CN115386868A - Zinc-plating black passivation solution and preparation method thereof - Google Patents
Zinc-plating black passivation solution and preparation method thereof Download PDFInfo
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- CN115386868A CN115386868A CN202211159378.7A CN202211159378A CN115386868A CN 115386868 A CN115386868 A CN 115386868A CN 202211159378 A CN202211159378 A CN 202211159378A CN 115386868 A CN115386868 A CN 115386868A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/24—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
- C23C22/26—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also organic compounds
- C23C22/27—Acids
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
- C23C22/77—Controlling or regulating of the coating process
Abstract
The invention belongs to the technical field of electroplating, and particularly relates to a zinc-plating black passivation solution and a preparation method thereof; according to the invention, by researching the components and the content of the black galvanized passivation solution, the problems of part appearance defects, weak adhesion of a passivation film and film thickness of the passivation film after passivation by using a conventional black passivation solution are solved. By researching the component content of the passivation solution, a new galvanized black passivation solution is obtained, and the appearance consistency of a product can be ensured; the wear resistance of the passive film of the product, and the like. The one-time acceptance and verification yield and the production efficiency of the product are improved.
Description
Technical Field
The invention belongs to the technical field of electroplating, and particularly relates to a zinc-plating black passivation solution and a preparation method thereof.
Background
The passivating solution can make the metal surface be in a passive state. Generally used for post-plating treatment of zinc plating, cadmium plating and other plating layers. The purpose is to form a surface state on the surface of the plating layer which can prevent the normal reaction of metal, improve the corrosion resistance of the plating layer and increase the product appearance. The main components of the common passivation solution are chromic acid, nitric acid and sulfuric acid. However, since chromic acid causes environmental pollution, in some occasions, the product requires silvery white or blue white, and the iridescent passivation film generated after the three-acid passivation treatment can also be subjected to alkali liquor bleaching treatment (white passivation), but the corrosion resistance of the coating is reduced.
The prior art often adopts two formulas: 1. chromic anhydride, sulfuric acid, nitric acid, molybdate, and the like; 2. dichromate, copper sulfate, sulfuric acid, and the like. The product processing practice through the field processing condition and the production period of the product shows. The product processed by the formula of (chromic anhydride, sulfuric acid, nitric acid and molybdate) has the same passivation time and solution temperature when the product is processed even if the chemical materials are added after the components of the bath solution are changed rapidly in the process of processing the product. Each passivation is 200dm 2 After the product is produced, the appearance color difference of the parts is large. After long-term processing of products, customers have differences in product appearance consistency, do not accept the product appearance, and need to keep the appearance consistency of the same batch of products after black passivation approximately consistent. By adopting the traditional formulas of dichromate, copper sulfate, sulfuric acid and the like, after the product is passivated, the bonding force of a passivation film is poor, parts rub against each other, the surface of the part is scratched by the passivation film, the appearance of the part is inconsistent, and the part is in black and white alternate stripes.
Patent document CN101899658B discloses a zinc-plating dark green passivation solution, which comprises the following components per liter: 20-35g/L of chromic anhydride, 10-11ml/L of phosphoric acid with d =1.7, 2-2.5ml/L of nitric acid with d =1.4, 2-2.5ml/L of sulfuric acid with d =1.84, 4-5ml/L of glacial acetic acid and 0.007-0.008g/L of silver nitrate. The essence of the method is to provide a passivation solution with a new color (dark green), and the passivation solution prepared by matching chromic anhydride, sulfuric acid, nitric acid and other raw materials still has the condition of appearance color difference during long-term processing.
Disclosure of Invention
The invention provides a zinc-plating black passivation solution and a preparation method thereof for solving the problems.
The method is realized by the following technical scheme:
1. a black passivating solution for zinc plating, which comprises a zinc plating solution,the formula of the galvanized black passivation solution is as follows: silver nitrate (AgNO) 3 ) 0.8-1.2g/L of sulfuric acid (H) 2 SO 4 ) 0.4-0.6ml/L of chromic anhydride (CrO) 3 ) 1.2-1.8g/L, acetic acid (CH) 3 COOH) 1.2-1.8ml/L, potassium dichromate (K) 2 Cr 2 O 7 ) 0.6-0.8g/L of water and 1L of water.
Further, the optimal formula is as follows: 1.0g/L of silver nitrate, 0.5ml/L of sulfuric acid, 1.5g/L of chromic anhydride, 1.5ml/L of acetic acid, 0.7g/L of potassium dichromate and 1L of water.
