Electrochemical testing device and method suitable for corrosion under high-temperature scale

Abstract

The invention relates to an electrochemical testing device and method suitable for high-temperature under-scale corrosion, the bottom of a reaction tank is connected with a metal sample through a variable-diameter sealing assembly in an inserted manner, the metal sample is connected to an electrochemical workstation through a conductive copper adhesive tape, and a Pt counter electrode and an Hg / HgO reference electrode are mounted at the top of the reaction tank. The Pt counter electrode and the Hg / HgO reference electrode are connected to the electrochemical workstation, the Pt counter electrode, the Hg / HgO reference electrode and the metal sample form a three-electrode system, and the heating assembly is arranged on the side wall of the reaction tank. The three-electrode system is reasonable in arrangement, disturbance to a scale layer is avoided, the heating assembly can stably heat a test solution to 80 DEG C or above, and the under-scale corrosion process in a real industrial service environment is simulated; the device can realize an electrochemical test under the coverage of sediments, and provides a rapid, high-precision and repeatable experimental platform for researching a local corrosion mechanism under the influence of a deposition layer.

Description

Technical Field

[0001] The invention belongs to the technical field of corrosion simulation experiments and electrochemical testing, and particularly relates to an electrochemical testing device and method suitable for high-temperature under-scale corrosion. Background Art

[0002] Under-Deposit Corrosion (UDC) is a form of localized corrosion common in the chemical, petrochemical, power, and marine engineering industries. It typically occurs where metal surfaces are covered with sediment, scale, or silt. The presence of these deposits creates a localized corrosive microenvironment, which, along with oxygen concentration differences, electrolyte enrichment, and pH fluctuations, can lead to accelerated corrosion and even pitting or crevice corrosion. This type of corrosion is particularly common in equipment such as heat exchangers, pipelines, and reactors, and in severe cases can cause perforation and failure.

[0003] Existing electrochemical testing methods are mostly based on clean electrode surfaces, performing electrochemical impedance spectroscopy (EIS) and polarization curves in standard electrolytes, which struggle to accurately reproduce the local environment beneath the scale. Some studies have attempted to cover the sample surface with deposits for in-situ testing, but these methods suffer from unstable deposition, poor sealing, and interference from electrode structure with test accuracy. Furthermore, high temperatures (e.g., 60-80°C) are common in actual service environments, and existing testing equipment still has significant limitations in temperature control, test stability, and deposit layer retention.

[0004] Therefore, there is an urgent need to develop a device and method with controllable temperature function, stable deposition coverage, and suitable for in-situ electrochemical testing, so as to systematically study the under-deposit corrosion behavior under high-temperature environment and improve the authenticity and reliability of simulation tests. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an electrochemical testing device and method suitable for high-temperature under-scale corrosion.

[0006] The present invention solves the technical problem by the following technical solutions: An electrochemical testing device suitable for high-temperature corrosion under scale, comprising a reaction cell, a reducing seal assembly, a heating assembly, a Pt counter electrode, and an Hg / HgO reference electrode. The bottom of the reaction cell is plugged and connected to a metal sample via the reducing seal assembly, and the metal sample is connected to an electrochemical workstation via a conductive copper tape. The top of the reaction cell is provided with counter electrode and reference electrode slots, in which the Pt counter electrode and Hg / HgO reference electrode are installed, and the Pt counter electrode and Hg / HgO reference electrode are connected to the electrochemical workstation. The Pt counter electrode, Hg / HgO reference electrode, and metal sample form a three-electrode system. The heating assembly is provided on the side wall of the reaction cell, and the heating assembly maintains the solution temperature of the reaction cell at 80°C±1°C.

[0007] Moreover, the variable diameter sealing assembly includes a small sealing ring, a variable diameter plug and a large sealing ring which are arranged in sequence, and can be adapted to metal samples of different sizes and thicknesses.

[0008] Moreover, the heating component is a ring-shaped electric heating plate regulated constant temperature heating belt, and the ring-shaped electric heating plate regulated constant temperature heating belt is equipped with a thermistor and a temperature control instrument to form a closed-loop temperature control system.

[0009] Moreover, the reaction tank is made of corrosion-resistant glass.

[0010] Moreover, the metal sample is made of stainless steel 316L alloy material.

[0011] Moreover, a sealing cover is provided between the reaction cell and the Pt counter electrode and the Hg / HgO reference electrode.

