DE102014108588B3 - Pickling solution and process for pickling metals - Google Patents

Abstract

The invention relates to a pickling solution for pickling a metal, wherein the pickling solution based on one liter of the pickling solution comprises: 200 to 500 ml of concentrated hydrochloric or sulfuric acid, 500 to 800 ml of water, 1.5 to 2.5 g of sodium metasilicate, From 0.08 to 0.5 g of an alkyl arylsulfonate containing an alkyl chain, from 0.01 to 0.13 g of polyalkylene glycol ether, from 0.01 to 0.13 g of ethoxylated fatty amine, from 0.005 to 0.06 ml of a A 50% aqueous fluorosurfactant alcohol solution wherein the fluorosurfactant is selected from the group of quaternary fluoroalkylammonium salts.

Description

The invention relates to a pickling solution for pickling a metal and a method for pickling a metal.

Clean surfaces are the prerequisite for coating or processing metals. For this purpose, usually pickling used. The pickling thus serves the pretreatment of the metal surface and has as its goal to produce physically and chemically pure surfaces, which are free of impurities. Impurities can include oxide and oxide hydrate layers, tarnish layers, grease residues and corrosion products.

In the broadest sense, activating surfaces is often associated with the pickling of metals. The activating serves z. B. the exposure of Valenzen to optimize and facilitate subsequent coating operations. So z. For example, in the case of stainless steel exposed to the stainless steel surface iron and nickel, activated and coated with chemical nickel, to make it possible at all an effective coatability of stainless steel alloys.

The DE 10 2008 020 037 A1 discloses a method for coating components and apparatus whose surface is first pretreated using an activator and then subsequently coated with a layer of a Ni-P alloy by electroless plating in the plating bath.

EP 1 630 251 A2 discloses a method for coating metals, in particular stainless steels for chemical plant construction, in which the surfaces to be coated are pretreated and subsequently coated with at least one layer of a Ni-P alloy.

Also the DE10 156 624 B4 discloses a method and pickling solution for cleaning pads of a steel workpiece.

The invention has for its object to provide an improved pickling solution and an improved method for pickling a metal.

The objects underlying the invention are achieved by the features of the independent claims. Preferred embodiments of the invention are indicated in the dependent claims.

• – 200 bis 500 ml konzentrierter Salz- oder Schwefelsäure,
• – 500 bis 800 ml Wasser,
• – 1,5 bis 2,5 g Natriummetasilikat,
• – 0,08 bis 0,5 g eines eine Alkylkette aufweisenden Alkali-Arylsulfonats,
• – 0,01 bis 0,13 g Polyalkylenglycolether,
• – 0,01 bis 0,13 g ethoxiliertes Fettamin,
• – 0,005 bis 0,06 ml einer 20–50%igen wässrigen Fluortensid-Alkohollösung, wobei das Fluortensid aus der Gruppe der quarternären Fluoralkylammoniumsalze stammt.

A pickling solution for pickling a metal is indicated, the pickling solution based on one liter of the pickling solution having:

• 200 to 500 ml of concentrated hydrochloric or sulfuric acid,
• - 500 to 800 ml of water,
• 1.5 to 2.5 g of sodium metasilicate,
• 0.08 to 0.5 g of an alkyl arylsulfonate alkyl chain,
• 0.01 to 0.13 g of polyalkylene glycol ether,
• 0.01 to 0.13 g of ethoxylated fatty amine,
• 0.005 to 0.06 ml of a 20-50% aqueous fluorosurfactant alcohol solution, the fluorosurfactant being selected from the group of quaternary fluoroalkylammonium salts.

Embodiments of the invention have the advantage that the steps of degreasing, the actual pickling (removal of oxide residues, corrosion products, scale, sulfite and silicate films, corrosive salts, etc.) and the surface activation can be carried out together with a single pickling solution.

As already mentioned, thorough pretreatment of metal surfaces is a basic prerequisite for enabling subsequent chemical or galvanic depositions, including metallic and non-metallic deposits. For base and precious metals, this pretreatment process takes place z. B. classic by degreasing, etching, acid immersion, activation, each interrupted by thorough rinsing to remove residual liquid residues from inclusions, pores, cracks, ridges, etc. on the surface of the material with water.

