METHOD FOR PRODUCE A PHOSPHATED WIRE COATED WITH A CORROSION INSULATOR, IN PARTICULAR A STEEL WIRE

Description

[0001] The invention relates to a method for producing a phosphated wire, in particular a steel wire, coated with a corrosion inhibitor, in which the corrosion inhibitor is applied to the previously phosphated wire, wherein an emulsion and / or dispersion containing a surfactant and an oil as the disperse phase is applied as the corrosion inhibitor.

[0002] EP 3 305 882 A1 discloses a water-based lubricant and coating agent used for plastic metal forming and having a water content of 3 to 50 wt.%. It contains a lipophilic lubricant component and / or a splittable solid lubricant dispersed in water and containing a fatty acid component.

[0003] WO 2009 / 095374 A1 describes a method for preparing metallic workpieces for cold forming by applying a lubricant layer to a metallic surface, wherein the lubricant layer is formed by contacting the surface with an aqueous lubricant composition containing at least two waxes with different properties and an organic polymeric material.

[0004] WO 88 / 07069 describes an anti-corrosive, storage-stable oil-based composition which is emulsified and intended for application to solid metal substrates.

[0005] It is well known that metal surfaces can be coated with a metal phosphate conversion layer through chemical reaction with phosphate solutions. This conversion layer serves as a primer and carrier layer for forming lubricants. Although the phosphatization of metal surfaces itself has a certain anti-corrosive effect, corrosion can still occur during extended storage periods and under unfavorable conditions.

[0006] Furthermore, it is known through experience that the corrosion resistance of phosphated metals can be sufficiently improved by applying a layer of oil. It has proven particularly advantageous that the corrosion protection is not lost even when the metal surface is subjected to mechanical stress.

[0007] However, the handling of metal workpieces whose surface has been coated with oil is problematic, among other things because oil dripping from the metal workpieces causes contamination and makes handling of the metal workpieces unpleasant.

[0008] The invention is based on the object of creating a method of the type mentioned at the outset which is easier to handle.

[0009] According to the invention, this object is achieved in that an active component of the corrosion inhibitor, which comprises a disperse phase of the emulsion and / or dispersion, has the following composition: Oil: 5 to 75 wt%, surfactant: 25 to 95 wt%.

[0010] The method according to the invention makes it possible to provide a surface of a metallic wire with such a small amount of oil that the surface is completely covered with the oil to achieve corrosion protection, but no excess oil is arranged on the surface, so that the oil does not run off the surface by itself.

[0011] It was also found that when drawing wire, especially steel wire, the drawing agent adheres better to wire coated with the corrosion inhibitor than to uncoated phosphated wire. Furthermore, unlike previously, no dust forms during the drawing process after leaving the drawing die, and no drawing agent residue flakes off. This advantageously reduces contamination of the environment in which the wire is drawn. Furthermore, the particularly uniform coating of the wire surface achieved with this process, particularly in subsequent processing steps, allows for better metal processability and a more uniform component geometry.

[0012] Furthermore, it has surprisingly been shown that phosphated wire arranged in rings, especially steel wire coated with the corrosion inhibitor according to the invention, can be compressed significantly more tightly than wire not coated with the corrosion inhibitor. This has the advantage of saving storage and transport costs for the wire.

[0013] Another advantage is that the corrosion inhibitor contains no heavy metals or other harmful substances, making it relatively easy to handle and environmentally friendly for occupational safety and hygiene. Furthermore, it can be manufactured exclusively from renewable raw materials.

[0014] The process is particularly suitable for preparing the wire for subsequent forming, especially cold forming. It has proven particularly advantageous when used with steel wire. With regard to forming, one advantage of the process is that, unlike conventional corrosion inhibitors, the oil does not coat the wire with an oily, greasy or sticky layer. Such a layer makes handling the coated wire difficult and time-consuming, as the wire cannot be readily passed on and may require repeated repackaging. The oil expediently has a viscosity of 200 to 800 mPa*s, preferably 300 to 700 mPa*s. The oil is preferably a mineral oil, which particularly preferably has a neutral reaction. Purified paraffinic oil or rapeseed oil has proven particularly suitable for producing the corrosion inhibitor.

