A method for evaluating the stabilization state of weathering steel rust layer and its application

Abstract

The invention discloses a method for evaluating the stabilization state of rust layer of weathering steel and an application thereof, and relates to the technical field of corrosion protection and application of weathering steel, in order to solve the problem that the existing evaluation method requires precision instruments; the invention comprises the following steps: after the rust layer of the weathering steel is stabilized, an atmospheric exposure experiment is performed on the weathering steel sample, and the weathering steel sample is weighed once at regular intervals and the weighing result is recorded, during the weighing, the weathering steel sample is ensured to be dry and the surface rust layer is intact, until the weighing results show a continuous downward trend for three or more consecutive times, it is determined that the rust layer of the weathering steel is in a stabilized state, if the surface rust layer of the weathering steel sample is found to be damaged or detached during the weighing, the atmospheric exposure experiment needs to be continued after the weighing record, and the surface rust layer of the weathering steel sample is waited for self-repair, and the stabilization state of the rust layer is determined after the weighing result gradually increases; the method of the invention is simple and easy to implement, only requires a balance for weighing, does not require precision instruments, does not require scanning, XRD and other detection costs, and has less personnel errors.

Description

Technical Field

[0001] The invention relates to the technical field of weathering steel anticorrosion and application, and in particular to a method for evaluating the stabilization state of a weathering steel rust layer and an application thereof. Background Art

[0002] With increasingly stringent environmental protection policies, the use of weathering steel without painting can save subsequent maintenance, and its economy and environmental friendliness throughout the life cycle are becoming more and more prominent. It has been used more and more widely in landscape architecture, railway vehicles, power towers, bridges and other fields. The surface of weathering steel can form a dense protective rust layer under long-term atmospheric exposure, thereby effectively blocking the infiltration and diffusion of corrosive media. However, the stabilization formation cycle of the rust layer on the surface of weathering steel is long. At the same time, during the formation of the stable rust layer, rust liquid will drip, which seriously affects the appearance and pollutes the environment. Therefore, the development of rust layer stabilization treatment agents is of great significance to expand the application scope of unpainted weathering steel and reduce the maintenance cost of the entire life cycle of buildings.

[0003] Many universities and enterprises at home and abroad have conducted research on weathering steel rust layer stabilization treatment liquid, mainly by adding Cr, Cu, Ni aqueous solution and spraying it on the surface of the sample after shot blasting to form a stable rust layer. The United States uses a direct water spray method to stabilize the rust layer. To judge whether the rust layer has reached a stable state, the main methods used are visual evaluation and stable phase detection, and there are fewer evaluation methods. In addition, the visual method has significant subjectivity, and the stable phase detection method requires the use of precision instruments. At the same time, there are still many controversies about the above methods for judging whether the rust layer has reached a stable state.

[0004] CN113466117A discloses a method for evaluating the surface rust layer of weathering steel after rapid rusting. The surface of the weathering steel sample is precisely divided into sections using a standard grid plate, and a microscopic analysis is performed using Raman spectroscopy to confirm the composition of the rust layer and the ratio of each component. The color of the rust layer is semi-quantitatively analyzed using a colorimeter to determine the correspondence between the macroscopic color of the rust layer on the surface of the weathering steel and the microscopic components. The content range of each component in the rust layer is determined by measuring the color difference value of the rust layer. This invention is a combination of visual inspection and phase analysis, but there are certain errors. First, there are subjective human errors in the selection of the location of the rust layer on the weathering steel. Secondly, while being exposed to the atmosphere, dust will be adsorbed onto the surface of the weathering steel, interfering with the results. Raman spectroscopy equipment is a precision equipment, and the measurement area is cm 2 Below this, the corrosion particles in the rust layer may be captured instead of the actual situation of the entire area. The more sophisticated the instrument, the smaller the scanning area, and the greater the error.

[0005] CN102866104A discloses a method for evaluating the protective capacity of weathering steel rust layer based on freeze-thaw treatment. However, the scanning electron microscope is a precision device and the measurement area is um 2Below the grade, there are both loose and dense rust layers on the surface of the sample, and there are subjective human errors in the selection. At the same time, the author believes that the freeze-thaw treatment has less damage to the dense rust layer and more damage to the loose rust layer. However, when the rust layer of weathering steel is in a stable state, the surface is mainly dense rust layer, and the effect of this method will be greatly reduced, and even the opposite result will occur due to system and human errors.

