External field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior and corrosion rate quantitative characterization method

Abstract

The invention discloses an external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behaviors and a corrosion rate quantitative characterization method. The invention aims to solve the problems that real-time monitoring of components and quantitative measurement of products in a stainless steel surface electrochemical passivation process are difficult to realize by an existing external field detection method and the like. The device comprises an external field stainless steel substrate, a passivation solution container, a cover glass, an electrochemical workstation, a portable Raman spectrometer, a Raman laser emission source, a peristaltic pump passivation solution inlet pipe, a peristaltic pump passivation solution outlet pipe and the like. According to the method, in-situ, real-time and quantitative detection of the stainless steel surface of the external field equipment can be efficiently and accurately realized, and in-situ tracing analysis of the stainless steel passivation behavior at low cost can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of metal analysis and detection, and specifically relates to an external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior and a corrosion rate quantitative characterization method. Background Art

[0002] Stainless steel is widely used in the fields of ocean, petroleum, petrochemical, aerospace, etc., such as marine pipeline systems and aircraft engine parts, due to its good strength, toughness, plasticity and excellent corrosion resistance. Among them, the key to the excellent corrosion resistance of field equipment is that stainless steel can form an ultra-thin passivation film on the surface. However, the traditional methods of studying the passivation behavior of stainless steel have certain limitations, which seriously restrict the development of real-time monitoring technology of equipment field. On the one hand, conventional electrochemical testing methods, such as polarization curve measurement and electrochemical impedance spectroscopy, can provide some electrode reaction kinetics and surface passivation film impedance information, but it is difficult to directly obtain the structure and composition of the passivation film at the molecular level. On the other hand, offline analysis methods require the sample to be removed from the reaction environment, such as surface analysis methods such as X-ray photoelectron spectroscopy and Auger electron spectroscopy. The offline environment will destroy the real information of the sample in the original reaction state, resulting in the measured results being unable to accurately reflect the in-situ dynamic process.

[0003] In-situ electrochemical Raman spectroscopy provides a solution to the above problems. This technology can detect the molecular rotation and vibration information of the electrode surface material in real time during the operation of the electrochemical system, explore the changes in molecular structure with the help of the displacement and intensity changes of the Raman peak, and then reveal the microscopic behaviors of the formation, growth, dissolution and reconstruction of the passivation film during the passivation process. However, most of the existing in-situ electrochemical Raman devices are limited to relatively closed and idealized environments built inside the laboratory.

[0004] In actual industrial field application scenarios, there are many complex and harsh conditions. Traditional laboratory-type in-situ electrochemical Raman devices are difficult to move directly to the field environment. This is because the precision components of the instrument itself are easily damaged, and various interference signals in the field environment can easily mask weak Raman signals. Therefore, it is urgent to develop an electrochemical Raman field detection device and method that can adapt to complex field conditions and can accurately and reliably trace the passivation behavior of stainless steel in situ. This will not only help fill the current situation of less research on field equipment stainless steel in-situ detection technology, promote the transformation of basic research to practical field applications, but also provide strong technical support for the safety and long-term service of stainless steel in various industrial fields.

[0005] This patent develops an electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior in the field detection device and corrosion rate quantitative characterization method, which provides in-situ electrochemical information and chemical information for the field equipment stainless steel passivation research. By designing a new electrochemical workstation test and Raman spectroscopy test combined system, it can realize the in-situ recording of surface electrochemical / chemical information and accurate real-time tracking of composition changes during the passivation process of stainless steel in field equipment at low cost. Summary of the invention

[0006] The purpose of the present invention is to solve the problems that the existing field detection methods are difficult to achieve real-time monitoring of components and quantitative measurement of products during the electrochemical passivation process of the stainless steel surface, and to provide an field detection device for electrochemical Raman in-situ tracing analysis of the passivation behavior of stainless steel and a method for quantitative characterization of corrosion rate.

[0007] The in-situ electrochemical Raman system of the present invention comprises an external stainless steel substrate (1), a passivation liquid container (2), a cover glass (3), an electrochemical workstation (4), a portable Raman spectrometer (5), a Raman laser emission source (6), a peristaltic pump passivation liquid inlet pipe (7), a peristaltic pump passivation liquid outlet pipe (8) and other components.

[0008] The present invention performs simple pretreatment such as grinding and polishing on the stainless steel equipment or parts for external field work, and uses the stainless steel substrate (1) for external field work, and places the passivation liquid container (2) with platinum wire / silver wire in the middle close to the stainless steel substrate (1) for external field work. The passivation liquid container (2) has a circular ring structure in the top view, and the passivation solution is dripped into it, and then flattened with a cover glass (3) to prevent air from entering, solution contamination, and limit the Raman light scattering effect.

[0009] The electrochemical workstation (4) of the present invention adopts a two-electrode test system, a high-purity platinum wire / silver wire connects the counter electrode and the reference electrode, and the external stainless steel substrate (1) serves as the working electrode. The optical lens of the portable Raman spectrometer (5) is moved to the geometric center position of the passivation liquid container (2) and focused.

