阅读说明：本技术 一种阀体铸造件的表面处理工艺 (Surface treatment process for valve body casting part ) 是由 季豪敏 季奇章 于 2021-01-26 设计创作，主要内容包括：本申请涉及阀体表面处理领域,具体公开了一种阀体铸造件的表面处理工艺。一种阀体铸造件的表面处理工艺,将阀体铸造件经过预处理、第一次表面处理、第二次表面处理得到。第一次表面处理的方法为：将预处理后的阀体铸造件浸泡于由双(二巯基-1,3,4-噻二唑)、三氯化铈、二甲基甲酰胺、95wt%乙醇制得的处理剂中并捞出晾干。第二次表面处理的方法为：将第一次表面处理后的阀体铸造件表面涂覆耐腐蚀涂料,耐腐蚀涂料的原料包括环氧树脂、丙烯酸树脂、乙基纤维素、柠檬酸、乙腈、二月桂酸二丁基锡和甲基环戊二烯基三氯化锆。通过本表面处理工艺处理得到的阀体铸造件具有较好的耐腐蚀性能,且耐腐蚀涂料对其表面结合强度较好,不易脱落。(The application relates to the field of valve body surface treatment, and particularly discloses a surface treatment process for a valve body casting part. A surface treatment process for a valve body casting part is obtained by carrying out pretreatment, primary surface treatment and secondary surface treatment on the valve body casting part. The first surface treatment method comprises the following steps: soaking the pretreated valve casting in a treating agent prepared from bis (dimercapto-1, 3, 4-thiadiazole), cerium trichloride, dimethylformamide and 95wt% ethanol, and fishing out and drying in the air. The method for the second surface treatment comprises the following steps: and coating the surface of the valve body casting after the first surface treatment with a corrosion-resistant coating, wherein the corrosion-resistant coating is prepared from the raw materials of epoxy resin, acrylic resin, ethyl cellulose, citric acid, acetonitrile, dibutyltin dilaurate and methylcyclopentadienyl zirconium trichloride. The valve body casting part obtained by the surface treatment process has better corrosion resistance, and the corrosion-resistant coating has better surface bonding strength and is not easy to fall off.)

1. A surface treatment process for a valve body casting part is characterized by comprising the following steps:

s1, pretreatment of the valve body casting part: washing, pickling and washing the cast valve body casting in sequence, and airing to obtain a pretreated valve body casting;

s2, surface treatment of the valve body casting for the first time: soaking the pretreated valve body casting in a treating agent, fishing out and drying to obtain a valve body casting after primary surface treatment;

the treating agent comprises the following raw materials in parts by weight:

4-6 parts of bis (dimercapto-1, 3, 4-thiadiazole);

1-2 parts of cerium trichloride;

20-22 parts of 95wt% ethanol.

2. The surface treatment process for the valve body casting as claimed in claim 1, wherein the surface treatment process comprises the following steps: the raw material of the treating agent also comprises 1-2 parts of dimethylformamide.

3. The surface treatment process for the valve body casting as claimed in claim 2, wherein the surface treatment process comprises the following steps: the preparation method of the treating agent comprises the following steps:

s1, pretreatment of bis (dimercapto-1, 3, 4-thiadiazole): dissolving bis (dimercapto-1, 3, 4-thiadiazole) in an acetone solution, carrying out suction filtration, evaporating the obtained filtrate under reduced pressure, dissolving the filtrate in 95wt% ethanol, and recrystallizing the solution to remove acetone to obtain pretreated bis (dimercapto-1, 3, 4-thiadiazole);

s2, preparation of a treating agent: according to the weight portion, 4-6 portions of bis (dimercapto-1, 3, 4-thiadiazole) are dissolved in 20-22 portions of 95wt% ethanol, 1-2 portions of dimethylformamide are added under the stirring state, and 1-2 portions of cerium trichloride are added to obtain the treating agent.

4. The surface treatment process for the valve body casting as claimed in claim 1, wherein the surface treatment process comprises the following steps: and S3, carrying out secondary surface treatment on the valve body casting part: and coating corrosion-resistant paint on the surface of the valve body casting subjected to the first surface treatment, and airing to obtain the valve body casting subjected to the second surface treatment.

