JPS61587A - Solution for chemical conversion treatment - Google Patents

Abstract

PURPOSE:To obtain a soln. for chemical conversion treatment capable of forming a film having high corrosion resistance and a fine appearance on the surface of a metal such as a zinc film formed by galvanizing without causing environmental pollution by adding tervalent Cr ions, a silicate, a fluoride and an acid. CONSTITUTION:This soln. for chemical conversion treatment contains 0.1-10g/l tervalent Cr ions from a feeding source such as Cr2(SO4)3 or CrCl3, 0.1-20g/l (expressed in terms of silicate ions) silicate such as sodium metasilicate or sodium orthosilicate, 0.1-10g/l (expressed in terms of fluorine ions) fluoride such as hydrofluoric acid or borofluoric acid and 0.5-20g/l acid such as nitric acid or sulfuric acid. The soln. is preferably adjusted to about 0.1-2.5pH. A dye can be added to the soln. so as to provide a desired color tone to a film formed by chemical conversion treatment. An acid mordant dye or a mordant dye is preferably added as the dye at 0.05-2g/l concn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chemical conversion treatment solution used to treat a metal surface such as a galvanized film to form a chemical conversion film with high corrosion resistance and good appearance on the metal surface. After that, chromate treatment is performed to improve the corrosion resistance of this zinc plating, but conventional chromate treatment solutions generally contain hexavalent chromium compounds such as chromic anhydride and potassium dichromate as main components. There is. but,
The chromate treatment solution using this hexavalent chromium compound has the excellent advantage of providing a chromate film with good appearance, gloss, and high corrosion resistance, but hexavalent chromium compounds have moderate problems in terms of pollution prevention. For this reason, it is desired to use a trivalent chromium compound instead of a hexavalent chromium compound, and for this reason, various chromate treatment solutions using trivalent chromium compounds have been proposed.

However, with the conventional chromate treatment liquid using a trivalent chromium compound, it is difficult to form a chromate film that has a good appearance and high corrosion resistance. for example,
The chromate treatment solution described in JP-A-54-142141 contains trivalent chromium ions, fluoride ions, and acids other than nitric acid. However, the chromate coating formed by this treatment liquid does not have sufficient corrosion resistance. Additionally, the chromate treatment solution described in U.S. Pat. No. 4,222,779 is
Although it contains valent chromium ions, sulfuric acid, hydrogen peroxide, and silicic anhydride, the chromate coating produced by this treatment liquid has a poor color tone and poor corrosion resistance.

Furthermore, the chromate treatment solution described in U.S. Pat. No. 4,169,741 contains trivalent chromium ions, phosphate, and silicic anhydride, and the chromate treatment solution described in U.S. Pat. No. 4,384,902 contains trivalent chromium.

Although they contain an oxidizing agent and anhydrous silicic acid, the chromate coatings produced by these treatment solutions also lack sufficient corrosion resistance and color tone.

In view of the above circumstances, the present inventors have conducted intensive research into a chemical conversion treatment solution that can impart excellent corrosion resistance to metal surfaces such as galvanized coatings and form a chemical conversion film with a glossy and good color tone. As a result, a chemical conversion treatment solution containing trivalent chromium ions, silicates, fluorides, and acids reliably achieves the above objectives, and when a metal surface is treated with this treatment solution, it has high corrosion resistance. The present inventors have discovered that it is possible to form a chemical conversion film with a glossy appearance and a good appearance, leading to the present invention.

The present invention will be explained in more detail below.

The chemical conversion treatment liquid according to the present invention contains trivalent chromium ions, silicate, fluoride, and acid, and combines the trivalent chromium compound with the king of silicate, fluoride, and acid. Particularly, for the first time, it has been possible to form a chemical conversion coating with high corrosion resistance and a good appearance. On the other hand, if any one of silicate, heptadide, and acid is missing, a conversion coating with high corrosion resistance and good appearance cannot be obtained.
The object of the present invention cannot be achieved 1. Particularly, when silicate is not contained, the corrosion resistance is not sufficient, and the gloss and color tone are also insufficient. Furthermore, if it does not contain fluoride or acid, it will be glossy.

The color tone is not good enough.

Here, the source of trivalent chromium ions contained in the chemical conversion treatment solution of the present invention may be any source as long as it is soluble in water, for example, □Crt (
SO4)s + KCr(SO4)t, CrCe5 +
Examples include CrR, Cr(N)s)a, etc., and these 1
A species or two or more species may be used. The concentration of trivalent chromium ions in the chemical conversion treatment solution is not necessarily limited, but is usually 0.
1~10f7. , particularly preferably from 0.5 to 224.

In addition, the silicate can be supplied by one or more of sodium metasilicate, sodium orne silicate, etc., and the concentration of the silicate is 0.1 to 20' as silicate ions in the chemical conversion treatment solution. /7, 0.5 to 3'/l in %
It is preferable that it be contained.

Furthermore, examples of the fluoride include hydrofluoric acid, hydroborohydric acid, sodium silicofluoride, sodium borofluoride, acidic ammonium fluoride, and sodium fluoride, and one or more of these may be used. .

The concentration of fluoride is 0.1-10'/ as fluorine ion.
It is preferable that g, % is 0.5 to 5″/e.