With the described pickling solution, this multiplicity of different steps of the pretreatment process can be reduced to 2 stages or baths in a timely and cost-effective manner. By preferably two process steps, namely the active bath with the said pickling and rinsing bath, metals can be pretreated in order to create clean and activated surfaces of components and apparatus to be galvanically and accurately contoured, without extensive optimization by adapting them to the respective base materials of dive time and temperature are necessary. Thus, the conditions can be created in an optimized manner, the metal workpieces then by galvanic or electroless plating in the electrolyte bath z. B. to coat with chemical nickel.

The hydrochloric or sulfuric acid may act as a primary mordant here. The added metasilicate leads to the removal of fatty substances from the metal surface. This is supported by the combination of ethoxylated fatty amine and the alkyl chain-containing alkali arylsulfonate, which each contribute as surfactants for fat removal.

The alkyl arylsulfonate-containing alkyl chain can on the one hand act particularly effectively as a surface-active agent. On the other hand, the alkali arylsulfonate act as a pickling inhibitor due to its sulfur-containing components. The same also applies to the added polyalkylene glycol ether: In addition to its action as a nonionic surfactant as a pickling inhibitor, the polyalkylene glycol ether can ensure that the acid attack on the pure metal surface is minimized. This not only prevents the unnecessary removal of metal, but also the unnecessary contamination of the stain is avoided, which increases the life of the stain.

The fluorosurfactant finally activates the cleaned metal surfaces.

The chosen combination of active ingredients can be precisely due to the z. T. low selected concentrations unfold their effect in a synergistic manner, without this in particular leads to a mutual negative impact on the result of the Beizings. The mordant can be used for the pickling of a variety of metals such as iron, copper, etc.

In one embodiment of the invention, the ethoxylated fatty amine is selected from the group consisting of tallow fatty amine, coconut fatty amine. These are degreasing agents, which support the cleaning process in a particularly effective manner.

In one embodiment of the invention, the polyalkylene glycol ether is selected from the group consisting of polyoxyethylene (4) lauryl ether, polyoxyethylene (4) isodecyl ether, polyoxyethylene (6) isodecyl ether.

According to one embodiment of the invention, the pickling solution further comprises 10 to 80 ml of a carboxylic acid. For example, the carboxylic acid is selected from the group: citric acid, tartaric acid, formic acid. The carboxylic acid can serve as a stabilizer for the substances dissolved in the acid, such as chromium. Furthermore, the carboxylic acid may help to maintain the overall effectiveness of the pickling solution over a longer period of use. Although the use of carboxylic acids can basically lead to a passivation of metal surfaces. In concrete connection with the other additives of the pickling solution, however, this property of the carboxylic acid can be neglected negligibly or even in a positive manner.

According to one embodiment of the invention, the pickling solution further comprises 2 to 7 g of nickel chloride and 2 to 8 g of iron (II) sulfate. However, these additives should only apply in the case of pickling of stainless steels, so in this case z. B. a partial nickel plating takes place in the pickling bath with exclusion of oxygen.

In one embodiment of the invention, the anions of the quaternary fluoroalkylammonium salts include chloride, bromide or iodide anions. So it is z. Example, in the fluorosurfactant to quaternary fluoroalkylammonium chloride, quaternary fluoroalkylammonium bromide or quaternary Fluoralkylammoniumiodid.

According to one embodiment of the invention, the alcohol is selected from the group: ethanol, isopropanol, glycerol, propylene glycol, 2-methyl-2,4-pentanediol. In particular, 2-methyl-2,4-pentanediol may be particularly suitable here because of its properties as a surfactant and its emulsion-stabilizing properties: This may have the advantage that even after degreasing the metal surfaces, the fat particles now adhering to the surfactants so stable in the solution be kept without it z. B. occurs during removal of the metal from the pickling solution to accidental re-adhesion of the fat particles on the metal surface. Here can z. As well as the combination with an addition of 0.06 to 0.3 g of sodium carbonate be helpful, which also effectively hold in the pickling solution dirt and fat particles in the balance.

