Method for detecting pinholes in surface of enamel steel

Abstract

The invention provides a method for detecting pinholes in the surface of enamel steel. The method comprises the following steps: 1) surface cleaning: cleaning the surface of an enamel steel product and then drying; 2) electrochemical treatment: carrying out electrochemical treatment on the dried enamel steel product in an electrolyte solution by adopting a two-electrode system and a constant current mode; wherein the working electrode adopts a steel substrate of the enamel steel product treated in the step 1), and the auxiliary electrode adopts an inert electrode; the color of the electrolyte solution is different from that of an enamel layer on the surface of the enamel steel product; and 3) detection and identification: after the electrochemical treatment is finished, taking out the enamel steel product, drying, and detecting whether a color mark of the electrolyte solution appears on the surface of the enamel steel. According to the method, an electrochemical method is adopted, obvious color marking (different from the color of a surface enamel layer) is carried out at pinhole positions through electrochemical treatment, so that pinholes in the surface of the enamel steel are exposed and easy to find, and rapid and accurate identification of the pinholes in the surface of the enamel steel is realized.

Description

Technical Field

[0001] The invention relates to the technical field of material detection, in particular to a method for detecting pinholes on the surface of enameled steel. Background Art

[0002] Enameled steel products are widely used in many industrial fields due to their excellent corrosion resistance, aesthetics and durability. However, during the preparation of the enamel layer, due to the influence of various factors, such as material purity, firing temperature control, etc., various defects, especially pinhole defects, may appear on the surface of the enamel layer. These pinholes not only affect the appearance quality of the product, but may also become the starting point of corrosion, reducing the overall performance and service life of the product. Therefore, the development of an efficient and accurate pinhole detection method is of great significance to improve the quality of enameled steel products.

[0003] In the prior art, the method of analyzing the camera images is often used to detect defects. For example, the Chinese invention application with application number CN201711135842.8 discloses a comprehensive detection system for defects in enamel liner, which involves a comprehensive detection system for defects in enamel liner, including three parts: a motion mechanism, a detection mechanism, and image processing. The pulley in the motion mechanism rotates, driving the rubber material rotating shaft to rotate, and the enamel liner is placed on the rubber material rotating shaft to rotate. At the same time, the reduction motor drives the gear to rotate, and the gear and the rack are engaged to make the rack drive forward. The industrial camera images the inside of the enamel liner at the front end of the rack. The imaged data is presented on the display screen after image processing by the visual controller. The defects such as leaks and pinholes in the image are provided for reference by the staff. The system can accurately detect leaks and pinholes in the enamel liner, with high detection accuracy and fast detection speed, which can reach >1 / min, and the detection effect is obvious, avoiding the situation of manual missed detection and misjudgment. The Chinese utility model patent with application number 202122856850.X discloses a surface detection device for enameled steel plates, including a linear light source group, a linear array camera group, an industrial control cabinet and an enameled steel plate positioning device; the industrial control cabinet is respectively connected to the linear light source group, the linear array camera group and the enameled steel plate positioning device; the linear light source group and the linear array camera group are located on a bracket and arranged in front of the enameled steel plate; the linear array camera group includes a plurality of vertically arranged scanning cameras, and the scanning cameras are facing the bright area irradiated by the linear light source group on the enameled steel plate; the enameled steel plate positioning device includes an encoder, a photoelectric switch and a code reading camera, the encoder is used to monitor the displacement of the enameled steel plate, the photoelectric switch is used to detect whether an enameled steel plate passes, and the code reading camera is used to read and identify the two-dimensional code on the enameled steel plate. The utility model can automatically identify and analyze defects, classify and summarize them, and is used to improve the production process, improve product quality, and improve production efficiency.

[0004] The above-mentioned existing technologies all rely on camera images to judge the defects of the enamel liner. The detection effect is better for the dew point with obvious defects, but for the enamel pinholes, since the pinholes are very small, it is easy to miss the detection or misjudge.

