An electrochemical probe for in-situ testing of coating corrosion resistance and a method of using the same

Abstract

The present invention discloses a method for in-situ testing of the corrosion resistance of coatings and a dedicated electrochemical probe. The method for in-situ testing of the corrosion resistance of coatings of the present invention can detect metal-based, ceramic-based, non-metallic material-based coatings and the like by directly adsorbing the probe on the surface of the coating to be tested with the help of negative pressure without destroying the coating, and can realize in-situ non-destructive testing of coatings and coating samples of in-service equipment, ensure the repeatability of the test results, and is suitable for corrosion resistance testing of various coating materials. The dedicated electrochemical probe has a simple device structure, strong designability, and a wide range of applications. In addition, it has the advantages of easy operation and high efficiency.

Description

Technical Field

[0001] The invention belongs to the field of physical and chemical detection technology, and relates to a coating corrosion resistance detection technology, in particular to a method for in-situ testing of coating corrosion resistance and a special electrochemical probe thereof. Background Art

[0002] During use, the coating is affected by physical and chemical factors and ages. Rapid evaluation of the anti-corrosion performance of the coating can improve the service safety of the equipment.

[0003] After aging, the coating will show loss of gloss, discoloration, powdering, blistering, rust, mildew, shedding, staining, etc., which in essence will show a decline in several properties such as barrier, electrochemical (corrosion inhibition or cathodic protection) and adhesion, and eventually lose the protection of the metal. Since the coating always contains more or less hydrophilic groups and water-soluble components, it will be affinity with water and absorb water and electrolyte ions, so the corrosion resistance of metal-based coatings can be determined by electrochemical methods.

[0004] At present, the main method of electrochemical testing is electrochemical impedance spectroscopy, which requires the base metal as the working electrode, the silver / silver chloride electrode as the reference positive electrode, and the graphite electrode or platinum electrode as the reference negative electrode. This requires the base metal of the coating to be exposed and connected to the working electrode lead of the electrochemical workstation. For the coating in service, the base metal is completely covered by the coating. Therefore, it is impossible to achieve in-situ testing of the barrier performance of the organic coating to the corrosive medium, and the aging degree, corrosion resistance and remaining life of the coating of the in-service equipment cannot be effectively evaluated.

[0005] Therefore, exploring scientific and practical coating electrochemical detection and evaluation methods and in-situ detection test devices has become a key issue in current coating electrochemical detection technology. Invention patent CN1224837A discloses a portable coating / metal corrosion resistance rapid testing system, which is equipped with a movable electrochemical probe, a test circuit, a laptop computer, a power supply circuit and computer software. The probe is a double electrolytic cell three-electrode system, which can be fixed on the iron-based coating through a strong magnetic sheet, and the corrosion resistance of the coating / metal is tested through the entire system. Obviously, the electrochemical probe of this invention is only suitable for testing iron-based coatings, and cannot be used for corrosion resistance testing of steel-based, aluminum-based, ceramic-based and other non-metallic material-based coatings. The present invention aims to provide an electrochemical probe suitable for all substrate coatings, which is used in conjunction with an electrochemical workstation to perform in-situ detection of the corrosion resistance of various coatings. Summary of the invention

[0006] The purpose of the present invention is to provide a method for in-situ testing of coating corrosion resistance and a dedicated electrochemical probe thereof, so as to solve the problems of aging degree assessment, rapid evaluation of corrosion resistance and remaining life prediction of coatings of in-service equipment.

[0007] The purpose of the present invention is achieved in this way: using a vacuum adsorption device that can generate negative pressure, two independent flexible conductors connected to a positive electrode and a negative electrode are tightly adsorbed on the coating, and then the positive electrode and the negative electrode are respectively connected to the positive and negative electrode leads of the electrochemical workstation, and the test program is started to perform corrosion resistance testing.

[0008] The present invention relates to a method for in-situ testing of coating corrosion resistance, and the steps are as follows:

[0009] 1) Assemble a dedicated electrochemical probe, including a vacuum adsorption device, a flexible conductor, a positive electrode, a negative electrode, an electrode connector and a flexible insulator; the vacuum adsorption device includes an insulating shell and a vacuum pump, the insulating shell is made of a hard insulating material, a groove with an opening at the lower end is arranged along its height direction, and a through hole is opened in the height direction of the opposite side plate; the flexible conductor, which is not less than two, and can be surrounded by a gapless structure with the flexible insulator in a staggered connection manner, is located below the side wall of the insulating shell; the positive electrode and the negative electrode are connected to the positive electrode connector and the negative electrode connector at one end respectively, and the other end passes through the through hole of the opposite side plate of the insulating shell to contact with the flexible conductor; the positive electrode connector and the negative electrode connector are connected to the positive and negative electrode leads of the electrochemical workstation respectively;

[0010] 2) Place the coated object to be tested with the coating facing upwards;

[0011] 3) Place the assembled dedicated electrochemical probe on top of the coating and press down the insulating housing with force to achieve a sealed connection between the probe and the coating with the help of the flexible conductor and the flexible insulator;

[0012] 4) With the help of a vacuum device, the inner cavity between the insulating shell and the coating is evacuated to a negative pressure so that the two are firmly adsorbed;

[0013] 5) Start the electrochemical workstation and perform corrosion resistance test on the coated objects.

