JP2003183846A - Phosphate treatment solution, condensate, and treatment process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a phosphate treatment solution containing a minimum amount of an accelerator while enabling sufficiently uniform phosphate treatment. <P>SOLUTION: The phosphate treatment solution is an acidic aqueous solution for phosphate treatment of metal surfaces. The solution has a pH of 2.5-3.6 and continues to contain 0.3-5 g/L zinc (II) ion, 3-50 g/L phosphate ion calculated as PO<SB>4</SB><SP>3-</SP>, 0.05-2.5 g/L free, ionic or bound hydroxylamine and 0.02-0.18 g/L at least one organic nitrogen compound selected from ionic m- nitrobenzenesulfonate, nitroarginine, nitroguanidine and organic N-oxides for a period accounting for at least 90% of the treatment time. Here, the mass ratio of the phosphate ion to zinc ion is 3.7-30. A condensate is used for preparing the aqueous solution. A treatment process uses this aqueous solution. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a phosphating solution,
Concentrated liquid therefor and a method for phosphating a metal surface. The phosphate treatment of the present invention is a film-forming phosphate treatment, which produces a crystalline metal phosphate coating that adheres to the metal surface. The coating improves corrosion resistance and enhances adhesion of the coating to the metal surface, especially in combination with subsequent coating.

[0002]

The present invention is a further development of the phosphate treatment method described in WO 95/07370. This reference uses an acidic phosphating aqueous solution containing zinc ion, manganese ion and phosphate ion, and hydroxylamine or a hydroxylamine compound and / or m-nitrobenzenesulfonic acid or a water-soluble salt thereof as a promoter. A method of phosphating a metal surface, the metal surface being free of nickel, cobalt, copper, nitrite, and halogen oxo anions, 0.3-2 g / L Zn (II) Ion, 0.
3-4 g / L Mn (II) ions, 5-40 g / L phosphate ions, 0.1-5 g / L free, ionic or bound forms of hydroxylamine, and / or 0.2
Characterized in that it is contacted with a phosphating solution containing ~ 2 g / L of m-nitrobenzene sulphonate ion and 0.5 g / L or less of nitrate ion and having a Mn content of at least 50% of the zinc content. .

Further details regarding this relevant prior art will be found in that document.

[0004]

The phosphating solution contains only a minimal amount of promoter and nevertheless the material actually used is sufficiently homogeneous, even when using an aged phosphating solution. Phosphating (pho
sphating process) is required.

[0005]

According to a first aspect of the present invention, there is provided an acidic phosphate treatment aqueous solution for a metal surface, which has a pH of 2.5 to 3.6 and a treatment time ( operating
During at least 90% of the time), the following components 0.3-5
g / L zinc (II) ion, 3 to 50 g / L of PO
₄ calculated phosphate ions as ^3-, 0.05 to 2.5
g / L hydroxylamine in free, ionic or bound form, and one or more selected from 0.02-0.18 g / L m-nitrobenzenesulfonate ion, nitroarginine, nitroguanidine and organic N-oxides. And a phosphate treatment solution containing a phosphate ion / zinc ion mass ratio of 3.7 to 30.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The conditions under which a phosphating solution must contain the above components "for at least 90% of the treatment time" should be understood as follows: During phosphating , The concentration of active ingredients is reduced. This is especially true for accelerators, such as hydroxylamine, which on the one hand are consumed by chemical reactions with hydrogen produced on the metal surface and on the other hand spontaneously decompose. Therefore, the content of promoter decreases during phosphating.
Even when the bath is allowed to stand, the promoter content can be reduced due to spontaneous decomposition. Unless supplemented with appropriate accelerators,
Accelerator content can fall below the minimum actually required. However, this is acceptable unless the metal surface is contacted with the phosphating solution. Thus, in prior art phosphating treatments, the promoter content may remain in the range of values of the inventive treatment for a short period of time. However, the treatment of the present invention differs from the treatments of the prior art in that it deliberately maintains the promoter concentration within the stated range even when the metal surface is phosphated. This
Expressed by the statement that the concentration of the accelerator and of the other active substances mentioned above are within the stated ranges for at least 90% of the treatment time.