Further, the pH value of the zinc-plating black passivating solution is 1.3-1.8.
2. The preparation method of the galvanized black passivation solution comprises the following steps:
(1) Adding potassium dichromate into distilled water with the volume of 1/3 of the volume of the solution preparation volume, and fully dissolving; adding chromic anhydride into the solution while stirring to fully dissolve the chromic anhydride; finally, adding sulfuric acid according to the formula;
(2) And (2) fully dissolving silver nitrate in distilled water, adding the solution prepared in the step (1), fully stirring to fully dissolve the silver nitrate, adding the residual distilled water in the formula, standing the solution for 1-2 hours, and adding an acetic acid solution to obtain the galvanized black passivation solution.
Further, the distilled water for dissolving the silver nitrate in the step (2) is distilled water in the formula, and the dosage of the distilled water is as follows: and (2) silver nitrate: distilled water =1.
3. The specific using method of the zinc-plating black passivating solution comprises the following steps:
under the condition of normal temperature (generally at 20 ℃), the part before passivation is subjected to light extraction in nitric acid solution for 2-5 seconds. Passivating after the secondary water washing and the primary purified water washing, wherein the passivating temperature is 15-30 ℃, and the passivating time is 50-75s. And after passivation, washing with purified water, and then washing with water and drying.
1. Formulation screening of zinc-plating black passivation solution and corresponding salt spray test
In the test, the salt spray test time (h) represents the time from the start of the test to the occurrence of white rust of the test piece.
1. Content of sulfuric acid in passivation solution: 0.5ml/L; chromic anhydride: 1.5g/L; acetic acid: 1.5ml/L; potassium dichromate: 0.7g/L; the silver nitrate content was tested from 0.6-1.3g/L and the results are shown in Table 1.
TABLE 1
When the content of silver nitrate in the solution is lower than 0.8g/L, silver ions in the solution cannot be completely complexed with other metal ion solutions, the color difference of a black passive film formed on the surface of a part is large, the film is slightly light and white, the film is thin, and the corrosion resistance of the film is poor. When the content of silver nitrate in the solution exceeds 1.2 g/L; the silver nitrate in the solution can precipitate, the solution is turbid, the precipitate can be attached to the surface of the part, and the black passivation film layer is loosened and poor in adhesion. The raw material waste is large, and a good black passivation film layer of the part cannot be obtained.
2. Content of silver nitrate in passivation solution: 0.8g/L; chromic anhydride: 1.5g/L; acetic acid: 1.5ml/L; potassium dichromate: 0.7g/L; the sulfuric acid content was tested from 0.35-0.65ml/L and the results are shown in Table 2.
TABLE 2
The main role of sulfuric acid is the rate at which black passive films are formed. When the content is less than 0.4, the time for forming a black passive film on the surface of the part is long, and it takes more than 70 seconds to form the black passive film. The formed passive film is thin and has relatively poor corrosion resistance. When the content is higher than 0.6, the acidity of the solution is higher, the time for forming the passive film is shorter, the black passive film can be formed only in about 25s, but the formed black passive film is loose, the adhesion force of the film layer is poor, and black marks can be formed by lightly wiping the film with hands.
3. Content of silver nitrate in passivation solution: 0.8g/L; sulfuric acid: 0.5ml/L; acetic acid: 1.5ml/L; potassium dichromate: 0.7g/L; the chromic anhydride content was tested from 1.1-1.9g/L and the results are shown in Table 3.
TABLE 3
Chromic anhydride in the solution is used for complexing silver nitrate, and the silver nitrate is complexed into a complex silver chromate compound in the solution and is deposited on the surface of the part to form a black conversion film layer (namely a black passivation film). At lower contents, the complexing speed of silver ions is slower, and the solution will precipitate. When the content is higher, the complexing speed of silver ions is higher, and the acidity of the solution is enhanced. The formed passivation film layer has high content of chromium anhydride ions, and the formed black passivation film layer has reddish appearance and poor corrosion resistance.
4. Content of silver nitrate in passivation solution: 0.8g/L; sulfuric acid: 0.5ml/L chromic anhydride: 1.5g/L; acetic acid: 1.5ml/L; potassium dichromate: 0.7g/L; the acetic acid content was tested from 1.1-1.9ml/L and the results are shown in Table 4.
TABLE 4
The higher the content of acetic acid in the solution is, the poor adhesion of the passivation film is; the lower the content, the thinner the film layer of the passivation film.