According to one embodiment of the invention, the alcohol is contained in a proportion of 5-25% in the aqueous fluorosurfactant alcohol solution.

In one embodiment of the invention, the aryl portion of the alkali aryl sulfonate comprises benzene and the alkyl chain comprises a 4-C 10-13 sec alkyl derivative and / or the aryl portion of the alkali aryl sulfonate comprises benzene and the alkyl group contains 1-4 carbon atoms , preferably 1 or 2 carbon atoms.

For example, the methyl-arylated-arylsulfonate may result from a reaction of benzenesulfonic acid, 4-C 10-13 sec-alkyl derivatives, ethylbenzenesulfonic acid (or instead methylbenzenesulfonic acid) and NaOH, generally the alkyl group of the alkylbenzenesulfonic acid being 1-4 carbon atoms, preferably 1 or Contains 2 carbon atoms. This may result in a dissolved anionic surfactant, an agent which due to its surface activity may contribute to the dissolution of fat on metal surfaces.

• – 200 bis 500 ml konzentrierter Salz- oder Schwefelsäure,
• – 500 bis 800 ml Wasser,
• – 1,5 bis 2,5 g Natriummetasilikat,
• – 0,08 bis 0,5 g eines eine Alkylkette aufweisenden Alkali-Arylsulfonats,
• – 0,01 bis 0,13 g Polyalkylenglycolether,
• – 0,01 bis 0,13 g ethoxiliertes Fettamin,
• – 0,005 bis 0,06 ml einer 20–50%igen wässrigen Fluortensid-Alkohollösung, wobei das Fluortensid aus der Gruppe der quarternären Fluoralkylammoniumsalze stammt,

wobei das Verfahren ferner ein Behandeln des Metalls mit der Beizlösung umfasst, wobei die Behandlung bei Raumtemperatur durchgeführt wird.In a further aspect, the invention relates to a method for pickling a metal, the method comprising providing a pickling solution, wherein the pickling solution based on one liter of the pickling solution comprises:

• 200 to 500 ml of concentrated hydrochloric or sulfuric acid,
• - 500 to 800 ml of water,
• 1.5 to 2.5 g of sodium metasilicate,
• 0.08 to 0.5 g of an alkyl arylsulfonate alkyl chain,
• 0.01 to 0.13 g of polyalkylene glycol ether,
• 0.01 to 0.13 g of ethoxylated fatty amine,
• From 0.005 to 0.06 ml of a 20-50% aqueous fluorosurfactant alcohol solution, the fluorosurfactant being selected from the group of quaternary fluoroalkylammonium salts,

the method further comprising treating the metal with the pickling solution, wherein the treatment is performed at room temperature.

Room temperature is understood to mean a temperature range between 15 and 30 degrees Celsius, preferably between 17 and 25 degrees Celsius.

According to one embodiment of the invention, the treatment is carried out in non-stainless steels for a period of 2 to 60 seconds and carried out on stainless steels for a period of 5 to 20 minutes. Compared to traditional methods, the pickling solution can reduce the time required for this by using a single bath for pickling, degreasing and activating. In addition, the described pickling solution can be so highly effective that, secondly, the usual pickling times can in principle be greatly reduced.

According to one embodiment of the invention, providing the pickling solution comprises mixing the hydrochloric or sulfuric acid with the sodium metasilicate, the alkyl-containing alkali aryl sulfonate and the polyalkylene glycol ether before adding the fluorosurfactant alcohol solution. This may have the advantage that, due to this order, the effect of the cationic fluorosurfactant as activator is maximally maintained despite the mixture with the other components. Also should preferably be used in the use of the carboxylic acid as an additive until the end of the mixing process. Finally, after mixing the active components to the desired concentration, the resulting solution can be diluted with water.

In the following, preferred embodiments of the invention are explained in more detail with reference to the drawing.

Show it:

1 a schematic view of various baths for coating metals,

2 a flow diagram of a method for coating metals.