[0006] At present, the evaluation of weathering steel rust layer requires the use of precision testing equipment, and the errors caused by human factors are difficult to avoid, so the credibility of the results is also questionable; therefore, a method for evaluating the stabilization state of weathering steel rust layer and its application are urgently needed to solve this problem. Summary of the invention

[0007] The object of the present invention is to provide a method for evaluating the stabilization state of rust layer of weathering steel and its application, so as to solve the problem that the existing evaluation method requires precision instruments.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for evaluating the stabilization state of the rust layer of weathering steel, comprising: after the rust layer of the weathering steel is stabilized, the weathering steel sample is subjected to an atmospheric exposure experiment, weighed once at regular intervals and the weighing results are recorded, and the weathering steel sample is ensured to be dry and the surface rust layer is intact during weighing, until the weighing results show a continuous downward trend for three or more consecutive times, it is determined that the rust layer of the weathering steel is in a stabilized state.

[0009] Preferably, if the rust layer on the surface of the weathering steel sample is found to be damaged or fallen off during weighing, the atmospheric exposure test needs to be continued after the weighing record to wait for the rust layer on the surface of the weathering steel sample to self-repair. After the weighing result gradually increases, and then the weighing result shows a continuous downward trend for three or more consecutive times, it is determined that the rust layer of the weathering steel is in a stable state.

[0010] Preferably, after recording the weighing results, a corrosion weight gain curve of the weathering steel sample is drawn, and the curve includes at least two consecutive stages, namely, a continuous weight gain stage and a continuous weight loss stage; in the continuous weight gain stage, the corrosion weight gain shows a continuous increasing trend, and in the continuous weight loss stage, the corrosion weight gain shows a continuous decreasing trend; the continuous weight loss stage is a stabilized state, and the continuous weight loss stage part of the curve is fitted with the function y=a+bx, and the confidence level of the fitting is not less than 0.95.

[0011] Preferably, there is a constant or fluctuating weight gain stage between the continuous weight gain stage and the continuous weight loss stage; the continuous weight gain stage consists of a rapid weight gain stage and a slow weight gain stage, the slope of the curve is the largest during the rapid weight gain stage, and the slope of the curve gradually decreases during the slow weight gain stage.

[0012] Preferably, the samples are weighed every three days in the first three weeks after the atmospheric exposure experiment begins, and weighed every 7-10 days starting from the fourth week.

[0013] Preferably, the above-mentioned method ensures that the weathering steel sample is dry. If the weathering steel sample is found to be damp, or there is humid weather during the atmospheric exposure experiment, hot air is used to slowly dry it to ensure that the weathering steel sample is dry.

[0014] Preferably, if there is severe weather during the atmospheric exposure test that may easily cause the rust layer on the surface of the weathering steel sample to be damaged or fall off, the condition of the rust layer on the surface of the weathering steel sample is checked and confirmed.

[0015] Preferably, before the weathering steel is subjected to rust stabilization treatment, a sandblasting or shot blasting process is used to ensure that the surface is rust-free.

[0016] Another technical solution provided by the present invention is: an application of the above-mentioned evaluation method, after determining that the rust layer of the weathering steel is in a stabilized state, the weathering steel product can be shipped.

[0017] Another technical solution provided by the present invention is: an application of the above-mentioned evaluation method, comparing the partial fitting results of the continuous weight loss stage of the curves of different materials, which is used for comparative evaluation of corrosion performance. The larger -b is, the worse the corrosion resistance of the material itself is.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The method for evaluating the stabilization state of the rust layer of weathering steel and its application are based on the research of corrosion weight gain and the nature of corrosion. After a large number of atmospheric exposure experiments, it is determined that the rust layer state and the corrosion weight gain (loss) are well matched, and the rust layers of different weathering steels are consistently linear after being in a stabilized state. The method of the present invention is simple and easy to implement, only requires the use of a balance, no special inspection of chemical composition and corrosion resistance, no large-scale precision instruments, no scanning, XRD and other testing costs, and there is no problem of personnel error except weighing. It is especially suitable for construction parties in remote areas and mountainous areas with tight scientific research funds or such as Sichuan, Xinjiang, Tibet, Qinghai, etc.

