An experimental device for measuring pH near the surface of metal corrosion and adjusting the distance between pH electrodes

Abstract

The invention relates to an experimental device for measuring pH near the surface of metal corrosion and adjusting the distance between pH electrodes. The device comprises a base with a central hole, the base is sealed and fixed on the side wall of a test water tank, a simulated corrosion solution is stored in the test water tank, a metal sample is fixedly connected to the front end surface of the base, a sleeve is installed in the base, the front end of the sleeve is inserted into the metal sample, the rear end of the sleeve is fixedly connected to the base, an inner rod is slidably arranged in the sleeve, a piston is fixed to the front end of the inner rod, a pH microelectrode and a reference electrode are embedded in the inner rod, and the front ends of the pH microelectrode and the reference electrode are flush with the outer side surface of the metal sample; a differential head coaxial with the inner rod is arranged at the rear end of the inner rod, and when the differential head is rotated, the measuring rod of the differential head drives the inner rod to move axially to adjust the distance between the end of the pH microelectrode and the end of the reference electrode and the outer side surface of the metal sample at the micrometer level; the device is simple to operate, and the distance between the pH microelectrode, the reference electrode and the metal sample can be adjusted at the micrometer level by adjusting the differential head, thereby improving the measurement accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of metal material corrosion and protection, in particular to an experimental device for measuring pH near the metal corrosion surface and adjusting the distance between pH electrodes. Background Art

[0002] In the study of metal corrosion and protection, pH changes at the metal / solution interface are one of the important signs of metal corrosion. Being able to measure the micro-area pH value of the metal / medium interface and deduce possible electrochemical reactions can provide important parameters for explaining specific corrosion behaviors and revealing corrosion mechanisms.

[0003] Micro-metal pH electrodes are an effective means of detecting the pH of micro-areas near the surface of solutions / metals. However, since the pH changes of metals / solutions during corrosion only occur in a very small micro-area where corrosion occurs, it is impossible to accurately control the distance between the micro-electrode and the corrosion surface when measuring the pH value of the micro-area, and it is also impossible to adjust the position of the pH micro-electrode during the measurement process.

[0004] Traditionally, when conducting indoor simulation experiments to study the changes in pH during metal corrosion and protection, free electrodes are generally used. This not only makes it difficult to ensure the relative position between the pH electrode and the metal sample, but also makes it difficult to ensure that the pH electrode remains relatively motionless during the experiment. At the same time, when the electrode is manually adjusted, it is impossible to achieve micron-level accuracy, which affects the measurement accuracy. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, the present invention provides an experimental device for measuring the near-surface pH of metal corrosion and adjusting the distance of pH electrodes, so as to achieve precise adjustment of the position of the pH microelectrode when simulating metal corrosion and protection experiments.

[0006] The technical solution adopted by the present invention to solve its technical problems is: an experimental device for measuring the pH near the surface of metal corrosion and adjusting the distance of pH electrodes, comprising a base with a central hole, a metal sample fixedly connected to the front end surface of the base, a sleeve installed in the base, the front end of the sleeve penetrates into the metal sample, the rear end of the sleeve is fixed to the base, an inner rod is slidably arranged in the sleeve, a piston is fixed to the front end of the inner rod, a pH microelectrode and a reference electrode are embedded in the inner rod, the pH microelectrode and the reference electrode pass through the piston and the front end surface is flush with the outer side surface of the metal sample; a differential head coaxial with the inner rod is arranged at the rear end of the inner rod, when the differential head is rotated, the measuring rod of the differential head drives the inner rod to move axially, and the distance between the end of the pH microelectrode and the end of the reference electrode and the outer side surface of the metal sample is adjusted at the micrometer level;

[0007] The experimental device also includes a test water tank, an electrochemical workstation and a platinum electrode. The base is sealed and fixed on the side wall of the test water tank. The test water tank contains a simulated corrosion solution that submerges the metal sample and the platinum electrode. The WE interface of the electrochemical workstation is connected to the pH microelectrode circuit, the CE interface of the electrochemical workstation is connected to the platinum electrode circuit, and the RE interface of the electrochemical workstation is connected to the reference electrode circuit.

