阅读说明：本技术 一种镀锌、镀镉钝化溶液调配方法 (Method for preparing passivation solution for zinc plating and cadmium plating ) 是由 刘伟 韦信 于 2020-12-29 设计创作，主要内容包括：本发明公开一种镀锌、镀镉钝化溶液调配方法,包括以下步骤：铬酐(CrO-3)(3-7)g/L；硝酸(HNO-3)(1-4)g/L；硫酸(H-2SO-4)(0.2-0.9)g/L；当溶液中CrO-3的含量降至4克/升时,取几份样分别进行硝酸和硫酸加药量试验,直至得到颜色符合要求的膜层。本发明方法方便了生产,提高了劳动效率,同时减少了对环境的污染。(The invention discloses a method for preparing a passivation solution for galvanizing and cadmium plating, which comprises the following steps: chromic anhydride (CrO) 3 ) (3-7) g/L; nitric acid (HNO) 3 ) (1-4) g/L; sulfuric acid (H) 2 SO 4 ) (0.2-0.9) g/L; when CrO is in solution 3 The content of the active component is reduced to 4 g/l, and a plurality of samples are respectively subjected to nitric acid and sulfuric acid dosage tests until a film layer with the color meeting the requirements is obtained. The method of the invention facilitates production, improves labor efficiency and reduces environmental pollution.)

1. A preparation method of a passivation solution for zinc plating and cadmium plating is characterized by comprising the following steps:

chromic anhydride (CrO)₃) (3-7) g/L; nitric acid (HNO)₃) (1-4) g/L; sulfuric acid (H)₂SO₄）(0.2-0.9)g/L；

When the solution needs to be adjusted, every liter of the solution increases CrO by 1 g₃In an amount of 368 mg of H₂SO₄And 705 mg of HNO₃。

2. The method for preparing a passivating solution for zinc plating and cadmium plating according to claim 1, wherein the specific experimental process comprises: when CrO is in solution₃The content of the active component is reduced to 4 g/l, and a plurality of samples are respectively subjected to nitric acid and sulfuric acid dosage tests until a film layer with the color meeting the requirements is obtained.

3. The method for preparing a passivating solution for zinc plating and cadmium plating according to claim 2, wherein the extracted parts are not less than 5 times, and 1 g of CrO is added for each experiment₃Content of (1), HNO₃Adding 0.36-0.5 g of H₂SO₄0.100-0.720 g is added.

4. The blending method of passivation solution for zinc plating and cadmium plating according to claim 1, wherein the passivated parts have full color and luster, and are beautiful rainbow colors with green color in red and red color in green, and the passivation film is qualified by salt spray test for 72 hours, i.e. the corrosion resistance meets the requirement.

Technical Field

The invention relates to the technical field of surface treatment methods of metal parts, in particular to a method for preparing a passivation solution for galvanizing and cadmium plating.

Background

The main process of metal surface treatment zinc (cadmium) plating comprises the following steps: chemical oil extraction → strong corrosion → electrochemical oil removal → weak corrosion → zinc (cadmium) plating → light extraction → passivation. The passivation process is to improve the corrosion resistance of the zinc (cadmium) plating layer, and in chromic acid or chromate solution, the surface of the zinc (cadmium) plating layer is covered with a chromate film with higher stability, so that the protective performance of the zinc (cadmium) plating layer can be greatly improved and the surface appearance can be improved through passivation. The passivation is classified according to the concentration of chromic acid in the passivation solution, and can be classified into two categories, namely high chromic acid and low chromic acid, and can also be classified into two categories, namely non-environment-friendly type and environment-friendly type. Through visiting investigation, the same industry mostly adopts high chromic acid passivation, and the solution is easy to maintain, and the chemical analysis method of each component in the solution is relatively simple. When the high chromic acid passivation process is adopted, the consumption of chromic acid for passivation is less than 5%, and 95% of chromic acid is carried out by the workpiece, and causes serious pollution to the environment. And the quality of the obtained passive film is equivalent to that of high chromic acid passivation by adopting a low chromic acid passivation process, the cost can be reduced, and the pollution to the environment is reduced. Therefore, the zinc (cadmium) plating production line of our company adopts the following formula according to aviation standard:

chromic anhydride (CrO)₃) (3-7) g/L; nitric acid (HNO)₃) (1-4) g/L; sulfuric acid (H)₂SO4） (0.2-0.9)g/L。

However, the formula has the disadvantage that the solution is difficult to maintain because the solution consists of three kinds of acid liquor, and the chemical analysis method is complicated and has a long period. It is difficult to meet the production requirements.