5. The surface treatment process for the valve body casting as claimed in claim 4, wherein the surface treatment process comprises the following steps: the corrosion-resistant coating comprises the following raw materials in parts by weight: 30-35 parts of epoxy resin, 30-35 parts of acrylic resin, 7-12 parts of ethyl cellulose, 2-3 parts of citric acid, 1-3 parts of acetonitrile, 2-3 parts of dibutyltin dilaurate and 1-2 parts of methylcyclopentadienyl zirconium trichloride.

6. The surface treatment process for the valve body casting as claimed in claim 5, wherein the surface treatment process comprises the following steps: the pH value of the corrosion-resistant coating is 4-5.5.

7. The surface treatment process for a valve body casting as claimed in claim 6, wherein: the preparation method of the corrosion-resistant coating comprises the following steps: according to the weight portion, 30-35 portions of epoxy resin and 30-35 portions of acrylic resin are mixed and stirred uniformly at 60 ℃, and the obtained mixture is mixed and stirred uniformly with 7-12 portions of ethyl cellulose, 2-3 portions of citric acid, 1-3 portions of acetonitrile, 2-3 portions of dibutyltin dilaurate and 1-2 portions of methylcyclopentadienyl zirconium trichloride to obtain the corrosion-resistant coating.

8. The surface treatment process for the valve body casting as claimed in claim 1, wherein the surface treatment process comprises the following steps: further comprising S4: and (3) carrying out irradiation crosslinking on the valve body casting after the second surface treatment, adjusting the irradiation dose rate to be 1-2kGy/s, the irradiation total amount to be 500-700kGy, the electron beam energy to be 0.1-10 MeV and the irradiation temperature to be 70-80 ℃.

Technical Field

The application relates to the field of valve body surface treatment, in particular to a surface treatment process of a valve body casting part.

Background

At present, the valve is more and more widely used at home and abroad, and the requirement on the valve is higher and higher. Valves are generally comprised of a closure member (such as a ball in a ball valve) and a valve stem, with the closure member being carried by the valve stem to close or open the valve.

The inner cavity of the valve is in liquid for a long time and is impacted and corroded by the liquid, the inner wall of the valve cavity is corroded and then is difficult to form a sealing state with the opening and closing piece, and therefore the ball valve is failed, and corrosion resistance of the ball valve needs to be improved.

Disclosure of Invention

In order to improve the corrosion resistance of the surface of the valve body casting part, the application provides a surface treatment process of the valve body casting part.

The application provides a surface treatment process of valve body casting spare adopts following technical scheme:

a surface treatment process of a valve body casting part comprises the following steps:

s1: pretreatment of a valve body casting part: washing, pickling and washing the cast valve body casting in sequence, and airing to obtain a pretreated valve body casting;

s2: surface treatment of a valve body casting part for the first time: soaking the pretreated valve body casting in a treating agent, fishing out and drying to obtain a valve body casting after primary surface treatment;

the treating agent comprises the following raw materials in parts by weight:

4-6 parts of bis (dimercapto-1, 3, 4-thiadiazole);

1-2 parts of cerium trichloride;

20-22 parts of 95wt% ethanol.

By adopting the technical scheme, the valve body casting part is pretreated to remove surface dust and oil stains, so that the next step of processing is facilitated. The bis (dimercapto-1, 3, 4-thiadiazole) is a metal polydentate chelating agent, six sulfur atoms and four nitrogen atoms which can be matched with metal are arranged in the molecular formula of the metal polydentate chelating agent, 4 sulfur atoms in the six sulfur atoms are arranged on the same plane and form a chelating ring after being complexed with the metal, a layer of compact protective film is formed on the surface of the metal, the chelating ring has good stability, and oxygen and liquid can be effectively shielded from contacting with the surface of a valve casting, so that the corrosion resistance of the surface of the valve casting is improved.

The shielding of electrons in the 4f orbital of cerium to atomic nuclei is incomplete, and the atomic nuclei cannot be effectively shielded like electrons in s, p and d energy levels, so that cerium has stronger internal adsorption capacity; cerium ions in the cerium trichloride can be adsorbed on the metal surface and preferentially adsorbed on crystal defects (dislocation, crystal boundary and the like) on the metal surface, and the adsorption of the cerium ions on the metal surface influences a chelate formed by bis (dimercapto-1, 3, 4-thiadiazole) and metal, so that the structure of the protective film is more delicate and compact, the isolation capability on oxygen and liquid is improved, and the corrosion resistance of a valve body casting piece is further improved.

