DE1945715A1 - Process for applying nickel layers before enamelling - Google Patents

Description

Henkel & Cie GmbH Düsseldorf, 9.9.1969

Patent department Henkels tr. 67

Dr. Ar / ku

Patent application D

"Process for applying nickel layers before Enamel"

The invention relates to a method for applying nickel layers before enamelling, especially before direct white enamelling, degreased and stained Steel surfaces.

To prepare steel surfaces for enamelling, degreasing and a corresponding stain are required. Furthermore, a nickel layer is often applied to improve the adhesion. Such Layer is required if direct white enameling is provided. A wide variety of processes are known for degreasing and pickling, which are flawless Produce result. However, these methods generally require relatively long times. There are already attempts been undertaken, the treatment times, which are generally around 20-30 minutes, through use suitable measures, such as ultrasound, electrolytic degreasing and pickling, to be greatly reduced.

The deposition of a corresponding nickel layer is carried out in the praxig by electroless chemical processes,

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either in the so-called exchange process or in the reduction process. Relatively long times of approx. 6 minutes required. It has therefore already been proposed to carry out the nickel plating by electroplating and so on to achieve a reduction in the treatment time. The galvanic applied nickel layers have so far not been satisfactory in practice, since the adhesion of the enamel layers, primarily the direct white enamel chemically applied nickel layers is much better than on electroplated layers. The treatment times were about 60 seconds in the proposed galvanic process.

It has now been found that perfect adhesion of the enamel layers to the steel surface is achieved if the procedure described below is used to apply nickel layers prior to enamelling. That new method is characterized in that the steel surfaces with solutions containing water-soluble nickel salts and 10-60 mg / l non-ionic wetting agent with a cloud point included below the treatment temperature, at a Current strength of 1-10 A / dm and a temperature of 45-7O ° C less than 15 seconds are treated and the solutions to achieve a constant nickel layer in the meantime completely or partially cooled to below the cloud point and then back to the working temperature of the Solution to be warmed.

The treatment solutions according to the invention contain water-soluble ones Nickel salts in concentrations as they are usually used for galvanic nickel deposition. The preferred nickel salts are nickel sulfate and nickel

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Chloride or mixtures of these salts, for example in Quantities of 130 - 200 g / l used. The nickel baths contain generally an addition of suitable weak acids, such as in particular, to regulate the pH value Boric acid. The pH value of the nickel baths is generally between 3 - 5> preferably between 4-5 · Die It is practical if nickel-plating baths do not contain any brighteners or levelers.

In addition to the water-soluble nickel salts, the solutions contain 10-60 mg / 1 non-ionic wetting agents with a cloud point below the treatment temperature. The cloud point is determined in each case by the slow heating the solution and the observation of the first optically clearly recognizable cloudiness.

Reaction products, for example, can be used as nonionic wetting agents of ethylene oxide, propylene oxide or ethylene and propylene oxide in any order with saturated and unsaturated fatty alcohols, fatty amines, fatty acids, Fatty acid amides, poorer fatty acids, dimeric fatty alcohols, other polyhydric alcohols and also cycloaliphatic and aromatic alcohols, lower amines and Alkanolamines and substituted and unsubstituted phenols are suitable. Preferably ethylene and Polypropylene oxide adducts obtained by reacting polypropylene oxide with ethylene oxide or polyethylene oxide with propylene oxide are obtained, ver used as nonionic wetting agents. The cloud point of the ethylene and used Propylene oxide adducts are generally 25-35 ° C below the treatment temperature.

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Henkel &Cl'e GmbH page T " xvr patent application D 4004

The nickel layers are deposited at currents of 1-10 A / dm "and preferably Dei currents of 2-5 A / dm. The treatment time at these currents is less than 15 seconds, but generally not less than one second, preferably between 1-8 seconds. Longer treatment times have an unfavorable effect on the adhesive strength of the enamel layers.

The treatment temperature is between 4-5 - 70 ° C. To the In order to achieve constant nickel layers, it is necessary to completely or partially remove the solution in the meantime Cool to below the cloud point of the non-ionic wetting agent and then return to working temperature to warm up. In order to keep the solution functional longer, the cooled solution can be filtered through suitable filters be directed. Appropriately, only part of the solution, namely 1/3 - 1/20 per hour, is cooled and reheated. A preferred embodiment exists consist of continuously removing, cooling, heating and adding again.

According to the method according to the invention, it is possible in to apply a nickel layer in a very short time represents an excellent primer for the subsequently applied enamel. Combined with Appropriate measures for degreasing and pickling can greatly reduce the treatment times will. It is even possible to shorten the treatment times so much that direct white enamelling is also possible can be carried out with the steel belt running without the systems reaching the technically acceptable length must exceed.

