Trivalent chromium rapid chromium plating solution of sulfate and chloride mixed system as well as preparation and application of trivalent chromium rapid chromium plating solution

Abstract

The invention discloses a preparation method and an electroplating method of a trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system. The plating solution comprises chromium salt, a complexing agent, conducting salt, a buffering agent, a stabilizing agent and a wetting agent. The preparation method comprises the following steps: heating 50% of water to 50-60 DEG C, adding the conducting salt and the buffer agent, stirring until the conducting salt and the buffer agent are completely dissolved, sequentially adding the chromium salt, the complexing agent and the stabilizer, finally adding the wetting agent, adjusting the pH value to 2.0-3.0 by using sulfuric acid or sodium hydroxide, and keeping the temperature at 50-60 DEG C for 4 hours to obtain the electroplating solution. The plating solution is easy to prepare, the average deposition speed of chromium is 0.48 microns / min, the thickness of a plating layer is 29 microns, and the hardness is larger than or equal to 1000 HV.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system and a preparation method and application thereof. Background Art

[0002] Chromium plating has the advantages of white and bright appearance, high hardness, corrosion resistance and low friction coefficient. It is a widely used plating, including automotive, aviation, electronics, medical equipment, furniture, bathroom and decoration. The traditional chrome plating process uses hexavalent chromium, which is a known human carcinogen. The treatment of chrome plating wastewater is difficult and costly. It is difficult to completely remove it with traditional treatment methods, which easily causes secondary pollution. In this context, the environmentally friendly trivalent chromium electroplating process has been widely studied. The toxicity of trivalent chromium is only 1% of that of hexavalent chromium, which is relatively friendly to the environment. No chromium mist is generated during the electroplating process, which reduces the harm to the operating environment. Wastewater treatment is relatively easy, reducing treatment costs.

[0003] For example, in the patent CN 108456898 A of the full sulfate system, "A low-concentration sulfate trivalent chromium rapid chromium plating solution and its preparation method", the main salt is 15-35 g / L, the main complexing agent and the auxiliary complexing agent are 7.5-18 g / L, the molar ratio of the main salt to the total complexing agent is 1:0.95-2.6, the conductivity is 80-120 g / L, the buffer is 60-100 g / L, the surfactant is 10-500 mg / L, and the brightener is 60-750 mg / L. The hardness of the coating obtained by the plating solution is 780-830 HV, and the chromium deposition rate is 0.25 μm / min. It is difficult to increase the deposition rate.

[0004] Another example is a room temperature environment-friendly trivalent chromium electroplating solution and an electroplating method thereof disclosed in CN 103014784A of a full chloride system: chromium trichloride 150-200 g / L, potassium thiosulfate 80-90 g / L, potassium chloride 65-75 g / L, boric acid 30-50 g / L, ammonium oxalate 10-15 g / L, ammonium bromide 5-10 g / L, coumarin 0.2-0.5 g / L, sodium dodecyl sulfate 0.02-0.04 g / L, sodium dioctyl sulfosuccinate 0.02-0.2 g / L. The electroplating solution can obtain 10-15 μm and a hardness of 600-800 HV after electroplating for 20-30 min. The plating solution contains a large amount of chloride, and a large amount of chlorine gas will be generated during electroplating, which has certain environmental hazards.

[0005] It can be seen that trivalent chromium electroplating has not completely replaced hexavalent chromium. At present, there are still color problems, slow deposition speed, difficulty in thickening, and low hardness. It is mainly used in decorative trivalent chromium electroplating with relatively low film thickness requirements. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation and electroplating method of a trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system, wherein the chromium layer deposition rate is 0.5 to 1 μm / min, the thickness can reach 29 μm after electroplating for 1 hour, the coating is bright, and the hardness is ≥1000 HV. The problems of slow deposition rate and difficulty in thickening of trivalent chromium electroplating are solved, and the chloride content of the present invention is small.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system comprises: a trivalent chromium salt, a complexing agent, a conductive salt, a stabilizer, a buffer, a wetting agent and water.

[0009] Preferably, the following components are included: 50-75 g / L of the trivalent chromium salt, 15-30 g / L of the complexing agent, 150-200 g / L of the conductive salt, 3-5 ml / L of the stabilizer, 60-80 g / L of the buffer, and 1-3 ml / L of the wetting agent, and the volume is fixed with water.