The method comprises the steps of taking ethanol as a solvent, dissolving cerium trichloride and bis (dimercapto-1, 3, 4-thiadiazole) in the ethanol to prepare a treating agent, enabling the cerium trichloride and the bis (dimercapto-1, 3, 4-thiadiazole) to be attached to the surface of the valve casting in a soaking mode, and volatilizing the ethanol to form a protective film to obtain the valve casting with good corrosion resistance.

Optionally, the raw material of the treating agent further comprises 1-2 parts of dimethylformamide.

By adopting the technical scheme, the bis (dimercapto-1, 3, 4-thiadiazole) can be complexed with divalent and trivalent metal ions, so that the bis (dimercapto-1, 3, 4-thiadiazole) has certain complexing capability with the trivalent cerium ions. Dimethyl formamide is used as a blocking agent, and is filled in the treating agent, so that the complexation between bis (dimercapto-1, 3, 4-thiadiazole) and cerium trichloride is reduced. The surface action rate of cerium ions and bis (dimercapto-1, 3, 4-thiadiazole) in the treating agent on the valve body casting is improved, so that the corrosion resistance rate is improved.

Optionally, the preparation method of the treating agent comprises the following steps:

s1, pretreatment of bis (dimercapto-1, 3, 4-thiadiazole): dissolving bis (dimercapto-1, 3, 4-thiadiazole) in an acetone solution, carrying out suction filtration, evaporating the obtained filtrate under reduced pressure, dissolving the filtrate in 95wt% ethanol, and recrystallizing the solution to remove acetone to obtain pretreated bis (dimercapto-1, 3, 4-thiadiazole);

s2, preparation of a treating agent: according to the weight portion, 4-6 portions of bis (dimercapto-1, 3, 4-thiadiazole) are dissolved in 20-22 portions of 95wt% ethanol, 1-2 portions of dimethylformamide are added under the stirring state, and 1-2 portions of cerium trichloride are added to obtain the treating agent.

By adopting the technical scheme, the bis (dimercapto-1, 3, 4-thiadiazole) is pretreated and purified to remove impurities. Adding dimethylformamide into an ethanol solution of bis (dimercapto-1, 3, 4-thiadiazole), and adding cerium trichloride to ensure that the bis (dimercapto-1, 3, 4-thiadiazole) and the cerium trichloride are not easy to associate with each other in a treating agent system, thereby obtaining the treating agent.

Optionally, the method further includes S3: and (3) performing secondary surface treatment on the valve body casting part: and coating corrosion-resistant paint on the surface of the valve body casting subjected to the first surface treatment, and airing to obtain the valve body casting subjected to the second surface treatment.

By adopting the technical scheme, the corrosion-resistant coating further prevents corrosion on the surface of the valve body casting part, and the corrosion resistance of the valve body casting part is improved.

Optionally, the corrosion-resistant coating comprises the following raw materials in parts by weight: 30-35 parts of epoxy resin, 30-35 parts of acrylic resin, 7-12 parts of ethyl cellulose, 2-3 parts of citric acid, 1-3 parts of acetonitrile, 2-3 parts of dibutyltin dilaurate and 1-2 parts of methylcyclopentadienyl zirconium trichloride.

By adopting the technical scheme, the epoxy resin has better adhesive property, and the epoxy resin and the ethyl cellulose are used as film forming substances to cover the surface of the valve body casting part, so that the corrosion resistance is improved. The fluidity of the corrosion-resistant coating is improved by adding the acrylic resin. The composition of citric acid and acetonitrile is used for adjusting the physical polarity of the corrosion-resistant coating, so that the polarity of the corrosion-resistant coating is similar to that of bis (dimercapto-1, 3, 4-thiadiazole), the compatibility of the corrosion-resistant coating and bis (dimercapto-1, 3, 4-thiadiazole) is improved, the bonding capability of the corrosion-resistant coating is improved, and the corrosion resistance of a valve casting is improved. Dibutyltin dilaurate and methylcyclopentadienyl zirconium trichloride are combined to form a curing system, so that the solidification speed of the corrosion-resistant coating is improved.

Optionally, the pH of the corrosion resistant coating is 4-5.5.

By adopting the technical scheme, the corrosion-resistant coating is more finely and tightly combined with the surface of the valve body casting part when the pH value is 4-5.5.