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Henkel & Cie GmbH page 5 ^for patent application D 4004

example 1

Steel sheets made of decarburized steel, which had been pretreated in a known manner by alkaline degreasing and intensive pickling, were, after the usual intermediate rinsing, in a solution containing 240 g / l NiSO ₂ ^ · 7 H ₃ O, 50 g / l NiCl ₂ · 6 HpO , 30 g / l boric acid and J50 mg / l of a water-soluble Äthylenoxid- Propylenoxidadduktes and having a cloud point of 22 ⁰ C in this solution at a current density of 4 a / dm and a temperature of 50 C for 5 seconds treated. It was then rinsed and passivated with a soda-phosphate solution. After drying, the steel sheets were enamelled directly in white in the usual manner. The enamel layer showed a smooth flow and perfect adhesion. The impact resistance test according to DIN 51155 showed no differences compared to the sheets that were degreased and pickled in the same way, but after the exchange or reduction process, chemically nickel-plated sheets within 6 minutes.

1/5 of the volume per hour was continuously withdrawn from the bath. The drawn off solution was heated to 20.degree cooled and filtered, then back to bath temperature heated and then continuously fed back into the bath. This ensured that even with longer Service life a consistent effect is achieved with the nickel-plating bath.

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Hsnkel & Cie GmbH s «it« 6 _x ,, _r p _n i, nitinm «.idun, d η OO ^ Example 2

The same steel material as described in Example 1, which was also degreased and pickled in the same way, was treated with a solution containing 280 g / l NiSO ^ 7.H ₂ O, 60 g / l NiCl ₃ · 6 H ₂ O, 35 g / l boric acid and 45 mg / l of a water-soluble ethylene oxide and propylene oxide adduct with a cloud point of 25 ° C in the treatment solution at a current of 6 A / dm and a temperature of 60 ° C for 2 seconds. It was then rinsed and passivated with a soda-phosphate solution. After drying, the steel sheets were enamelled directly in white in the usual way. The enamel layer had perfect adhesion and was smooth. In the impact resistance test according to DIN 51155, no differences could be found compared to comparison sheets which were chemically nickel-plated.

The same results were achieved if, instead of the aforementioned ethylene oxide and propylene oxide adduct, 40 mg / l of a reaction product of 20 moles of ethylene oxide and 10 moles of propylene oxide with 1 mole of cetyl alcohol or 50 mg / l of a reaction product of 9 moles of ethylene oxide and 10 moles of propylene oxide with 1 mole Nonylphenol or ~ $ 0 mg / l of a reaction product of 40 moles of ethylene oxide and 40 moles of propylene oxide with 1 mole of ethylenediamine was added.

As described in Example 1, the bath became continuous about 1/5 of the volume per hour deducted and after Continuous cooling and filtration as well as reheating fed back into the bathroom.

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Henkel & Cie GmbH page "J iur patent application D Example 3

As in Example 1 degreased and pickled steel sheets WUR with a solution containing 250 g / l NiSO ^ · 7 HgO, 50 g / l NiCIp · 6 HgO, 30 g / l boric acid and 25 mg / l of a water-soluble ethylene oxide and propylene oxide adduct treated with a cloud point of 20 ⁰ C in the treatment solution at a current strength of 4 A / dm and a temperature of 55 C 2, 5 * 10 or 20 seconds. The metal sheets were then rinsed and passivated with a soda-phosphate solution. After drying, direct white enameling was carried out in the usual manner. In the case of steel sheets that had been nickel-plated for 2.5 and 10 seconds, the adhesion of the enamel layer was very good to good (impact resistance test according to DIN 51155) > while the sample that was nickel-plated for 20 seconds showed poor adhesion.

1/8 of the volume per hour was continuously withdrawn from the bath. The drawn off solution was brought to 15 ° C cooled and filtered, then heated again to bath temperature and then continuously re-added to the bath fed. This ensured that also with longer service lives a consistent effect is achieved with the nickel-plating bath.

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Claims (10)

Henkel & Cie GmbH page, Ο for patent application D 4004 patent claims 1. Method of applying nickel layers before Enamelling on degreased and stained steel surfaces, characterized in that the steel surfaces with solutions containing water-soluble nickel salts and 10-60 mg / l non-ionic wetting agents with a cloud point contain below the treatment temperature, are treated at a current strength of 1-10 A / dm and a temperature of 45-7O ⁰ C for less than 15 seconds and the solutions to achieve a constant nickel layer in the meantime completely or partially cooled to below the cloud point and then again to the working temperature of the solution be heated. 2. The method according to claim 1, characterized in that - * that the solutions contain ethylene and propylene oxide adducts as nonionic wetting agents. 5. The method according to claim 1 and 2, characterized in that that the steel surfaces are treated at a current strength of about 2-5 A / dm 1 to 8 seconds. 4. The method according to claim 1 to J5> characterized in that l / j to 1/20 of the solution removed per hour, cooled and is reheated. 5. The method according to claim 1 to 4, characterized in that the removal, cooling, heating and re-addition is carried out continuously. Henkel & Cie. GmbH i.V. i.V. (Zuriegl) (Dr. Arnold ^ / 10 9 8 11/17 4 0 '