CN108866586B - A kind of electroplating solution of trivalent chromium system electrodepositing ferrochromium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses an electroplating solution for electrodepositing ferrochromium alloy in a trivalent chromium system and a preparation method thereof. Valence chromium auxiliary complexing agent, ferrous main salt, conductive salt, buffer, stabilizer, surfactant and compound brightener. The present invention coordinates trivalent chromium by means of complex coordination, which reduces the coordination ability of water molecules to trivalent chromium, thereby improving the deposition efficiency of chromium on the cathode surface. The specific main complexing agents of the present invention are all small molecular carboxylic acids and their salts, which can replace water molecules to complex with trivalent chromium to promote the electroreduction of trivalent chromium, and the main complexing agent and the specific auxiliary complexing agent together The trivalent chromium ion is complexed to form a combined complex complex, which further promotes the electroreduction of trivalent chromium.

Description

A kind of electroplating solution of trivalent chromium system electrodepositing ferrochromium alloy and preparation method thereof

technical field

The invention belongs to the technical field of electroplating solutions, and in particular relates to an electroplating solution for electrodepositing ferrochromium alloys in a trivalent chromium system and a preparation method thereof.

Background technique

Ferrochromium alloys have high mechanical strength and hardness, and amorphous ferrochromium alloys also have excellent magnetic properties, excellent corrosion resistance and electrocatalytic activity.

The preparation methods of ferrochromium alloy are mainly electric furnace method, shaft furnace method, plasma method, smelting reduction method and electrodeposition method. Among them, the preparation of ferrochromium alloy by electrodeposition has the advantages of simple operation, low cost, controllable alloy composition and thickness, and can be electroplated on the surface of complex parts.

Ma Zhengqing, et al. (Ma Zhengqing, Li Wenxian, Tan Dunqiang, Xiao Yude, Yu Kun. Study on Electrodeposited Fe-Cr Alloy [J]. Surface Technology, 2001, 30(1): 1-2, 9) on the effect of trivalent chromium salts Electrodeposition of Fe-Cr alloys in dimethylamide (DMF) aqueous solution system was carried out, and bright alloy coatings containing Cr12%-65% (mass fraction) were obtained, and the cathode current density, bath pH value, three Effect of valence chromium salt concentration on coating composition and corrosion resistance of alloy coating. However, no stabilizer is added to the plating solution, Fe ²⁺ is easily oxidized to Fe ³⁺ , which reduces the stability of the plating solution, and the current density only has a good deposition effect in the range of 3-6A/dm ² . Xu Zhixian et al (Xu Zhixian, Chen Ji, Chen Xiaoming, Sun Yanwei, Pu Nan. Effect of Current Density on Corrosion Resistance of Fe-Cr Alloy Coatings [J]. Electroplating and Environmental Protection, 2016, 36(2): 12-14) in chloride -In the electrolyte of sulfate mixed system, nanocrystalline Cr-Fe alloy coatings with iron content of 60%-85% were prepared on brass substrates by changing the current density, and the corrosion resistance of ferrochromium coatings was studied. However, only a single complexing agent is used in the composition of the bath. Lv Wei et al. (Lv Wei, Zhang Yongxiang, Lin Aiqin. Discussion on Electrodeposition Mechanism of Amorphous Fe-Cr Alloy Coatings [J]. Journal of Fujian Normal University Fuqing Branch, 2008, (1): 13-17) in simple trivalent chromium The effect of glycine on co-deposition of ferrochromium alloys was studied in ferrous main salt solution. There are also problems in the plating solution of this process, such as the lack of stabilizer and the direct use of hydrated complex trivalent chromium main salt as the research object.

At present, the electroplating process for preparing ferrochromium alloys mostly uses a single complexing agent, which easily leads to a large difference in the deposition potential of trivalent chromium and divalent iron complexes in the plating solution, which is not conducive to the co-deposition of ferrochromium alloys; most of the plating solutions lack suitable As the stabilizer, Fe ²⁺ is easily oxidized to Fe ³⁺ , which affects the stability of the plating solution; the structure and iron content of the ferrochromium alloy coating are single, and the controllability of the content ratio of chromium and iron in the coating and the crystal structure of the coating are lacking.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects of the prior art, and to provide a kind of electroplating solution for electrodepositing ferrochromium alloy of trivalent chromium system.