Optionally, 30-35 parts of epoxy resin and 30-35 parts of acrylic resin are mixed and stirred uniformly at 60 ℃, and the obtained mixture is mixed and stirred uniformly with 7-12 parts of ethyl cellulose, 2-3 parts of citric acid, 1-3 parts of acetonitrile, 2-3 parts of dibutyltin dilaurate and 1-2 parts of methylcyclopentadienyl zirconium trichloride to obtain the corrosion-resistant coating.

By adopting the technical scheme, the corrosion-resistant coating is prepared.

Optionally, the method further includes S4: and (3) carrying out irradiation crosslinking on the valve body casting after the second surface treatment, adjusting the irradiation dose rate to be 1-2kGy/s, the irradiation total amount to be 500-700kGy, the electron beam energy to be 0.1-10 MeV and the irradiation temperature to be 70-80 ℃.

By adopting the technical scheme, the valve body casting after the secondary treatment is subjected to irradiation crosslinking, so that the number of active groups in the corrosion-resistant coating is increased, a film formed by the corrosion-resistant coating is finer, and the corrosion resistance of the valve body casting is improved; meanwhile, the binding force between the film formed by the corrosion-resistant coating and the protective film formed by the treating agent is enhanced, so that the corrosion-resistant coating is not easy to fall off.

In summary, the present application has the following beneficial effects:

1. the bis (dimercapto-1, 3, 4-thiadiazole) is associated with the surface of the valve body casting, so that the corrosion resistance of the valve body casting is improved.

2. The dimethyl formamide is added into the treating agent to inhibit the association between the bis (dimercapto-1, 3, 4-thiadiazole) and the cerium ions, so that the action rate of the bis (dimercapto-1, 3, 4-thiadiazole) and the cerium ions on the surface of the valve body casting is improved.

3. The physical polarity of the corrosion-resistant coating is adjusted by citric acid and acetonitrile, and the compatibility of the corrosion-resistant coating and bis (dimercapto-1, 3, 4-thiadiazole) is improved.

Detailed Description

The present application will be described in further detail with reference to examples and comparative examples.

Bis (dimercapto-1, 3, 4-thiadiazole) is sold by Nicotiana henno new material Co., Ltd, the purity is 99.00wt%, and the purity is industrial grade; 95wt% ethanol is sold by Shanghai Aladdin Biotechnology, Inc., product number A112717, AR; the epoxy resin is an epoxy resin paint sold by the Yongsheng scientific and technological development limited company in the Tianjin century, and the brand is Jinchaohui; the acrylic resin is waterborne epoxy modified acrylic resin A990 sold by Hongshan Australia Shengyuan New Material science and technology Co., Ltd; ethyl cellulose is sold by Xinhong trade company of Guangzhou city, and the brand is Aladdin; citric acid is sold by chemical Limited of Jinan Yifengda, and the brand is Yingxuan; dibutyltin dilaurate is sold by Xinhong trade company, Inc. in Guangzhou city, and the brand is Mecline; the methylcyclopentadienyl zirconium trichloride is sold by Anhuitong New Material science and technology Limited and has a purity of 99 wt%.

Example 1:

a surface treatment process for a valve body casting part is characterized by comprising the following steps:

s1, pretreatment of the valve body casting part: washing the cast valve body casting in sequence with water, washing with 10wt% hydrochloric acid, washing with water, and drying to obtain a pretreated valve body casting;

s2, surface treatment of the valve body casting for the first time: and (3) soaking the pretreated valve body casting in a treating agent for 5min, and fishing out and drying to obtain the valve body casting after the first surface treatment.

The preparation method of the treating agent comprises the following steps:

s1, preprocessing: dissolving bis (dimercapto-1, 3, 4-thiadiazole) in an acetone solution, carrying out suction filtration, evaporating the obtained filtrate under reduced pressure, dissolving the filtrate in 95wt% ethanol, and recrystallizing the solution to remove acetone to obtain pretreated bis (dimercapto-1, 3, 4-thiadiazole);

s2, dissolving 4 parts of bis (dimercapto-1, 3, 4-thiadiazole) in 20 parts of 95wt% ethanol by weight, adding 1 part of dimethylformamide while stirring, stirring for 3min, and adding 1 part of cerium trichloride while stirring to obtain the treating agent.

