JPS589158B2 - Electroplating liquid used to form a Zn-Ti alloy plating film on steel surfaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroplating solution used to form a Zn-Ti alloy plating film that can contain up to 15% by weight of Ti on the surface of steel.

Generally, it is well known that an electroplating solution containing zinc sulfate is used to form a Zn film on the surface of steel by electroplating.

In addition, in order to refine the crystal grains of the electrolytic Zn plating film, add gloss to it, and further improve its electrodepositivity, electroplating was performed in which titanium gluconate was added to the electrolytic Zn plating solution. A solution has also been proposed, and when this electrolytic Zn plating solution is used, the Zn plating film contains Ti, so this plating film exhibits relatively good corrosion resistance.

However, since the Ti content in the Ti-containing electrolytic Zn plating film is about 1.2% by weight at most, it does not exhibit sufficiently satisfactory corrosion resistance in a severe corrosive environment.

Therefore, from the above-mentioned point of view, the present inventors investigated the T content in the Zn-Ti alloy plating film electroplated on the steel surface.
Zn has a dramatically high i content and exhibits outstanding corrosion resistance no matter how harsh the corrosive environment is.
-As a result of research to form a Ti alloy plating film, it was found that ammonium sulfate, titanium sulfate, and a lower organic acid having a carboxylic acid group were added to an acidic electrolytic Zn plating solution containing zinc sulfate, and further plating was performed. Ammonium fluoride, ammonium silicofluoride, ammonium persulfate, as liquid stabilizing components.
When one or more of hydrogen peroxide and aqueous hydrogen peroxide are included, the resulting plating solution becomes acidic and has extremely low electrical resistance, since the main component is sulfate. Furthermore, according to this plating solution, even if electroplating on steel surfaces is performed at high current density and for long periods of time, there will be no precipitation of Ti compounds in the plating solution due to the action of the plating solution stabilizing components. , plating can be performed in an extremely stable state, and the Zn-Ti alloy plating film formed on the steel surface contains Ti at a maximum of 15% by weight, with the content freely adjustable. Zn-Ti can be contained up to
It was discovered that the alloy plating film exhibits dramatically superior corrosion resistance due to its extremely high Ti content, and also that the action of the lower organic acid makes the crystals fine and glossy.

Therefore, this invention was made based on the above findings, and includes zinc sulfate: 80 to 400 g/l, ammonium sulfate: 20 to 120 g/l, and titanium sulfate = 5 to 80 g/l.
g/l, lower organic acid with carboxylic acid group: 2-160
Electroplating having a composition of 1 to 20 g/l, plating solution stabilizing component of one or more of ammonium fluoride, ammonium silicate, ammonium persulfate, and hydrogen peroxide solution: 1 to 20 g/l By applying electroplating to the steel surface in a state that can be operated for a long time at high current density in liquid,
Zn with excellent corrosion resistance containing up to 15% by weight of Ti
-It is characterized by the stable formation of a Ti alloy plating film.

Next, in the electroplating solution of this invention, zinc sulfate,
The reason why the contents of ammonium sulfate, titanium sulfate, lower organic acid having a carboxylic acid group, and plating solution stabilizing component were limited to the above values will be explained.

(a) If the content of zinc sulfate is less than 80 g/l, the rate of formation of a plating film on the steel surface is slow; on the other hand, if the zinc sulfate content exceeds 400 g/l, it is difficult to completely dissolve it in the plating solution, and the plating film may deteriorate. Since it may cause deterioration of properties, its content was set at 80 to 400 g/l.

(b) Ammonium sulfate Ammonium sulfate is a T
Improves the solubility of i-ions, maintains the Ti concentration in the plating solution at a high level, and increases the conductivity of the plating solution.
This has the effect of rapidly forming a Zn-Ti alloy plating film containing high Ti content, but if the content is less than 20 g/l, the desired effect cannot be obtained;
If the content exceeds 20 to 120 g/l, the plating properties will be impaired.

(c) Titanium sulfate If the content is less than 5 g/l, the Ti content in the Zn-Ti base metal plating film will be less than 1.5% by weight, making it difficult to secure the desired excellent corrosion resistance. can be,
Therefore, 1.5% by weight in the Zn-Ti alloy plating film
In order to contain more than 5 g/l of Ti, it is necessary to contain more than 5 g/l, but it is only 80 g/l to completely dissolve in the plating solution.
1, and even if more than this is added, it is not possible to make the Zn-Ti base metal plating film contain more than 15% by weight of Ti, rather undissolved titanium sulfate is present in the plating solution. Since the plating properties are inhibited by this, the content was determined to be 5 to 80 g/l.