[0010] In the present invention, while the electrochemical workstation (3) is turned on to perform electrochemical potential scanning and other tests, the Raman spectrum laser emission source (6) performs tests at fixed intervals, thereby achieving in-situ tracking and recording of the composition changes of stainless steel during the passivation process.

[0011] The invention provides an inlet pipe (7) and an outlet pipe (8) in a passivation liquid container (2), and adopts a peristaltic pump as a liquid exchange power source. The peristaltic pump flows the passivation liquid from the inlet pipe (7) into the passivation liquid container and flows out of the passivation liquid container from the outlet pipe (8), thereby realizing real-time exchange of the solution.

[0012] The Raman spectrometer (5) in the present invention adopts a portable Raman spectrometer, and uses a previously established correlation model between the Raman characteristic peak intensity and the concentration of the standard substance to be tested. The correlation model is a linear regularity model between the Raman characteristic peak intensities corresponding to the standard solutions with different concentration gradients. The Raman intensity measured in the external field is compared with the correlation model, and then the concentration of the substance ions in the passivation solution at this stage is inferred, and finally the passivation and intergranular corrosion of the key positions of stainless steel of the external field equipment (such as welds) are evaluated.

[0013] The invention discloses an external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior and a corrosion rate quantitative characterization method, which can record in real time in-situ the electrochemical information and Raman information of the microscopic interface during the passivation process of the stainless steel surface, and can be applied to external field in-situ, real-time and quantitative passivation evaluation of stainless steel.

[0014] The present invention has the following beneficial effects:

[0015] (1) The present invention can efficiently and accurately realize in-situ, real-time, and quantitative detection of the stainless steel surface of field equipment.

[0016] (2) The present invention is easy to operate. The stainless steel used in the field only needs to be pre-treated by grinding and polishing. The size of the passivation solution container can be designed according to the requirements by means of 3D printing, etc., so as to realize in-situ tracing analysis of the passivation behavior of stainless steel at a low cost.

[0017] (3) The present invention converts the surface information of stainless steel into the composition information of the solution, which can realize the in-situ real-time electrochemical-Raman information tracking of the sample surface in a liquid environment, and is more suitable for the actual corrosion environment.

[0018] (4) The corrosion rate quantitative characterization method provided by the present invention is helpful for evaluating the corrosion behavior of stainless steel in the field, which is of great significance for the safety protection of field equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A three-dimensional diagram of the structure of the external field detection device for in-situ tracing analysis of the passivation behavior of stainless steel by the electrochemical Raman device of the present invention

[0020] Figure 2 This is a structural plan view of the field detection device for in-situ tracing analysis of stainless steel passivation behavior by the electrochemical Raman device of the present invention (field stainless steel substrate 1, passivation liquid container 2, cover glass 3, electrochemical workstation 4, portable Raman spectrometer 5, Raman laser emission source 6, peristaltic pump passivation liquid inlet pipe 7, peristaltic pump passivation liquid outlet pipe 8)

[0021] Figure 3 The electrochemical passivation curve of 304 stainless steel in 0.5 mol / L H2SO4+0.01 mol / L bipy solution in the embodiment of the present invention is shown in FIG.

[0022] Figure 4 The Raman spectrum test of 304 stainless steel in the electrochemical passivation process of 0.5mol / L H2SO4+0.01mol / L bipy solution over time in the embodiment of the present invention

[0023] Figure 5 This is a flow chart of the application of the Raman quantitative detection model of divalent iron ions in the corrosion assessment of stainless steel equipment in the implementation example of the present invention DETAILED DESCRIPTION

[0024] In view of the existing problems, the present invention provides an external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior and a corrosion rate quantitative characterization method, which is further described below in conjunction with examples and drawings. The examples are provided to more clearly explain the embodiments of the present invention, but are not intended to limit the present invention.

[0025] Specific implementation method 1: This implementation method is an in-situ electrochemical Raman tracing analysis device and test method for the passivation behavior of stainless steel equipped in the field, which is implemented according to the following steps:

[0026] The stainless steel equipment or parts for field work are polished to form the stainless steel substrate (1) for field work. A passivation liquid container (2) with a platinum wire / silver wire in the middle is placed tightly on the stainless steel substrate (1) for field work, and the passivation solution is dripped into the passivation liquid container (2), and then flattened with a cover glass (3). The peristaltic pump is turned on, and the passivation solution flows into the passivation liquid container from the inlet pipe (7) through the peristaltic pump, and flows out of the passivation liquid container from the outlet pipe (8).

[0027] The electrochemical workstation (4) adopts a two-electrode test system, with high-purity platinum wire / silver wire connecting the counter electrode and the reference electrode, and the external stainless steel substrate as the working electrode. The optical lens of the portable Raman spectrometer (5) is moved to the geometric center of the rubber ring and focused. After the open circuit potential of the electrochemical workstation (3) is stabilized, the electrochemical potential scanning and the Raman spectrum laser emission source (6) are turned on at the same time to collect information. The Raman spectrum laser emission source (6) uses a static / dynamic scanning mode at fixed intervals to test the passivation liquid composition information, so as to realize in-situ tracking and recording of the composition changes of stainless steel during the passivation process.

