CN101660182A - Trivalent chromium electroplate liquid stabilizer and electroplate liquid thereof - Google Patents

Abstract

A trivalent chromium electroplating solution stabilizer and its electroplating solution, characterized in that the stabilizer is an aqueous solution composed of 0.5-2mol/L methanol, 0.4-2.0mol/L sodium sulfite, and 0.5-2.5mol/L ferrous sulfate; The amount added is 1-30ml per liter of electroplating solution. The invention also discloses a trivalent chromium electroplating solution. The basic composition of the electroplating solution is: 0.2-0.6 mol/L of chromium sulfate; 0.5-1.5 mol/L of potassium sulfate; 0.02-0.5 mol/L of ammonium bromide; 0.5 mol/L of boric acid -1.2mol/L; sodium hypophosphite 0.2-0.5mol/L; aminoacetic acid 0.2-2.0mol/L; stabilizer 1-30ml/L; the rest is solvent water. The invention has the advantages of adding the stabilizer into the trivalent chromium electroplating solution, which can greatly improve the stability and service life of the existing trivalent chromium electroplating process. Used in different trivalent chromium electroplating processes.

Description

A kind of trivalent chromium electroplating liquid stabilizer and its electroplating liquid

technical field

The invention belongs to the technical field of electrochemistry, and relates to a trivalent chromium electroplating solution stabilizer and an electroplating solution thereof.

Background technique

The European Parliament and the Council promulgated the RoHS Directive on January 23, 2003, stipulating that Europe will completely ban electronic and electrical equipment containing hexavalent chromium from circulating in the European market on July 1, 2006; Valence chromium electroplating process; China's "Electronic Information Product Pollution Control and Management Measures" stipulates that the use of hexavalent chromium should be controlled since March 2007. Trivalent chromium electroplating is one of the most promising technologies to replace hexavalent chromium electroplating. It has the characteristics of low toxicity, only one percent of hexavalent chromium, low energy consumption, good dispersion ability and covering performance. The patent number is ZL94105903.0 Chinese invention patent "a trivalent chromium electroplating solution" (authorized announcement number: CN1042753C), the plating solution in this patent is composed of 0.3-0.4mol/L CrCl ₃ 6H ₂ O, 0.6-0.8mol /L HCOOH or HCOONH ₄ , 0.1-0.2mol/L NaBr, 0.8-1.0mol/L NaCl or KCl, 2.0-2.5mol/L NH ₄ Cl, 0.6-0.8mol/L H ₃ BO ₃ and appropriate amount of surfactant and Composed of rare earth additives, the electroplating process of this plating solution will inevitably produce a large amount of chlorine gas and pollute the environment. At the same time, there are still shortcomings such as unstable plating solution, dark coating color, slow crystallization speed, and low current efficiency. "Research on Trivalent Chromium Electroplating of Full Sulfate System" by Wu Huimin et al. in the 2nd issue of Volume 50 of "Journal of Wuhan University (Journal of Science)" in April 2004 introduced the sulfate trivalent chromium plating process and influencing factors. The composition of the plating solution (in L) in this document is as follows: Cr ₂ (SO ₄ ) ₃ 6H ₂ O (25-50g), Na ₂ SO ₄ (100-150g), H ₃ BO ₃ (50-60g) , complexing agent (20-25g), stabilizer (20-25mL), brightener (5-10mL), but the stability of the plating solution is poor, and refer to "Material Protection" in June 2007, Volume 40, Issue 6 In "Sulphate System Trivalent Chromium Electroplating Process Research" written by Yong et al., the electroplating solution in this document is composed of the following components: cylinder opening agent 80-140ml/L, conductive salt 280-340ml/L, auxiliary agent 8- 12ml/L, wetting agent 2-4ml/L, impurity remover 5-10ml/L, wherein the cylinder opening agent contains chromium sulfate double salt and complexing agent composed of various carboxylic acids or carboxylates, and the conductive salt contains Various inorganic salts such as boric acid and sodium sulfate, and auxiliary agents contain various rare metal salts and organic compounds containing phenyl, -C≡C- and other groups.