Disclosure of Invention

The invention aims to provide a simple preparation and maintenance method suitable for a low-chromic acid passivation solution, in particular to a preparation method of a zinc-plating and cadmium-plating passivation solution.

The technical scheme of the invention is as follows:

a preparation method of a passivation solution for zinc plating and cadmium plating comprises the following steps:

chromic anhydride (CrO)₃) (3-7) g/L; nitric acid (HNO)₃) (1-4) g/L; sulfuric acid (H)₂SO₄） (0.2-0.9)g/L；

When the solution needs to be adjusted, every liter of the solution increases CrO by 1 g₃In an amount of 368 mg of H₂SO₄And 705 mg of HNO₃。

Preferably, the specific experimental process is as follows: when CrO is in solution₃The content of the active component is reduced to 4 g/l, and a plurality of samples are respectively subjected to nitric acid and sulfuric acid dosage tests until a film layer with the color meeting the requirements is obtained.

Preferably, the taken parts are not less than 5 times, and 1 g of CrO is added in each experiment₃Content of (1), HNO₃Adding 0.36-0.5 g of H₂SO₄0.100-0.720 g is added.

Preferably, after the parts are passivated, the parts are full in color and luster, the parts are beautiful rainbow colors with green color in red and red color in green, and the passivation film is qualified after a salt spray test for 72 hours, namely the corrosion resistance meets the requirement.

The invention has the beneficial effects that:

the solution adjusted according to the scheme of the invention has full color and luster after the parts are passivated, the parts are beautiful rainbow colors with green color in red and red color in green, and the passivation film is qualified after a salt spray test for 72 hours, namely the corrosion resistance is qualified. And the passivating solution only needs to test one CrO every week according to the scheme of the invention₃The content of the active carbon is enough, so that the production is convenient, the labor efficiency is improved, and the pollution to the environment is reduced.

Detailed Description

Because the forming mechanism of the passive film is complex, mainly a dissolving and generating process, when zinc (cadmium) is treated in the passive solution, the zinc (cadmium) is dissolved to generate chromate, and as a result, a large amount of acid is consumed, so that the acidity of the interface between a part and the solution is reduced, the pH value is increased, and when the pH value is increased to about 4, insoluble basic chromate and hydrate are formed and separated out to cover the surface of the part to form the passive film. The passive film is composed of trivalent and hexavalent basic chromates and hydrates thereof. Wherein, the trivalent chromium is green, the hexavalent chromium is red, and the colors of the passive film are formed due to different refractive indexes of various colors. The ratio of trivalent chromium to hexavalent chromium in the passivation film is typically 1.5:1, but this ratio varies with various factors, and the color of the passivation film changes accordingly. The color of the passivation film is one of the signs for judging the quality of the passivation film, and the passivation film with good quality has bright beautiful rainbow colors of transparent green in red and transparent red in green, thereby giving people a compact and bright feeling. Three acids in the solution are continuously consumed in the production process, but the consumption speeds are different due to different actions, in order to better grasp the consumption of the three components, sampling and testing are regularly and quantitatively carried out in the production process, and one component CrO which is easier to test and analyze is used₃The variable quantity of (2) is the benchmark, other two kinds of compositions are respectively added with different dosages, contrast tests are carried out, and the test results are summarized and summarized, finally a set of simple preparation maintenance scheme suitable for the low chromic acid passivation solution is obtained, namely: when the solution needs to be adjusted, taking one liter of the solution as an example, every 1 g of CrO is increased₃In an amount of 368 mg of H₂SO₄And 705 mg of HNO₃(ii) a The specific experimental data are as follows:

when the content of CrO3 in the solution is reduced to 4 g/l, taking several samples to respectively perform a dosing test until a film layer with the color meeting the requirement is obtained; the following experiment is CrO₃、HNO₃And H₂SO₄The respective amounts added were:

the solution adjusted by the method has full color and luster after the parts are passivated, the parts are beautiful rainbow colors with green color in red and red color in green, and the passivation film is qualified by a salt spray test for 72 hours, namely the corrosion resistance is qualified. And the passivating solution only needs to test one CrO every week according to the scheme of the invention₃The content of the active carbon is enough, so that the production is convenient, the labor efficiency is improved, and the pollution to the environment is reduced.

The invention is widely applied to the production of aviation products, such as Y5B airplanes, eagle 500 airplanes and seagull 300 airplane parts, and the production of civil parts of companies and various military enterprises of other defense industry units, and is very satisfactory to the product quality.

The embodiments of the present invention are preferred embodiments of the present application, and the scope of protection of the present application is not limited by the embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.