Another object of the present invention is to provide a method for preparing the above-mentioned electroplating solution.

The technical scheme of the present invention is as follows:

An electroplating solution for electrodepositing ferrochromium alloy in trivalent chromium system, the solvent is water, pH=2.7-4.5, and the solute includes trivalent chromium main salt, trivalent chromium main complexing agent, trivalent chromium auxiliary complexing agent, ferrous iron Main salt, conductive salt, buffer, stabilizer, surfactant and compound brightener; wherein, the molar ratio of Cr ³⁺ and Fe ²⁺ is 4.5～27:1, and the content of iron in the corresponding coating is 9.3～ 45.4wt%; the molar ratio of the total complexing agent to the trivalent chromium main salt is 0.9-2.2:1, and the total complexing agent is composed of the trivalent chromium main complexing agent and the trivalent chromium auxiliary complexing agent;

The above trivalent chromium main salt is chromium sulfate, chromium sulfate hydrate (Cr ₂ (SO ₄ ) ₃ ·6H ₂ O), chromium potassium sulfate or chromium potassium sulfate hydrate (KCr(SO ₄ ) ₂ ·12H ₂ O), Its content in the electroplating solution is 10-80g/L, and the content of trivalent chromium in the above-mentioned electroplating solution is 2.1-8.4g/L;

Above-mentioned trivalent chromium main complexing agent comprises at least one in adipic acid, adipate, succinic acid, succinate, oxalic acid and oxalate, and this trivalent chromium main complexing agent is in this electroplating. The content in the liquid is 2～18.4g/L;

The content of the above-mentioned trivalent chromium auxiliary complexing agent in the electroplating solution is 1～9.2g/L;

The above-mentioned ferrous main salt includes ferrous glycinate ((NH ₂ CH ₂ COO) ₂ Fe), and its content in the electroplating solution is 0.31-8.24 g/L;

The above conductive salt can improve the conductivity of the plating solution and reduce power consumption, and the content of the conductive salt in the plating solution is 70-100 g/L;

The above-mentioned buffer can stabilize the pH of the electroplating solution and maintain the stability of the electroplating solution, and its content in the electroplating solution is 70-120 g/L;

The above stabilizer is used to prevent Fe ²⁺ from being oxidized into Fe ³⁺ , improve the stability of the plating solution, and reduce the stress of the plating layer, and its content in the plating solution is 1-8 g/L;

The content of the above-mentioned surfactant in the electroplating solution is 5-120 mg/L;

The content of the above-mentioned composite brightener in the electroplating solution is 45-550 mg/L.

In a preferred embodiment of the present invention, the trivalent chromium auxiliary complexing agent comprises at least one of glycine, aspartic acid, polyaspartic acid and niacin.

In a preferred embodiment of the present invention, the conductive salt includes at least one of potassium sulfate, sodium sulfate and ammonium sulfate.

In a preferred embodiment of the present invention, the buffer comprises at least one of acetic acid, acetate, boric acid, borate, phthalic acid and phthalate.

In a preferred embodiment of the present invention, the stabilizer includes at least one of carotenoids, ascorbic acid, sodium erythorbate, hydrazine hydrate and selenium dioxide.

In a preferred embodiment of the present invention, the surfactant includes at least one of sodium lauryl sulfate, lignosulfonate, polyoxyethylene ether, polyethylene glycol and isomeric decahydrin.

In a preferred embodiment of the present invention, the composite brightener is composed of a first component and a second component, wherein the first component is bisbenzenesulfonimide, and the second component is allylsulfonic acid At least one of sodium, thiourea, ethylene thiourea, 2-mercaptobenzimidazole and sodium phenyl polydithiopropane sulfonate.

The preparation method of above-mentioned electroplating solution, comprises the steps:

(1) adding trivalent chromium main salt, trivalent chromium main complexing agent and trivalent chromium auxiliary complexing agent to water, stirring and dissolving, and keeping the temperature at 60～65 ℃ for 1.8～2.5h to obtain the first solution;

(2) adding ferrous main salt and stabilizer in the first solution, and stirring and dissolving to obtain the second solution;

(3) adding conductive salt and buffer in the second solution, stirring and dissolving to obtain the third solution;

(4) in the 3rd solution, add surfactant and compound brightener, add water again to the required volume to obtain the 4th solution;

(5) The electroplating solution is obtained after the pH of the fourth solution is adjusted to 2.7-4.5 with sulfuric acid or sodium hydroxide.

