DE3023479A1 - PHOSPHATING PROCESS - Google Patents

Description

METALLGESELLSCHAFT Frankfurt / M., June 18, 1980 Aktiengesellschaft DrOz / HGa

6000 Frankfurt / M.

Prov. No. 8576 M.

Phophatization process

The invention relates to a method for producing phosphate coatings on metal surfaces of iron and Steel using an acidic phosphating solution containing nitrate accelerated zinc and manganese ions at elevated temperatures in the immersion process.

It is known to dipping iron and steel with phosphating solutions in order to form a phosphate layer that contain zinc, hydrogen, nitrate and phosphate ions. The phosphate layer that on produced in this way are particularly suitable as lubricant carriers for cold forming. With a After-treatment with anti-rust oil, they lead to corrosion resistance, the galvanically applied metal cover

.15 zinc, cadmium, etc.

In particular for corrosion protection with oils and the facilitation of cold forming, such as. B. cold extrusion, layers with a higher applied weight, e.g. B. in the range between 8 to 30 g / m, required. In some cases, the demands on corrosion protection are particularly high. This can be achieved by increasing the layer weight. An increase in the layer weight would also occur in cold forming allow higher degrees of deformation.

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The separation of thick zinc phosphate layers can according to DE-AS 12 87 412 and US-PS 32 68 367 by Bringing iron and steel into contact with a nitro-accelerated acidic zinc phosphating solution Addition of polycarboxylic acids in which the at least one carboxyl group adjacent carbon atom is a hydroxyl, Amino or carboxyl group can be achieved. This phosphating solution can also contain additives such as nickel, Contains cobalt, lithium, bismuth and manganese in low concentrations of less than 0.5 g / l. You activate favor the metal surface to be phosphated and the deposition of zinc phosphate layers.

The deposition of such thick phosphate layers for The solution to the problem described has the disadvantage that the consumption of chemicals is comparatively high. Furthermore, in some cases, e.g. B. depending on the type of alloy of the workpiece to be phosphatxerenden, the generation limits can be imposed by thicker layers. 20th

The object of the invention is to provide a phosphating process which does not have the disadvantages outlined has, in particular is universally applicable, manages with a low chemical requirement and is of higher quality Phosphate layers leads.

The object is achieved in that the method of the type mentioned is designed according to the invention in such a way that the metal surfaces are brought ^{into contact at treatment temperatures of 50 to 98 °} C. with a phosphating solution which contains at least 0.6 g / l manganese ions,

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in which the weight ratio

P ₂ O ₅ : NO ₃ = 1: (0.3 Ms 3.0)

Total P ₂ 0 ₅ : Free PgO ^ = 1: (0.25 to 0.70)

Mn: Zn = 1: (22 Ms 0.2) is land

which when incorporated has a total acid score of at least 20 points.

Such a process leads to zinc-manganese-phosphate layers which, with comparable layer thicknesses, are zinc-phosphate layers are superior in terms of corrosion protection and cold forming properties. Preferably, the metal surfaces with a Phosphating solution brought into contact in which the Manganese ion content is at least 1 g / l. This results in a higher, the aforementioned properties Even better manganese phosphate content achieved in the layer.

Optimal results with regard to the layer quality are achieved if in a further preferred embodiment according to the invention, the metal surfaces are brought into contact with a phosphating solution, in which the weight ratio of Mn: Zn is equal

"25 1: (0.8 to 12).

It was also found that the proportion of manganese phosphate increases their suitability for preparation for cold forming improves in the layer. Manganese ion contents in the phosphating solution above the range of 1: 0.2 lead to not closed, holey layers.

Within the required limits, baths with e.g. 80 total acid points can be composed as follows:

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Zn g / 1 I.
I. 11.7 6.08 33.3 10.3 Mn g / 1 4.28 2.18 3.11 20.2 P ₂ O ₅ g / 1 33.6 28.9 19.3 20.0 NO ₃ g / 1 10.1 8.68 57.7 55.0 P ₂ O ₅ ZNO ₃ 1: 0.3 1: 0.3 1: 2.99 1: 2.74 Total P ₂ 0 ₅ ; free S-P ₂ O ₅ 1: 0.26 1: 0.69 1: 0.26 1: 0.42

Mn: Zn 1: 2.7 1: 2.8 1: 10.7 1: 0.5

The total acid number can be determined by titrating a 10 ml bath sample with 0.1 η NaOH against phenolphthalein Determine the indicator until it changes from colorless to pink.

To activate the steel or iron surfaces to be phosphated Nickel and / or cobalt and / or copper ions and the like can be added to the bath. Appropriately, these metal ions are in a concentration of, for. B. 0.02-0.10 g / l added to the bath. The anion belonging to the metal ions can, for. B. nitrate or sulfate.

If a further increase in the layer weight is desired, it is advisable to bring the metal surfaces into contact with a phosphating solution that contains _{simple and / or complex fluorides such as NaF, NaHF 2} and / or Na _{2 SiFg.}

If desired, a certain reduction in the layer weight can be brought about when the phosphating bath is used condensed phosphates are added.