[0005] Based on this, the applicant considered providing a method for detecting pinholes on the surface of enameled steel to achieve rapid and accurate identification of pinhole defects. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned technology, the purpose of the present invention is to provide a method for detecting pinholes on the surface of enameled steel. The method adopts the electrochemical principle and performs obvious color marking on the pinhole position through electrochemical treatment. The color of the mark is obviously different from the color of the enamel layer on the surface of the enameled steel, so that the pinholes on the surface of the enameled steel are exposed, thereby realizing rapid and accurate identification of pinholes on the surface of the enameled steel.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for detecting pinholes on the surface of enameled steel comprises the following steps:

[0009] 1) Surface cleaning: clean the surface of the enameled steel product and dry it;

[0010] 2) Electrochemical treatment: using a two-electrode system and a constant current mode, the dried enameled steel product is subjected to electrochemical treatment in an electrolyte solution; wherein the working electrode is the steel substrate of the enameled steel product treated in step 1), and the auxiliary electrode is an inert electrode; the electrolyte solution has a color, and the color of the electrolyte solution is different from the color of the enamel layer on the surface of the enameled steel product;

[0011] 3) Detection and identification: After the electrochemical treatment is completed, the enameled steel product is taken out and dried to detect whether the color mark of the electrolyte solution appears on the surface of the enameled steel. The position of the color mark of the electrolyte solution is the pinhole position.

[0012] Preferably, in step 1), the surface of the enameled steel product is cleaned with a degreasing agent or ethanol to remove oil stains and dust, and then rinsed with deionized water and dried.

[0013] Preferably, in step 2), the electrolyte solution comprises an aqueous solution of any one of inorganic salts, inorganic acids and inorganic bases; the concentration of the inorganic salts / organic acids / inorganic bases in the electrolyte solution is 0.1 to 10 wt%.

[0014] Preferably, the inorganic salts include any one of NaCl, NaSO4, and KCl; the inorganic acids include any one of H2SO4 and HCl; and the inorganic bases include NaOH.

[0015] Preferably, in step 2), the electrolyte solution includes an acid-base indicator, and the pH value of the electrolyte solution is controlled by a pH regulator to be within the color change range of the acid-base indicator, and the color displayed by the acid-base indicator after color change is different from the color of the enamel layer on the surface of the enameled steel product.

[0016] Preferably, the acid-base indicator includes any one of phenolphthalein, methyl orange, and litmus; and the pH adjuster includes any one or more of NaOH, H2SO4, and HCl.

[0017] Preferably, in the electrolyte solution, the concentration of the acid-base indicator is 0.1-0.5 wt %.

[0018] Further preferably, in step 2), the electrochemical treatment comprises:

[0019] Equipment preparation: prepare an electrochemical workstation or a constant current instrument, using a two-electrode system, the working electrode is the steel substrate of the enameled steel product, the steel substrate of the enameled steel product is connected to the positive electrode of the electrochemical workstation or the constant current instrument through a wire, and the auxiliary electrode is an inert electrode, which is connected to the negative electrode of the electrochemical workstation or the constant current instrument; select the constant current mode;

[0020] Applying current: placing the enameled steel product and the auxiliary electrode in the electrolyte solution, and connecting them to the positive and negative electrodes of the electrochemical workstation or the constant current instrument respectively, and starting the electrochemical workstation or the constant current instrument for processing.

[0021] Preferably, in step 2), the inert electrode material is graphite or platinum.

[0022] Preferably, during the electrochemical treatment, the current density is 0.2-0.8 A and the treatment time is 5-10 min.

[0023] Preferably, the steel substrate of the enameled steel product is connected to the conductor by clamping or welding, and the connection is sealed by an insulating material.

[0024] Preferably, the insulating material includes any one of silica gel and epoxy resin.

[0025] Preferably, the detection in step 3) comprises visual inspection or taking a photo of the enameled steel surface and then performing statistics using an image processing tool.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a method for detecting pinholes on the surface of enameled steel based on the electrochemical principle. The method has the advantages of high efficiency, accuracy, non-destructiveness and wide applicability, and provides a new technical means for quality inspection of enameled steel products. The present invention adopts the electrochemical principle and performs obvious color marking (different from the color of the surface enamel layer) at the pinhole position through electrochemical treatment, so that the pinholes on the surface of the enameled steel are exposed and easy to be found, thereby realizing rapid and accurate identification of pinholes on the surface of the enameled steel. DETAILED DESCRIPTION

[0028] In order to better explain the present invention, the main contents of the present invention are further explained below in conjunction with specific embodiments, but the contents of the present invention are not limited to the following embodiments.