Example 2:

a surface treatment process for a valve body casting part is characterized by comprising the following steps:

s1, pretreatment of the valve body casting part: washing the cast valve body casting in sequence with water, 10wt% hydrochloric acid, washing with water, and drying to obtain a pretreated valve body casting;

s2, surface treatment of the valve body casting for the first time: and (3) soaking the pretreated valve body casting in a treating agent for 5min, and fishing out and drying to obtain the valve body casting after the first surface treatment.

The preparation method of the treating agent comprises the following steps:

s1, preprocessing: dissolving bis (dimercapto-1, 3, 4-thiadiazole) in an acetone solution, carrying out suction filtration, evaporating the obtained filtrate under reduced pressure, dissolving the filtrate in 95wt% ethanol, and recrystallizing the solution to remove acetone to obtain pretreated bis (dimercapto-1, 3, 4-thiadiazole);

s2, dissolving 6 parts by weight of bis (dimercapto-1, 3, 4-thiadiazole) in 22 parts by weight of 95wt% ethanol, adding 2 parts by weight of dimethylformamide while stirring, stirring for 3min, and adding 2 parts by weight of cerium trichloride while stirring to obtain the treating agent.

Example 3:

a surface treatment process for a valve body casting part is characterized by comprising the following steps:

s1, pretreatment of the valve body casting part: washing the cast valve body casting in sequence with water, 10wt% hydrochloric acid, washing with water, and drying to obtain a pretreated valve body casting;

s2, surface treatment of the valve body casting for the first time: and (3) soaking the pretreated valve body casting in a treating agent for 5min, and fishing out and drying to obtain the valve body casting after the first surface treatment.

The preparation method of the treating agent comprises the following steps:

s1, preprocessing: dissolving bis (dimercapto-1, 3, 4-thiadiazole) in an acetone solution, carrying out suction filtration, evaporating the obtained filtrate under reduced pressure, dissolving the filtrate in 95wt% ethanol, and recrystallizing the solution to remove acetone to obtain pretreated bis (dimercapto-1, 3, 4-thiadiazole);

s2, dissolving 5 parts by weight of bis (dimercapto-1, 3, 4-thiadiazole) in 21 parts by weight of 95wt% ethanol, adding 2 parts by weight of dimethylformamide while stirring, stirring for 3min, and adding 1 part by weight of cerium trichloride while stirring to obtain the treating agent.

Example 4:

the difference from example 3 is that dimethylformamide was not added in S2 of the method for producing the treating agent.

Example 5:

the difference from embodiment 3 is that the surface treatment process of the valve body casting further includes S3, and the valve body casting is subjected to a second surface treatment: and coating epoxy resin paint on the surface of the valve body casting subjected to the first surface treatment, wherein the thickness of the coating layer is 0.1mm, and airing to obtain the valve body casting subjected to the second surface treatment.

Example 6:

the difference from the embodiment 5 is that the surface of the valve body casting after the first surface treatment is coated with corrosion-resistant coating, the thickness of the coating layer is 0.1mm, and the valve body casting after the second surface treatment is obtained after drying.

The preparation method of the corrosion-resistant coating comprises the following steps:

according to the weight portion, 30 portions of epoxy resin and 30 portions of acrylic resin are mixed and stirred uniformly at 60 ℃, the obtained mixture is stirred and mixed uniformly with 7 portions of ethyl cellulose, 2 portions of citric acid, 1 portion of acetonitrile, 2 portions of dibutyltin dilaurate and 1 portion of methylcyclopentadienyl zirconium trichloride, and the pH value is adjusted to 7 by adopting sodium hydroxide, so that the corrosion-resistant coating is obtained.

Example 7:

the difference from the embodiment 5 is that the surface of the valve body casting after the first surface treatment is coated with corrosion-resistant coating, the thickness of the coating layer is 0.1mm, and the valve body casting after the second surface treatment is obtained after drying.

The preparation method of the corrosion-resistant coating comprises the following steps:

according to parts by weight, 35 parts of epoxy resin and 35 parts of acrylic resin are uniformly mixed and stirred at 60 ℃, the obtained mixture is uniformly stirred and mixed with 12 parts of ethyl cellulose, 3 parts of citric acid, 3 parts of acetonitrile, 3 parts of dibutyltin dilaurate and 2 parts of methylcyclopentadienyl zirconium trichloride, and the pH value is adjusted to 7 by adopting sodium hydroxide, so that the corrosion-resistant coating is obtained.