[0014] The invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, which is characterized in that it also includes a vacuum adsorption device, a flexible conductor and a flexible insulator; the vacuum adsorption device includes an insulating shell and a vacuum pump, the insulating shell is made of a hard insulating material, a groove with an opening at the lower end is arranged along its height direction, and a through hole is opened in the height direction of the opposite side plate; the flexible conductors are no less than two, and the two are non-adjacent to the flexible insulator to form a gapless structure, and are located below the side wall of the insulating shell; the positive electrode and the negative electrode, the ends not connected to the joint pass through the through hole of the opposite side plate of the insulating shell and contact with the flexible conductor; the positive electrode joint and the negative electrode joint are respectively connected to the positive and negative electrode leads of the electrochemical workstation.

[0015] The invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, which is characterized in that the conductive flexible body is an elastomer filled with metal conductive material or a highly water-absorbent polymer material saturated with electrolyte.

[0016] The present invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, which is characterized in that: the vacuum pumping device comprises a sealing ring, a piston, a rotatable fixed pin and a fixed pin support; the piston is made of a hard insulating material, and comprises a flat plate and a long rod fixed to its upper surface, the shape of the flat plate matches the groove of the insulating shell, and a through hole is opened above the long rod; the rotatable fixed pin is made of a hard insulating material, has an elliptical structure, and a through hole is provided at one end of its long axis; the fixed pin support is made of a hard insulating material, and comprises two vertical brackets and a transverse rod, the two vertical brackets are placed opposite to each other, and corresponding oblong holes are opened at the upper ends, and the two ends of the transverse rod are respectively placed in the oblong holes of the two vertical brackets, and can move up and down in the vertical direction; the sealing ring is fixed to the outer edge of the piston; the transverse rod of the fixed pin support passes through the through hole of the piston long rod; there are two rotatable fixed pins, which are arranged on both sides of the piston and are sleeved on the transverse rod of the fixed pin support through their through holes.

[0017] The invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, characterized in that the hard insulating material is glass fiber reinforced plastic or polycarbonate.

[0018] The invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, which is characterized in that the rotatable fixing pin is an ellipsoidal structure with a hole at the long axis end.

[0019] The invention relates to a special electrochemical probe for an in-situ test method of coating corrosion resistance, which is characterized in that the flexible insulator is made of insulating silicone rubber or hydrogenated nitrile rubber.

[0020] The method for in-situ testing of coating corrosion resistance of the present invention can detect metal-based, ceramic-based, non-metallic material-based coatings without destroying the coating by directly adsorbing the probe on the surface of the coating to be tested with the help of negative pressure, and can realize in-situ non-destructive testing of coatings and coating samples of in-service equipment, ensure the repeatability of test results, and is suitable for corrosion resistance testing of various coating materials. Its special electrochemical probe has a simple device structure, strong designability, and wide applicability. In addition, it has the advantages of easy operation and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A front cross-sectional view of an electrochemical probe for in-situ testing of coating corrosion resistance according to the present invention.

[0022] Figure 2 A top view cross-sectional view of an electrochemical probe used for in-situ testing of coating corrosion resistance according to the present invention.

[0023] Among them, 1 is a flexible conductor, 2 is a positive electrode, 3 is a positive electrode connector, 4 is a negative electrode connector, 5 is a negative electrode, 6 is an insulating shell, 7 is a sealing ring, 8 is a piston, 9 is a rotatable fixing pin, 10 is a fixing pin support, 11 is a vacuum chamber, 12 is a coating, 13 is a base metal, and 14 is a flexible insulator. DETAILED DESCRIPTION

[0024] Example 1

[0025] The electrochemical probe used for in-situ testing of corrosion resistance of metal-based coatings in this embodiment includes a vacuum adsorption device, a flexible conductor 1, a positive electrode 2, a negative electrode 5, an electrode connector and a flexible insulator 14, such as Figure 1 and Figure 2 shown.

[0026] The flexible conductor 1 is a square plate made of silicone rubber filled with conductive nano-silver particles, with a size of 50 mm×10 mm×2 mm.

[0027] The positive electrode 2 is a silver electrode.

[0028] The electrode connector includes a positive electrode connector 3 and a negative electrode connector 4.