There are also many disclosures in the patent literature, referring to the Chinese invention patent application publication "Method for Plating Hard Chrome on Metallic Materials" (publication number: CN1687486A) whose application number is 200510020382.5. Anhydride 220-280g/L, sulfuric acid 2.5-4.5g/L, trivalent chromium 1.5-7g/L, also refer to the application number 20061009033.6 of the Chinese invention patent application "a trivalent chromium electroplating solution and preparation method of a full sulfate system "(Publication No.: CN1880512A), the electroplating solution in this patent is prepared from the following molar content components: chromium sulfate 0.05-0.25mol/L, sodium sulfate 0.4-0.8mol/L, boron 0.7-1.2mol/L, Aluminum sulfate 0.075-0.18mol/L, sodium lauryl sulfate 0.0001-0.004mol/L, complexing agent 0.2-1.0mol/L, stabilizer 0.04-0.5mol/L, and the rest is solvent water.

One of the main problems in trivalent chromium plating at present is that the plating layer cannot be continuously thickened, the plating solution is unstable, the tolerance to impurities is low, and it is easy to fail. The use of stabilizers can prevent the introduction of impurity ions and keep the components of the plating solution stable, thereby improving the service life of the plating solution and the quality of electroplating. The present invention is to develop a trivalent chromium electroplating solution and a stabilizer thereof, which can greatly improve the stability of trivalent chromium electroplating and promote its industrial application.

Contents of the invention

The first technical problem to be solved by the present invention is to provide a trivalent chromium electroplating solution stabilizer in view of the above-mentioned technical status. Using this stabilizer can prevent the effective components of the plating solution from being oxidized, suppress the uneven dispersion of the components, and prolong the Time keeps the trivalent chromium plating process stable.

The second technical problem to be solved by the present invention is to provide a trivalent chromium electroplating solution with stable performance, long service life and good coating quality.

The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a stabilizer for trivalent chromium electroplating solution, characterized in that the stabilizer is an aqueous solution composed of the following substances: 0.5-2mol/L methanol, 0.4-2.0mol /L sodium sulfite, 0.5-2.5mol/L ferrous sulfate.

The trivalent chromium electroplating solution stabilizer is used in the trivalent chromium electroplating process, and the addition amount is 1-30ml per liter of electroplating solution.

The technical solution adopted by the present invention for solving the above-mentioned second technical problem is: a kind of trivalent chromium electroplating solution, it is characterized in that being formulated by the component of following molar concentration:

Chromium sulfate 0.2～0.6mol/L;

Potassium sulfate 0.5～1.5mol/L;

Ammonium bromide 0.02～0.5mol/L;

Boric acid 0.5～1.2mol/L;

Sodium hypophosphite 0.2～0.5mol/L;

Glycine 0.2～2.0mol/L;

Stabilizer 1～30ml/L;

The rest is solvent water;

The stabilizer is an aqueous solution composed of the following substances: 0.5-2mol/L methanol, 0.4-2.0mol/L sodium sulfite, and 0.5-2.5mol/L ferrous sulfate.

The pH value of the trivalent chromium electroplating solution is 2.0-3.5.

The process temperature of the trivalent chromium electroplating solution is 30-40°C, the cathode current density is 5-20A/dm ² , the pH value of the plating solution is 2.0-3.5, the electroplating time is 1-10 minutes, and the anode is a coated electrode .

In the trivalent chromium electroplating solution formula component of the present invention, chromium sulfate provides chromium ions for the plating solution, and potassium sulfate and ammonium bromide are conductive salts, which are used to increase the conductivity of the plating solution, improve the dispersibility of the plating solution and reduce power consumption; boric acid is Plating solution buffer, used to maintain the pH value of the plating solution within the process range; aminoacetic acid complexes with trivalent chromium ions, and converts inert trivalent chromium hydrate into easily deposited complex ions with high electroactivity to improve the plating efficiency. The deposition speed and current efficiency of the electroplating solution can improve the quality of the coating; boric acid can effectively stabilize the pH value of the plating solution, maintain the stability of the acidity of the plating solution for a long time, and ensure the continuous thickening of the coating. The stabilizer is used to prevent trivalent chromium ions from being oxidized to hexavalent chromium ions, and at the same time reduce the existing hexavalent chromium ions in the plating solution to trivalent chromium ions to improve the stability and service life of the plating solution

The scope of application of the trivalent chromium electroplating solution stabilizer of the present invention is not limited to the formulation of the above trivalent chromium electroplating solution, and can be widely used in different trivalent chromium electroplating processes.