[0028] Prepare standard mixed solutions of different concentrations, establish a correlation model between the Raman characteristic peak intensity and concentration of the standard substance, compare the external field stainless steel surface Raman intensity measured by the Raman spectrum laser emission source (6) with the standard substance intensity concentration model, and infer the concentration of the substance in the passivation solution at this stage.

[0029] The external field detection device and method for testing the electrochemical Raman in-situ tracing analysis of the passivation behavior of stainless steel in this embodiment are implemented by the following steps:

[0030] 1. According to Figure 1 and Figure 2 Build an in-situ electrochemical Raman integrated device. Connect the polished surface of 304 stainless steel sample to the working electrode of the electrochemical workstation, and connect the platinum wire through the rubber ring passivation liquid container to the reference electrode and counter electrode of the electrochemical workstation. Use a pipette to drop a 0.5 mol / L H2SO4+0.01 mol / L bipyridine (bipy) mixed solution into the rubber ring as the passivation solution, and seal it with a cover glass.

[0031] 2. Turn on the electrochemical workstation and monitor the open circuit potential for at least 30 minutes to ensure the stability of the 304 stainless steel / solution interface. Then measure the potentiodynamic polarization curve at a scan rate of 2mV / s. While performing the potentiodynamic polarization test, perform a Raman spectrum test every 2 to 3 minutes. Figure 4 This is the Raman spectrum test result of the electrochemical passivation process changing with time. The generation and disappearance of Raman characteristic peaks indicate that the passivation process is accompanied by the generation and disappearance of substances.

[0032] three, Figure 5 The application of the present invention in in-situ quantitative detection of divalent iron ions on the surface of stainless steel in the external field is demonstrated. II (bipy)3] 2+ The relationship between the Raman intensity and concentration of the standard is standardized and measured, and it can be known that [Fe II (bipy)3] 2+ The Raman spectrum intensity and concentration show two linear functions, where the fitting curves of regions I and II are shown in formula (1-2). The stainless steel sample of the equipment was analyzed by in-situ electrochemical-Raman experiment, and the 1492 cm -1 The Raman intensity at [Fe II (bipy)3] 2+ The Raman quantitative detection model of the standard solution is compared. If the intensity is in region I or region II, the I1 or I2 fitting equation is used respectively. If the intensity is at the junction of region I and region II, it is more appropriate to choose the I2 fitting equation. Finally, the intensity is converted into the required divalent iron ion concentration. It has been verified that the results inferred by the model are compared with the results of inductively coupled plasma (ICP) measurement, and the error can be controlled within 5%.

[0033] I1 = 2.84 × 10 5 c1 - 8.02 (1)

[0034] I2 = 9.83 × 10 5 c2 - 1440.9 (2)

[0035] Where I represents [FeII (bipy)3] 2+ Raman spectrum intensity of standard solution, au; c represents [Fe II (bipy)3] 2+ The ferrous iron concentration of the standard solution, mol / L.

Claims

1. An external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior, characterized in that The in-situ electrochemical Raman system includes an external stainless steel substrate, a passivation liquid container, a cover glass, an electrochemical workstation, a portable Raman spectrometer, a Raman laser emission source, a peristaltic pump passivation liquid inlet pipe, a peristaltic pump passivation liquid outlet pipe and other components.

2. The external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior according to claim 1 is characterized in that The passivation liquid container can be designed in shape according to demand through 3D printing and other technologies, or existing products such as washers can be used.

3. The external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior according to claim 1 is characterized in that The height of the passivation liquid container is 0.1-5 mm, preferably 0.5 mm.

4. An external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior, characterized in that The passivation solution is common stainless steel passivation solution such as sulfuric acid, nitric acid, sodium dichromate or potassium dichromate, hydrogen peroxide, benzotriazole, dipyridine, etc.

5. An external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior, characterized in that The passivation liquid container has a metal electrode in the middle which is in direct contact with the passivation liquid.

6. The external field detection device for electrochemical Raman in-situ tracing analysis of stainless steel passivation behavior according to claim 5 is characterized in that The metal electrode penetrating the passivation liquid container may be a platinum wire / silver wire electrode, or may be a saturated calomel electrode, a standard hydrogen electrode, a carbon rod or other electrode materials.

7. Electrochemical Raman in-situ tracer analysis of the corrosion rate of stainless steel passivation behavior quantitative characterization method, characterized by The correlation model is a linear regularity model for testing the Raman characteristic peak intensities corresponding to standard solutions with different concentration gradients, and the concentration of the standard solution does not exceed 0.1M.

8. The method for quantitatively characterizing the corrosion rate of stainless steel passivation behavior by electrochemical Raman in-situ tracing analysis according to claim 7, characterized in that The established model can be targeted at the ions or molecules involved in the passivation process of iron-containing substances, chromium-containing substances, nickel-containing substances, etc.

Images