Cyanide-free cadmium plating passivation anti-tarnishing agent after high-temperature baking and application thereof
By adding imidazole compounds as anti-discolorant to the cyanobacterial cadmium plating solution, the passivation layer has been solved by adding imidazole compounds as anti-discolorant agents after high temperature baking, which has achieved high purity and fineness of the cadmium plating layer and maintaining the vividness of the passivation layer.
Patent Information
- Application Number
- CN202411906199.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-03-28
AI Technical Summary
After the cyanide-free cadmium plating layer is baked at high temperature, the organic compounds, hydroxides, oxides and other elements in the plating layer form cadmium compounds with cadmium, resulting in the color of the passivation layer being foggy, bleak, and dim, and losing its brightness.
Imidazole compounds are used as passivation and anti-discolorant after high-temperature baking of cadmium-free plating. By adding them to the cyano-free cadmium-plating solution, the purity and fineness of the cadmium-plating layer are effectively improved, and the inclusion of organic additives is prevented, and the coating structure and state are kept unchanged.
The quality of the cadmium plating layer after high temperature baking of cyanide-free cadmium plating is effectively improved, and the passivation layer is bright and thorough, which is basically the same as the state of the unbaked passivation layer.
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Figure CN119710839A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent and application thereof. Background Art
[0002] The cadmium plating layer has excellent corrosion resistance and is widely used in aviation, aerospace, marine and other anti-corrosion. In the past, cyanide cadmium plating process was mostly used, but cyanide is highly toxic and has a great impact on the environment and social safety. Therefore, the cyanide cadmium plating process is gradually being eliminated and replaced by the cyanide-free cadmium plating process.
[0003] After cadmium plating, high-strength steel parts often need to be baked at 200℃ for dehydrogenation treatment to prevent hydrogen embrittlement of parts. Due to the effect of high temperature, some organic matter, hydroxides, oxides and other elements in the plating layer will form cadmium compounds with cadmium, resulting in the passivation layer becoming foggy and dim in color during the subsequent chromate passivation. That is, when the cadmium-plated parts are passivated after high-temperature baking, the color of the passivation film will be greatly different from that of the direct passivation without baking. The color of the passivation layer of the baked parts is light, foggy and not bright; and this problem is more obvious for the cyanide-free cadmium plating layer than the cyanide cadmium plating layer. Summary of the invention
[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the main purpose of the present invention is to provide a cyanide-free cadmium plating high-temperature baking passivation anti-discoloration agent, which is added to the cyanide-free cadmium plating solution to effectively improve the purity and fineness of the cadmium plating layer, thereby preventing the structure and state of the cadmium plating layer from changing after the subsequent high-temperature baking.
[0005] The main purpose of the present invention is also to provide the application of the non-cyanide cadmium plating high-temperature baking post-passivation anti-discoloration agent in the non-cyanide cadmium plating solution.
[0006] The objective of the present invention is achieved through the following technical solutions:
[0007] A cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent, the anti-discoloration agent is an imidazole compound.
[0008] In some specific embodiments, the imidazole compound is one or a mixture of 2-hydroxybenzimidazole, 2-aminobenzimidazole, and 5-aminobenzimidazole.
[0009] Furthermore, the imidazole compound is a mixture of 2-hydroxybenzimidazole and 2-aminobenzimidazole in a mass ratio of 1:1.
[0010] Furthermore, the imidazole compound is a mixture of 2-hydroxybenzimidazole and 5-aminobenzimidazole in a mass ratio of 2:1.
[0011] Further, the imidazole compound is a mixture of 2-aminobenzimidazole and 5-aminobenzimidazole in a mass ratio of 4:1.
[0012] The purpose of the present invention is to provide an application of a cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent in a cyanide-free cadmium plating solution.
[0013] In certain specific embodiments, the mass concentration of the non-cyanide cadmium plating high-temperature baking post-passivation anti-discoloration agent in the non-cyanide cadmium plating solution is 0.05-1 g / L.
[0014] In some specific embodiments, the cyanide-free cadmium plating solution is a carboxyammonia cyanide-free cadmium plating solution, which includes the following components by mass concentration: 30 g / L EDTA, 50-70 g / L nitrilotriacetic acid, 150-200 g / L ammonium chloride, 30-50 g / L cadmium chloride, 0.5-1.5 g / L sodium dodecyl sulfate, and the pH is adjusted to 6.5 with sodium hydroxide, and the balance is water.
[0015] In some specific embodiments, the cyanide-free cadmium plating solution is an alkaline cyanide-free cadmium plating solution, which includes the following components by mass concentration: cadmium sulfate 30-50 g / L, triethanolamine 40-60 g / L, potassium tartrate: 50-150 g / L, potassium hydroxide: 5-15 g / L, DPE-III: 0.5-1.5 g / L.