At the stated pH values, the phosphate ions have only a small fraction of the tertiary phosphate (PO ₄
^3- )) and most of them exist in the form of primary phosphate ion (H ₂ PO ₄ ) ⁻ and secondary phosphate ion (HPO ₄ ) ²⁻ together with free phosphate. There is. However, for purposes of calculating content, phosphate and all phosphate ions are treated as being present in the form of the tertiary phosphate ion.

Due to its acid-base equilibrium, at the pH values stated, hydroxylamine is present in part in free amine form and partly in protonated form.
Therefore, it is immaterial whether hydroxylamine is used in the free base or salt form. When hydroxylamine is used in salt form, sulfates and primary phosphates are particularly suitable. Hydroxylamine can also be present in the form of compounds which release hydroxylamine in the stated pH range. Examples of such compounds include acetaldehyde oxime and acetoxime (WO 96/16204).

The above-mentioned organic nitrogen compounds and the forms in which they are used in phosphating solutions are known in the prior art: for example m-nitrobenzene sulphonate, DE 199 from WO 95/07370 and references cited therein.
39519 to nitroarginine, DE 196346
85 to nitroguanidine, and DE 1973397
8 to organic N-oxides.

When organic N-oxides are used as the organic nitrogen compound, pyridine N-oxide, 2-methylpyridine N-oxide, 4-methylpyridine N-oxide, morpholine N-oxide and N-methylmorpholine N-oxide. Preference is given to choosing from oxides.

One embodiment of the phosphating solution of the present invention is characterized in that it further contains 0.7-5 g / L of nitrate ions. Nitrate is a co-promoter (co-
Acts as an accelerator and forms a coating format
improve n). In the phosphating of galvanized steel, the chloride ion content (chloride cont
ent) is recommended not to exceed 100 mg / L. Otherwise, white flake on the galvanized steel (white f
laws) (pinhole) may occur. However, the chloride ion content of the phosphating solution is only monitored at best and rarely in practice, so when phosphating galvanized steel, the nitrate ion concentration of the phosphating solution is concentration) to 0.
It is recommended to keep below 5 g / L. In that case,
Even if the chloride ion content exceeds 50 mg / L, the formation of white pinholes can be avoided.

The phosphating solution further comprises 0.001
~ 3 g / L free and / or complex fluoride ion (complex f
luoride ions), of which free fluorine ions (fr
The ee fluoride ions) are preferably 0.8 g / L or less. As a result, the phosphatability of hot dip galvanized steel, and especially of aluminum and its alloys.
y) is improved. However, relatively high free and / or complex fluoride ion content can lead to flaws. Free fluoride ions are ions that exist in hydrated form in aqueous solution. They are in the form of hydrofluoric acid,
Alternatively, it can be used in the form of a soluble fluoride such as sodium fluoride, potassium fluoride or ammonium fluoride. Complex fluoride ions are understood as being anions in which two or more fluorine atoms are bonded to the central atom. Suitable central atoms are, in particular, boron, silicon, titanium and zirconium. Hexafluorosilicate ions are particularly preferred. The complex fluoride ion can be introduced into the phosphating solution in the form of free acid or water-soluble salt.

As is generally known in the field of phosphating, the presence of manganese and / or nickel ions in the phosphating solution further improves the corrosion resistance and paint adhesion of the crystalline zinc phosphate coating. Is improved.
In such a case, mixed metal phosphate containing not only zinc but also these metal ions is produced. Therefore, within the scope of the present invention, the phosphating solution further comprises:
0.2-4 g / L manganese (II) ion and 0.0
It is preferable to contain one or both of nickel (II) ions of 5 to 2.5 g / L. The presence of nickel ions is undesirable from a wastewater perspective. Therefore, the phosphating solution preferably does not contain nickel ions. However, it is possible to remove nickel ions from the phosphate-treated wastewater to a level well below the legal wastewater limit by suitable membrane filtration or ion exchange treatments. Therefore, when such a plant is available, the phosphating solution preferably contains both manganese and nickel ions.