[0015] The corrosion inhibitor may contain a wax. The wax is preferably a mineral, synthetically produced, or naturally occurring organic compound with a melting point ≥ 40 °C, which in the liquid state, particularly in the molten state, exhibits the properties of an oil and is preferably miscible in the molten state with a natural or mineral oil, e.g., rapeseed oil or paraffin oil.

[0016] In one embodiment of the invention, the wax meets at least one of the following requirements: a) Depending on the mixing ratio, after solidification of a mixture of one or more waxes with a natural or mineral oil at a temperature ≥ 40 °C, thixotropy occurs until the oil is completely immobilized. b) The wax is inherently hydrophobic, especially when it is not mixed with the oil and when it is present as a coating on a metal surface.

[0017] In one embodiment of the invention, the wax a) a mineral wax, preferably montan wax or ozokerite (ceresin), b) a mineral oil wax, a synthetic or partially synthetic wax, preferably a polyalkylene wax, e.g. polyethylene wax, propylene wax, (iso)butylene wax and / or their oxidates, paraffinic wax (paraffins) as a long-chain aliphatic compound and / or a Fischer-Tropsch wax, c) a natural wax, preferably beeswax, carnauba wax, a long-chain, essentially aliphatic alcohol or a fatty acid with at least 16 carbon units (e.g. cetyl or stearyl alcohol) or mixtures thereof (e.g. cetylstearyl alcohol), and / or an ester produced from these (e.g. cetyl stearate) or their amides as so-called amide waxes (e.g. distearylethylenediamide) or d) a mixture of at least two of the aforementioned waxes.

[0018] In one embodiment of the invention, a continuous phase of the emulsion and / or dispersion contains or is water, preferably deionized or distilled water. Alternatively, another substance suitable for forming a solution, emulsion, and / or dispersion with the oil or with the oil and wax, for example, white spirit, could be used to form the continuous phase.

[0019] In one embodiment of the invention, the surfactant comprises or is a water-soluble soap, preferably an alkali metal salt of a carboxylic acid. The carboxylic acid is preferably monovalent, divalent, or polyvalent. In a preferred embodiment of the invention, the carboxylic acid is a fatty acid. The carboxylic acid expediently has a chain length of at least 10 carbon atoms (C10).

[0020] Particularly suitable salts are, for example, salts of palmitic acid (hexadecanoic acid, C16), stearic acid (octadecanoic acid, C18), or sebacic acid (decanedioic acid, C10). These are inexpensive to obtain. However, the use or addition of unsaturated carboxylic acids, preferably fatty acids that also have a chain length of at least 10 carbon atoms, such as oleic acid (octadec-9-enoic acid, C18) or linoleic acid (octadeca-9,12-dienoic acid, C18), would also be conceivable.

[0021] In one embodiment of the invention, the mass ratio of the oil to the surfactant is 0.7:1 to 1.3:1, preferably 0.8:1 to 1.2:1.

[0022] Since the corrosion inhibitor contains relatively large amounts of surfactant and therefore tends to re-emulsify, for example upon contact with water, it has proven advantageous to dissolve any remaining excess surfactant components from the corrosion inhibitor when it coats the metallic surface in order to avoid re-emulsification of the corrosion inhibitor.

[0023] Therefore, in a particularly preferred embodiment of the invention, the surfactant is provided in such a way that it decomposes completely upon application of the corrosion inhibitor to the phosphated metal surface and subsequent drying.

[0024] Particularly when a zinc phosphate layer is applied to the metallic surface, the surfactant in the corrosion inhibitor is partially decomposed by the zinc in the zinc phosphate layer. Using an alkali stearate produces zinc stearate, which is not only advantageously water-insoluble and has hydrophobic properties, but is also used as a drawing soap during cold forming and can therefore also have a beneficial effect during subsequent cold forming. If the wire is coated with a calcium-containing phosphate layer, calcium stearate is produced in a similar manner, which is also used as a drawing soap or as a lubricant during cold forming.

