DE1924407A1 - Process for the electrolytic deposition of chromium-nickel alloys and an electrolyte suitable for this - Google Patents

Description

Description of the patent application relating to processes for electrolytic Deposition of chromium-nickel alloys and a suitable electrolyte for this.

The invention relates to the electrolytic deposition of chromium-nickel alloys using an electrolyte containing 50 to 500 g / l in aqueous solution Nickel sulfate, 250 to 800 g / l chromic acid and an alkali and / or alkaline earth metal sulfate or boric acid. A concentration of nickel sulfate between 100 and 350 g / l, e.g. 200 g / l and of chromic acid between 300 and 600 g / l, e.g. 400 g / l.

The alkali or alkaline earth salts can be primary or secondary Be sulfates of sodium, potassium, lithium, calcium, or magnesium. Particularly good ones Results are obtained with potassium sulfate K2S04. The concentration of alkali or Alkaline earth sulfates should preferably be 2.5 to 60 g / l, in particular 10 to 40 g / l, e.g. be about 30 g / l.

The concentration of boric acid is preferably between 5 and 30 g / l in particular between 5 and 25 g / l. Mixtures of boric acid and alkali sulfate can be used or use alkaline earth sulfate.

It has often proven convenient to use ethylenediaminetetraacetic acid up to about 60 g / L for ease of alloy deposition and adjustment add the desired alloy composition to the electrolyte. Advantageous Additions of trisodium citrate were also found to be up to 40 g / l.

The electrolysis should be carried out at a high current density, and about 10 to 65 A / dm2, in particular 40 to 60 A / dm2, e.g. 55 A / dm2 The electrolysis temperature can be at room temperature, but you can also go up to about 750C. Good results obtained between 55 and 650c, especially at low boric acid concentrations.

An acidic pH value is preferred for alloy deposition, in particular 1.1 to 3.5, especially 1.5 to 2.8.

In electrolysis, the object to be plated is used as a cathode switched. It can be made of copper, soft steel or a lead-tin alloy, for example exist. An inert anode is preferred, e.g. made of platinized titanium, graphite, Platinum or a lead-tin alloy.

The nickel content of the coatings from the chromium-nickel alloy is generally under 50, with the appropriate choice of process conditions adjust the alloy compositions as desired. With the invention procedure you can get layer thicknesses in the order of 7.6 to Make 25, u (0.3 to 1 mil). The electrolyte can optionally be customary Incorporate additives.

The invention is illustrated by the following examples: EXAMPLE 1 An electrolyte containing 400 g / l chromic acid, 50 g / l nickel sulfate, 4 g / l Potassium sulfate applied in distilled water. Working temperature 25 ° C; Electrodes made of lead-tin alloys. Different current densities were used. The process conditions and properties of the coatings are summarized in Table 1.

Table 1 Current density% Ni V adhesion A / dm² 20 9 4.7 good more uneven, grayer Metal coating, gas development at the cathode 30 1 7 good, even, gray - metal coating, more violent evolution of gas 40 4 8 well, even, gray metal coating, more violent Gas development 50 3 8.6 good, even, gray metal coating, more violent gas development, but dark gray Example 2 In a modification of example 1, 100 g / l nickel sulphate applied.

Table 2 Current density% Ni V adhesion vdm 20 5 6.5 good gray metal coating, Gas evolution 30 4 7.5 good open-pored on the surface, including a gray metal coating, Gas development 40 7 10 good - II -50 5 12 no gray, spotty deposit, strong Gas evolution Example 3 In a modification of the method according to Example 1, 200 g / l nickel sulphate applied.

Table 3 Current density Ni% V Adhesion A / dm² 10 37 4.25 good gloss gray metal coating, violent gas development 20 6 6.25 good gray metal coating, Gas evolution Continuation of table 3 Current density% Ni v adhesion A / dm2 30 6 8 good dark gray metal coating, upper surface flaking off, violent gas development 40 7 10 a good gray coating that becomes flaky towards the top, gas development 50 5 12 very dark, metallic poor powder layer, strong gas evolution Example 4 An electrolyte containing 250 g / l chromic acid, 50 g / l nickel sulfate and 2.5 g / l potassium sulfate in distilled water according to Example 1 applied.

Table 4 Current density Ni% V adhesion A / dm2 20 8 5 good light gray Metal coating, gas generation 30 8 8 good gray metal coating, gas generation 40 4.5 8.5 good gray metal coating, slightly more gas development 50 4 10 good - II - example 5 As a modification of example 4, 100 g / l nickel sulfate were used.

Table 5 Current density% Ni V adhesion A / dm2 20 7 6 good gray metal coating with a somewhat flaky surface, violent evolution of gas 30 8 6.5 good dark gray coating with powdery surface, violent gas development 40 6 7 poorly gray, powdery Metal coating, strong evolution of gas 50 2 poor - II - Example 6 Modified of Example 4, 200 g / l of nickel sulfate were used.

Table 6 Electricity density% Ni V adhesion A / dm² 20 20 6 good gray metal coating, Gas development 30 19 7.5 good - II -40 .4 8.5 dark gray metal coating, above about scaly, violent development of gas From Examples 1 to 6 goes shows that by appropriate selection of the process conditions, firmly adhering Alloy coatings of the desired composition by the process of the invention can get.

Example 7 A series of electrolytes containing 390 g / l chromic acid was used and 60 g / l nickel sulfate and varying amounts of boric acid, namely between 5 and 25 g / l examined. Temperature 55 to 700C, current density 55 to 65 A / dm2.

The alloy layers obtained were characterized by a high Resistance to acids. The nickel content was between 50 and 90%.

Claims

Claims (10)

Claims 1. Process for the electrolytic deposition of Chromium-nickel alloys, marked as an electrolyte an aqueous solution containing 50 to 500 g / l nickel sulfate, 250 to 800 g / l chromic acid and an alkali and / or alkaline earth sulfate and / or boric acid are used. 2. The method according to claim i, characterized in that g e k e n n -z e i c h n e t that one electrolyzes with a current density between 40 and 60 A / dm2. 3. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that one electrolyzes at a temperature between 55 and 650c. 4. electrolyte for performing the method according to claim 1 to 3, not indicated by a content of 50 to 500 g / l nickel sulphate, 250 to 800 g / l chromic acid as well as alkali and / or alkaline earth sulfate or boric acid. 5. Electrolyte according to claim 4 g e k e n n z e i c h n e t by a Content of 100 to 350 g / l nickel sulphate. 6. Electrolyte according to claim 4 or 5 g e k e n n -z e i c h n e t with a content of 300 to 600 g / l chromic acid. 7. ElCktrolyte according to claim 4 to 6 g e k e n n z e i c h -n e t through a content of 10 to 40 g / l alkali and / or alkaline earth sulfate. 8. Electrolyte according to claim 4 to 7 g e k e n n -z e i c h n e t through a content of 5 to 25 g / l boric acid. 9. Electrolyte according to claim 4 to 8 g e k e n n -z e i c h n e t through an additional content of up to 60 g / l ethylenediaminetetraamine, 10. Electrolyte according to claims 4 to 9 g e k e n n -z e i c h n e t by an additional content of up to 40 g / l trisodium citrate. na electrolyte according to claim 4 to 10 g e k e n n -z e i c h n e t with a pH between 1.1 and 3.5.