Compared with the prior art, the present invention has the following advantages and effects:

1. The trivalent chromium electroplating solution developed by the present invention only precipitates oxygen at the anode during the chromium plating process, is clean and pollution-free, the coating has a bright appearance, less cracks, good bonding force, abundant raw material sources, low cost, and excellent cost performance.

2. After the introduction of the stabilizer of the present invention, the stability of the plating solution can be effectively improved, which is helpful for its industrialization.

Detailed ways

1. Prepare trivalent chromium plating solution stabilizer:

0.5-2mol/L methanol;

0.4-2.0mol/L sodium sulfite;

0.5-2.5mol/L ferrous sulfate;

The remainder is water.

The above-mentioned raw materials can be uniformly mixed in water.

2. Prepare the trivalent chromium electroplating solution, which is prepared from the following molar concentration components:

Chromium sulfate 0.2-0.6mol/L;

Potassium sulfate 0.5-1.5mol/L;

Ammonium bromide 0.02-0.5mol/L;

Boric acid 0.5-1.2mol/L;

Sodium hypophosphite 0.2-0.5mol/L;

Glycine 0.2-2.0mol/L;

Stabilizer 1-30ml/L prepared in step 1;

The rest is water.

Weigh the raw materials according to the above ratio, first dissolve chromium sulfate in water; then dissolve boric acid in water and stir until dissolved. Since boric acid has a low solubility in water, it is necessary to heat the boric acid solution to 60-70°C to make it All dissolved. Then mix the boric acid solution and the chromium sulfate solution, stir, and then add aminoacetic acid. After the aminoacetic acid is added, it should be fully stirred to generate more stable and moderately electroactive complex ions. If the trivalent chromium in the electroplating solution is not well complexed with the complexing agent, or the concentration of the complexing agent is too low, the maximum current density allowed by the plating solution will be reduced, or only black deposits or even no coating will be obtained. Therefore, the trivalent chromium should be completely complexed with the complexing agent.

Potassium sulfate, ammonium bromide, sodium hypophosphite, stabilizers are then added. Potassium sulfate is a conductive salt to improve the dispersion ability of the plating solution and reduce power consumption. Ammonium bromide and sodium hypophosphite have reducing properties, which can effectively inhibit the oxidation of trivalent chromium ions and enhance the stability of the plating solution. The boric acid in the plating solution has a strong buffering effect on the pH value, which can effectively stabilize the pH value of the plating solution. The stabilizer can maintain the stability of the acidity of the plating solution during the long-term electroplating process and ensure the continuous thickening of the plating layer. After all the components are added, adjust the pH of the plating solution to the specified range, then stir at a constant temperature for 1 hour, and then let it stand for 1 hour to completely complex the trivalent chromium ions and improve the stability of the plating solution.

The process parameters of the electroplating solution of the present invention are as follows: working temperature 30-40°C, cathode current density 5-20A/dm ² , pH value of the plating solution 2.0-3.5, electroplating time 1-10min, and the anode is a coated electrode. After the workpiece is cleaned, derusted and activated according to the conventional pre-plating pretreatment, the plated workpiece is used as the cathode, and the area of the cathode and anode is about 1:2.

Below by embodiment, further illustrate outstanding feature and remarkable progress of the present invention, only in order to illustrate the present invention and in no way limit the present invention.

Example 1

Take 2mol methanol, 0.5mol sodium sulfite, and 1mol ferrous sulfate to prepare 1000mL stabilizer aqueous solution.

Take 0.2mol of chromium sulfate, dissolve it in distilled water, and stir until completely dissolved; dissolve 0.5mol of boric acid in water, stir until dissolved; mix the above-mentioned chromium sulfate solution with boric acid solution, and stir; add 0.5mol of ammonium bromide and Glycine, stirred for 0.5 hours, then added 0.5 mol potassium sulfate and 0.3 mol sodium hypophosphite successively. Finally, add 5ml of stabilizer aqueous solution, add water to close to 1L; then check and adjust the pH value of the solution to 2.0; after constant volume, control the temperature at 30°C, and clean, derust and activate the workpiece according to the conventional pre-plating pretreatment. Electroplate at a current density of 10A/ ^dm2 for 3 minutes, take it out and rinse it with water. After the test piece dries, a bright and smooth trivalent chromium hard chromium coating with a thickness of about 2μm and no cracks is obtained.