[0016] Compared with the prior art, the present invention has at least the following advantages:
[0017] The present invention provides a passivation anti-discoloration agent for high-temperature baking of cyanide-free cadmium plating. The nitrogen atom in the imidazole ring of the imidazole compound has strong coordination and activation ability on the cathode surface. The rich electron cloud on the heterocyclic ring can inhibit the transitional adsorption of organic matter. The nitrogen atom in the heterocyclic ring can inhibit the generation of oxides and hydroxides, thereby effectively improving the purity of the coating and effectively preventing excessive inclusion of organic additives. After subsequent high-temperature dehydrogenation baking, the state of the coating after chromate passivation remains consistent with that before baking, and there is no fogging, misting, or dull color, thereby effectively improving the quality of the cadmium plating layer after high-temperature baking of the cyanide-free cadmium plating. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.
[0019] Figure 1 The appearance of the passivated carboxyammonia cyanide-free cadmium plating layer after baking provided in Example 1 of the present invention;
[0020] Figure 2 The appearance of the carboxyammonia cyanide-free cadmium plating layer containing an anti-discoloration agent provided in Example 1 of the present invention;
[0021] Figure 3 It is the appearance of alkaline cyanide-free cadmium plating;
[0022] Figure 4 It is the appearance of passivation after baking of alkaline cyanide-free cadmium plating containing anti-tarnish agent;
[0023] Figure 5 It is the passivated appearance of the alkaline cyanide-free cadmium plating layer containing anti-tarnish agent without baking. DETAILED DESCRIPTION
[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.
[0025] When a certain amount, concentration or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper and lower numerical limit, it should be understood that it is equivalent to specifically revealing any range by combining any pair of upper range limits or preferred numerical values with any lower range limit or preferred numerical value, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values listed herein include the endpoints of the range, and all integers and fractions within the range.
[0026] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.
[0027] The materials, methods, and examples herein are illustrative and are not to be construed as limiting unless specifically stated.
[0028] In the following examples, 2-hydroxybenzimidazole was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd. with a specification of 100 g / bottle and a content of 98%; 2-aminobenzimidazole was purchased from Bashifu Biomedical Technology Co., Ltd. with a specification of 25 kg / barrel and a content of 99%; 5-aminobenzimidazole was purchased from Zhengzhou Huiju Chemical Co., Ltd. with a specification of 100 g / bottle and a content of 97%.
[0029] Example 1
[0030] This embodiment provides a cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent, the mass ratio of 2-hydroxybenzimidazole to 2-aminobenzimidazole is 1:1;
[0031] Take the preparation of 1L of carboxyammonia cyanide-free cadmium plating solution containing anti-tarnish agent as an example, specifically:
[0032] An anti-discoloration agent (0.1 g of 2-hydroxybenzimidazole and 0.1 g of 2-aminobenzimidazole dissolved in deionized water) is added to a carboxyammonia cyanide-free cadmium plating solution, wherein the cyanide-free cadmium plating solution is a carboxyammonia cyanide-free cadmium plating solution, 30 g of EDTA, 60 g of nitrilotriacetic acid, 180 g of ammonium chloride, 40 g of cadmium chloride, and 1 g of sodium dodecyl sulfate, and the pH is adjusted to 6.5 with sodium hydroxide; finally, the volume is adjusted to 1 L with deionized water to obtain a carboxyammonia cyanide-free cadmium plating solution with an anti-discoloration agent.
[0033] In another technical solution of this embodiment, taking the preparation of 1L of alkaline cyanide-free cadmium plating solution containing an anti-discoloration agent as an example, the specific steps are as follows:
[0034] An anti-discoloration agent (0.1 g of 2-hydroxybenzimidazole and 0.1 g of 2-aminobenzimidazole dissolved in deionized water) is added to an alkaline cyanide-free cadmium plating solution, wherein the alkaline cyanide-free cadmium plating solution contains 40 g of cadmium sulfate, 50 g of triethanolamine, 100 g of potassium tartrate, 10 g / mol of potassium hydroxide, and 1 g of DPE-III. Finally, the volume is adjusted to 1 L with deionized water to obtain an alkaline cyanide-free cadmium plating solution with an anti-discoloration agent.
[0035] The workpiece is placed in the prepared carboxyammonia cyanide-free cadmium plating solution (alkaline cyanide-free cadmium plating solution) for chemical plating. After plating, the plated workpiece is taken out, the thickness of the coating is measured, and the appearance of the coating is observed.
