Reagent applicable to integrity evaluation of anti-corrosion coating as well as preparation method and application of reagent

Abstract

The invention belongs to the technical field of steel corrosion prevention, and particularly relates to a reagent applicable to integrity evaluation of an anti-corrosion coating as well as a preparation method and application of the reagent. The reagent comprises the following components: 1-3% of cross-linked polyacrylic resin, 1-10% of NaCl, 0.1-2% of K3 [Fe (CN) 6] and deionized water, and the prepared reagent has the apparent characteristic of being a yellow transparent pasty substance. After the surface of an anti-corrosion coating is coated with the reagent, pores in the coating can be clearly shown, and the integrity of the coating can be graded according to a standard map; the invention relates to a reagent suitable for rapidly evaluating the integrity of an anti-corrosion coating plated with Cr, Ni, Cu and the like on the surface of steel.

Description

Technical Field

[0001] The invention belongs to the technical field of steel anticorrosion, and relates to reagents and methods for evaluating the integrity of anticorrosion coatings, and in particular to reagents and methods for quickly evaluating the integrity of anticorrosion coatings such as Cr, Ni or Cu coatings on steel surfaces, and applications thereof. Background Art

[0002] It is an effective metal anti-corrosion treatment method to attach a coating with excellent corrosion resistance to the surface of susceptible metal materials by electroplating, chemical plating or other methods. Among them, the preparation of a Cr and Ni anti-corrosion coating on the surface of iron-based materials is the most common. The integrity of the coating is one of the key factors affecting its anti-corrosion effect. The corrosive medium in the environment can directly contact the protected substrate through the pores of the coating, causing pitting corrosion of the protected substrate. The corrosion products formed during the gradual expansion of the pitting will cause the surrounding coating to rupture, and eventually cause large-scale corrosion of the protected substrate due to coating failure. Coating integrity detection is a key item in coating quality evaluation and an important basis for production quality control. Therefore, the ability to quickly and accurately evaluate the integrity of the coating is of great significance for the quality control of anti-corrosion coatings.

[0003] Currently, the commonly used methods for detecting porosity in coatings include corrosion method, electrical imaging method, gas penetration method, and photography method. The corrosion method is to detect the porosity of the coating by placing the coated sample in an environmental medium that can cause corrosion of the substrate for a period of time based on the corrosion spots on the surface of the coating; the electrical imaging method is to energize the base metal inside the coating to dissolve the anode, and the dissolved metal ions migrate to the test paper through the pores on the coating through electrophoresis, and then react with some chemical reagents on the test paper to form dye spots. The integrity of the coating is evaluated based on the dye spots on the test paper; the gas permeation method is based on the penetration of gas through the electroplated layer. This measurement requires a special vacuum device and can only measure thin coatings (within 5μm) peeled off from the base metal. The measurement results are quite different from the actual situation; the photographic method uses light to pass through the peeled coating, and develops and fixes it on a photographic plate to obtain a photo with black spots, which makes the coating pores clear at a glance. Its disadvantages are the same as those of the gas permeation method. The coating needs to be peeled off from the body, and small and tortuous pores are not easy to find. The corrosion method is currently the most widely used method for coating integrity detection due to its advantages such as simple operation, low economic cost and good result reliability.

[0004] In order to conveniently evaluate the integrity of an anti-corrosion coating with a complex surface structure, the inventor hopes to obtain a reagent and method suitable for evaluating the integrity of an anti-corrosion coating with a complex surface structure.

[0005] The Chinese patent document with the publication date of June 1, 2016, the publication number of CN 105628694A, and the name of "a test paper and method for detecting the integrity of the copper or chromium plating layer on the steel surface" discloses a coating pore detection test paper and a preparation method, which is to soak the non-woven fabric in the pre-configured 28-92.3wt.% NaCl+6.5-61.1wt.% penetrant+1.2-13wt.% o-phenanthroline developer, and then apply the soaked non-woven fabric to the surface of the tested coating for 1-20 minutes, and finally judge the location and number of coating pores according to the color development degree of the non-woven fabric surface. This patent is more suitable for workpieces with large flat surfaces, and it is difficult for non-woven fabrics with complex surface structures to fully cover the coating.