[0008] Specifically, the sleeve has a cylindrical body and a connecting flange of an integral structure, the cylindrical body of the sleeve is inserted into the central hole of the base, the inner rod is slidably matched with the inner wall of the cylindrical body, and the connecting flange is fixed to the rear end surface of the base.

[0009] Furthermore, a polytetrafluoroethylene ring is arranged at a distance behind the connecting flange, the center of the polytetrafluoroethylene ring is fixed to the mounting sleeve of the micrometer head by a nut, and the upper and lower ends of the polytetrafluoroethylene ring are fixed to the connecting flange by a double-headed screw.

[0010] In order to accurately place the pH microelectrode and the reference electrode, the inner rod includes a piston support at the front end, a tail handle at the rear end and a rod core in the middle. The piston is fixed on the piston support. A groove for placing the pH microelectrode and the reference electrode is opened at the front end of the rod core. The pH microelectrode and the reference electrode pass through the piston support and the piston and then extend from the front end of the sleeve into the simulated corrosion solution.

[0011] Furthermore, in order to facilitate the connection and disassembly of the micrometer head and the inner rod, a fixing ring is installed at the front end of the measuring rod of the micrometer head, and the fixing ring is fixedly connected to the tail handle of the inner rod by bolts.

[0012] The beneficial effects of the present invention are as follows: the present invention is easy to operate, and the distance between the pH microelectrode, the reference electrode and the metal sample can be regulated at the micron level by adjusting the differential head; at the same time, in the process of simulating metal corrosion, the experimental device is fixed to the side wall of the test water tank, thereby realizing the measurement of the pH of the micro-area near the metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0014] Figure 1 It is a structural schematic diagram of the present invention.

[0015] Figure 2 It is a schematic diagram of the present invention applied to simulated metal corrosion and protection experiments.

[0016] In the figure: 1. base, 2. metal sample, 3. pH microelectrode, 4. reference electrode, 5. waterproof gasket, 6. O-ring, 7. sleeve, 8. double-head screw, 9. fixing ring, 10. differential head, 11. polytetrafluoroethylene ring, 12. inner rod, 13. piston, 14. electrochemical workstation, 15. platinum electrode, 16. test water tank, 17. acrylic plate, 18. computer. DETAILED DESCRIPTION

[0017] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0018] like Figure 1 , Figure 2 The experimental device shown is for measuring the pH value near the surface of metal corrosion and adjusting the distance between pH electrodes, and comprises a test water tank 16 , an electrochemical workstation 14 and a base 1 , wherein the base 1 is sealed and fixed to the side wall of the test water tank 16 .

[0019] The base 1 has a center hole with a diameter of 1 cm at its center, the front end face of the base 1 is fixedly connected to a metal sample 2 by a hexagonal bolt, and an O-ring 6 is embedded between the front end face of the base 1 and the metal sample 2 to achieve a waterproof seal.

[0020] A countersunk hole with a diameter of 5 mm and a depth of 5 mm is opened in the center of the metal sample 2 , and two small holes with a diameter of 2 mm are opened on the inner wall of the countersunk hole until they penetrate to the outer side surface of the metal sample 2 .

[0021] A sleeve 7 is installed in the base 1. Specifically, the sleeve 7 has a cylindrical body and a connecting flange of an integral structure. The cylindrical body of the sleeve 7 is installed in the center hole of the base 1, and the raised portion at the front end of the cylindrical body is inserted into the countersunk hole of the metal sample 2. A waterproof gasket 5 is provided between the outer step surface of the raised portion at the front end of the cylindrical body and the metal sample 2. An inner rod 12 is slidably provided in the cylindrical body of the sleeve 7, and the connecting flange of the sleeve 7 is fixed to the rear end surface of the base 1.