[0012] An electrochemical testing method for high-temperature corrosion under scale, using the above-mentioned testing device, the steps of the testing method are as follows: S1. Grind and polish the metal sample with #600, #1200, and #2000 grit sandpaper, clean it ultrasonically, and then install it in the bottom sealing port of the reaction tank; S2. Add CaCl2 aqueous solution and Na2CO3 aqueous solution (or MgCl2 and Na2CO3) to the reaction tank in sequence at room temperature to induce the formation of CaCO3 or MgCO3 deposition scale on the surface of the metal sample, forming a white deposit; S3. Start the heating component to heat the solution in the reaction tank to 80°C and maintain it stably at ±1°C to simulate the under-deposit corrosion conditions in a high-temperature service environment; S4. Insert a Pt counter electrode and a Hg / HgO reference electrode and connect them to an electrochemical workstation to perform open circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests to record the corrosion behavior of the metal sample under the deposit coverage. S5. During the test, the heating assembly and electrode position are adjusted to ensure that the Pt electrode and the metal sample are in the corrosion active area below the deposit to obtain the true electrochemical response curve of under-deposit corrosion.

[0013] The advantages and beneficial effects of the present invention are: 1. True reduction of under-scale corrosion environment: The device induces in-situ deposition of simulated scale layers such as CaCO3 or MgCO3 on the sample surface, which can stably cover the metal surface and truly simulate the under-scale corrosion phenomenon caused by sediment accumulation in industry, solving the problem of sediment shielding effect that is difficult to reproduce in traditional tests.

[0014] 2. Controllable high-temperature conditions to improve simulation accuracy: A heating component is used to precisely control the solution temperature in the reaction tank within the range of 80°C ± 1°C, simulating the high-temperature corrosion environment of equipment such as heat exchangers and heat exchange systems during actual operation, thereby improving the engineering applicability of the test results.

[0015] 3. Reasonable structural design and strong test stability: The three-electrode system is scientifically arranged, and the sealing component adopts a variable-diameter flexible double-gasket structure to ensure stable conductivity and liquid-tight sealing of the sample. It is suitable for samples of various specifications and improves the versatility and adaptability of the device.

[0016] 4. Suitable for long-term corrosion behavior research and material evaluation: The deposition time and corrosion cycle can be adjusted, which is suitable for studying the evolution of corrosion behavior of scale layers at different stages, facilitating the systematic evaluation of the service life and protective performance of materials in a deposition coverage environment, and providing data support for material design and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 This is a top view of the metal sample after a scale layer is deposited on the surface of the metal sample of the present invention; Figure 3 This is a temperature stability curve diagram of the reaction pool of the present invention under a constant temperature heating state; Figure 4 The potentiodynamic polarization curves of the metal samples at different deposition times of the present invention are shown; Figure 5 This is the Nyquist plot of the electrochemical impedance spectroscopy (EIS) of the metal sample of the present invention.

[0018] Description of Reference Numerals 1-reaction cell, 2-reducing sealing assembly, 3-heating assembly, 4-Pt counter electrode, 5-Hg / HgO reference electrode, 6-metal sample, 7-conductive copper tape, 8-small sealing ring, 9-reducing plug, 10-large sealing ring, 11-sealing cover. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0020] like Figure 1 As shown, an electrochemical testing device suitable for high-temperature corrosion under scale includes a reaction cell 1, a reducing seal assembly 2, a heating assembly 3, a Pt counter electrode 4 and a Hg / HgO reference electrode 5. The bottom of the reaction cell is connected to a metal sample 6 through the reducing seal assembly, and the metal sample is connected to an electrochemical workstation through a conductive copper tape 7. The top of the reaction cell is provided with a counter electrode and a reference electrode slot, in which the Pt counter electrode and the Hg / HgO reference electrode are installed. The Pt counter electrode and the Hg / HgO reference electrode are connected to the electrochemical workstation. The Pt counter electrode, the Hg / HgO reference electrode and the metal sample form a three-electrode system. The heating assembly is provided on the side wall of the reaction cell, and the heating assembly maintains the solution temperature of the reaction cell at 80°C±1°C.

[0021] Moreover, the variable diameter sealing assembly includes a small sealing ring 8, a variable diameter plug 9 and a large sealing ring 10 which are arranged in sequence, and can be adapted to metal samples of different sizes and thicknesses.

[0022] Moreover, the heating component is a ring-shaped electric heating plate regulating constant temperature heating belt, and the ring-shaped electric heating plate regulating constant temperature heating belt is equipped with a thermistor and a temperature control instrument to form a closed-loop temperature control system, such as Figure 3 As shown, the temperature is stably maintained at 80℃, verifying the reliability of the temperature control system.

[0023] Moreover, the reaction tank is made of corrosion-resistant glass.

[0024] Moreover, the metal sample is made of stainless steel 316L alloy material.

[0025] Furthermore, a sealing cover 11 is provided between the reaction cell and the Pt counter electrode and the Hg / HgO reference electrode.