Example 8:

the difference from the embodiment 5 is that the surface of the valve body casting after the first surface treatment is coated with corrosion-resistant coating, the thickness of the coating layer is 0.1mm, and the valve body casting after the second surface treatment is obtained after drying.

The preparation method of the corrosion-resistant coating comprises the following steps:

according to parts by weight, 33 parts of epoxy resin and 33 parts of acrylic resin are mixed and stirred uniformly at 60 ℃, the obtained mixture is stirred and mixed uniformly with 9 parts of ethyl cellulose, 3 parts of citric acid, 2 parts of acetonitrile, 2 parts of dibutyltin dilaurate and 2 parts of methylcyclopentadienyl zirconium trichloride, and the pH value is adjusted to 7 by adopting sodium hydroxide, so that the corrosion-resistant coating is obtained.

Example 9:

the difference from example 8 is that the corrosion resistant coating has a pH of 4.

Example 10:

the difference from example 8 is that the corrosion resistant coating has a pH of 5.5.

Example 11:

the difference from example 8 is that the corrosion resistant coating has a pH of 5.

Example 12:

the difference from example 8 is that the corrosion resistant coating has a pH of 11.

Example 13:

the difference from example 8 is that citric acid is not added to the corrosion resistant coating.

Example 14:

the difference from example 8 is that no acetonitrile was added to the corrosion resistant coating.

Example 15:

the difference from example 8 is that citric acid and acetonitrile are not added to the corrosion resistant coating.

Example 16:

the difference from the embodiment 11 is that the valve body casting after the second surface treatment is subjected to irradiation crosslinking by gamma rays, the irradiation dose rate is adjusted to 1kGy/s, the total irradiation amount is 500kGy, the electron beam energy is 0.1MeV, and the irradiation temperature is 70 ℃.

Example 17:

the difference from the embodiment 11 is that the valve body casting after the second surface treatment is subjected to irradiation crosslinking by gamma rays, the irradiation dose rate is adjusted to 2kGy/s, the total irradiation amount is 700kGy, the electron beam energy is 10MeV, and the irradiation temperature is 80 ℃.

Example 18:

the difference from the embodiment 11 is that the valve body casting after the second surface treatment is subjected to irradiation crosslinking by gamma rays, the irradiation dose rate is adjusted to 2kGy/s, the total irradiation amount is 600kGy, the electron beam energy is 5MeV, and the irradiation temperature is 75 ℃.

Comparative example 1:

the difference from example 3 is that the valve casting was not subjected to a first surface treatment.

Comparative example 2:

the difference from example 8 is that the valve casting surface was not subjected to a first surface treatment and was coated with a corrosion-resistant coating.

Comparison 3:

the difference from example 3 is that bis (dimercapto-1, 3, 4-thiadiazole) is not added to the treating agent.

Comparative example 4:

the difference from example 3 is that cerium trichloride was not added to the treating agent.

Performance test

Salt spray corrosion test:

the valve body castings of the examples and comparative examples were subjected to a neutral salt spray test (NSS test) with reference to GB/T10125-2012 salt spray test for artificial atmosphere corrosion test. The test is carried out after 1000h of test, and the test results are detailed in Table 1.

And (3) testing the binding capacity:

the valve body casting is treated by the treatment processes of examples 5 to 18 and comparative example 2 to obtain a sample to be tested, and reference is made to GB/T5210-2006 adhesion test by color paint and varnish pulling method. The test was carried out by using an AGS-J tensile testing machine sold by Shimadzu corporation, hong Kong, at a tensile speed of 10mm/min, and the adhesive was ALTECO110 type super glue. The test results are detailed in table 1.

TABLE 1

Combining example 3 and example 4 and table 1, it can be seen that dimethylformamide is added to the treating agent, and is used as a blocking agent, so that the association between bis (dimercapto-1, 3, 4-thiadiazole) and cerium trichloride is blocked, and the surface acting rate of cerium ions and bis (dimercapto-1, 3, 4-thiadiazole) in the treating agent on the valve body casting is improved, so that the corrosion resistance rate is improved.