The electroplating process parameters of the electroplating solution for electrodepositing ferrochromium alloy using the trivalent chromium system of the present invention are preferably as follows: the use temperature of the electroplating solution is 40-65° C., the optimal cathodic current density range is 1.0-25.0A/dm ² , and the electroplating solution The time is 1 to 120 minutes, and the stirring method of the electroplating solution is mechanical stirring.

When using the electroplating solution of the trivalent chromium system for electrodepositing ferrochromium alloy for electroplating, DSA (titanium alloy surface coated with a coating such as iridium oxide) material is used as the anode. The DSA anode is beneficial to the precipitation of oxygen in the anode, preventing the oxidation of trivalent chromium to hexavalent chromium, and improving the stability of the electroplating solution.

The beneficial effects of the present invention are:

1. The present invention uses the complex coordination method to coordinate trivalent chromium, which reduces the coordination ability of water molecules to trivalent chromium, thereby improving the deposition efficiency of chromium on the cathode surface.

2. The specific main complexing agents of the present invention are small molecular carboxylic acids and their salts, which can replace water molecules to complex with trivalent chromium and promote the electroreduction of trivalent chromium. The agent complexes trivalent chromium ions together to form a combined complex complex, which further promotes the electroreduction of trivalent chromium.

3. The present invention selects ferrous glycinate as the main ferrous salt, and the ferrous glycinate is dissolved in water to form a six-coordinate complex, so that the reduction potentials of trivalent chromium and ferrous ions are similar, and the co-deposition of ferrochromium alloys is promoted, Improve co-deposition efficiency.

4. A specific stabilizer is added to the electroplating solution of the present invention to prevent Fe ²⁺ from being oxidized to Fe ³⁺ , thereby improving the stability of the electroplating solution and reducing the tensile stress of the ferrochromium alloy coating.

5. Adding specific brighteners and surfactants to the electroplating solution of the present invention, the quality of the ferrochromium alloy coating is significantly improved, showing the characteristics of fine grains, bright and smooth appearance, less pores and the like; wherein the ferrochromium alloy plating process is accompanied by a large amount of hydrogen evolution . Surfactant has surface activity and can be used as the carrier of brightener, which can improve the brightness and bright current density range of the coating, reduce the pores of the coating, and improve the bonding force between the coating and the substrate. The brightener can refine the particles of the coating, significantly Improve the performance of the coating and improve the brightness of the coating.

6. In the present invention, by adjusting the ratio of chromium and iron metal salts in the plating solution, ferrochromium alloys can be electroplated to replace solid solution crystalline alloys (iron content is greater than or equal to 9.3wt%, less than 13.8wt%), crystalline and amorphous mixed states. Alloys (iron content of 13.8-24.1 wt %) and amorphous alloys (iron content of more than 24.1 wt % and less than or equal to 45.4 wt %) achieve controllable structure of chromium-iron alloys.

Description of drawings

FIG. 1 is a SEM topography diagram of the coating of Example 1 of the present invention.

Fig. 2 is the XRD pattern of different iron contents of the ferrochromium alloy coating layer of the present invention.

Detailed ways

The technical solutions of the present invention will be further illustrated and described below through specific embodiments in conjunction with the accompanying drawings.

Examples 1 to 3

The preparation method of the electroplating solution of the present embodiment is as follows:

(1) adding trivalent chromium main salt, trivalent chromium main complexing agent and trivalent chromium auxiliary complexing agent to water, stirring and dissolving, and keeping the temperature at 60～65 ℃ for 1.8～2.5h to obtain the first solution;

(2) adding ferrous main salt and stabilizer in the first solution, and stirring and dissolving to obtain the second solution;

(3) adding conductive salt and buffer in the second solution, stirring and dissolving to obtain the third solution;

(4) in the 3rd solution, add surfactant and compound brightener, add water again to the required volume to obtain the 4th solution;

(5) The electroplating solution is obtained after the pH of the fourth solution is adjusted to 2.7-4.5 with sulfuric acid or sodium hydroxide.