[0010] Preferably, a pH regulator is also included; the pH of the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system is within the range of 2.0 to 3.0.

[0011] Preferably, the trivalent chromium salt includes one or more of chromium sulfate and chromium chloride; the complexing agent includes one or more of formic acid, acetic acid, glycine, tartaric acid, malic acid, citric acid and salts thereof; the conductive salt includes one or more of potassium sulfate and sodium sulfate; the buffer includes one or more of aluminum sulfate and boric acid; the stabilizer includes one or more of methanol and sodium sulfite; the wetting agent includes one or more of sodium dodecyl sulfate, sodium sulfosuccinate and polyethylene glycol 200; the pH adjuster includes one or more of sulfuric acid and sodium hydroxide.

[0012] A method for preparing the above-mentioned trivalent chromium rapid chromium plating solution of a mixed system of sulfate and chloride comprises the following steps:

[0013] A. heating a portion of water, adding the conductive salt and the stabilizer, and stirring to obtain a second premixed solution;

[0014] B. adding the trivalent chromium salt, the complexing agent, the stabilizer, and the wetting agent to the premixed solution in sequence, adjusting the pH to be acidic, and adding the remaining amount of water to obtain a second premixed solution;

[0015] C. Keeping the second premixed liquid warm, and then cooling it down, to obtain the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system.

[0016] Preferably, in step A, the heating temperature includes 50-60°C; in step B, the pH adjustment includes adjusting the pH to 2.0-3.0; in step C, the insulation temperature includes 50-60°C, the insulation time includes 4 hours, and the cooling temperature includes 30-40°C; the volume ratio of water added in step A and step B includes 1:1.

[0017] An application of the above-mentioned trivalent chromium rapid chromium plating solution of a mixed system of sulfate and chloride, characterized in that it is used for electroplating.

[0018] Preferably, the method comprises the following steps:

[0019] S1, degreasing;

[0020] S2, washing;

[0021] S3, activation;

[0022] S4, washing;

[0023] S5, Chrome plating:

[0024] S5-1, filling the plating tank with the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system;

[0025] S5-2, set the working temperature;

[0026] S5-3, adjusting the circulation flow rate of the plating solution;

[0027] S5-4, immersing the workpiece into the plating solution tank;

[0028] S5-5, setting the distance between cathode and anode;

[0029] S5-6, set the current density and start chrome plating;

[0030] S6. Wash with water to obtain the electroplated workpiece.

[0031] Preferably, in step S5-2, the operating temperature is 30-40°C; in step S5-3, the plating solution circulation flow rate is twice per hour; in step S5-5, the distance between the cathode and the anode is 4-6 cm, and the area ratio of the cathode to the anode is 1:1.2; in step S5-6, the current density is 8-13 A / dm 2 , so that the chromium layer deposition rate is within the range of 0.5 to 1 μm / min.

[0032] The plating solution circulation flow rate is to circulate the plating solution in the tank twice per hour. If the plating solution circulation speed is too fast, it will be difficult to successfully deposit the chromium layer on the cathode. If it is too slow, the chromium hydroxyl bridge compounds formed during electroplating will accumulate near the cathode, preventing further thickening of the plating layer.

[0033] The distance between the cathode and the anode is 4 to 6 cm, the cathode and anode area ratio is 1:1.2, and the anode adopts a DSA anode, which can reduce the oxygen precipitation potential, prevent trivalent chromium from being oxidized to hexavalent chromium at the anode, and improve the stability of the plating solution.

[0034] Current density 8~13A / dm 2 Generally speaking, during trivalent chromium electroplating, hydrogen evolution is serious at the cathode, and the pH near it will increase. When the pH exceeds 4, the generated hydroxyl radicals and trivalent chromium ions in the plating solution are prone to undergo hydroxyl bridge polymerization. The polymer is very stable, making it difficult for chromium ions to deposit. It also gathers near the cathode to hinder chromium deposition. This is the main reason why the deposition rate of traditional trivalent chromium electroplating is difficult to increase. However, through long-term research, the present invention has successfully increased the deposition rate of the chromium layer to 0.5-1μm / min, and the thickness can reach 29 microns after 1 hour of electroplating. The coating is bright and has a hardness of ≥1000HV.

