with good paint adhesion to every corner in the bag structure of the vehicle body,
This adopts a step method in which the vehicle body is immersed in a phosphate bath containing Zn ²⁺ , PO ₄ ³⁻ and ClO ³⁻ as main components.

By the way, when this chemical conversion treatment is applied to pure iron, phosphophyllite (Phosphophyllite: Zn ₂ Fe (PO ₄ )
₂ · 4H ₂ O) film is produced by a chemical reaction below.

On the other hand, among the surface-treated steel sheets, when this chemical conversion treatment is performed on the most common zinc-based plated steel sheet, there is no or little Fe phase on the surface, so other than the Fe phase, that is, on the Zn phase, Hopeite (Zn ₃
(PO ₄ ) ₂・ 4H ₂ O) film is formed.

Since the phosphophyllite film and the hopeite film have different film structures, they also have different acid resistance and alkali resistance. Particularly with respect to alkali resistance, as apparent from FIG. 1 showing their solubility, Ph11.0
The subsequent solubility of the Hopeite coating is much higher than that of the Phosphophyllite coating.

This is a result of the alkali acting on the vehicle body surface, that is, the surface of the chemical conversion film, as the object to be coated, since the precipitation reaction of the cationic electrodeposition coating follows the following reaction.

2H ₂ O + 2e → 2OH ⁻ + H ₂ ↑ OH ⁻ + RNH ³⁺ (paint) → RNH ₂ (coating deposition) + H ₂ O Therefore, the conventional Hopeite film was insufficient in alkali resistance, and was not used in electrodeposition coating. Dissolution of the film occurs due to the action of increasing Ph, and the coating adhesion between the chemical conversion film and the electrodeposition coating film is reduced, and when performing cationic electrodeposition coating, an unfavorable problem on rust prevention occurs, and zinc If part or all of the system-plated steel sheet is subjected to surface grinding, corrosion resistance at a part where the iron base is partially exposed becomes a problem. For example, if salt water comes into contact with the wound on the outer plate, or severe dry / wet weather changes repeatedly act on that portion, rust (scab corrosion) occurs on the surface of the iron plate.

(Problems to be Solved by the Invention) The present invention has been made in view of such a problem, and an object of the present invention is to provide a surface-treated steel sheet, particularly a zinc-based metal material having a ground portion, on a phosphorous phosphite. It is an object of the present invention to provide a new phosphating method capable of forming a film having the same level of film adhesion and high rust-preventive effect as the film.

(Means for Solving the Problems) That is, the present invention relates to a method for treating a surface of a zinc-based metal material having a ground portion for phosphating the zinc-based metal material having a ground portion at least in part. A, phosphate ions 5 to 30 g /, manganese ions 0.7 to 3.0
g /, zinc ion 0.5 ~ 1.5g /, nickel ion 0.1 ~
4.0 g /, a total of one or both of fluorine ions and chlorate ions is 0.04 to 1.5 g /, silicotungstic acid, a soluble tungsten compound selected from alkali metal salts of silicotungstic acid, ammonium salts and alkaline earth metal salts. By immersing for 30 seconds to 120 seconds in an acidic phosphating treatment aqueous solution containing 0.01 to 20.0 g / tungsten as tungsten and mainly containing a film formation accelerator, and a weight ratio of manganese and zinc of Mn / Zn of 1.0 to 2.0. The chemical conversion film is formed on the entire surface of the zinc-based metal material including the ground portion.

(Examples) Therefore, the present invention will be described in detail below with reference to examples and comparative examples.

The present invention relates to a method for forming a modified hopeite film having the same level of film adhesion and a high rust-preventive effect as a phosphophyllite film on the surface of a surface-treated steel sheet, particularly a zinc-based metal material having a ground portion. So, this hopeite film is
It is composed of a composition represented by the following chemical formula.