[0029] The present invention provides a method for detecting pinholes on the surface of enameled steel, comprising the following steps:

[0030] 1) Preparation of test solution

[0031] Select an electrolyte solution, such as NaCl solution, NaSO4, KCl and other inorganic salt solutions, or acid-base solutions, such as dilute sulfuric acid, NaOH solution, etc. The concentration of the electrolyte in the test solution is 0.1-10wt%. The basic solution has no significant corrosive effect on the surface of the enameled steel and can produce an electrochemical reaction in the gas or defect in the pinhole so that the test solution can enter the pinhole; the electrolyte concentration should not be too high to avoid unnecessary damage to the enamel layer. At the same time, add an appropriate amount of acid-base indicator to the electrolyte solution, and adjust the pH value of the electrolyte solution until the acid-base indicator changes color to obtain the test solution. Acid-base indicators such as phenolphthalein, methyl orange, litmus, etc. can be used. The concentration of the acid-base indicator in the test solution is 0.1-0.5wt%. These acid-base indicators will change color at a specific pH value, which is used to mark the location of the reaction, thereby determining the location of the pinhole. The color displayed by the acid-base indicator is different from the color of the enamel layer on the surface of the enameled steel product. The color change range of common acid-base indicators is as follows.

[0032] Methyl orange: red at pH < 3.1, orange at pH 3.1-4.4, yellow at pH > 4.4.

[0033] Litmus: red at pH < 5, purple at pH 5-8, blue at pH > 8.

[0034] Phenolphthalein: colorless at pH < 8.2, light red at pH 8.2-10, red at pH > 10.

[0035] 2) Surface cleaning:

[0036] Use degreasing agent or solvents such as ethanol to clean the surface of enameled steel products to remove impurities such as oil, dust, etc., and then rinse with ionized water. Make sure not to damage the enamel layer during the cleaning process. Place the cleaned enameled steel products in a dry environment to dry naturally or use tools such as a hair dryer to accelerate the drying process.

[0037] 3) Electrochemical treatment:

[0038] Equipment preparation: Prepare an electrochemical workstation or galvanostat or other equipment with the same function, which can accurately control the output of current. A two-electrode system is used, and the working electrode is a steel substrate of enameled steel products. The steel substrate of enameled steel products is connected to the wire. The steel substrate of enameled steel products and the wire can be connected by clamping or welding. The connection is sealed with insulating materials such as silicone and epoxy resin. The auxiliary electrode is a graphite or platinum electrode. In constant current mode, the working electrode is connected to the positive electrode of the electrochemical workstation or galvanostat, and the auxiliary electrode is connected to the negative electrode of the electrochemical workstation or galvanostat.

[0039] Apply current: Place the enameled steel product and the auxiliary electrode in the test solution, and connect them to the positive and negative electrodes of the electrochemical workstation or constant current instrument respectively. Set the current density to between 0.2 and 0.8A, the treatment time to 5 to 10 minutes, and start the electrochemical workstation or constant current instrument for treatment. If the current density is small and the treatment time is short, the electrochemical reaction is not sufficient, which will eventually lead to some pinholes not being accurately marked. If the current density is large and the treatment time is long, when the surface enamel layer is thin, it is easy for non-pinhole positions to be broken down, resulting in incorrect marking.

[0040] Observe the reaction: During the experiment, pay close attention to the changes on the surface of the enameled steel. Since there are air gaps or microcracks at the pinhole, these areas will preferentially undergo electrochemical reactions, allowing the test solution to enter the pinhole, resulting in the acid-base indicator producing obvious color marks at the pinhole position. After the electrochemical reaction is over, when the enameled steel is taken out, the color of the acid-base indicator will remain in the air gaps or microcracks, making the pinhole surface color different from the color of the enamel layer on the surface of the enameled steel product. Since there are no air gaps or microcracks in other areas, the solution cannot be filled and the enameled steel itself color is displayed.

[0041] The electrochemical reaction equation is as follows:

[0042] In neutral and alkaline solutions, the reaction formula is Fe + 2H2O = Fe(OH)2 + H2;

[0043] In acidic solution, the reaction equations are:

[0044] Fe+2HCl=FeCl2+H2(when the pH of the solution is adjusted with hydrochloric acid);

[0045] Fe+H2SO4=FeSO4+H2 (when the pH of the solution is adjusted with sulfuric acid).