[0006] The Chinese patent document with the publication date of August 16, 2019, the publication number of CN 110132825A, and the name of "A method for evaluating the corrosion resistance of the surface of a chrome-plated plate" discloses a reagent and method for detecting the porosity of the chrome-plated plate coating, which is to immerse the chrome-plated plate sample in a 0.5-2mol / LNH4SCN+1.5-2.5v / v%CH3COOH+0.5-2v / v%H2O2 erosion solution prepared in advance with deionized water, and then use an ultraviolet spectrophotometer to compare and analyze the eroded solution with the standard colorimetric solution, and finally calculate the corresponding integrity. This patent is suitable for small samples and is not operational for large workpieces.

[0007] The Chinese patent document with the publication date of April 20, 2016, the publication number of CN 105510310A, and the name of "Coating Integrity Detection Method" discloses a coating integrity detection reagent and method for brass-plated steel wire, which is to directly immerse the brass-plated steel wire in a 100mL aqueous solution of 10±2g K3[Fe(CN)6]+18±5g NaCl, and then observe the color state of the steel wire surface and compare it with the standard spectrum to evaluate the coating integrity. The method provided by the patent is suitable for small-volume samples and is not operable for large-volume workpieces.

[0008] Based on patent search, it was found that there are currently no detection reagents and methods for evaluating the integrity of anti-corrosion coatings with complex surface structures. According to the research of the present invention, a high-viscosity yellow transparent paste reagent can be obtained by reasonably formulating the reagents. After being coated on the coating surface, the pore distribution of the coating can be clearly displayed, and then the coating integrity can be rated against the standard spectrum. This invention is particularly suitable for rapid evaluation of the integrity of anti-corrosion coatings with complex surface structures. Summary of the invention

[0009] The integrity of the coating is an important basis for quality control in the anti-corrosion coating treatment process, but the traditional filter paper (cloth) method has low operability for coatings with complex surface structures. In view of the above problems, the present invention designs a transparent paste that can be directly applied to the surface of the coating to be tested, and the pores that are not easily observed in the coating are revealed through a color reaction, and then the integrity rating is performed against the standard spectrum. It is a reagent and method suitable for rapid evaluation of the integrity of anti-corrosion coatings such as Cr, Ni, or Cu on steel surfaces.

[0010] The technical solution of the present invention:

[0011] A reagent suitable for evaluating the integrity of an anti-corrosion coating, the components of which are as follows, in percentage by mass:

[0012] Cross-linked polyacrylic acid resin 0.5-10%,

[0013] NaCl 0.5-20%,

[0014] K3[Fe(CN)6]0.1-5%,

[0015] The balance was deionized water.

[0016] More preferably, the mass percentage content of the cross-linked polyacrylic acid resin is 1-3%.

[0017] More preferably, the mass percentage content of NaCl is 1-10%.

[0018] More preferably, the mass percentage content of K3[Fe(CN)6] is 0.1-2%.

[0019] The present invention also provides a method for preparing a reagent suitable for evaluating the integrity of an anti-corrosion coating, comprising the following steps:

[0020] (1) Weigh the amount of NaCl specified above and dissolve it in deionized water and stir evenly;

[0021] (2) Weigh K3[Fe(CN)6] and dissolve it in the solution prepared in step (1) and stir evenly;

[0022] (3) Weigh a cross-linked polyacrylic acid resin and evenly sprinkle it on the surface of the solution prepared in step (2), and let it stand to swell for 12 to 48 hours. After the swelling is completed, a yellow transparent paste is obtained.

[0023] More preferably, the solution prepared in step (2) is heated to a constant temperature of 50-90° C., and then the cross-linked polyacrylic acid resin is sprinkled on the surface of the solution and stirred rapidly.

[0024] The present invention also provides an application of the reagent suitable for evaluating the integrity of anti-corrosion coatings in rapid evaluation of the integrity of Cr, Ni or Cu anti-corrosion coatings plated on the surface of steel.