Zn _3-X Me (PO ₄ ) ₂ .4H ₂ O (Me: Fe and Ni and / or Mn) The aqueous solution of acid phosphate treatment for forming this modified hopeite film is Zn ²⁺ , PO ₄ ^{3 -} , Ni ²⁺ , Mn ²⁺ , ClO ^3- and
F ^- been made to either one or both, the main component a soluble tungsten compound and a chemical conversion accelerator, phosphate ions 5 to 30 g /, preferably 10 to 20 g /, manganese ions 0.7～3.0G / preferably 0.8 to 2.0 g /, zinc ion 0.5 to 1.5 g /, nickel ion 0.1 to 4.0 g /, preferably 0.3 to 2.0 g /, total of fluorine ion and chlorate ion 0.04 to 1.5 g /, and soluble tungsten compound tungsten 0.01 to 20 g /, preferably 0.05 to 10.0 g /
, More preferably 0.1 to 3.0 g / and a film conversion accelerator as a main component, and the weight ratio of Mn / Zn of manganese and zinc is
It is a treatment liquid having a composition of 1.0 to 2.0.

Among them, 5 g /
If the amount is less than 30 g, a non-uniform film is apt to be formed. If the amount exceeds 30 g /, no further effect is produced, and the amount of chemicals used increases, which is economically disadvantageous.

In addition, for manganese ions, when it is less than 0.7 g /, the manganese content in the film formed on the zinc surface is reduced, and the adhesion after cationic electrodeposition coating becomes insufficient, and also exceeds 3.0 g / No further effect is produced, and the use of chemicals increases, which is economically disadvantageous.

For zinc ions, if it is less than 0.5 g /, a uniform zinc phosphate film is not generated, and if it exceeds 1.5 g /, a uniform zinc phosphate film is generated It is easily crystallized, and faces downward as a cationic electrodeposition base.

For nickel ions, if it is less than 0.1 g /
The nickel content in the film formed on the zinc surface is reduced and the adhesion after cationic electrodeposition coating becomes insufficient, and if it exceeds 2.0 g /, no further effect occurs and the amount of chemical used Increases, which is disadvantageous economically.

For fluorine ions and chlorate ions, the total is 0.
If it is less than 04 g /, yellow rust tends to occur, and if it exceeds 1.5 g /, the film becomes tempered and the corrosion resistance after painting is reduced.

Furthermore, for soluble tungsten compounds, 0.01
If it is less than g / g, the effect of increasing the film thickness of the alkali resistance at the grinding portion becomes insufficient, and the scuff resistance does not improve.
If the amount exceeds 20 g /, no further effect is produced, and the amount of chemicals used increases, which is economically disadvantageous.

On the other hand, as the above-mentioned film formation accelerator, those which generate nitrite ion, m-nitrobenzenesulfonic acid ion and hydrogen peroxide are used.
01 g / -0.2 g / and / or m-nitrobenzenesulfonic acid ion 0.05-2.0 g / and / or hydrogen peroxide 0.5 g /
Use in the range of ~ 5.0g /.

When the amount of the film formation accelerator is less than the above range, the film formation is not sufficiently performed and yellow rust or the like is easily generated, and when the amount is more than the above range, a blue-collar non-uniform film is formed. Easy to be.

Further, the following can be exemplified as the source of the main component constituting the aqueous solution of the acidic phosphating treatment.

That is, zinc ions include zinc oxide and zinc nitrate, and phosphate ions include sodium phosphate and zinc phosphate.
Nickel phosphate, manganese phosphate, etc., as manganese ions, manganese carbonate, manganese nitrate, manganese chloride,
Manganese phosphate, etc., nickel ions include nickel carbonate, nickel nitrate, nickel chloride, nickel phosphate, etc., and fluorine ions include HBF ₄ , NaBF ₄ , KBF ₄ (above boron fluoride ion), H ₂ SiF ₆ , Na ₂ SiF ₆ , K ₂ SiF ₆ (above silicon fluoride ion), NaCl as chlorate ion
O ₃ , KClO ₃ , and HClO ₃ are used, respectively. As the soluble tungsten compound, silicotungstic acid and silicotungstate compound are used, and silicotungstic acid may be a commercial product, and the soluble tungstate compound may be an alkali metal salt, an ammonium salt, an alkaline earth metal of silicotungstic acid. Soluble compounds such as salts are used, and sodium nitrite, ammonium nitrite, sodium m-nitrobenzenesulfonate, aqueous hydrogen peroxide, and the like are used as film formation accelerators.