[0025] The surfactant expediently comprises ammonia and / or a preferably volatile amine. The amine is preferably at least one short-chain alkyl or alkanol derivative of ammonia with a maximum of 3 linear carbon units (≤ C3), which forms water- and oil-soluble soaps with saturated and / or unsaturated fatty acids with chain lengths ≥ C10 and / or, in particular, dibasic carboxylic acids (≥ C10). An example of such a soap is ammonium stearate, which is formed from ammonia and stearic acid.

[0026] In a particularly preferred embodiment of the invention, the surfactant comprises monoethanolamine, diethanolamine, triethanolamine, and / or isopropanolamine. Advantageously, the surfactant comprising monoethanolamine, triethanolamine, and / or isopropanolamine not only exhibits surfactant properties comparable to those of alkali soaps, but also decomposes even at room temperature and particularly well at typical drying temperatures above 50°C. For example, once the surfactant comprising monoethanolamine, triethanolamine, and / or isopropanolamine has decomposed, only the oil, fatty acid, and zinc stearate, which was already formed upon application of the corrosion inhibitor to the metal surface, remain on the metal surface. These not only have a corrosion-protective effect but are also hydrophobic. The same applies to the aforementioned calcium stearate.

[0027] The use of monoethanolamine has proven particularly suitable due to its high basicity (pK B = 4.5), its good solubility in water and oil and the comparatively good thermal decomposition of its soaps.

[0028] In addition to a continuous phase of the emulsion and / or dispersion, the corrosion inhibitor comprises an active component that comprises the disperse phase.

[0029] The active ingredient advantageously comprises 5 to 75% by weight, preferably 50 to 75% by weight, particularly preferably 60 to 70% by weight of oil, preferably purified paraffin oil or rapeseed oil.

[0030] The surfactant is present in the active ingredient at 25 to 95 wt.%, preferably 25 to 50 wt.%, particularly preferably 30 to 50 wt.%. It has proven particularly advantageous to provide the surfactant at 30 to 40 wt.%, based on the active ingredient.

[0031] In one embodiment of the invention, the active ingredient contains palmitic acid and / or stearic acid in 15 to 65% by weight, preferably 20 to 40% by weight, particularly preferably 25 to 35% by weight, based on the active ingredient.

[0032] It has proven expedient to provide the amine, preferably monoethanolamine, isopropanolamine, or triethanolamine, in a concentration of at least 3%, preferably at least 4.5% by weight, based on the active ingredient. In one embodiment of the invention, the amine is provided in a concentration of at most 30% by weight, preferably at most 20% by weight, based on the active ingredient. In a preferred embodiment of the invention, the amine is provided in a concentration of at most 12% by weight, particularly preferably 10% by weight.

[0033] The active ingredient in the corrosion inhibitor is expediently present in a concentration of at least 0.25 wt.%, preferably at least 0.5 wt.%, particularly preferably at least 0.8 wt.%, with the remainder being formed by the continuous phase of the emulsion and / or dispersion. The continuous phase can be formed, for example, by water or white spirit. Particularly good results can be achieved if the active ingredient is at least 1 wt.%. In one embodiment of the invention, the active ingredient in the corrosion inhibitor is present in a concentration of at most 5 wt.%, preferably at most 3 wt.%, particularly preferably at most 2.5 wt.%. It has proven particularly advantageous for handling the corrosion inhibitor to provide the active ingredient in the corrosion inhibitor in a concentration between 1 wt.% and 1.8 wt.%.

[0034] Advantageously, concentrations within the latter values ​​prevent the wire from looking oily and releasing oil when touched, while at the same time achieving sufficiently good corrosion protection.

[0035] The corrosion inhibitor advantageously comprises 0.0125 to 3.75 wt.%, preferably 0.125 to 3.75 wt.%, particularly preferably 0.15 to 3.5 wt.%, of oil, preferably purified paraffin oil or rapeseed oil.

[0036] In one embodiment of the invention, the surfactant is present in the corrosion inhibitor at 0.0625 to 4.75 wt.%, preferably 0.0625 to 2.5 wt.%, particularly preferably 0.075 to 2.5 wt.%. It has proven particularly advantageous to provide the surfactant in the corrosion inhibitor at 0.075 to 2 wt.%.