It is in the nature of a nitrate-accelerated phosphating bath, that as a result of the throughput of metal surfaces, iron (II) ions accumulate in the bath and the

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Total acid score decreases. To a deterioration To counteract the phosphating result, a supplement of the phosphating bath is necessary.

Particularly advantageous results are achieved if the phosphating bath is used in terms of the components Zinc, manganese, phosphate and nitrate ions in weight ratio

P ₂ O ₅ : NO ₃ = 1: (0.3 to 2.0) total P ₂ 0K: free P ₂ 0, = = 1: (0.3 to 0.8)

Mn: Zn = 1: (2 to 80)
added.

The workpieces to be phosphated should be free of grease and scale or be rustproof. The degreasing can be done e.g. B. by means of aqueous, alkaline, surface-active substances containing Cleaner done.

Descaling is expediently carried out using sulfuric acid or hydrochloric acid.

After cleaning and / or pickling, the workpieces should be rinsed well with water.

Before phosphating, the workpieces can be pre-rinsed in a known manner, for example with titanium orthophosphate or manganese orthophosphate suspensions in water, in order to form finely crystalline layers. It has proved in practice that in some cases, even a pre-rinse with 50 to 98 ⁰ C hot water activates the surface.

^{The phosphating bath is operated between 50 and 98 °} C. depending on the type of workpiece, the alloy and the type of application. It has been found that an immersion time of 5 to 15 minutes is sufficient for most applications.

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As mentioned, due to the nitrate acceleration, iron (II) will accumulate in the phosphating bath in the course of the throughput. This does not affect the way the bath works. In special cases, e.g. B. at high nitrate concentrations or at high bath temperatures, however, it can also happen that the bath remains iron-II-free as a result of the oxidation of fur to FeIII. This also does not affect the way the bath works. The addition of the bath is expediently carried out on
Constancy of the total acid score.

The layer weight of the zinc-manganese-phosphate layers obtained depends on the composition of the phosphating bath and alloy of the workpiece to be treated normally between about 5 and about 30 g / m 2.

After the phosphating, it is rinsed with water, if necessary aftertreated and, if necessary, dried.

For corrosion protection, for. B. post-treated with chromic acid solutions, followed by treatment with anti-corrosion oil emulsions. For cold forming
can the workpieces z. B. be treated with soap solutions.

The workpieces treated in this way are those with conventional nitrate-accelerated zinc phosphating systems
superior to treated workpieces in terms of corrosion protection and cold forming properties.

The invention is illustrated by way of example and in greater detail on the basis of the following examples.

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Example 1 ,

Steel bolts were "treated as follows:

a) pickling in 15% sulfuric acid with an addition of a pickling inhibitor "at 60 ⁰ C and an immersion time of 10 minutes Id) rinsing with cold water c) rinsing with 60 ⁰ C hot water

d) 10 screws each were phosphated in the phosphating baths A, B and C for 10 min.

Bad A 0.03 1: 1.06 Bad B 0.03 Bad C Zn phosphate 24.8 Zn phosphate 20.3 Zn-Mn-pho sphat Zn g / l 20.7 26.3 1: 0.40 26.8 39.6 12.7 Mn g / l - Total Acid Points 75 - - 75 10.8 Ni g / l P ₂ O ₅ : NO ₃ ⁰ C 98 1: 1.95 0.03 P ₂ O ₅ g / l Total PpO, -: Layer weight g / m ^ 24.9 19.4 NO ₃ g / l free S-P ₂ O ₅ 1: 0.36 37.9 Mn: Zn - 70 Bath temperature 75 1: 1.95 18.6 1: 0.36 1: 1.2 75 15.1

e) Rinsing with cold water f) Rinsing in fully demineralized water with an additive

of 0.5 g / l sodium ^{dichromate at 80 0} C g) treatment with a 13 % lgen emulsion of a

Corrosion protection oil at 60 ⁰ C h) oven drying at 70 ⁰ C. 35 The screws were then tested in the salt spray test according to DIN 50021 SS, for each of the three methods A, B and C were

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10 screws checked. After 72 hours of testing, 50 % of the screws in methods A and B were rusted; in method C all 10 screws were not attacked, although the layer weight is lower than in methods A and B.

Example 2

Cold extrusions were treated as follows: 10

a) Pickling in 15% hydrochloric acid with the addition of a pickling inhibitor at room temperature and a treatment time of 10 minutes

b) Rinse with cold water

c) Rinsing with hot water ^{at 75 ° C}

d) 100 cold extruded parts each were treated by immersion in phosphating baths D and E for 10 minutes.