(d) Lower organic acid having a carboxylic acid group The electroplating solution of the present invention is usually used at a pH of 3 to 4, but at this pH value, titanium sulfate becomes a hydroxide and precipitates. Significantly impairs plating properties.

Therefore, in the electroplating solution of the present invention, a lower organic acid having a carboxylic acid group is contained to suppress the precipitation of titanium hydroxide, thereby stabilizing the electroplating solution. If it is less than 2 g/l, the desired stabilizing effect of the plating solution cannot be secured;
Since the electrical resistance of the plating solution increases significantly if the content exceeds 1.0 g/l, the content was set at 2 to 160 g/l.

In addition, as the lower organic acid having a carboxylic acid group, it is preferable to use, for example, tartaric acid, citric acid, and gluconic acid.

(e) Plating solution stabilizing components As mentioned above, these components all have the ability to prevent Ti compounds such as titanium hydroxide from precipitating in the plating solution during long-term plating operations at high current densities. This has a uniform effect of stabilizing the plating solution by ensuring a high amount of Ti in the Zn-Ti alloy film, but when the content is 1g
/l, the desired effect cannot be obtained;
If the content exceeds 0 g/l, the Ti ions in the plating solution become stabilized, making it difficult to contain a large amount of Ti in the Zn-Ti base metal film. was set at 1 to 20 g/l.

Next, the electroplating solution of the present invention will be specifically explained with reference to Examples.

First, the material to be plated is 100mm x 100mm x 0.
A low carbon steel plate with a size of 24 mm was prepared, and this steel plate was degreased and washed with water, then pickled by dipping in 13% hydrochloric acid for 25 seconds, and then washed with water to obtain a surface-clean copper plate.

Next, the surface-cleaned steel plates were immersed in an acidic electroplating solution prepared separately, each having a plating solution composition shown in Table 1, and having a pH of 3.4 and a solution temperature of 70°C. Electroplating was performed under the conditions of current density: 6 A/dm2 (conventional Zn-plated steel sheet was 8 A/dm2), plating time: 2 minutes, and the surface of the steel sheet was coated with a thickness of 3 μm.
Zn-Ti alloy plated steel sheets using the electroplating solution of the present invention (hereinafter referred to as the Zn-Ti alloy plated steel sheets of the present invention) are obtained by forming plating films of m respectively.
No. 21, and a Zn-plated steel sheet using a conventional electroplating solution (hereinafter referred to as conventional Zn-plated steel sheet) were manufactured, respectively.

The Ti content in the plating film of the Zn-Ti alloy plated steel sheets 1 to 21 of the present invention is shown in Table 1, and the resulting Zn-Ti alloy plated steel sheets 1 to 21 of the present invention and Regarding conventional Zn-plated steel sheets, JI
A salt spray test based on S-Z2371 was conducted to measure the time until red rust appeared on the plated surface of the steel plate.

The measurement results are shown in Table 1.

As shown in Table 1, in the conventional Zn-plated steel sheet, red rust appeared after 30 hours, whereas
The Zn-Ti alloy plated steel sheet of the present invention requires at least 120 hours to develop red rust and exhibits excellent corrosion resistance.
Moreover, this corrosion resistance is due to the Ti in the Zn-Ti alloy plating film.
The higher the content, the better the quality, and in the case of the Zn-Ti alloy plated steel sheet 10 of the present invention in which the Ti content in the Zn-Ti alloy plating film is 15% by weight, after about 1400 hours elapsed. It is clear that the electroplating solution of this invention has amazing corrosion resistance, as red rust is finally observed.
As a result, a Zn-Ti alloy plating film with an extremely high content can be stably formed on the steel surface under normal operating conditions as well as under high current density, allowing for long-term operation. Zn-Ti alloy plated products are
It has industrially useful effects such as extremely high corrosion resistance.

Claims (1)

[Claims] 1 Zn containing up to 15% by weight of Ti on the steel surface
-The electroplating solution used to form the Ti alloy plating film has a zinc sulfate content of 80 to 40%.
0f/e, ammonium sulfate = 20 to 120 g/l, titanium sulfate = 5 to 80 g/l, lower organic acid having a carboxylic acid group = 2 to 160 g/l, ammonium fluoride, ammonium silicofluoride, ammonium persulfate, A method for forming a Zn-Ti alloy plating film on a steel surface characterized by having a composition consisting of one or more plating solution stabilizing components of hydrogen peroxide solution and hydrogen peroxide solution: 1 to 20 g/l. Electroplating solution used for.