[0036] The process parameters of chemical plating are: current density 1A / dm 2 , room temperature, the ratio of anode to cathode area is greater than 2:1, the electroplating time is 1 hour; select 50mm×50mm×2mm iron-based test pieces as workpieces for plating, one piece is directly chromic acid color passivation after plating, and the other piece is baked at 200℃ for 8h after plating, and then chromic acid color passivation is performed. Finally, the states of the passivation layers of the two test pieces are compared. The specific results are:
[0037] The carboxyammonia cyanide-free cadmium plating layer without adding anti-discoloration agent is beige, with cadmium whiskers produced in the high area, and the chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright; while the carboxyammonia cyanide-free cadmium plating layer with adding anti-discoloration agent is a uniform and delicate beige, and the chromate color passivation layer baked at 200℃ for 8h is bright and transparent colorful, which is basically the same as the unbaked passivation layer.
[0038] The alkaline cyanide-free cadmium plating layer without adding anti-discoloration agent is gray, and the chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright; the alkaline cyanide-free cadmium plating layer with adding anti-discoloration agent is uniform and delicate beige, and the chromate color passivation layer baked at 200℃ for 8h is bright and transparent colorful, which is basically the same as the unbaked passivation layer.
[0039] Example 2
[0040] This embodiment provides a cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent, the mass ratio of 2-hydroxybenzimidazole to 5-aminobenzimidazole is 2:1;
[0041] Take the preparation of 1L of carboxyammonia cyanide-free cadmium plating solution containing anti-tarnish agent as an example, specifically:
[0042] An anti-discoloration agent (0.1 g of 2-hydroxybenzimidazole and 0.05 g of 2-aminobenzimidazole dissolved in deionized water) is added to a carboxyammonia cyanide-free cadmium plating solution, wherein the cyanide-free cadmium plating solution is a carboxyammonia cyanide-free cadmium plating solution, 30 g of EDTA, 60 g of nitrilotriacetic acid, 180 g of ammonium chloride, 40 g of cadmium chloride, and 1 g of sodium dodecyl sulfate, and the pH is adjusted to 6.5 with sodium hydroxide; finally, the volume is adjusted to 1 L with deionized water to obtain a carboxyammonia cyanide-free cadmium plating solution with an anti-discoloration agent.
[0043] In another technical solution of this embodiment, taking the preparation of 1L of alkaline cyanide-free cadmium plating solution containing an anti-discoloration agent as an example, the specific steps are as follows:
[0044] An anti-discoloration agent (0.1 g of 2-hydroxybenzimidazole and 0.05 g of 2-aminobenzimidazole dissolved in deionized water) is added to an alkaline cyanide-free cadmium plating solution, wherein the alkaline cyanide-free cadmium plating solution contains 40 g of cadmium sulfate, 50 g of triethanolamine, 100 g of potassium tartrate, 10 g / mol of potassium hydroxide, and 1 g of DPE-III. Finally, the volume is adjusted to 1 L with deionized water to obtain an alkaline cyanide-free cadmium plating solution with an anti-discoloration agent.
[0045] The workpiece is placed in the prepared carboxyammonia cyanide-free cadmium plating solution (alkaline cyanide-free cadmium plating solution) for chemical plating. After plating, the plated workpiece is taken out, the thickness of the coating is measured, and the appearance of the coating is observed.
[0046] The process parameters of chemical plating are: current density 1A / dm 2 , room temperature, the ratio of anode to cathode area is greater than 2:1, and the electroplating time is 1 hour. A 50mm×50mm×2mm iron-based test piece was selected as the workpiece for plating. One piece was directly subjected to chromic acid color passivation after plating, and the other piece was baked at 200℃ for 8h after plating, and then subjected to chromic acid color passivation. Finally, the states of the passivation layers of the two test pieces were compared. The specific results are:
[0047] The carboxyammonia cyanide-free cadmium plating layer without anti-discoloration agent is beige, with cadmium whiskers in the high area. The chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright. Its appearance is as follows: Figure 1 The carboxyammonia cyanide-free cadmium plating layer with anti-discoloration agent is a uniform and delicate beige color. Figure 2 , the chromic acid color passivation layer baked at 200℃ for 8h is bright and transparent in five colors, and the unbaked passivation layer state ( Figure 5 ) are basically the same;
[0048] The alkaline non-cyanide cadmium plating layer without anti-tarnish agent is gray, and its appearance is as follows: Figure 3 The chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright; the alkaline cyanide-free cadmium plating layer with anti-discoloration agent is uniform and delicate beige, and the chromate color passivation layer baked at 200℃ for 8h is bright and transparent five-color. Its appearance is as follows Figure 4 , which is basically the same as the state of the unbaked passivation layer.