Zn g / l I.
I. Mh g / l Ni g / l P ₂ O ₅ g / l Bath temperature ⁰ C NO ₃ g / l Total acid points P ₂ O ₅ : NO ₃ Total P ₂ 0 ₅ : £ reies-Po0 ₅ Mn: Zn

Bad D Bath E. Zn phosphate Zn-Mh-pho sphat 20.5 18.7 - 5.8 0.2 0.03 24.9 19.4 29.3 37.9 80 70 1: 1.2 1: 1.95 1: 0.53 1: 0.36 - 1: 3.2 98 75 18.3 17.5

Layer weight g / m

e) Rinse with cold water

f) treatment in a 5% sodium soap at 73 ^° C. and an immersion time of 5 min

1300627021t

g) Drying by means of its own heat in the air.

The parts were reverse extrusion molded into sleeves. In the case of the parts that have been treated in bath D ″, the sleeves had grooves to about 80% and the surface had a shiny metallic appearance. In the case of the parts that have been treated in bath E, no grooves could be found and the surface was gray, which indicates a considerable residual phosphate layer

Example 3

Steel sheets of the USt 1405 m quality were treated as follows:
15th

a) Cleaning in a strongly alkaline aqueous cleaner at 95 ^° C. and an immersion time of 15 minutes

b) Rinse with cold water

c) pickling in H ₂ SO ^, 20% strength with the addition of a pickling inhibitor, at 65 ⁰ C and an immersion time of 10 min

d) Rinse with cold water

e) Phosphating at 75 ^° C. and an immersion time of 10 minutes in baths P and G

f) Rinse with cold water.

The composition of baths F and G is as follows. listed in the table. The total acid score of the baths was 90 points in each case. ■

ρ After a throughput of 0.2 m sheet surface per liter of bath solution, the baths were kept constant with the supplementary concentrates listed in the table added.

At the beginning of throughput and after throughput of 4 m The steel surface per liter of bath solution was used as sample sheets

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branched off for determining the layer weight and for the corrosion test in the salt spray test according to DIN 50021 SS. The metal sheets for the corrosion test were treated beforehand with a 15% strength emulsion of an anti-corrosion oil and then ^{dried at 70 °} C. in the oven. Tabel

g / l % Bad F 0 % Bad G Zn g / l % 22.3 0 % 22.6 Mn g / i % 2.1 8.11 Ni g / l % 0.04 0.03 P ₂ O ₅ g / l % 29.8 24.3 NO ₃ Total Acid Score 31.6 50.4 Total PgOc: 90 90 free S-P ₂ O ₅ P ₂ O ₅ : NO ₃ 1: 0.40 1: 0.50 Mn: Zn Beginning 1: 1.06 1: 2.07 after 4 m * 1: 10.6 1: 2.79 Supplementary Supplementary concentrate concentrate Zn for bathroom F for Bad G Mn 12.6 11.8. Ni 0.31 1.88 P ₂ O ₅ 0.03 0.03 NO ₃ 25.8 22.9 Total P ₂ 0 ₅ : 11.4 17.7 free S-P ₂ O ₅ P ₂ O ₅ : NO ₃ 1: 0.41 1: 0.55 Mn: Zn 1: 0.44 1: 0.77 Layer weight 1: 40.6 1: 6.3 Layer weight 15.6 g / m ² 18.2 g / m ² Rust after 72 hours - / 1 16.2 g / m ² 19.0 g / m ² test according to DIN I. Salt spray at the beginning 50021 pp after 4m / 0 % 0 %

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It can be clearly seen that the phosphating baths too, thanks to the preferred configuration of the supplement

after a throughput of 4 m / 1 lead to layers that have retained their good properties.

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Claims (5)

Claims M. Process for the production of phosphate coatings on metal surfaces of iron and steel using an acidic phosphating solution containing nitrate-accelerated zinc and manganese ions at elevated temperatures in the immersion process, characterized in that the metal surfaces are in contact with a phosphating ^{solution at treatment temperatures of 50 to 98 ° C} which contains at least 0.6 g / l manganese ions,
in which the weight ratio P ₂ O ₅ : NO ₃ = 1: (0.3 to 3.0) Total-P ₂ 0 ₅ : free-P ₂ 0 ₅ = 1: (0.25 to 0.70) Mn: Zn = 1: (22 to 0.2) is and which in the incorporated state a total has an acid score of at least 20 points. 2. The method according to claim 1, characterized in that the metal surfaces are brought into contact with a phosphating solution in which the content of manganese ions is at least 1 g / l. 3. The method according to claim 1 or 2, characterized in that the metal surfaces are brought into contact with a phosphating solution in which the weight ratio of Mn: Zn = 1: (0.8 to 12). 130082 / Q211 4; Process according to Claim 1, 2 or 3, characterized in that the metal surfaces are brought into contact with a phosphating solution which contains simple and / or complex fluorides such as NaF, NaHF ₂ and / or Na ₂ SiFg. 5. The method according to claim 1, 2, 3 or 4, characterized in that the phosphating bath with regard to the components zinc, manganese, phosphate and nitrate ions in a weight ratio P ₂ O ₅ : NO ₃ = 1: (0.3 to 2.0) Total P ₂ 0 ₅ : Free PgO ^ = 1: (0.3 to 0.8) Mn: Zn = 1: (2 up to 80)
15th added. 130062/0211