[0035] The working temperature range of the plating solution is 30-40° C. If the temperature is too high, the deposition rate of the coating will be reduced. If the temperature is too low, precipitation will occur and the conductivity of the plating solution will decrease.

[0036] An electroplated workpiece obtained by the above application.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] First, the complexing agent added in the present invention can inhibit the hydroxylation reaction of chromium and improve the stability of the plating solution. The optimal solution can be achieved by selecting different complexing agents and proportions.

[0039] Second, the present invention adds a high concentration buffer to stabilize the pH, so that the electroplating can be maintained for a longer time.

[0040] Third, the present invention renews the plating solution in the tank through appropriate plating solution circulation, thereby reducing the hydroxy bridge compounds in the plating solution and reducing the hindrance to chromium deposition.

[0041] Fourth, the plating solution of the present invention can be used for electroplating at a lower current density, thereby reducing the occurrence of hydroxyl bridging reaction.

[0042] Fifth, the chromium chloride in the trivalent chromium salt of the present invention can both increase the deposition rate and prevent the anode from generating hexavalent chromium during electroplating. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the SEM image of the chromium plating layer in Example 1;

[0044] Figure 2 This is the metallographic phase diagram of the chromium plating layer in Example 1. DETAILED DESCRIPTION

[0045] In order to make the technical scheme of the present invention easier to understand, the present invention will be further described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Without departing from the spirit and essence of the present invention, modifications or replacements made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0046] Example 1

[0047] Chrome plating solution preparation:

[0048] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 5g / L of sodium acetate and 4ml / l of stabilizer methanol in sequence, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, keep the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0049] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0050] Chrome plating method:

[0051] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness of the electroplating is 29 microns after 1 hour, the chromium layer deposition rate is 0.48μm / min, the coating is bright, and the hardness is 1040HV.

[0052] Example 2

[0053] Chrome plating solution preparation:

[0054] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 5g / L of sodium acetate and 4ml / l of stabilizer methanol in sequence, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, maintain the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0055] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0056] Chrome plating method:

[0057] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 , electroplating for 5 minutes, thickness of 5 microns, chromium layer deposition rate of 1μm / min, bright coating, hardness of 286HV.

[0058] Example 3

[0059] Chrome plating solution preparation:

[0060] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 70g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 5g / L of sodium acetate and 4ml / l of stabilizer methanol in sequence, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, keep the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0061] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0062] Chrome plating method:

[0063] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness of the electroplating is 27 microns after 1 hour, the chromium layer deposition rate is 0.45μm / min, the coating is bright, and the hardness is 887HV.

[0064] Example 4

[0065] Chrome plating solution preparation:

[0066] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 5g / L of glycine and 4ml / l of stabilizer methanol in turn, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, maintain the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0067] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0068] Chrome plating method:

[0069] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness is 25 microns after electroplating for 1 hour, the chromium layer deposition rate is 0.42μm / min, the coating is bright, and the hardness is 856HV.

[0070] Example 5

[0071] Chrome plating solution preparation:

[0072] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 9g / L of tartaric acid and 4ml / l of stabilizer methanol in turn, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, keep the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0073] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0074] Chrome plating method:

[0075] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness of the electroplating is 22 microns after 1 hour, the chromium layer deposition rate is 0.37μm / min, the coating is bright, and the hardness is 841HV.

[0076] Example 6

[0077] Chrome plating solution preparation:

[0078] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 8g / L of malic acid and 4ml / l of stabilizer methanol in turn, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, maintain the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0079] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0080] Chrome plating method:

[0081] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness of the electroplating is 23 microns after 1 hour, the chromium layer deposition rate is 0.38μm / min, the coating is bright, and the hardness is 845HV.

[0082] Example 7

[0083] Chrome plating solution preparation:

[0084] First, heat 50% of the volume of water to 50-60°C, add 120g / L of conductive salt sodium sulfate, 50g / L of potassium sulfate, 70g / L of buffer boric acid, stir until completely dissolved, then add 50g / L of chromium salt chromium sulfate, 5g / L of chromium chloride, 10g / L of complexing agent formic acid, 12g / L of citric acid and 4ml / l of stabilizer methanol in turn, finally add 2ml / l of 10% by weight sodium dodecyl sulfate solution of wetting agent, adjust the pH to between 2.0-3.0 with sulfuric acid or sodium hydroxide, add the remaining amount of water, keep the temperature between 50-60°C for 4 hours, and then cool to 30-40°C to obtain the plating solution.