Hydroxylamine and 1 as accelerators
The combination according to the invention with the above organic nitrogen compounds makes it possible to achieve a lower promoter content compared to the promoter content in the phosphating solution which is customary in the prior art. For example, the phosphating solution may contain hydroxylamine in free, ionic or bound form at a concentration of 0.05-0.75 g / L. This makes phosphating less expensive and, in particular, facilitates wastewater treatment. In particular, phosphating problems caused by relatively high concentrations of accelerator degradation products can be avoided. When combining promoters in the present invention, it is preferred to link the concentrations of the individual promoters: the higher the concentration of one promoter, the lower the concentration of the other promoter selected. Therefore, when using the minimum concentration of hydroxylamine,
The organic nitrogen compound is preferably present at the maximum concentration.
On the other hand, it is not necessary to use the two promoters together at the maximum concentration according to the invention. Therefore, the total of the hydroxylamine concentration and the organic nitrogen compound concentration in the phosphating solution is 0.23 to 1 g / L, particularly 0.23 to 0.9 g / L.
It is preferably L.

The individual components in the phosphating solution are preferably present in the following concentrations: zinc ion 0.5-2
g / L, manganese ion 0.5 to 1.5 g / L, nickel ion 0.1 to 1.5 g / L, phosphate ion 10 to 2
0 g / L, nitrate ion 0.7-2 g / L. The pH of the phosphating solution is preferably adjusted within the range of 3 to 3.4. Phosphating solutions are not only characterized by indicating the concentration of the individual components, but are often characterized by the parameters "free acid" and "total acid". These terms are known to those of ordinary skill in the art. The "free acid" can be quantified, for example, by diluting a 10 mL bath sample to 50 mL with water and titrating with 0.1 N sodium hydroxide solution to pH 3.8. mL
The amount of sodium hydroxide consumed at gives the free acid content at the point value. The total acid content at point values can be determined in a similar manner by titrating the bath sample to pH 8.5. The free acid is preferably in the range 0.3 to 1.5 points and the total acid is preferably in the range 15 to 30 points.

In the field of phosphating it is common to prepare phosphating solutions by diluting the appropriate concentrates with water, rather than by dissolving the individual components in water. . Concentrates are also commonly used to replenish phosphating solutions with actives. Accordingly, the present invention is, in a further aspect, an aqueous concentrate for preparing or supplementing a phosphating solution, wherein the aqueous concentrate is water and the concentrate: water mass ratio is from 1: 5 to 1: 1. Three
It relates to an aqueous concentrate which, when diluted to 0, gives the above-mentioned phosphating solution.

In a further aspect, the invention relates to steel, galvanized steel, zinc alloy plated steel, aluminum plated steel,
A method for phosphating a metal surface selected from aluminum alloy-plated steel, aluminum, and an aluminum alloy in which at least 50% by atomic percentage is aluminum, the metal surface being treated with the phosphoric acid at 30 to 70 ° C. And a method of contacting with a salt treatment solution for 1 to 8 minutes. The treatment time is preferably in the range of 2 to 4 minutes. The phosphating solution preferably has a temperature of 40-55 ° C.

The method of phosphating according to the invention comprises, in particular, a metal surface selected from aluminum-plated steel, aluminum alloy-plated steel, aluminum and aluminum alloys in which at least 50% by atomic percentage is aluminum.
It is preferably used alone or together with the surface of steel, galvanized steel or galvanized steel, for phosphating. The method does not cause the phosphating problem on the aluminum surface, which can be caused as a result of its degradation products by higher concentrations of organic nitrogen compounds, even when using an aged bath. Therefore, the present phosphating method is particularly suitable for phosphating automotive bodies containing aluminum or aluminum alloys alone or together with steel and / or galvanized steel.

[0019]

EXAMPLES Test plates of the following materials were used in the tests: cold rolled steel (CRS), electrolytic galvanized steel (EG), hot dip galvanized steel (HDG) and aluminum alloy AC120 which are commonly used in the automotive sector. The test plate is subjected to alkali cleaning in the usual manner in the automobile industry (Ri
doline (R) 1559 Cleaner (Henkel
KGaA), 2% in water, 5 minutes) and activated with a suspension containing titanium phosphate (Fixodine (R) C9112).
(Henkel KGaA), 0.1% in deionized water,
1 min) and then phosphating with one of the following phosphating solutions: Accelerator content and parameters (“T” at phosphating solution temperature = ° C., free acid = “FS” at point, coating mass = “SG” at g / m ² ) are detailed in each table. It is shown. The phosphate treatment time was 3 minutes.
Then, the test plate was washed with water and dried. The phosphate treatment results were visually evaluated. The mass of the phosphate coating with respect to the area (coating mass) was quantified by dissolving the phosphate coating and measuring the mass of the test plate before and after the dissolution of the coating.