[0037] In one embodiment of the invention, the corrosion inhibitor contains palmitic acid and / or stearic acid in 0.0375 to 3.25 wt.%, preferably 0.05 to 2 wt.%, particularly preferably 0.0625 to 1.75 wt.%.

[0038] It has proven expedient to provide the amine, preferably monoethanolamine, isopropanolamine, or triethanolamine, in a concentration of at least 0.0075 wt.%, preferably at least 0.01125 wt.%. It has proven particularly advantageous to provide the amine in the corrosion inhibitor in a concentration of at most 1.5 wt.%, preferably at most 1 wt.%. In a preferred embodiment of the invention, the amine is provided in a concentration of at most 0.6 wt.%, particularly preferably 0.5 wt.%.

[0039] In a preferred embodiment of the invention, the overall composition of the corrosion inhibitor is as follows: Continuous phase, preferably water and / or white spirit: 97 to 99.5 wt.%, preferably 98.5 to 99 wt.%, oil, preferably purified paraffin oil or rapeseed oil: 0.375 to 2.25 wt.%, preferably 0.5 to 1.125 wt.%, particularly preferably 0.6 to 1.0 wt.%, surfactant: 0.125 to 1.5 wt.%, preferably 0.25 to 0.75 wt.%, particularly preferably 0.3 to 0.65 wt.%, wherein the following components of the surfactant are preferably present in the following proportions: o Palmitic acid or stearic acid: 0.1 to 1.2 wt.%, preferably 0.2 to 0.6 wt.%, particularly preferably 0.24 to 0.52 wt.%, ∘ Amine, preferably monoethanolamine, isopropanolamine or triethanolamine: 0.0075 to 1.5 wt.%, particularly preferably 0.025 to 0.03 wt.%, in particular 0.06 to 0.08 wt.%

[0040] In one embodiment of the invention, the corrosion inhibitor is prepared before application to the wire in such a way that at least the oil, the surfactant and the continuous phase are stored separately from one another. Before application of the corrosion inhibitor, the surfactant is first dissolved in the oil and the resulting solution is then emulsified and / or dispersed in the continuous phase. By mixing the active component thus formed with the continuous phase, preferably the water, the corrosion inhibitor is ready for use, wherein the pH is optionally adjusted to 8 to 11, preferably to 8.4 to 10.5, particularly preferably to 8.7 to 9.5 by additionally adding the amine. The amount of additional amine to be added depends in particular on the hardness of the water, i.e. the sum of the concentrations of the cations of alkaline earth metals in the water forming the continuous phase.

[0041] In one embodiment of the invention, the wire is immersed in a bath of the corrosion inhibitor. Alternatively or additionally, the wire can be sprayed or misted with the corrosion inhibitor.

[0042] The wire is then removed from the bath, or the corrosion inhibitor is allowed to drip off after spraying or misting. The wire is then expediently dried, preferably at a drying temperature above 50°C, particularly preferably above 110°C, during which any remaining surfactant residues are thermally decomposed. A corrosion inhibitor film remaining on the wire after drying advantageously contains the oil and the carboxylic acid remaining from the thermal decomposition of the emulsifier, preferably a fatty acid. The fatty acid preferably has a chain length ≥ C10 and is, for example, stearic acid or palmitic acid. The carboxylic acid has a hydrophobic effect and is preferably dissolved in the oil. Since the corrosion inhibitor film contains almost no surfactant residues after drying, it can no longer re-emulsify and is thus protected from detachment from the wire.

[0043] In one embodiment of the invention, after drying, the aforementioned film is formed on the wire with a surface area of ​​0.1 to 1.5 g / m², preferably at least 0.2 to 0.8 g / m². Advantageously, the phosphated surface then completely absorbs the corrosion inhibitor and therefore does not have an oily sheen and does not readily release the corrosion inhibitor, yet is adequately protected against corrosion. Furthermore, the inherently very thin corrosion inhibitor film, being located within the phosphate layer, is well protected against abrasion by the surrounding phosphate layer.

[0044] In a further development of the invention, the wire is formed after being coated with the corrosion protection agent, preferably by cold forming.