[0085] Electroplating process: degreasing → water washing → activation → water washing → chrome plating → water washing

[0086] Chrome plating method:

[0087] The plating solution circulation flow rate is twice per hour, the distance between the cathode and the anode is 4-6cm, the cathode and anode area ratio is 1:1.2, and the current density is 10A / dm 2 The thickness is 20 microns after electroplating for 1 hour, the chromium layer deposition rate is 0.33μm / min, the coating is bright, and the hardness is 809HV.

[0088] Effect Example 1

[0089] Taking Example 1 as an example, the workpiece after electroplating was tested and analyzed by SEM and metallographic images. The results are as follows: Figure 1 , Figure 2 As shown. Figure 1 , Figure 2 It can be seen that the chrome plating is free of cracks and particles, and the coating film thickness can reach up to 29 microns, achieving an excellent chrome plating effect.

[0090] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system, characterized in that: include: Trivalent chromium salt, complexing agent, conductive salt, stabilizer, buffer, wetting agent, water.

2. The trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system as claimed in claim 1, characterized in that: The invention comprises the following components: 50-75 g / L of the trivalent chromium salt, 15-30 g / L of the complexing agent, 150-200 g / L of the conductive salt, 3-5 ml / L of the stabilizer, 60-80 g / L of the buffer, 1-3 ml / L of the wetting agent, and the volume is fixed with water.

3. The trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system as claimed in claim 1, characterized in that: It also includes a pH regulator; the pH of the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system is within the range of 2.0 to 3.

0.

4. The trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system as claimed in claim 3, characterized in that: The trivalent chromium salt includes one or more of chromium sulfate and chromium chloride; the complexing agent includes one or more of formic acid, acetic acid, glycine, tartaric acid, malic acid, citric acid and salts thereof; the conductive salt includes one or more of potassium sulfate and sodium sulfate; the buffer includes one or more of aluminum sulfate and boric acid; the stabilizer includes one or more of methanol and sodium sulfite; the wetting agent includes one or more of sodium dodecyl sulfate, sodium sulfosuccinate and polyethylene glycol 200; the pH adjuster includes one or more of sulfuric acid and sodium hydroxide.

5. A method for preparing a trivalent chromium rapid chromium plating solution of a sulfate and chloride mixed system as claimed in claim 1, characterized in that: The steps include: A. heating a portion of water, adding the conductive salt and the stabilizer, and stirring to obtain a second premixed solution; B. adding the trivalent chromium salt, the complexing agent, the stabilizer, and the wetting agent to the premixed solution in sequence, adjusting the pH to be acidic, and adding the remaining amount of water to obtain a second premixed solution; C. Keeping the second premixed liquid warm, and then cooling it down, to obtain the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system.

6. The preparation method according to claim 5, characterized in that: In step A, the heating temperature includes 50-60°C; in step B, the pH adjustment includes adjusting the pH to 2.0-3.0; in step C, the insulation temperature includes 50-60°C, the insulation time includes 4 hours, and the cooling temperature includes 30-40°C; the volume ratio of water added in step A and step B includes 1:

1.

7. An application of the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system as claimed in claim 1, characterized in that: Used for electroplating.

8. The use according to claim 7, characterized in that The steps include: S1, degreasing; S2, washing; S3, activation; S4, washing; S5, Chrome plating: S5-1, filling the plating tank with the trivalent chromium rapid chromium plating solution of the sulfate and chloride mixed system; S5-2, set the working temperature; S5-3, adjusting the circulation flow rate of the plating solution; S5-4, immersing the workpiece into the plating solution tank; S5-5, setting the distance between cathode and anode; S5-6, set the current density and start chrome plating; S6. Wash with water to obtain the electroplated workpiece.

9. The use according to claim 8, characterized in that In step S5-2, the working temperature includes 30 to 40°C; in step S5-3, the plating solution circulation flow rate includes circulating the plating solution in the tank twice per hour; in step S5-5, the distance between the cathode and the anode includes 4 to 6 cm, and the area ratio of the cathode to the anode includes 1:1.2; in step S5-6, the current density includes 8 to 13 A / dm 2 .

10. An electroplated workpiece obtained by the use as claimed in claim 7.

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