[0025] The application method comprises the following steps:

[0026] (1) Use organic solvents or other cleaning agents to remove stains such as oil on the surface of the coating and keep the coating surface clean and dry;

[0027] (2) The coating paste prepared in claim 5 is evenly applied to the surface of the coating layer, with the coating thickness not exceeding 2 mm. After coating, the coating is allowed to stand for 3-5 minutes;

[0028] (3) Observe the color change of the bottom of the ointment, and compare Figure 5 The integrity level of the coating is assessed using the graph in the figure. Detailed description of the invention:

[0030] The design idea of ​​the reagent in the present invention is to add cross-linked polyacrylic acid resin to provide viscosity, add sodium chloride (NaCl) as a corrosion accelerator, and add potassium ferrocyanide (K3[Fe(CN)6]) as a color developer. After the prepared yellow transparent paste is applied to the surface of the coating, if there are pores in the coating, the paste will penetrate into the pores and directly contact the steel substrate, inducing corrosion of the steel substrate and releasing ferrous ions (Fe 2+ ), Fe 2+ Combined with K3[Fe(CN)6], it turns blue. 2+ As the blue spots continue to spread around, their area gradually increases, thus making the pores that are difficult to observe visible.

[0031] The specific contents of the components in the present invention are as follows (all in mass percentage):

[0032] Table 1. Composition of the coating integrity evaluation reagent of the present invention

[0033] Element Cross-linked polyacrylic acid resin NaCl <![CDATA[K3[Fe(CN)6]]]> Deionized water content 0.5-10％ 0.5-20％ 0.1-5％ margin

[0034] The cross-linked polyacrylic acid resin can be dissolved in water to form a high-viscosity paste. If the added amount is too small, the paste viscosity is too low, and it is very easy to flow after being coated on the surface of the coating, which is not conducive to the observation of color spots; if the added amount is too large, the paste viscosity is too large, which is not conducive to the coating operation. Therefore, the added amount of the cross-linked polyacrylic acid resin in the present invention is 0.5-10%, preferably 1-3%.

[0035] NaCl can improve the conductivity in a corrosive environment, promote substrate corrosion, and accelerate the color development reaction. If the concentration is too low, the color development reaction slows down, reducing the detection efficiency. If the amount added is too large, it will cause difficulty in swelling the acrylic resin and forming a paste. Therefore, the amount of NaCl added in the present invention is 0.5-20%, preferably 1-10%.

[0036] K3[Fe(CN)6] dissolves in water and turns yellow. 2+ It reacts with it and turns blue. If the added amount is too high, the color of the paste will appear dark brown, which is not conducive to observing the color change. Therefore, the added amount in the present invention is 0.1-5%, preferably 0.1-2%.

[0037] The ointment preparation method is:

[0038] ①Weigh a certain amount of NaCl and dissolve it in deionized water and stir evenly;

[0039] ② Weigh a certain amount of K3[Fe(CN)6] and dissolve it in the solution prepared in step ① and stir evenly;

[0040] ③ Weigh a certain amount of cross-linked polyacrylic acid resin and evenly sprinkle it on the surface of the solution prepared in step ②, let it stand to swell, and the swelling time is ≥ 12 hours; in order to shorten the swelling time, the solution prepared in step ② can also be heated appropriately at a constant temperature (generally heated to 50-90°C), and then the cross-linked polyacrylic acid resin is sprinkled on the surface of the solution and stirred quickly. After the swelling is completed, a yellow transparent paste can be obtained.

[0041] How to use the ointment:

[0042] ① Use organic solvents or other cleaning agents to remove stains such as oil on the surface of the coating to keep the surface of the coating clean and dry;

[0043] ② Take an appropriate amount of paste and evenly cover the surface of the coating. The thickness of the paste is recommended not to exceed 2mm. After coating, let it stand for 3-5 minutes;

[0044] ③Observe the discoloration of the ointment and compare Figure 5 The integrity level of the coating is assessed using the graph in the figure. If the discoloration of the paste varies in local areas, the highest level is rated.