[0045] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, which relate to the exemplary embodiments. They show: Fig. 1a phosphated metal surface in cross section, Fig. 2the phosphated metal surface after Fig. 1 in cross-section after application of the corrosion protection agent according to the invention in the state before drying, and Fig. 3 the phosphated metal surface after the Fig. 1 and 2 in cross-section after application of the corrosion protection agent according to the invention and subsequent drying. 1. Example:

[0046] A liquid corrosion inhibitor according to the invention is formed with the following composition in wt.%: Distilled water: 98,5 Paraffin oil: 1,125 Stearic acid: 0,3 Monoethanolamine: 0,075

[0047] The corrosion inhibitor is poured into a tub designed to hold a coil of phosphated steel wire wound into a ring shape. The ring is immersed in the corrosion inhibitor and then removed, allowing excess corrosion inhibitor to drip off.

[0048] Fig. 1 shows a cross-section of a steel wire 1 and a phosphate layer 2 arranged thereon in the state before coating with the corrosion protection agent.

[0049] How Fig. 2 As can be seen, immediately after the ring is removed from the bath, paraffin oil droplets 3 remain on the phosphate layer or the metal surface. In the process, zinc stearate is formed from the stearic acid by reacting with zinc, which is present in the phosphate layer.

[0050] The steel wire is then dried at 110 °C, during which a surfactant formed from the stearic acid and monoethanolamine is decomposed and the paraffin oil and zinc stearate remain on the steel wire. Fig. 3 shows that a continuous layer 4 forms on the metal surface.

[0051] Layer 4 is hydrophobic, remains firmly attached to the steel wire, and does not re-emulsify when exposed to water. It protects the steel wire against corrosion due to the continuous coating on the steel wire surface. 2. Example:

[0052] A phosphated steel wire is sprayed with a corrosion inhibitor according to the composition of Example 1, so that its entire surface is covered with the corrosion inhibitor. After spraying, excess corrosion inhibitor is allowed to drip off, and the steel wire is then treated as described above. Even with this procedure, a hydrophobic layer of paraffin oil and zinc stearate remains on the steel wire surface, protecting it against corrosion. 3. Example:

[0053] A liquid corrosion inhibitor according to the invention is formed with the following composition in wt.%: Distilled water: 98,5 Rapeseed oil: 0,5 Stearic acid: 0,2 Sebacic acid: 0,2 Monoethanolamine: 0,3 Triethanolamine: 0,3

[0054] A phosphated steel wire is coated with the corrosion inhibitor by immersion, as described above using Example 1, and then dried. Alternatively, the steel wire can be sprayed with the corrosion inhibitor as described in Example 3 and then dried. This process leaves a hydrophobic layer on the steel wire surface, consisting of rapeseed oil on the one hand and zinc stearate and / or zinc sebacate on the other, which protects the steel wire against corrosion. The corrosion inhibitor can therefore be produced from purely plant-based raw materials and is therefore particularly sustainable. 4. Example:

[0055] A liquid corrosion inhibitor according to the invention is formed with the following composition in wt.%: Distilled water: 97 Paraffin oil: 1 Montan wax: 1 Stearic acid: 0,8 Isopropanolamine: 0,2

[0056] The corrosion inhibitor is poured into a tub suitable for holding a ring of phosphated steel wire wound several times into a ring shape and heated to 65 °C. A phosphated steel wire is coated with the corrosion inhibitor by immersion as described above in Example 1 and then dried.

[0057] Alternatively, the steel wire can be sprayed with the corrosion inhibitor as described in Example 3 and then dried.

[0058] This process leaves a hydrophobic layer of paraffin oil, montan wax and zinc stearate on the steel wire surface, which protects the steel wire against corrosion.

Claims

1. Process for producing a phosphated wire, in particular steel wire, coated with a corrosion inhibitor, in which the corrosion inhibitor is applied to the previously phosphated wire, where the corrosion inhibitor applied is an emulsion or / and dispersion comprising a surfactant and, as disperse phase, an oil, characterized in that an active component of the corrosion inhibitor comprising a disperse phase of the emulsion or / and dispersion has the following composition: - oil: 5% to 75% by weight, - surfactant: 25% to 95% by weight.