[0029] The negative electrode 5 is a graphite electrode.

[0030] The vacuum adsorption device includes an insulating shell 6, a sealing ring 7, a piston 8, a rotatable fixed pin 9 and a fixed pin support 10. The insulating shell 6 is made of polycarbonate material, has a rectangular shape, and has a size of 50mm×30mm×50mm. The inner cavity is a groove with an opening at the lower end and a size of 30mm×30mm×40mm. A through hole with a diameter of 10mm is opened at the center of the top plate; through holes in the height direction are opened at the center of the opposite side plates. The sealing ring 7 is a natural rubber lip ring. The piston 8 is made of polycarbonate material, including a square plate and a cylinder with a diameter of 10mm fixed at the middle position of its upper surface, and a radial through hole is opened above the cylinder. The rotatable fixed pin 9 is made of polycarbonate material, has an ellipsoidal structure, and a through hole is set at one end of its long axis. The fixed pin support 10 is made of polycarbonate material, including two vertical brackets and a transverse rod. The two vertical brackets are placed opposite to each other, and corresponding oblong holes are opened at the upper ends. The two ends of the transverse rod are respectively placed in the oblong holes of the two vertical brackets and can move up and down in the vertical direction. The sealing ring 7 is fixed to the edge of the square plate of the piston 8 and is located in the middle groove of the insulating shell 6. The cylinder of the piston 8 extends out from the central through hole of the top plate of the insulating shell 6; the two vertical brackets of the fixed pin support 10 are fixed to the upper surface of the top plate of the insulating shell 6, and its transverse rod passes through the radial through hole of the cylinder of the piston 8; two rotatable fixed pins 9 are arranged on both sides of the piston 8 and are sleeved on the transverse rod of the fixed pin support 10 through their through holes.

[0031] The flexible insulator 14 is a square plate made of insulating silicone rubber material with a size of 30 mm×3 mm×2 mm.

[0032] In the electrochemical probe of this embodiment, two flexible conductors 1 are placed side by side, and a flexible insulator 14 is placed between the two ends of the two conductors, and the four of them form a U-shaped structure without gaps, such as Figure 2 As shown; the insulating shell 6 of the vacuum adsorption device, its two opposite side plates with through holes are placed above the two flexible conductors 1, and the other two opposite side plates are placed above the two flexible insulators 14; the positive electrode 2 and the negative electrode 5 are respectively placed in the two through holes of the insulating shell 6, and the lower ends are respectively in contact with the upper surfaces of the two flexible conductors 1, and the upper ends are respectively connected to the positive electrode connector 3 and the negative electrode connector 4.

[0033] When the electrochemical probe of this embodiment is used for in-situ testing of corrosion resistance of metal-based coatings, the base metal 13 is placed at the bottom with its coating 12 facing upward; the electrochemical probe is placed above the coating 12, and the insulating shell 6 is pressed downward with force to achieve a sealed connection with the coating 12 by means of the flexible conductor 1 and the flexible insulator 14; the direction of the rotatable fixing pin 9 is adjusted to lift the piston 8, and under the action of the sealing ring 7, a negative pressure is generated between the lower part of the inner cavity of the insulating shell 6 and the coating 12, so that the insulating shell 6 and the coating 12 are firmly adsorbed. The rotating fixing pin 9 is fixed to maintain the state of the insulating shell 6 and the coating 12 being firmly adsorbed; then the electrode connectors of the positive electrode 2 and the negative electrode 5 are respectively connected to the positive and negative leads of the electrochemical workstation, and the corrosion resistance test is performed.

[0034] Example 2

[0035] The difference from Example 1 is that:

[0036] The electrochemical probe of this embodiment is used for in-situ testing of the corrosion resistance of ceramic-based coatings.

[0037] The flexible conductor 1 is a 1 / 4 circular ring plate with a thickness of 5 mm, an outer diameter of 50 mm and an inner diameter of 40 mm, and is made of a water-absorbing high molecular polymer filled with 3.5% NaCl electrolyte.

[0038] The positive electrode 2 is a platinum electrode.

[0039] The negative electrode 5 is a platinum black electrode.

[0040] The insulating shell 6 is made of glass fiber reinforced plastic material, and has the shape of a cylinder with a height of 60 mm and a diameter of 50 mm. The inner cavity is a groove with a height of 50 mm and a diameter of 40 mm. A through hole with a diameter of 8 mm is opened at the axial center of the top plate; through holes in the height direction are opened on both sides of the side wall. The sealing ring 7 is a hydrogenated nitrile rubber lip ring. The piston 8 is made of glass fiber reinforced plastic material, including a circular plate and a cylinder with a diameter of 8 mm fixed at the middle position of its upper surface, and a radial through hole is opened above the cylinder. The rotatable fixing pin 9 is made of glass fiber reinforced plastic material. The fixing pin support 10 is made of glass fiber reinforced plastic material.