5. Content of silver nitrate in passivation solution: 0.8g/L; sulfuric acid: 0.5ml/L; chromic anhydride: 1.6g/L; acetic acid: 1.5ml/L; the potassium dichromate content was tested from 0.5 to 0.9g/L and the results are shown in Table 5.
TABLE 5
The main function of potassium dichromate is to complex the silver ions in solution with chromic anhydride. Complex silver-complexing compounds are formed which in turn deposit on the surface of the part. The higher the content is, the redder the appearance of the formed black passivation film is, the film is not good in compactness, and the corrosion resistance of the film is poor. The lower the content, the more yellow the film appearance, the thinner the film and the longer the film forming time.
In conclusion, the invention has the beneficial effects that: according to the invention, by researching the components and the content of the black galvanized passivation solution, the problems of part appearance defects and weak adhesion of a passivation film after passivation by using a conventional black passivation solution are solved. And analyzing the solution according to the analysis period, and controlling the thickness of the membrane when the temperature of the solution is controlled to be 20-25 ℃ and the passivation time is controlled to be 55-65 seconds. By researching the component content of the passivation solution, a new galvanized black passivation solution is obtained, and the appearance consistency of a product can be ensured; the wear resistance of the passive film of the product, and the like. The one-time acceptance rate and the production efficiency of the product are improved.
The content of acetic acid in the passivation solution is as follows: 1.2 to 1.8ml/L, and a large amount of data show that the acetic acid in the formula of the passivation solution in the prior art is only used for adjusting the pH value of the solution, but no specific content value is required. According to the invention, through a large number of tests, the content of acetic acid is summarized, the pH value of the solution can be maintained, a black passivation film formed on a part can be ensured to have good adhesive force, and the passivation film can be ensured to have good corrosion resistance. When the contents of various chemical components in the formula are added according to the invention, the pH value of the solution can be naturally controlled to be as follows: 1.3-1.8, does not need to manually adjust the pH value again, and can meet the production requirement.
Drawings
Fig. 1 is a salt spray test report of a hex head bolt passivated with a passivating solution prepared in example 1.
Fig. 2 is a metallographic test report of the thickness of the hexagonal head bolt coating passivated by the passivating solution prepared in example 1.
Detailed Description
The following description will explain the embodiments of the present invention in further detail, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are still within the scope of the present invention as claimed in the claims.
Example 1
1. The galvanized black passivation solution comprises the following formula: silver nitrate (AgNO) 3 ) 1.0g/L sulfuric acid (H) 2 SO 4 ) 0.5ml/L of chromic anhydride (CrO) 3 ) 1.5g/L, acetic acid (CH) 3 COOH) 1.5ml/L, potassium dichromate (K) 2 Cr 2 O 7 ) 0.7g/L and 1L of water.
2. The preparation method of the galvanized black passivation solution comprises the following steps:
(1) Adding potassium dichromate into distilled water with the volume of 1/3 of the volume of the solution preparation volume, and fully dissolving; adding chromic anhydride into the solution while stirring to fully dissolve the chromic anhydride; finally, adding sulfuric acid according to the formula;
(2) And (2) fully dissolving silver nitrate by using distilled water (water in the formula) with equal mass, adding the dissolved silver nitrate into the solution prepared in the step (1), fully stirring to fully dissolve the dissolved silver nitrate, adding the residual distilled water in the formula, standing the solution for 2 hours, and adding an acetic acid solution to obtain the galvanized black passivation solution.
Example 2
1. The zinc-plating black passivation solution comprises the following formula: silver nitrate (AgNO) 3 ) 0.8g/L sulfuric acid (H) 2 SO 4 ) 0.4ml/L of chromic anhydride (CrO) 3 ) 1.2g/L, acetic acid (CH) 3 COOH) 1.2ml/L, potassium dichromate (K) 2 Cr 2 O 7 ) 0.6g/L and 1L of water.
2. The preparation method of the galvanized black passivation solution comprises the following steps:
(1) Adding potassium dichromate into distilled water with the volume of 1/3 of the volume of the solution preparation volume, and fully dissolving; adding chromic anhydride into the solution while stirring to fully dissolve the chromic anhydride; finally, adding sulfuric acid according to the formula;
(2) Fully dissolving silver nitrate in distilled water (water in the formula) with equal mass, adding the dissolved silver nitrate into the solution prepared in the step (1), fully stirring the solution to fully dissolve the silver nitrate, adding the residual distilled water in the formula, standing the solution for 1 hour, and adding an acetic acid solution to obtain the galvanized black passivation solution.