The 1 shows schematically various baths, which make it possible to coat metals with only a small number of steps. In the following it was assumed without restriction of generality that stainless steel should be galvanized.

This is done according to the method steps, as shown schematically in the flowchart of 2 are shown.

First, for a pickling bath 100 prepared a pickling solution, wherein the production takes place in a three-stage process. Starting from a 1 liter pickling solution takes place in step 200 first, a first mixing of 200 to 500 ml of concentrated hydrochloric or sulfuric acid with 2 to 7 g of nickel chloride, 2 to 8 g of iron (II) sulfate and a small amount of z. B. 0.06 to 0.3 g of sodium carbonate. The acid can be previously diluted in a desired manner with water so that the desired staining effect is caused without causing an excessive and destructive attack on the metal. Specifically, for. B. 400 ml of hydrochloric acid are diluted with 300 ml of water.

Also in step 200 the addition of 1.5 to 2.5 g of sodium metasilicate, as well as from 0.08 to 0.5 g of the alkyl-containing alkali aryl sulfonate. Further, 0.01 to 0.13 g of polyalkylene glycol ethers (eg, polyoxyethylene (4) isodecyl ether or polyoxyethylene (6) isodecyl ether), 0.01 to 0.13 g of ethoxylated fatty amine (eg, tallow fatty amine) and 0.06 to 0.3 g of sodium carbonate are added. As a substitute for tallow fatty amine, coconut fat amine can also be used.

After mixing in step 200 is the resulting mixture in step 202 the activator added. For this purpose, small amounts of an aqueous fluorosurfactant alcohol solution, z. B. 0.05 ml of a 20% aqueous fluorosurfactant-isopropyl alcohol solution. The alcohol can account for only a small proportion of 20% (ie 20% fluorosurfactant, 20% alcohol). After the further addition of 10 to 80 ml of a carboxylic acid, for. B. 40 ml of citric acid or 20 ml of formic acid can in step 204 the resulting mixture is made up to 1 liter of pickling solution with water.

The finished pickling solution can, as in the 1 shown schematically, in a pickling bath 100 be used. By means of the method described here, at room temperature, ie without heating and classified without classification as hazardous substance use a safe, efficient and effective pre-treatment in the pickling bath 100 After immersing the stainless steel for 15 minutes (step 206 ) immediately followed by a rinse of the pickled stainless steel with water. This purpose is served by the schematically indicated water bath 102 and the process step 208 ,

Then the stained, degreased and activated stainless steel surface in step 210 in a galvanizing bath 104 electrolytically and chemically with z. B. nickel are coated.

Thus, in particular with metals other than precious metals, the pickling in step 206 and thus the immersion of the metal (ie the workpiece to be sharpened) in the stain even stronger start-up and scale layers, as well as oxide, sulfite and silicate films are thoroughly removed. Step in one and the same operation 206 the activation or the (stainless steel) activator reliably destroys the passive layer of the workpiece to be coated by targeted release of iron and nickel. So afterwards in the coating bath 104 A germination of the surface without flaws on the body done so that functional requirements such as corrosion and wear resistance can be properly taken into account.

The in step 206 exposed metal surfaces can directly, ie without complete removal of the mordant, especially in complicated components of the adhered activator in step 210 be coated. For this purpose, a simple and short rinse in step is sufficient 208 , Optionally, it is still possible after the rinsing process in step 208 to perform a decaping process. This should then also be finished again with a rinsing process with water.

The method described above can be applied to many types of metals, with the nickel chloride and iron (II) sulfate additive preferably being used only for stainless steel. Another application is the application of the method for cleaning printed circuit boards. The process can be used for copper and non-ferrous metals (especially for annealed oil-treated copper). It shows its efficiency and effectiveness compared to the classical degreasing pickling activation by reducing the pretreatment process to 2 steps due to its lower investment requirement. So less bath tanks, suction devices, heating and cooling units are required. In addition, there are savings in chemistry, energy and working time, resulting in an overall higher throughput through a shorter and easier machining process. The pickling solution is an easy-to-handle product that is economical and reusable several times when, for. B. the fat dissolved in the stain is filtered now and then. The metal dissolved in the pickle can be removed from the pickling solution by means of suitable electrolysis processes.