[0045] Beneficial technical effects of the present invention:

[0046] The present invention prepares a yellow transparent paste, which can reveal the pores in the coating after being coated on the surface of the anti-corrosion coating, and can evaluate the integrity of the coating according to a standard atlas. The present invention is particularly suitable for rapid evaluation of the integrity of coatings with complex surface structures. Description of the drawings:

[0047] Figure 1It is the yellow transparent paste prepared in Example 1.

[0048] Figure 2 This is a diagram showing the effect of using the product prepared in Example 1.

[0049] Figure 3 This is a diagram showing the effect of using the product prepared in Example 2.

[0050] Figure 4 This is a diagram showing the effect of using the product prepared in Example 3.

[0051] Figure 5 It is the coating integrity rating standard atlas of the present invention. Specific embodiments

[0052] The following examples are used to specifically illustrate the present invention. These examples are only general descriptions of the present invention and do not limit the present invention.

[0053] The proportioning components of a reagent suitable for evaluating the integrity of an anti-corrosion coating and a comparative example of the present invention are as follows:

[0054] Table 3 Composition of the ointment prepared in the examples and comparative examples

[0055]

[0056]

[0057] Example 1: Preparation of a reagent for evaluating the integrity of an anti-corrosion coating and detecting the integrity of a Ni coating on a steel plate, the steps are as follows:

[0058] ① Weigh 10g NaCl and dissolve it in 100g deionized water, and stir evenly;

[0059] ② Weigh 0.15g K3[Fe(CN)6] and dissolve it in the solution prepared in step ①, and stir evenly;

[0060] ③ Weigh 2.2g of cross-linked polyacrylic acid resin and sprinkle it evenly on the surface of the solution prepared in step ②. Let it stand for 20 hours and stir evenly to obtain a yellow transparent test paste. Figure 1 As shown;

[0061] ④ Take an appropriate amount of test paste and evenly apply it on the surface of the Ni-plated layer to be tested. The thickness of the paste is about 1mm. After standing for 4 minutes, observe the color development of the paste. Figure 2 As shown, compared with the standard atlas, the coating integrity rating is Grade I, indicating that isolated pores exist in the coating in this area.

[0062] Example 2: Preparation of a reagent for evaluating the integrity of an anti-corrosion coating and detection of the integrity of a Cu coating on a carbon steel thread surface, the steps are as follows:

[0063] ① Weigh 4g NaCl and dissolve it in 300g deionized water, and stir evenly;

[0064] ② Weigh 3.5g K3[Fe(CN)6] and dissolve it in the solution prepared in step ①, and stir evenly;

[0065] ③ Place the solution prepared in step ② in a water bath with magnetic stirring function and heat to a constant temperature of 60°C;

[0066] ④ Weigh 7.0g of cross-linked polyacrylic acid resin and sprinkle it on the surface of the solution in step ③, turn on the magnetic stirring, set the stirring speed to 600r / min, and swell for 12 hours to obtain a yellow transparent detection paste;

[0067] ⑤ Take an appropriate amount of test paste and evenly apply it on the surface of the Cu-plated layer to be tested. The thickness of the paste is about 2mm. After standing for 5 minutes, observe the color development of the paste. Figure 3 As shown, compared with the standard atlas, the coating integrity rating is Grade III, indicating that there are long strip pores in the coating in this area.

[0068] Example 3: Preparation of a reagent suitable for evaluating the integrity of an anti-corrosion coating and detecting the integrity of a Ni coating on a carbon steel round bar surface, the steps are as follows:

[0069] ① Weigh 11g NaCl and dissolve it in 200g deionized water, and stir evenly;

[0070] ② Weigh 4.3g K3[Fe(CN)6] and dissolve it in the solution prepared in step ①, and stir evenly;

[0071] ③ Weigh 6.5g of cross-linked polyacrylic acid resin and sprinkle it evenly on the surface of the solution prepared in step ②, let it stand for 36 hours and then stir it evenly to obtain a yellow transparent detection paste;

[0072] ④ Take an appropriate amount of test paste and evenly apply it on the surface of the Ni-plated layer to be tested. The thickness of the paste is about 1mm. After standing for 3 minutes, observe the color development of the paste. Figure 4 As shown, compared with the standard atlas, the coating integrity rating is Grade IV, indicating that there are a large number of dense pores in the coating in this area.