[0022] The inner rod 12 includes a piston support at the front end, a tail handle at the rear end and a rod core in the middle. A piston 13 is fixed on the piston support. A groove is provided at the front end of the rod core. A pH microelectrode 3 and a reference electrode 4 are placed in the groove. The pH microelectrode 3 and the reference electrode 4 extend out of the front end of the sleeve 7 after passing through the piston support and the piston 13, and pass through the two small holes of the metal sample 2 to be flush with the outer side surface of the metal sample 2.

[0023] A polytetrafluoroethylene ring 11 is provided at a distance behind the connecting flange of the sleeve 7, and the upper and lower ends of the polytetrafluoroethylene ring 11 are fixedly connected to the connecting flange of the sleeve 7 by a double-headed screw 8; a differential head 10 coaxial with the inner rod 12 is provided at the rear end of the inner rod 12, and the differential head 10 is a flat-head nut structure, and the mounting sleeve of the differential head 10 is fixed to the center of the polytetrafluoroethylene ring 11 by a nut, and a fixing ring 9 is installed at the front end of the measuring rod of the differential head 10, and the fixing ring 9 is fixed to the tail handle of the inner rod 12 by bolts.

[0024] When the differential head 10 is rotated, the differential head 10 is fixed, and the measuring rod of the differential head 10 moves along the axis, driving the inner rod 12 to move axially, so that the pH microelectrode 3 and the reference electrode 4 placed in the groove of the inner rod 12 are synchronously moved axially into the simulated corrosion solution, thereby achieving micron-level adjustment of the distance between the end of the pH microelectrode 3 and the end of the reference electrode 4 and the outer side of the metal sample 2.

[0025] A platinum electrode 15 is provided in the test water tank 16, and a simulated corrosion solution for submerging the metal sample 2 and the platinum electrode 15 is stored in the test water tank 16. The WE interface of the electrochemical workstation 14 is connected to the pH microelectrode 3 line, the CE interface of the electrochemical workstation 14 is connected to the platinum electrode 15 line, and the RE interface of the electrochemical workstation 14 is connected to the reference electrode 4 line.

[0026] The manufacturing method of the pH microelectrode 3 comprises the following steps: a. polishing the platinum wire and the copper wire and then cleaning them with ultrasonic wave; b. spot welding the platinum wire and the copper wire and then placing them in a capillary glass tube; c. encapsulating the platinum wire with resin; d. taking 0.075g of iridium tetrachloride hydrate and adding it into 50mL of deionized water and stirring, stirring for 30min, adding 0.5mL of 30% hydrogen peroxide and stirring, stirring for 10min, adding 0.35g of oxalic acid and continuing to stir, stirring for 30min, slowly adjusting the pH value of the solution to 10.5 with anhydrous potassium carbonate (AR), placing the prepared solution in a constant temperature water bath at 50°C for oxidation for 6 days; e. using an electrochemical workstation 14, using cyclic voltammetry to deposit an electrode, placing the deposited electrode in deionized water and heating it to 100°C in a water bath for 2h to obtain a pH microelectrode 3 made of iridium / iridium oxide.

[0027] In the present invention, in order to ensure the anti-corrosion and insulation effects of the experimental device, the base 1, sleeve 7, and inner rod 12 are all made of polytetrafluoroethylene.