In addition, the aqueous solution of the acidic phosphate treatment may contain nitrate ions in the range of 0.1 g / to 15 g / in addition to the above main components.

The above-mentioned immersion treatment with the acidic phosphate treatment aqueous solution is performed at a treatment liquid temperature of 30 to 60 ° C, preferably 40 to 60%. If the temperature of the treatment liquid is lower than 30 ° C., the chemical conversion property of the film is poor, and a good film cannot be obtained unless it is immersed for a long time. On the other hand, if the temperature exceeds 60 ° C., decomposition or precipitation of the film formation accelerator occurs, and the balance of the aqueous solution of acidic phosphating is easily lost, so that a good film cannot be obtained. The treatment time required for immersion is 15 seconds or more, preferably in the range of 30 seconds to 120 seconds. If it is less than 15 seconds, desired crystals cannot be obtained, and if it exceeds 120 seconds, no further effect is produced.

[Comparative Test] Next, two kinds of test pieces made of an alloyed hot-dip galvanized steel sheet (GA) having a grinding portion were used as examples, and four kinds of test pieces made of a cold-rolled steel sheet (SPC) were used as a comparative example. These were subjected to the following treatments.

Degreasing: Spraying 2% by weight of alkaline degreasing agent (Surf Cleaner SD250, manufactured by Nippon Paint Co., Ltd.) at a temperature of 40 to 43 ° C for 1 minute, then immersion treatment in a dipping bath for 2 minutes Rinse: Rinse with tap water Surface adjustment: Surface Conditioner (Surf Fine 5N4HM manufactured by Nippon Paint Co., Ltd.) 0.1% by weight, immersed for 15 seconds at room temperature Chemical formation: 43-45 ° C in an acidic phosphating solution shown in Table 1
Immersion treatment for 120 seconds Water washing… Washing with tap water Pure water washing… Washing with ion exchange water Drying… Drying from room temperature to 100 ° C for 5 to 10 minutes Electrodeposition… Cation electrodeposition coating (Nippon Paint Co., Ltd. Power Top U-1000 film) the thickness 30.mu.) after performing the above processing, the name specimens for reforming their surfaces Hopuaito _{(Zn 3-X Mex (PO} 4) 2 · 4H 2 O) whether the ESR film is formed (Electron Spin Reson
ance), it was confirmed that the modified Hopeite film was formed in all of the examples of the present invention.

Next, a scab test, a salt spray test (SST), an adhesion test, an alkali resistance test, and a test for measuring the damage of a chemical conversion film during electrodeposition coating were performed on the respective test pieces under the following conditions.

Scab test: 25 painted scratches or cuts were formed on the painted test piece, and then the painted test piece was subjected to a salt spray test (JIS-Z-2871, 24).
Time) → Wet test (temperature 40 ° C, relative humidity 85%, 120 hours) → Leave indoors (24 hours) as one cycle and perform 10 cycles. Average value of maximum width of thread rust and blister of painted test specimen after test Find out.

Salt spray test (JIS-Z-2871); A cross cut that reaches a steel plate is put on the electrodeposition coating test piece,
A 5% salt spray test is performed for 1000 hours for cold-rolled steel sheets and 500 hours for galvanized steel sheets, and then the test pieces are air-dried, and the maximum width of thread rust and blisters of the test pieces is examined.