[0073] Comparative Example 1: Other conditions were the same as those in Example 2, except that the amount of cross-linked polyacrylic acid resin added was changed to 1.0 g. The viscosity of the resulting paste was too low, and it flowed after being applied to the surface of the threaded coating, resulting in a large area of ​​blue on the coating surface, making it impossible to evaluate the integrity of the coating.

[0074] Comparative Example 2: Other conditions were the same as those in Example 2, except that the amount of cross-linked polyacrylic acid resin added was changed to 40 g. The viscosity of the resulting paste was too high and it was difficult to evenly coat the surface of the thread coating.

[0075] Comparative Example 3: Other conditions were the same as those in Example 3, except that the amount of NaCl added was changed to 60 g, and the cross-linked polyacrylic acid resin was sprinkled therein and could not swell for a long time to form a paste.

[0076] Comparative Example 4: Other conditions were the same as those in Example 3, except that the amount of NaCl added was changed to 0.5 g. After the paste was applied to the surface of the steel plate coating, easily distinguishable blue spots appeared 30 minutes later, and the detection efficiency was low.

[0077] Comparative Example 5: Other conditions were the same as those in Example 1, except that the amount of K3[Fe(CN)6] added was changed to 10 g. The final paste was dark brown in color. After the paste was applied to the surface of the coating, it was difficult to accurately observe the color change.

[0078] The present invention can provide a reagent and method for evaluating the integrity of an anti-corrosion coating, which can be used for quickly evaluating the integrity of anti-corrosion coatings such as Cr, Ni, or Cu on the surface of steel, especially anti-corrosion coatings with complex surface structures.

Claims

1. A reagent suitable for evaluating the integrity of an anti-corrosion coating, characterized in that: Its component contents are as follows, in mass percentage: Cross-linked polyacrylic acid resin 0.5-10%, NaCl 0.5-20%, K3[Fe(CN)6]0.1-5%, The balance was deionized water.

2. A reagent suitable for evaluating the integrity of an anti-corrosion coating according to claim 1, characterized in that: The mass percentage content of the cross-linked polyacrylic acid resin is 1-3%.

3. A reagent suitable for evaluating the integrity of an anti-corrosion coating according to claim 1, characterized in that: The mass percentage content of the NaCl is 1-10%.

4. A reagent suitable for evaluating the integrity of an anti-corrosion coating according to claim 1, characterized in that: The mass percentage content of K3[Fe(CN)6] is 0.1-2%.

5. A method for preparing a reagent suitable for evaluating the integrity of an anti-corrosion coating, characterized in that The steps include: (1) Weigh the amount of NaCl specified in claim 1, dissolve it in deionized water and stir it evenly; (2) Weigh K3[Fe(CN)6] and dissolve it in the solution prepared in step (1) and stir evenly; (3) Weigh a cross-linked polyacrylic acid resin and evenly sprinkle it on the surface of the solution prepared in step (2), and let it stand to swell for 12 to 48 hours. After the swelling is completed, a yellow transparent paste is obtained.

6. A method for preparing a reagent for evaluating the integrity of an anti-corrosion coating according to claim 5, characterized in that: The solution prepared in step (2) is heated to a constant temperature of 50-90° C., and then the cross-linked polyacrylic acid resin is sprinkled on the surface of the solution and stirred rapidly.

7. An application of the reagent for evaluating the integrity of anti-corrosion coatings as claimed in claim 1 in the rapid evaluation of the integrity of anti-corrosion coatings plated with Cr, Ni or Cu on the surface of steel.

8. A use of the reagent for evaluating the integrity of an anti-corrosion coating according to claim 7, characterized in that: The application method includes the following steps: (1) Use organic solvents or other cleaning agents to remove stains such as oil on the surface of the coating and keep the coating surface clean and dry; (2) The coating paste prepared in claim 5 is evenly applied to the surface of the coating layer, with the coating thickness not exceeding 2 mm. After coating, the coating is allowed to stand for 3-5 minutes; (3) Observe the discoloration of the bottom of the coating and assess the integrity level of the coating.

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