Example 2

Take 0.5mol methanol, 0.4mol sodium sulfite, and 0.5mol ferrous sulfate to prepare 1000mL stabilizer aqueous solution.

Take 0.6mol of chromium sulfate, dissolve it in water, and stir until it dissolves; take 0.8mol of boric acid and dissolve it in distilled water, and stir until it dissolves; mix the above-mentioned chromium sulfate solution with boric acid solution, and stir; add 2.0mol aminoacetic acid, Stir at ℃ for 1 hour, then add 1.0mol potassium sulfate, 0.5mol sodium hypophosphite, 0.2mol ammonium bromide, 30ml stabilizer aqueous solution, stir while adding, until dissolved, then stir at constant temperature 60°C for 1 hour, stand still for 1 hour ; Add water to nearly 1L; then check and adjust the pH value of the solution to 3.0; after constant volume, control the temperature at 40°C, degrease, wash with water, acid etch, wash with water, and electroplate at a current density of 15A/ ^dm2 for 8 minutes , Take it out and rinse it with water to get a smooth trivalent chromium hard chromium coating.

Example 3

Take 1mol methanol, 2mol sodium sulfite, and 2.5mol ferrous sulfate to prepare 1000mL stabilizer aqueous solution. Add 1ml/L stabilizer every day before the working of the electroplating solution in Example 1, the electroplating process can be kept stable and run for a long time.

Example 4

Take 0.5mol methanol, 0.4mol sodium sulfite, and 2.5mol ferrous sulfate to prepare 1000mL stabilizer aqueous solution. Dissolve 0.4mol of chromium sulfate in water, 1.0mol of boric acid in water, 1.5mol of aminoacetic acid, 1.5mol of potassium sulfate, 0.4mol of sodium hypophosphite, and 0.5mol of ammonium bromide, mix and stir until dissolved, and stir at 55°C for 2 hour, add 15ml of the prepared stabilizer, add water to close to 1L; adjust the pH value of the solution at 3.5, control the temperature at 40°C, and degrease, wash with water, acid etch, wash with water in turn, at a current density of 10A/ ^dm2 Electroplate for 5 minutes, remove, rinse, and dry. The trivalent chromium electroplating solution has good stability, long service life and broad application prospects.

In a word, the trivalent chromium electroplating solution of the present invention has stable performance, long service life and good coating quality. The stabilizer of the present invention can greatly improve the process stability and coating quality of the plating solution, and has good application prospects and use value.

Claims (5)

1, a kind of trivalent chromium plating liquid stablizer is characterized in that stablizer is the aqueous solution that following material is formed: 0.5-2mol/L methyl alcohol, 0.4-2.0mol/L S-WAT, 0.5-2.5mol/L ferrous sulfate.

2, a kind of trivalent chromium plating liquid stablizer according to claim 1 is characterized in that stablizer is used for trivalent chromium plating technology, and addition is every liter of electroplate liquid 1～30ml.

3, a kind of trivalent chromium plating liquid is characterized in that comprising following component and corresponding volumetric molar concentration proportioning:

Chromium sulphate 0.2～0.6mol/L;

Vitriolate of tartar 0.5～1.5mol/L;

Brometo de amonio 0.02～0.5mol/L;

Boric acid 0.5～1.2mol/L;

Inferior sodium phosphate 0.2～0.5mol/L;

Padil 0.2～2.0mol/L;

Stablizer 1～30ml/L;

All the other are aqueous solvent;

Described stablizer is the aqueous solution that following material is formed: 0.5-2mol/L methyl alcohol, 0.4-2.0mol/L S-WAT, 0.5-2.5mol/L ferrous sulfate.

4, a kind of trivalent chromium plating liquid according to claim 3 is characterized in that described electroplate liquid pH value is 2.0-3.5.

5, a kind of trivalent chromium plating liquid according to claim 3, it is characterized in that the processing parameter of described electroplate liquid is: technological temperature is 30-40 ℃, cathode current density is 5-20A/dm ², bath pH value 2.0-3.5, electroplating time 1-10 minute, anode was a coated electrode.