[0049] Example 3
[0050] This embodiment provides a cyanide-free cadmium plating high-temperature baking post-passivation anti-discoloration agent, the mass ratio of 2-aminobenzimidazole to 5-aminobenzimidazole is 4:1;
[0051] Take the preparation of 1L of carboxyammonia cyanide-free cadmium plating solution containing anti-tarnish agent as an example, specifically:
[0052] Adding an anti-discoloration agent (0.2 g of 2-aminobenzimidazole and 0.05 g of 5-aminobenzimidazole dissolved in deionized water) into a carboxyammonia cyanide-free cadmium plating solution, wherein the cyanide-free cadmium plating solution is a carboxyammonia cyanide-free cadmium plating solution, 30 g of EDTA, 60 g of nitrilotriacetic acid, 180 g of ammonium chloride, 40 g of cadmium chloride, and 1 g of sodium dodecyl sulfate, and adjusting the pH value to 6.5 with sodium hydroxide; finally, making the volume to 1 L with deionized water to obtain a carboxyammonia cyanide-free cadmium plating solution with an anti-discoloration agent;
[0053] In another technical solution of this embodiment, taking the preparation of 1L of alkaline cyanide-free cadmium plating solution containing an anti-discoloration agent as an example, the specific steps are as follows:
[0054] An anti-discoloration agent (0.2 g of 2-hydroxybenzimidazole and 0.05 g of 2-aminobenzimidazole dissolved in deionized water) is added to an alkaline cyanide-free cadmium plating solution, wherein the alkaline cyanide-free cadmium plating solution contains 40 g of cadmium sulfate, 50 g of triethanolamine, 100 g of potassium tartrate, 10 g / potassium hydroxide, and 1 g of DPE-III. Finally, the volume is adjusted to 1 L with deionized water to obtain an alkaline cyanide-free cadmium plating solution with an anti-discoloration agent.
[0055] The workpiece is placed in the prepared carboxyammonia cyanide-free cadmium plating solution (alkaline cyanide-free cadmium plating solution) for chemical plating. After plating, the plated workpiece is taken out, the thickness of the coating is measured, and the appearance of the coating is observed.
[0056] The process parameters of chemical plating are: current density 1A / dm 2 , room temperature, the ratio of anode to cathode area is greater than 2:1, and the electroplating time is 1 hour. A 50mm×50mm×2mm iron-based test piece was selected as the workpiece for plating. One piece was directly subjected to chromic acid color passivation after plating, and the other piece was baked at 200℃ for 8h after plating, and then subjected to chromic acid color passivation. Finally, the states of the passivation layers of the two test pieces were compared. The specific results are:
[0057] The carboxyammonia cyanide-free cadmium plating layer without adding anti-discoloration agent is beige, with cadmium whiskers produced in the high area, and the chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright; the carboxyammonia cyanide-free cadmium plating layer with adding anti-discoloration agent is a uniform and delicate beige, and the chromate color passivation layer baked at 200℃ for 8h is bright and transparent colorful, which is basically the same as the unbaked passivation layer.
[0058] The alkaline cyanide-free cadmium plating layer without adding anti-discoloration agent is gray, and the chromate color passivation layer baked at 200℃ for 8h is light, foggy and not bright; the alkaline cyanide-free cadmium plating layer with adding anti-discoloration agent is uniform and delicate beige, and the chromate color passivation layer baked at 200℃ for 8h is bright and transparent colorful, which is basically the same as the unbaked passivation layer.
[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.
Claims
1. A cyanide-free cadmium plating high temperature baking post-passivation anti-discoloration agent, characterized in that: The anti-discoloration agent is an imidazole compound.
2. The cyanide-free cadmium plating high temperature baking post-passivation anti-discoloration agent according to claim 1, characterized in that: The imidazole compound is one or a mixture of 2-hydroxybenzimidazole, 2-aminobenzimidazole and 5-aminobenzimidazole.
3. Use of the anti-discoloration agent for post-high temperature baking of cyanide-free cadmium plating according to claim 1 or 2 in a cyanide-free cadmium plating solution.
4. The use according to claim 1, characterized in that: The mass concentration of the non-cyanide cadmium plating high-temperature baking passivation anti-discoloration agent in the non-cyanide cadmium plating solution is 0.05-1g / L.
5. The use according to claim 3, characterized in that: The cyanide-free cadmium plating solution is a carboxyammonia cyanide-free cadmium plating solution, which comprises the following components by mass concentration: 30 g / L EDTA, 50-70 g / L nitrilotriacetic acid, 150-200 g / L ammonium chloride, 30-50 g / L cadmium chloride, 0.5-1.5 g / L sodium dodecyl sulfate, and the pH is adjusted to 6.5 with sodium hydroxide, and the balance is water.
6. The use according to claim 3, characterized in that: The cyanide-free cadmium plating solution is an alkaline cyanide-free cadmium plating solution, which comprises the following components by mass concentration: cadmium sulfate: 30-50 g / L, triethanolamine: 40-60 g / L, potassium tartrate: 50-150 g / L, potassium hydroxide: 5-15 g / L, and DPE-III: 0.5-1.5 g / L.