[0028] When the present invention is applied to simulated metal corrosion and protection experiments, the base 1 is fixed to the side wall of the test tank 16 by bolts through the acrylic plate 17, and the simulated corrosion solution is poured into the test tank 16 until the metal sample 2, the pH microelectrode 3, the reference electrode 4 and the platinum electrode 15 are submerged; when the differential head 10 is adjusted, the measuring rod of the differential head 10 will move forward and backward along the axial direction, thereby driving the inner rod 12 to move forward and backward along the axial direction, and further driving the pH microelectrode 3 and the reference electrode 4 in the groove of the inner rod 12 to move forward and backward along the axial direction, thereby accurately controlling the pH microelectrode 3. The distance between the end of the reference electrode 4 and the outer side of the metal sample 2, and the adjustment of the distance can reach the micron level; during the experiment, the electrochemical workstation 14 is connected to the computer 18, the WE interface of the electrochemical workstation 14 is connected to the pH microelectrode 3, the RE interface of the electrochemical workstation 14 is connected to the reference electrode 4, and the CE interface of the electrochemical workstation 14 is connected to the platinum electrode 15. The potential change near the surface of the metal sample 2 during the corrosion process is monitored in real time by the computer 18, so as to obtain the pH change near the surface of the metal sample 2.

[0029] The various components of the present invention are assembled by bolts, which is convenient for installation during use and disassembly at the end of use; a pH microelectrode 3 made of iridium / iridium oxide and a reference electrode 4 made of silver / silver chloride are used, and a differential head 10 and an inner rod 12 are combined to realize the micrometer-level distance control function between the metal sample 2 and the pH microelectrode 3 and the reference electrode 4, thereby completing the measurement of the pH of the metal near-surface micro-area.

[0030] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An experimental device for measuring the pH near the surface of metal corrosion and adjusting the distance between pH electrodes, comprising a base with a central hole, characterized in that: The front end surface of the base is fixedly connected to a metal sample, a sleeve is installed in the base, the front end of the sleeve is inserted into the metal sample, the rear end of the sleeve is fixedly connected to the base, an inner rod is slidably arranged in the sleeve, a piston is fixed to the front end of the inner rod, and a pH microelectrode and a reference electrode are embedded in the inner rod; The inner rod comprises a piston support at the front end, a tail handle at the rear end and a rod core in the middle. The piston is fixed on the piston support. A groove for placing a pH microelectrode and a reference electrode is provided at the front end of the rod core. The pH microelectrode and the reference electrode extend from the front end of the sleeve into the simulated corrosion solution after passing through the piston support and the piston. The pH microelectrode and the reference electrode pass through the piston and the front end faces are flush with the outer side of the metal sample; the rear end of the inner rod is provided with a differential head coaxial with the inner rod, and the front end of the measuring rod of the differential head is installed with a fixing ring, and the fixing ring is fixedly connected to the tail handle of the inner rod by bolts; When the differential head is rotated, the measuring rod of the differential head drives the inner rod to move axially, and the distance between the end of the pH microelectrode and the end of the reference electrode and the outer side of the metal sample is adjusted at the micrometer level; The experimental device also includes a test water tank, an electrochemical workstation and a platinum electrode. The base is sealed and fixed on the side wall of the test water tank. The test water tank contains a simulated corrosion solution that submerges the metal sample and the platinum electrode. The WE interface of the electrochemical workstation is connected to the pH microelectrode circuit, the CE interface of the electrochemical workstation is connected to the platinum electrode circuit, and the RE interface of the electrochemical workstation is connected to the reference electrode circuit.

2. The experimental device for measuring the near-surface pH of metal corrosion and adjusting the distance between pH electrodes as claimed in claim 1, characterized in that: The sleeve has a cylindrical body and a connecting flange of an integral structure. The cylindrical body of the sleeve is inserted into the central hole of the base, the inner rod is slidably matched with the inner wall of the cylindrical body, and the connecting flange is fixed to the rear end surface of the base.

3. The experimental device for measuring the near-surface pH of metal corrosion and adjusting the distance between pH electrodes as claimed in claim 2, characterized in that: A polytetrafluoroethylene ring is arranged at a distance behind the connecting flange. The center of the polytetrafluoroethylene ring is fixed to the mounting sleeve of the micrometer head through a nut. The upper and lower ends of the polytetrafluoroethylene ring are fixed to the connecting flange through a double-headed screw.

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