With its proper and cost-effective pre-treatment, the pickling solution thus fulfills the prerequisites for successful coating of components of the most diverse materials and shapes.

LIST OF REFERENCE NUMBERS

100

stain

102

flush

104

electroplating bath

Claims (15)

Pickling solution for pickling a metal, wherein the pickling solution based on one liter of the pickling solution has: 200 to 500 ml of concentrated hydrochloric or sulfuric acid, - 500 to 800 ml of water, 1.5 to 2.5 g of sodium metasilicate, 0.08 to 0.5 g of an alkyl arylsulfonate alkyl chain, 0.01 to 0.13 g of polyalkylene glycol ether, 0.01 to 0.13 g of ethoxylated fatty amine, 0.005 to 0.06 ml of a 20-50% aqueous fluorosurfactant alcohol solution, the fluorosurfactant being selected from the group of quaternary fluoroalkylammonium salts. The pickling solution according to claim 1, wherein the ethoxylated fatty amine is selected from the group consisting of tallow fatty amine, coconut fatty amine. The pickling solution according to claim 1 or 2, wherein the polyalkylene glycol ether is selected from the group consisting of: polyoxyethylene (4) lauryl ether, polyoxyethylene (4) isodecyl ether, polyoxyethylene (6) isodecyl ether. A pickling solution according to any one of the preceding claims, further comprising 0.06 to 0.3 g of sodium carbonate. A pickling solution according to any one of the preceding claims, further comprising 10 to 80 ml of a carboxylic acid. The pickling solution according to claim 5, wherein the carboxylic acid is selected from the group: citric acid, tartaric acid, formic acid. A pickling solution according to any one of the preceding claims, further comprising 2 to 7 g of nickel chloride and 2 to 8 g of ferrous sulfate. A pickling solution according to any one of the preceding claims, wherein the anions of the quaternary fluoroalkylammonium salts comprise chloride, bromide or iodide anions. Pickling solution according to one of the preceding claims, wherein the alcohol of the fluorosurfactant alcohol solution is selected from the group: ethanol, isopropanol, glycerol, propylene glycol, 2-methyl-2,4-pentanediol. The pickling solution according to claim 9, wherein the alcohol is contained in a proportion of 5-25% in the aqueous fluorosurfactant alcohol solution. A pickling solution according to any one of the preceding claims wherein the alkali metal of the alkali aryl sulphonate comprises sodium or potassium. A pickling solution according to any one of the preceding claims wherein the aryl portion of the alkali aryl sulfonate comprises benzene and the alkyl chain comprises a 4-C 10-13 sec alkyl derivative and / or wherein the aryl portion of the alkali aryl sulfonate is benzene and the alkyl group 1- Contains 4 carbon atoms, preferably 1 or 2 carbon atoms. A method of pickling a metal, the method comprising providing a pickling solution, wherein the pickling solution based on one liter of the pickling solution comprises: 200 to 500 ml of concentrated hydrochloric or sulfuric acid, - 500 to 800 ml of water, 1.5 to 2.5 g of sodium metasilicate, 0.08 to 0.5 g of an alkyl arylsulfonate alkyl chain, 0.01 to 0.13 g of polyalkylene glycol ether, 0.01 to 0.13 g of ethoxylated fatty amine, From 0.005 to 0.06 ml of a 20-50% aqueous fluorosurfactant alcohol solution, the fluorosurfactant being selected from the group of quaternary fluoroalkylammonium salts, the method further comprising treating the metal with the pickling solution, wherein the treatment is performed at room temperature. The method of claim 13, wherein the treatment is carried out in non-stainless steels over a period of 2 to 60 seconds and is carried out on stainless steels over a period of 5 to 20 minutes. The method of claim 13 or 14, wherein providing the pickling solution comprises mixing the hydrochloric or sulfuric acid with the sodium metasilicate, the alkyl-containing alkali aryl sulfonate and the polyalkylene glycol ether before adding the fluorosurfactant alcohol solution.

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