[0046] 4) Detection and identification:

[0047] Visual inspection: After the electrochemical treatment, blow the enameled steel products dry and visually inspect whether there are obvious color marks on the surface of the enameled steel products. If there are few pinhole marks, the number of pinhole points can be counted visually.

[0048] Auxiliary tool inspection: When there are many pinhole marks, take a photo of the surface of the enamel product and count the number of pinholes using image processing tools.

[0049] 5) Data processing:

[0050] Record in detail the number, distribution location, size and other information of pinholes found during the inspection.

[0051] The method of the present invention is further illustrated by Examples 1 to 3 below.

[0052] The specific detection process parameters of Examples 1 to 3 are shown in Table 1. The surface of the enameled steel is cleaned with a degreasing agent, and the copper wire is connected to the steel substrate of the enameled steel product, and the connection is sealed with silicone. The degreasing agent can be a commercially available degreasing agent.

[0053] The test results of Examples 1 to 3 are shown in Table 2. All of them can complete the detection of pinholes on the surface of enameled steel by visual inspection.

[0054] In summary, the method for detecting pinholes on the surface of enameled steel produced by the present invention can perform obvious color marking (different from the color of the surface enamel layer) at the location of the pinholes in the enameled steel, so that the pinholes on the surface of the enameled steel are exposed and easy to find, thereby realizing rapid and accurate identification of the pinholes.

[0055] Table 1: Detection process parameters

[0056]

[0057] Table 2: Test results

[0058]

[0059] The above description only provides a specific exemplary description of the present invention. It should be noted that the specific implementation of the present invention is not limited to the above method. As long as various non-substantial improvements are made using the technical concept and technical solution of the present invention, or the technical concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for detecting pinholes on the surface of enameled steel, characterized in that: The following steps are involved: 1) Surface cleaning: clean the surface of the enameled steel product and dry it; 2) Electrochemical treatment: using a two-electrode system and a constant current mode, the dried enameled steel product is subjected to electrochemical treatment in an electrolyte solution; wherein the working electrode is the steel substrate of the enameled steel product treated in step 1), and the auxiliary electrode is an inert electrode; the electrolyte solution has a color, and the color of the electrolyte solution is different from the color of the enamel layer on the surface of the enameled steel product; 3) Detection and identification: After the electrochemical treatment is completed, the enameled steel product is taken out and dried to detect whether the color mark of the electrolyte solution appears on the surface of the enameled steel. The position of the color mark of the electrolyte solution is the pinhole position.

2. The detection method according to claim 1, characterized in that: In step 1), the surface of the enameled steel product is cleaned with a degreasing agent or ethanol to remove oil stains and dust, and then rinsed with deionized water and dried.

3. The detection method according to claim 1, characterized in that: In step 2), the electrolyte solution includes an aqueous solution of any one of inorganic salts, inorganic acids, and inorganic bases; the concentration of the inorganic salts / organic acids / inorganic bases in the electrolyte solution is 0.1 to 10 wt%.

4. The detection method according to claim 3, characterized in that: The inorganic salts include any one of NaCl, NaSO4, and KCl; the inorganic acids include any one of H2SO4 and HCl; and the inorganic bases include NaOH.

5. The detection method according to claim 1, characterized in that: In step 2), the electrolyte solution includes an acid-base indicator, and the pH value of the electrolyte solution is controlled by a pH regulator to be within the color change range of the acid-base indicator. The color displayed by the acid-base indicator after color change is different from the color of the enamel layer on the surface of the enameled steel product.

6. The detection method according to claim 5, characterized in that: The acid-base indicator includes any one of phenolphthalein, methyl orange, and litmus; the pH adjuster includes any one or more of NaOH, H2SO4, and HCl.

7. The detection method according to claim 5, characterized in that: In the electrolyte solution, the concentration of the acid-base indicator is 0.1-0.5 wt %.

8. The detection method according to claim 1, characterized in that: In step 2), the inert electrode material is graphite or platinum.

9. The detection method according to claim 1, characterized in that: During the electrochemical treatment, the current density is 0.2-0.8A and the treatment time is 5-10min.

10. The detection method according to any one of claims 1 to 9, characterized in that: The inspection in step 3) includes visual inspection or taking a picture of the enameled steel surface and then counting it using an image processing tool.

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