Using copper sheet as the base material, the process flow of the electroplating solution prepared above is: ultrasonic degreasing (50～70℃, time 3～5min)→water washing→pickling activation (sulfuric acid 30mL/L, 20～40s)→ Water washing → deionized water washing → electrochromic iron plating → water washing.

Examples 1-3 In the process of electrodepositing ferrochromium alloy in trivalent chromium system, the composition and dosage of raw materials of electroplating solution, as well as experimental parameters and some experimental results are shown in Table 1 below.

Table 1 prepares 1L of the ferrochromium alloy electroplating solution

Performance evaluation

When using the electroplating solution of the present invention for electroplating, the appearance of the coating is observed by visual method, and the coating is stainless steel within the allowable range of the process conditions;

After the thermal shock test, the copper chrome-plated iron parts were heated to 200 °C in an oven and kept for 2 hours, and then quenched in cold water.

Scanning electron microscopy (SEM) was used to observe the coating as a dense cellular structure (as shown in Figure 1). Through X-ray diffraction (XRD) analysis, it is found that there is a corresponding relationship between the coating structure and the coating iron content, as shown in Figure 2. With the increase of iron content, the coating structure transition sequence is replacement solid solution crystalline state → crystalline state and amorphous state mixed state → non-crystalline state Crystalline. By simply adjusting the proportion of metal salts in the plating solution, a coating with corresponding structural characteristics can be obtained.

Those of ordinary skill in the art know that when the technical solution of the present invention changes within the following scope, it can still obtain the same or similar technical effects as the above-described embodiments, and still belong to the protection scope of the present invention:

An electroplating solution for electrodepositing ferrochromium alloys in a trivalent chromium system is characterized in that: the solvent is water, pH=2.7-4.5, and the solute includes a trivalent chromium main salt, a trivalent chromium main complexing agent, and a trivalent chromium auxiliary complexing agent. agent, ferrous main salt, conductive salt, buffer, stabilizer, surfactant and composite brightener; wherein, the molar ratio of Cr ³⁺ and Fe ²⁺ is 4.5-27:1, corresponding to the iron in the coating layer. The content is 9.3-45.4wt%; the molar ratio of the total complexing agent to the trivalent chromium main salt is 0.9-2.2:1, and the total complexing agent is composed of the trivalent chromium main complexing agent and the trivalent chromium auxiliary complexing agent;

The above-mentioned trivalent chromium main salt is chromium sulfate, chromium sulfate hydrate, chromium potassium sulfate or chromium potassium sulfate hydrate, and its content in the electroplating solution is 10-80 g/L, and the content of trivalent chromium in the above-mentioned electroplating solution is 10-80 g/L. The content is 2.1～8.4g/L;

Above-mentioned trivalent chromium main complexing agent comprises at least one in adipic acid, adipate, succinic acid, succinate, oxalic acid and oxalate, and this trivalent chromium main complexing agent is in this electroplating. The content in the liquid is 2～18.4g/L;

The content of the above-mentioned trivalent chromium auxiliary complexing agent in the electroplating solution is 1～9.2g/L;

The above-mentioned ferrous main salt includes ferrous glycinate, and its content in the electroplating solution is 0.31-8.24 g/L;

The content of the above-mentioned conductive salt in the electroplating solution is 70～100g/L;

The content of the above buffer in the electroplating solution is 70 to 120 g/L;

The above stabilizer is used to prevent Fe ²⁺ from being oxidized into Fe ³⁺ , and its content in the electroplating solution is 1-8 g/L;

The content of the above-mentioned surfactant in the electroplating solution is 5-120 mg/L;

The content of the above-mentioned composite brightener in the electroplating solution is 45-550 mg/L.

The trivalent chromium auxiliary complexing agent includes at least one of glycine, aspartic acid, polyaspartic acid and niacin. The conductive salt includes at least one of potassium sulfate, sodium sulfate and ammonium sulfate. The buffer includes at least one of acetic acid, acetate, boric acid, borate, phthalic acid, and phthalate. The stabilizer includes at least one of carotenoids, ascorbic acid, sodium erythorbate, hydrazine hydrate and selenium dioxide. The surfactant includes at least one of sodium lauryl sulfate, lignosulfonate, polyoxyethylene ether, polyethylene glycol and isomeric decahydrin. The composite brightener is composed of a first component and a second component, wherein the first component is bisbenzenesulfonimide, and the second component is sodium allyl sulfonate, thiourea, ethylene thiourea, At least one of 2-mercaptobenzimidazole and sodium phenyl polydithiopropane sulfonate.