Furthermore, as the acid, both organic acids and inorganic acids can be used, but inorganic acids such as nitric acid, sulfuric acid, and hydrochloric acid are preferably used. Note that these acids may be used alone or in combination of two or more. The concentration of acid is 0.5-20
24, especially 2 to 1024 is preferred.

In addition, - of the chemical conversion treatment of the present invention is 0.1 to 2.5, particularly 0.
It is preferable that it is 5-1.5.

If necessary, conventionally known components may be added to the chemical conversion treatment solution of the present invention, and dyes, particularly acid mordant type or mordant type dyes, may be added to give various color tones to the chemical conversion coating. can do.

Examples of such dyes include Chrome Blue Black RC, Chrome Brown RH, Chrome Clean F, and Anthracene Blue 5WGG.

Examples include chrome black AC. In this case, the concentration of the dye is preferably 0.05 to 224, particularly 0.1 to 0.5.

The chemical conversion treatment solution of the present invention can be used for the chemical conversion treatment of zinc plating, zinc alloy plating, cadmium plating, parts made of zinc or zinc alloy, and even aluminum parts, but it can be used in the usual chemical conversion treatment. method can be adopted. For example, when treating a galvanized film, after galvanizing, the galvanized film is immersed in nitric acid, then immersed in the chemical conversion treatment solution of the present invention, and then left in the air for an appropriate period of time as necessary, and then washed with water. A method such as drying can be adopted. Further, after the chemical conversion treatment, an appropriate post-treatment such as immersion in an alkaline solution or immersion in a rust preventive agent can be performed.

The processing conditions for the chemical conversion treatment solution of the present invention are not particularly limited, but the immersion time is 2 to 20 seconds, particularly 5 to 15 seconds, and the solution temperature is 10
It is preferable to set the temperature to 30° C., especially 15° C. to 25° C., and leave it in the air for 2 to 20 seconds, especially 5 to 15 seconds.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

[Example 1] CrC(Is 8.f/(11Na,
5iO410/l Na1SiF6 5 #HNOa
s ta/1HISO45y/e [Example 2] Crt(Soaks 20t/INa
tSiOs 8 5NaJiFa
2 5HNOa 1
0 tt [Example 3] CrCe5 8 f/1lNa=S
iO,101/ NH4HF, 5 IfHNO3
5/f HISo, 5 tt Chrome Fast Blue 〇, 5〃BX (manufactured by Mikata) (Chrome Fast Blue BX) Chemical conversion treatment was performed in the following method using the chemical conversion treatment solutions of Examples 1 to 3. .

First, a zinc plating solution having the following composition is used to plate approximately 8 μm of zinc on steel.

Zinc plating solution composition and plating condition composition ZnC/l 40 f/INHiC
e 200 #7? Hishi y:+-le N
R-130yd/e (manufactured by Uezai Kogyo Co., Ltd.) Asahizincol NR-21# (manufactured by Uezai Kogyo Co., Ltd.) PH5,8 Plating conditions Bath temperature 25 °C Cathode current density 2 A/d dizziness time
Stir for 20 minutes, then soak the resulting galvanized plate in dilute nitric acid (concentrated HN0°10
g/l) for 10 seconds at room temperature and then immediately rinsed with water. Next, after being immersed in the chemical conversion treatment liquid at a temperature of 25° C. for 10 seconds, the chemical conversion treatment liquid was taken out and left in the air for 10 seconds. After that, wash with water, and then bath temperature 5o~6
It was immersed in warm water at 0'Q for about 5 seconds and dried at 50-60'Q.

For comparison, chemical conversion treatment was carried out in the same manner as above using the following chemical conversion treatment liquid and a unichromate liquid and a colored chromate liquid having the following compositions.

[Comparative Example 1] Cr, (SO4) $ 10 t/I
Na=SiFe2pHNOs
f3 p [Comparative Example 2] Crt (504) s 10 r /
INa, 5ins 10 #HNOa
8゜[Comparative Example 3] Crt(SO4)s 15 f/e
Na*510m 5 #Na, Si
F, 5 s [Unichromate solution] Cr0a 1 f/IH1S0
．． 0.8 #HNOs
10 f/1 [Colored chromate liquid] CrO35Y/(J Na2SO42g HN0.10 // The appearance of the sample on which the chemical conversion film was formed by the above method was visually observed. The results are shown in Table 1.
Conducted salt spray test specified in JIS-2371,
Corrosion resistance was investigated. The results are shown in Table 2.

Table 2 *Numbers indicate running numbers From the above results, it is found that the taming plates treated with the chemical conversion treatment solution of the present invention not only have a good appearance but also have high corrosion resistance.

Claims (1)

[Scope of Claims] 1. A chemical conversion treatment liquid characterized by containing trivalent chromium ions, silicate, fluoride, and acid. 2 The concentration of trivalent chromium ions is 0.1 to 10 g/l,
The concentration of silicate is 0.1-20g/ as silicate ion.
l, the concentration of fluoride is 0.1 to 10 as fluorine ions
The chemical conversion treatment liquid according to claim 1, wherein the acid concentration is 0.5 to 20 g/l. 3. The chemical conversion treatment liquid according to claim 1 or 2, which contains an acidic mordant type or mordant type dye at a concentration of 0.05 to 2 g/l.