[0041] The flexible insulator 14 is made of insulating hydrogenated nitrile rubber and is a 1 / 4 circular plate with a thickness of 5 mm, an outer diameter of 50 mm and an inner diameter of 40 mm.

Claims

1. An electrochemical probe for in-situ testing of coating corrosion resistance, comprising a positive electrode, a negative electrode, a positive electrode connector, and a negative electrode connector, characterized in that: It also includes a vacuum adsorption device, a flexible conductor (1) and a flexible insulator (14); the vacuum adsorption device includes an insulating shell (6) and a vacuum pumping device, the insulating shell (6) is made of a hard insulating material, a groove with an open lower end is arranged along its height direction, and a through hole is opened in the height direction of the opposite side plate; the flexible conductors (1) are not less than two, and the two are surrounded by the flexible insulator (14) in a non-adjacent manner to form a gapless structure, and are located below the side wall of the insulating shell (6); the positive electrode (2) and the negative electrode (5), the ends not connected to the connector pass through the through hole of the opposite side plate of the insulating shell (6) and contact with the flexible conductor (1); the positive electrode connector (3) and the negative electrode connector (4) are respectively connected to the positive and negative electrode leads of the electrochemical workstation; the flexible conductor (1) is an elastomer filled with metal conductive material or a highly absorbent polymer material saturated with electrolyte; the vacuum pumping device includes a sealing ring (7), A piston (8), a rotatable fixing pin (9) and a fixing pin support (10); the piston (8) is made of a hard insulating material, comprising a flat plate and a long rod fixed to its upper surface, the shape of the flat plate matches the groove of the insulating shell (6), and a through hole is opened on the top of the long rod; the rotatable fixing pin (9) is made of a hard insulating material, has an elliptical structure, and a through hole is provided at one end of its long axis; the fixing pin support (10) is made of a hard insulating material, comprises two vertical brackets and a transverse rod, the two vertical brackets are placed opposite to each other, corresponding oblong holes are opened at the upper ends, and the two ends of the transverse rod are respectively placed in the oblong holes of the two vertical brackets and can move up and down in the vertical direction; the sealing ring (7) is fixed to the outer edge of the piston (8); the transverse rod of the fixing pin support (10) passes through the through hole of the long rod of the piston (8); two rotatable fixing pins (9) are arranged on both sides of the piston (8) and are sleeved on the transverse rod of the fixing pin support (10) through their through holes.

2. The electrochemical probe for in-situ testing of coating corrosion resistance according to claim 1, characterized in that: The hard insulating material is glass fiber reinforced plastic or polycarbonate.

3. The electrochemical probe for in-situ testing of coating corrosion resistance according to claim 1, characterized in that: The rotatable fixing pin (9) is an ellipsoidal structure with a hole opened at the long axis end.

4. The electrochemical probe for in-situ testing of coating corrosion resistance according to claim 1, characterized in that: The flexible insulator (14) is made of insulating silicone rubber or hydrogenated nitrile rubber.

5. A method for using the electrochemical probe for in-situ testing of coating corrosion resistance according to claim 1, comprising the following steps: 1) Assembling a special electrochemical probe, comprising a vacuum adsorption device, a flexible conductor (1), a positive electrode (2), a negative electrode (5), an electrode connector and a flexible insulator (14); the vacuum adsorption device comprises an insulating shell (6) and a vacuum pump, the insulating shell (6) being made of a hard insulating material, having a groove with an open lower end arranged along its height direction, and having a through hole in the height direction of the opposite side plate; the flexible conductor (1) being at least two, and being connected with the flexible insulator (14) in an interlaced manner to form a gapless structure, and being located below the side wall of the insulating shell (6); the positive electrode (2) and the negative electrode (5), one end of which is respectively connected to the positive electrode connector (3) and the negative electrode connector (4), and the other end of which passes through the through hole of the opposite side plate of the insulating shell (6) and contacts with the flexible conductor (1); the positive electrode connector (3) and the negative electrode connector (4) are respectively connected to the positive and negative electrode leads of the electrochemical workstation; 2) placing the object with the coating (12) to be tested, with the coating (12) facing upwards; 3) placing the assembled dedicated electrochemical probe on the coating (12), and pressing the insulating housing (6) downward with force, so that the insulating housing (6) and the coating (12) are sealed with each other by means of the flexible conductor (1) and the flexible insulator (14); 4) using a vacuum device to evacuate the inner cavity between the insulating shell (6) and the coating (12) to a negative pressure, so that the two are firmly adsorbed; 5) Start the electrochemical workstation and perform corrosion resistance test on the object with coating (12).

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