It can be seen from a combination of examples 3 and 5 and table 1 that the epoxy resin paint is applied to the surface of the valve body casting to further isolate the surface of the valve body casting from air, thereby improving the corrosion resistance of the valve body casting.

As can be seen by combining example 5 with examples 6 to 8 and table 1, the corrosion-resistant coating is more effective than the epoxy resin paint in improving the corrosion resistance of the surface of the valve casting, and the corrosion-resistant coating has stronger adhesion strength to the surface of the valve casting. The epoxy resin and the ethyl cellulose are used as film forming substances, the acrylic resin improves the fluidity of the corrosion-resistant coating, the citric acid and the acetonitrile adjust the physical polarity of the corrosion-resistant coating to be close to that of the treating agent, and the compatibility of the corrosion-resistant coating and the treating agent is improved, so that the bonding capacity of the corrosion-resistant coating on the surface of a valve body casting part is improved.

Combining examples 8 and 9-12 with table 1, it can be seen that the corrosion resistant coating had better corrosion resistance and bond strength for the valve body castings at pH 4, 5, 5.5 than at pH 7, 11. The reason may be that the pH value influences the activity of citric acid and acetonitrile in the corrosion-resistant coating in acidity, so that the binding force of the corrosion-resistant coating and a treating agent layer is improved, a formed film represented by a valve body casting is finer, and the corrosion resistance and the binding strength of the valve body casting are improved.

It can be seen from the combination of example 8 and examples 13 to 15 and table 1 that the addition of citric acid and acetonitrile adjusts the polarity of the corrosion-resistant coating, improves the compatibility of the corrosion-resistant coating with the film formed by the treating agent, and thus significantly improves the adhesion strength of the corrosion-resistant coating on the surface of the valve body casting.

Combining example 11 and examples 16-18 with table 1, it can be seen that irradiation crosslinking increases the number of free radicals in the corrosion-resistant coating, so that new bonds are formed inside the corrosion-resistant coating through the mutual combination of the free radicals, thereby increasing the compactness of the mold formed by the internal composite coating and improving the corrosion resistance of the valve body casting. Meanwhile, the irradiation crosslinking improves the binding capacity with the treating agent and improves the bonding strength of the corrosion-resistant coating and the surface of the valve body casting part.

As can be seen by combining example 3 and comparative example 1 with table 1, the treating agent significantly improved the corrosion resistance of the valve body casting. The bis (dimercapto-1, 3, 4-thiadiazole) is complexed with the surface of the valve body casting to form a chelate ring, so that a layer of compact protective film is formed, the chelate ring has better stability, and external liquid and gas are effectively shielded from contacting the surface of the valve body casting, so that the corrosion resistance of the surface of the valve body casting is improved. Cerium has stronger internal adsorption capacity and is adsorbed on the surface of the valve body casting part, so that the structure of bis (dimercapto-1, 3, 4-thiadiazole) and the metal chelate is more detailed and compact, and the corrosion resistance of the valve body casting part is further improved.

It can be seen by combining example 8 and comparative example 2 and table 1 that when the internal composite coating is directly coated on the surface of the valve casting, the corrosion resistance and the bonding capability are not good, the valve casting is firstly subjected to the first surface treatment and then coated with the corrosion-resistant coating, the corrosion-resistant coating is attached to a mold formed by the treating agent, and a film formed by the corrosion-resistant coating and the treating agent has good bonding capability, so that the bonding strength between the corrosion-resistant coating and the surface of the valve casting is improved.

Combining example 3 and comparative example 3 with table 1, it can be seen that bis (dimercapto-1, 3, 4-thiadiazole) forms a dense protective film on the metal surface, which significantly enhances the corrosion resistance of the valve body casting.

As can be seen by combining example 3 and comparative example 4 with table 1, cerium ions are adsorbed on the surface of the valve body casting, which has the effect of improving the corrosion resistance of the valve body casting. The experimental data show that when cerium ions act on a valve casting piece singly, the effect of improving the corrosion resistance is weak, but the treatment liquid prepared from the composition of the cerium ions and the bis (dimercapto-1, 3, 4-thiadiazole) can obviously improve the corrosion resistance, and the reason may be that the cerium ions are adsorbed on the surface of metal to influence a chelate formed by the bis (dimercapto-1, 3, 4-thiadiazole) and the metal, so that the structure of a protective film is more delicate and compact, and the corrosion resistance of the valve casting piece is obviously improved.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.