Example 3
1. The galvanized black passivation solution comprises the following formula: silver nitrate (AgNO) 3 ) 1.2g/L sulfuric acid (H) 2 SO 4 ) 0.6ml/L of chromic anhydride (CrO) 3 ) 1.8g/L, acetic acid (CH) 3 COOH) 1.8ml/L, potassium dichromate (K) 2 Cr 2 O 7 ) 0.8g/L and 1L of water.
2. The preparation method of the galvanized black passivation solution comprises the following steps:
(1) Adding potassium dichromate into distilled water with the volume of 1/3 of the volume of the solution preparation volume, and fully dissolving; adding chromic anhydride into the solution while stirring to fully dissolve the chromic anhydride; finally, adding sulfuric acid according to the formula;
(2) Fully dissolving silver nitrate in distilled water (water in the formula) with equal mass, adding the dissolved silver nitrate into the solution prepared in the step (1), fully stirring the solution to fully dissolve the silver nitrate, adding the residual distilled water in the formula, standing the solution for 2 hours, and adding an acetic acid solution to obtain the galvanized black passivation solution.
Claims (6)
1. The galvanized black passivation solution is characterized in that the formula of the galvanized black passivation solution is as follows: 0.8-1.2g/L of silver nitrate, 0.4-0.6ml/L of sulfuric acid, 1.2-1.8g/L of chromic anhydride, 1.2-1.8ml/L of acetic acid, 0.6-0.8g/L of potassium dichromate and 1L of water.
2. The galvanized black passivation solution of claim 1, wherein the formulation of the galvanized black passivation solution is: 1.0g/L of silver nitrate, 0.5ml/L of sulfuric acid, 1.5g/L of chromic anhydride, 1.5ml/L of acetic acid, 0.7g/L of potassium dichromate and 1L of water.
3. The black zinc plating passivation solution of any of claims 1 or 2, wherein the black zinc plating passivation solution has a pH of 1.3 to 1.8.
4. The method for preparing a zinc-plating black passivation solution according to any one of claims 1 or 2, characterized by comprising the steps of:
(1) Adding potassium dichromate into distilled water with the volume of 1/3 of the volume of the solution preparation volume, and fully dissolving; adding chromic anhydride into the solution while stirring to fully dissolve the chromic anhydride; finally, adding sulfuric acid according to the formula;
(2) And (2) fully dissolving silver nitrate in distilled water, adding the solution prepared in the step (1), fully stirring to fully dissolve the silver nitrate, adding the residual distilled water in the formula, standing the solution for 1-2 hours, and adding an acetic acid solution to obtain the galvanized black passivation solution.
5. The method for preparing a zinc-plating black passivation solution according to claim 4, wherein the distilled water of the step (2) is distilled water in a formula, and the distilled water is used in the following amount: and (2) silver nitrate: distilled water =1.
6. A black galvanised passivation solution according to any one of claims 1 or 2, characterized in that it is used at a temperature of 15-30 ℃ and for a passivation time of 50-75s.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1074950A (en) * | 1992-01-28 | 1993-08-04 | 杭州大学 | Chemical blacking agent for surface of galvanized workpiece |
| CN101191208A (en) * | 2006-11-23 | 2008-06-04 | 天津市瀚隆镀锌有限公司 | Zinc plating surface blacking agent |
| CN101899658A (en) * | 2009-05-27 | 2010-12-01 | 潍坊学院 | Galvanized greenblack passivation solution and preparation method thereof |
| CN111101122A (en) * | 2020-02-19 | 2020-05-05 | 广州三孚新材料科技股份有限公司 | Electrogalvanizing black passivation solution and preparation method thereof |
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- 2022-09-22 CN CN202211159378.7A patent/CN115386868A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1074950A (en) * | 1992-01-28 | 1993-08-04 | 杭州大学 | Chemical blacking agent for surface of galvanized workpiece |
| CN101191208A (en) * | 2006-11-23 | 2008-06-04 | 天津市瀚隆镀锌有限公司 | Zinc plating surface blacking agent |
| CN101899658A (en) * | 2009-05-27 | 2010-12-01 | 潍坊学院 | Galvanized greenblack passivation solution and preparation method thereof |
| CN111101122A (en) * | 2020-02-19 | 2020-05-05 | 广州三孚新材料科技股份有限公司 | Electrogalvanizing black passivation solution and preparation method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 尚书定: "镀锌层的黑色钝化", 电镀与精饰, no. 01, pages 28 - 30 * |
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