The above are only the preferred embodiments of the present invention, so the scope of implementation of the present invention cannot be limited accordingly, that is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the description should still be covered by the present invention. In the range.

Claims (5)

1. the electroplating solution of a trivalent chromium system electrodepositing ferrochromium alloy, it is characterized in that: solvent is water, pH=2.7～4.5, and solute is assisted by trivalent chromium main salt, trivalent chromium main complexing agent, trivalent chromium Complexing agent, ferrous main salt, conductive salt, buffer, stabilizer, surfactant and composite brightener are composed; wherein, the mol ratio of Cr ³⁺ and Fe ²⁺ is 4.5～27: 1, and in the corresponding coating The content of iron is 9.3~45.4 wt%; the molar ratio of total complexing agent to trivalent chromium main salt is 0.9~2.2:1, and the total complexing agent is composed of trivalent chromium main complexing agent and trivalent chromium auxiliary complexing agent composition; The above-mentioned trivalent chromium main salt is chromium sulfate, chromium sulfate hydrate, chromium potassium sulfate or chromium potassium sulfate hydrate, and its content in the electroplating solution is 10 to 80 g/L, and the trivalent chromium is in the above-mentioned electroplating solution. The content is 2.1~8.4 g/L; Above-mentioned trivalent chromium main complexing agent comprises at least one in adipic acid, adipate, succinic acid, succinate, oxalic acid and oxalate, and this trivalent chromium main complexing agent is in this electroplating. The content in the liquid is 2~18.4 g/L; The above-mentioned trivalent chromium auxiliary complexing agent comprises at least one of glycine, aspartic acid, polyaspartic acid and niacin, and the content in this electroplating solution is 1～9.2 g/L; Above-mentioned ferrous main salt comprises ferrous glycinate, and its content in this electroplating solution is 0.31～8.24 g/L; Above-mentioned conductive salt comprises at least one in potassium sulfate, sodium sulfate and ammonium sulfate, and the content in this electroplating solution is 70～100 g/L; The content of above-mentioned buffer in this electroplating solution is 70～120 g/L; The above stabilizer is used to prevent Fe ²⁺ from being oxidized into Fe ³⁺ , and its content in the electroplating solution is 1-8 g/L; The content of the above-mentioned surfactant in the electroplating solution is 5-120 mg/L; The content of the above-mentioned composite brightener in the electroplating solution is 45 to 550 mg/L, and the composite brightener is composed of a first component and a second component, wherein the first component is bisbenzenesulfonimide, and the first component is bisbenzenesulfonimide. The two components are at least one of sodium allyl sulfonate, thiourea, ethylene thiourea, 2-mercaptobenzimidazole and sodium phenyl polydithiopropane sulfonate. 2. The electroplating solution according to claim 1, wherein the buffer comprises at least one of acetic acid, acetate, boric acid, borate, phthalic acid and phthalate. 3. The electroplating solution according to claim 1, wherein the stabilizer comprises at least one of carotenoids, ascorbic acid, sodium erythorbate, hydrazine hydrate and selenium dioxide. 4. The electroplating solution as claimed in claim 1, wherein the surfactant comprises sodium lauryl sulfate, lignosulfonate, polyoxyethylene ether, polyethylene glycol and isomerized ten alcohol polyoxyethylene ether at least one of them. 5. the preparation method of the electroplating solution described in any one of claim 1 to 4, is characterized in that: comprise the steps: (1) Add trivalent chromium main salt, trivalent chromium main complexing agent and trivalent chromium auxiliary complexing agent to water, stir and dissolve and keep at 60~65 ℃ for 1.8~2.5h to obtain the first solution; (2) adding ferrous main salt and stabilizer to the first solution, and stirring and dissolving to obtain the second solution; (3) Add conductive salt and buffer to the second solution, stir and dissolve to obtain a third solution; (4) Add surfactant and compound brightener to the third solution, and add water to the required volume to obtain the fourth solution; (5) The electroplating solution is obtained by adjusting the pH of the fourth solution to 2.7-4.5 with sulfuric acid or sodium hydroxide.

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