Adhesion test (1mm width, 2mm width); After immersing the coated test piece in deionized water at 40 ° C for 10 days,
100 goban eyes at 2 mm intervals (or 1 mm intervals) are sectioned with a cutter knife, an adhesive tape is adhered to the surface and peeled off, and the number of gobang eyes remaining on the painted test piece is counted.

Alkali resistance test; 1 / 10N at 25 ℃ for chemical conversion test plate before cationic electrodeposition coating
After being immersed in a glass container containing an aqueous sodium hydroxide solution (JIS-K-8576 reagent) for 5 minutes, the sample is taken out, and the amount of the chemical conversion film of the test piece eluted into the solution is measured.

Chemical film damage measurement test during electrodeposition coating; After removing the wet coating film of the electrodeposited test piece with a solvent, the corrosion current value (IC) of the test piece is measured, and the corrosion current before and after electrodeposition coating The damage of the chemical conversion film is determined based on the rate of change of the value. The measurement conditions for the corrosion current value were as follows: an automatic potentiostat as a measuring device, and 25 ° C., 3% as an electrolytic solution.
(W / W) A saline solution was stirred and used, and a silver / silver chloride electrode was used as a reference electrode, and a platinum electrode was used as a target electrode, with a liquid contact area of 1 cm ² .

As a result, the appearance, coating weight (CW),
The results of the salt spray test and the adhesion test are shown in Table 2, the results of the alkali resistance test are shown in Table 3, and the results of the chemical film damage measurement test during electrodeposition coating are shown in Table 4. Was.

From this, it has been found that when the phosphate treatment of the present invention is applied to the zinc-based metal surface, a modified hopeite film that does not dissolve even when the Ph is increased during electrodeposition coating is formed. And, since this modified hopeite film has the same level of film adhesion as the phosphophyllite film and can impart a high rust prevention effect, the surface-treated steel sheet for cationic electrodeposition coating is used. It proved to be extremely useful as a treatment.

(Effects) As described above, according to the present invention, a zinc-based metal material having at least a portion to be ground is immersed in an aqueous solution of an acidic phosphate treatment, and the entire surface including the portion to be ground is phosphorophyllite. A chemical conversion coating of the same level as the coating is formed, so not only does the coating not dissolve due to the rise in Ph during electrodeposition coating, but it also has a high rust prevention effect on the ground part where the substrate is partially exposed. By forming a coating having such a property, high rust resistance can be imparted to the entirety of this kind of metal material, and at the same time, a good coating film can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the solubility of the phosphophyllite film and the hopeite film in each Ph region.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Nobe 19-17 Ikedanakamachi, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Koetsu Endo 19-17 Ikedanakamachi, Neyagawa-shi, Osaka Japan Paint Co., Ltd. In-company (56) References JP-A-1-240671 (JP, A) JP-A-55-131176 (JP, A) JP-A-2-232379 (JP, A) JP-A-1-263280 (JP, A) JP-A-62-174385 (JP, A) JP-A-51-126940 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 C25D 13 / 20

Claims (1)

(57) [Claims] (1) A zinc-based metal material having a grinding portion at least in part is provided with phosphate ions of 5 to 30 g / manganese ions of 0.
7-3.0g /, zinc ion 0.5-1.5g /, nickel ion
0.1 to 4.0 g /, a total of one or both of fluorine ions and chlorate ions 0.04 to 1.5 g /, silicotungstic acid,
Alkali metal salts of silicotungstic acid, 0.01 to 20.0 g / as a soluble tungsten compound selected from ammonium salts and alkaline earth metal salts as a tungsten and a film formation accelerator as a main component, and Mn / Z of manganese and zinc
3 in an aqueous solution of acidic phosphating solution in which the weight ratio of n is 1.0 to 2.0
A phosphate treatment method for a surface of a zinc-based metal material having a ground portion, wherein a chemical conversion film is formed on the entire surface of the zinc-based metal material including the ground portion by immersion for 0 to 120 seconds.