[0026] An electrochemical testing method for high-temperature corrosion under scale, using the above-mentioned testing device, the steps of the testing method are as follows: S1. Grind and polish the metal sample with #600, #1200, and #2000 grit sandpaper, clean it ultrasonically, and then install it in the bottom sealing port of the reaction tank; S2. Add CaCl2 aqueous solution and Na2CO3 aqueous solution (or MgCl2 and Na2CO3) to the reaction tank in sequence at room temperature to induce the formation of CaCO3 or MgCO3 deposition scale on the surface of the metal sample, forming a white sediment, such as Figure 2As shown, the arrows point to the formed carbonate sediments, showing the scale layer coverage and adhesion morphology; S3. Start the heating component to heat the solution in the reaction tank to 80°C and maintain it stably at ±1°C to simulate the under-deposit corrosion conditions in a high-temperature service environment; S4. Insert a Pt counter electrode and a Hg / HgO reference electrode and connect them to an electrochemical workstation to perform open circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests to record the corrosion behavior of the metal sample under the deposit coverage. S5. During the test, the heating assembly and electrode position are adjusted to ensure that the Pt electrode and the metal sample are in the corrosion active area below the deposit to obtain the true electrochemical response curve of under-deposit corrosion.

[0027] like Figure 4 As shown in the figure, the polarization curves under different scale deposition times show that the corrosion potential has almost no change and the corrosion current has an upward trend.

[0028] like Figure 5 As shown in the figure, the EIS test results show that the capacitive reactance arc of 316L gradually decreases with the extension of the test scale deposition time.

[0029] In summary, this embodiment shows that the testing device provided by the present invention can truly simulate under-scale corrosion behavior in a controllable temperature environment, is suitable for the evaluation of metal materials, has good repeatability, stability and adaptability, and is particularly suitable for studying the influence of sediment coverage on high-temperature corrosion behavior and material screening applications.

[0030] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. An electrochemical testing device suitable for high-temperature under-scale corrosion, characterized by: The invention comprises a reaction cell (1), a reducing seal component (2), a heating component (3), a Pt counter electrode (4) and a Hg / HgO reference electrode (5); the bottom of the reaction cell (1) is connected to a metal sample (6) through the reducing seal component (2); the metal sample (6) is connected to an electrochemical workstation through a conductive copper tape (7); the top of the reaction cell (1) is provided with a counter electrode and a reference electrode slot; the Pt counter electrode (4) and the Hg / HgO reference electrode (5) are installed in the slot; the Pt counter electrode (4) and the Hg / HgO reference electrode (5) are connected to the electrochemical workstation; the Pt counter electrode (4), the Hg / HgO reference electrode (5) and the metal sample (6) form a three-electrode system; the heating component (3) is provided on the side wall of the reaction cell (1); the heating component (3) maintains the solution temperature of the reaction cell (1) at 80°C±1°C.

2. The electrochemical testing device for high-temperature under-scale corrosion according to claim 1, characterized in that: The variable diameter sealing assembly (2) comprises a small sealing ring (8), a variable diameter plug (9) and a large sealing ring (10) which are arranged in sequence, and can be adapted to metal samples of different sizes and thicknesses.

3. The electrochemical testing device for high-temperature under-scale corrosion according to claim 1, characterized in that: The heating component (3) is a ring-shaped electric heating plate regulated constant temperature heating belt, and the ring-shaped electric heating plate regulated constant temperature heating belt is equipped with a thermistor and a temperature control instrument to form a closed-loop temperature control system.

4. The electrochemical testing device for high-temperature under-scale corrosion according to claim 1, characterized in that: The reaction tank (1) is made of corrosion-resistant glass.

5. The electrochemical testing device for high-temperature under-scale corrosion according to claim 1, characterized in that: The metal sample (6) is made of stainless steel 316L alloy material.

6. The electrochemical testing device for high-temperature under-scale corrosion according to claim 1, characterized in that: A sealing cover (11) is provided between the reaction cell (1), the Pt counter electrode (4), and the Hg / HgO reference electrode (5).

7. An electrochemical testing method for high-temperature corrosion under scale, characterized by: Using the testing device according to any one of claims 1 to 6, the steps of the testing method are: S1. Grind and polish the metal sample with #600, #1200, and #2000 grit sandpaper, clean it ultrasonically, and then install it in the bottom sealing port of the reaction tank; S2. Add CaCl2 aqueous solution and Na2CO3 aqueous solution (or MgCl2 and Na2CO3) to the reaction tank in sequence at room temperature to induce the formation of CaCO3 or MgCO3 deposition scale on the surface of the metal sample, forming a white deposit; S3. Start the heating component to heat the solution in the reaction tank to 80°C and maintain it stably at ±1°C to simulate the under-deposit corrosion conditions in a high-temperature service environment; S4. Insert a Pt counter electrode and a Hg / HgO reference electrode and connect them to an electrochemical workstation to perform open circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests to record the corrosion behavior of the metal sample under the deposit coverage. S5. During the test, the heating assembly and electrode position are adjusted to ensure that the Pt electrode and the metal sample are in the corrosion active area below the deposit to obtain the true electrochemical response curve of under-deposit corrosion.

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