[0020]

[Table 1]

Tests and Comparative Tests Examples 1-3 : Phosphate Treated Solution C

[0022]

[Table 2]

Example 4 : Phosphating solution B

[0024]

[Table 3]

The visual evaluation of Examples 1 to 4 gave a good, unbroken film appearance. The coating mass was within the technically desirable range. Therefore, the phosphating solution of the present invention produces good phosphating results despite the low promoter concentration.

Example 5, Comparative Example 1 : Mixture of Aged Phosphating Solution A and Fresh Phosphating Solution B For this test, used in an automotive phosphating plant, concentrated m -Aged phosphating solution A was used, which exhibits a black color due to nitrobenzene sulphonate decomposition products. Comparative Example 1: Aged Phosphate Treatment Solution A: Fresh Phosphate Treatment Solution B Mixing Ratio = 1: 1

[0027]

[Table 4]

Visual evaluation gave only a partial test plate and thus gave poor phosphating. Example 5: Aging Phosphate Treatment Solution A: Fresh Phosphate Treatment Solution B Mixing Ratio = 1: 6

[0029]

[Table 5]

Visual evaluation gave a uniform, unbroken phosphate coating.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jens Kremer             Germany, 40225 Dusseldorf,             Birkenhof 18 (72) Inventor Patrick Doroniou             Germany, 92700 Colombes / Frank             Reich, 5th Tilly F-term (reference) 4K026 AA02 AA09 AA12 AA13 AA22                       BA03 BB06 BB08 CA13 CA23                       CA28 CA32 CA33 CA37 DA03                       DA13 EA08

Claims (10)

[Claims] 1. An acidic phosphating aqueous solution for metal surfaces, having a pH of 2.5 to 3.6 and containing 0.3-5 g of the following components for at least 90% of the treatment time: / L of zinc (II) ions, the 3 to 50 g / L, phosphate ions, calculated as _PO ^{4 3-,} of 0.05～2.5G / L, free hydroxylamine ionic or bound form, and 0 0.02 to 0.18 g
/ L of m-nitrobenzene sulfonate ion, nitroarginine, nitroguanidine and one or more organic nitrogen compounds selected from organic N-oxides, and a phosphate ion / zinc ion mass ratio of 3.7 to 30. Is a phosphating solution. 2. The organic N-oxides are pyridine N-oxide, 2-methylpyridine N-oxide, 4-methylpyridine N-oxide, morpholine N-oxide and N-.
The phosphate treatment solution according to claim 1, which is selected from methylmorpholine N-oxide. 3. The phosphate treatment solution according to claim 1, which further contains 0.7 to 5 g / L of nitrate ions. 4. The composition according to claim 1, which further contains 0.001 to 3 g / L of free and / or complex fluorine ions, of which free fluorine ions are 0.8 g / L or less. Phosphating solution. 5. Further, 0.2 to 4 g / L of manganese (I
I) ions and 0.05 to 2.5 g / L nickel (I
I) one or both of the ions are contained.
The phosphate treatment solution according to any one of 1. 6. The phosphating solution according to claim 1, wherein the concentration of hydroxylamine in free, ionic or bound form is 0.05 to 0.75 g / L. 7. The phosphating solution according to claim 1, wherein the total of the concentration of hydroxylamine and the concentration of organic nitrogen compound is 0.23 to 1 g / L. 8. An aqueous concentrate for preparing or replenishing a phosphating solution, which is water, such that the concentrate: water mass ratio is from 1: 5 to 1:30. An aqueous concentrate which, when diluted, gives the phosphating solution according to any of claims 1-7. 9. Steel, galvanized steel, zinc alloy plated steel,
A method of phosphating a metal surface selected from aluminum-plated steel, aluminum alloy-plated steel, aluminum, and an aluminum alloy in which at least 50% by atomic percentage is aluminum.
A method comprising contacting the phosphating solution according to claim 1 at ˜70 ° C. for 1 to 8 minutes. 10. A metal surface selected from aluminum-plated steel, aluminum alloy-plated steel, aluminum, and aluminum alloys having at least 50% aluminum in atomic percentage, alone or in steel, galvanized steel or zinc alloy-plated steel. The method of claim 9 wherein the phosphating solution is contacted with the surface.