2. Process according to Claim 1, characterized in that the oil applied is a paraffinic oil or rapeseed oil, preferably cleaned.

3. Process according to Claim 1 or 2, characterized in that the surfactant used is a water-soluble soap, preferably at least one salt of a carboxylic acid, preferably of a fatty acid, having a chain length of at least 10 carbon atoms.

4. Process according to any of Claims 1 to 3, characterized in that the surfactant includes a salt of stearic acid or / and of palmitic acid.

5. Process according to any of Claims 1 to 4, characterized in that the surfactant is provided such that it breaks down, preferably almost completely, on application of the corrosion inhibitor on the phosphated metallic surface and subsequent drying.

6. Process according to any of Claims 1 to 5, characterized in that the surfactant comprises an amine, preferably monoethanolamine, isopropanolamine or / and triethanolamine.

7. Process according to Claim 5 or 6, characterized in that the active component of the corrosion inhibitor has the following composition: - oil, preferably cleaned paraffin oil or rapeseed oil: 50% to 75% by weight, preferably 60% to 70% by weight - surfactant: 25% to 50% by weight - where the constituents of the surfactant, based on the active component, preferably have the following composition: o palmitic acid or / and stearic acid: 15% to 65% by weight, preferably 20% to 40% by weight, and o amine, preferably monoethanolamine, isopropanolamine or / and triethanolamine: at least 3% by weight, preferably at least 4.5% by weight, and / or at most 30% by weight, preferably at most 20% by weight.

8. Process according to Claim 7, characterized in that the active component of the corrosion inhibitor is mixed with the continuous phase to form a corrosion inhibitor liquid, where the corrosion inhibitor liquid preferably includes 0.25% to 5% by weight, more preferably 0.5% to 3% by weight, of the active component, and the remainder is formed by the continuous phase.

9. Process according to any of Claims 1 to 8, characterized in that the corrosion inhibitor has the following composition: - continuous phase, preferably water or white spirit: 95% to 99.75% by weight, preferably 97% to 99.5% by weight, - oil, preferably cleaned paraffin oil or rapeseed oil: 0.0125% to 3.75% by weight, preferably 0.125% to 3.75% by weight, more preferably 0.15% to 3.5% by weight, - surfactant: 0.0625% to 4.75% by weight, preferably 0.0625% to 2.5% by weight, more preferably 0.075% to 2% by weight, - where the constituents of the surfactant specified below are preferably present in the following proportions: o palmitic acid or stearic acid: 0.0375% to 3.25% by weight, preferably 0.05% to 2% by weight, more preferably 0.625% to 2% by weight, o amine, preferably monoethanolamine, isopropanolamine or / and triethanolamine: at least 0.0075% by weight, preferably at least 0.01125% by weight, and / or at most 1.5% by weight, preferably at most 1% by weight.

10. Process according to any of Claims 1 to 9, characterized in that the corrosion inhibitor, especially the corrosion inhibitor liquid, is applied to the surface of the wire, preferably by dipping the wire into the corrosion inhibitor liquid or by contacting the wire with a spray or mist of the corrosion inhibitor liquid.

11. Process according to any of Claims 1 to 10, characterized in that the wire, after being coated with the corrosion inhibitor, is shaped, preferably by cold forming.

12. Process according to any of Claims 1 to 11, characterized in that the corrosion inhibitor comprises wax.

13. Phosphated wire, in particular steel wire, the surface of which has been coated with a corrosion inhibitor comprising an oil, where there is a film of the corrosion inhibitor comprising the oil and additionally at least one carboxylic acid on the surface of the wire, where the corrosion inhibitor is an emulsion or / and dispersion comprising a surfactant and, as disperse phase, an oil, characterized in that an active component of the corrosion inhibitor comprising a disperse phase of the emulsion or / and dispersion has the following composition: - oil: 5% to 75% by weight, - surfactant: 25% to 95% by weight.

14. Wire according to Claim 13, characterized in that the film comprises zinc stearate and / or calcium stearate.

15. Wire according to Claim 13 or 14, characterized in that the film coverage of the wire is 0.1 to 1.5 g / m2 of surface area, preferably at least 0.2 to 0.8 g / m2 of surface area.