[0020] 2. The evaluation method for the stabilization state of the rust layer of weathering steel and its application can save a lot of time and manpower for special measurement and observation when the weight of the sample does not increase or decrease slowly after the rust layer is stabilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a corrosion weight gain curve diagram of Example 1 of the present invention;

[0022] Figure 2 This is a corrosion weight gain rate curve diagram of Example 1 of the present invention;

[0023] Figure 3 is a graph showing the weight loss rate from corrosion of Example 1 of the present invention;

[0024] Figure 4This is a physical picture of the surface of the weathering steel rust layer after stabilization in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] A method for evaluating the stabilization state of rust layer of weathering steel comprises: after the rust layer of weathering steel is stabilized, the weathering steel sample is subjected to an atmospheric exposure test, weighed at regular intervals and the weighing results are recorded, preferably, within the first three weeks after the atmospheric exposure test begins, weighed once every three days, and starting from the fourth week, weighed once every 7-10 days; until the weighing results show a continuous downward trend for three or more consecutive times, it is determined that the rust layer of the weathering steel is in a stabilized state, and the weathering steel sample should be kept dry during weighing. If the weathering steel sample is found to be damp, or there is humid weather during the atmospheric exposure test, it can be slowly dried with hot air to ensure the weathering steel sample is stable. The steel sample is dry; when weighing, the surface rust layer must be intact. A preferred processing method is as follows: if the rust layer on the surface of the weathering steel sample is found to be damaged or falling off during any weighing, the atmospheric exposure test needs to be continued after the weighing record, waiting for the rust layer on the surface of the weathering steel sample to self-repair. After the weighing results gradually increase, and then until three or more consecutive weighing results show a continuous downward trend, it is determined that the rust layer of the weathering steel is in a stable state; especially if there is bad weather during the atmospheric exposure experiment that can easily cause the rust layer on the surface of the weathering steel sample to be damaged or fall off, it is best to focus on checking and confirming the rust layer on the surface of the weathering steel sample before weighing to ensure the reliability of the results.

[0026] In a preferred embodiment, the corrosion weight gain curve of the weathering steel sample is drawn after recording the weighing results. The curve can be drawn using origin or other software, and the curve includes at least two consecutive stages, namely, a continuous weight gain stage and a continuous weight loss stage. In the continuous weight gain stage, the corrosion weight gain shows a continuous increasing trend, and in the continuous weight loss stage, the corrosion weight gain shows a continuous decreasing trend. The continuous weight loss stage is a stabilized state, and the continuous weight loss stage part of the curve is fitted with the function y=a+bx, and the confidence level of the fitting is not less than 0.95. Common software with fitting function function can be used for fitting, such as origin, excel, matlab, python, etc.

[0027] There is generally a stage of constant or fluctuating weight gain between the continuous weight gain stage and the continuous weight loss stage of the above-mentioned corrosion weight gain curve; usually, the continuous weight gain stage consists of a rapid weight gain stage and a slow weight gain stage. During the rapid weight gain stage, the slope of the curve is the largest, and during the slow weight gain stage, the slope of the curve gradually decreases.

[0028] Example:

[0029] This embodiment adopts the method in the above embodiment, and respectively performs atmospheric exposure experiments under the same conditions on three kinds of weathering steels (in embodiments 1, 2, and 3, before the rust layer stabilization treatment, a sandblasting or shot blasting process is used to ensure that the surface of the weathering steel is rust-free) treated with rust layer stabilization in the same way, weathering steel that has not been stabilized (the same steel type as in embodiment 3), and two different carbon steels, for 180 days. The samples are weighed at regular intervals and the recorded weighing results are used to draw corrosion weight gain curves of the samples. The continuous weight loss stage of each curve is fitted with the function y=a+bx, and the ASTM standard of the American Society for Testing and Materials is referred to. The weathering index I of this steel grade is calculated by the modified Legault-Leckie formula in G101-01, I = 26.01 (%Cu) + 3.88 (%Ni) + 1.20 (%Cr) + 1.49 (%Si) + 17.28 (%P) - 7.29 (%Cu) × (%Ni) - 9.10 (%Ni) × (%P) - 33.39 (%Cu) 2 ≥6.0, the fitting results and calculated weathering index I are as follows:

[0030] Steel Type Fitting results Confidence Weight loss slope / -b Weathering Index I Example 1 Stabilized weathering steel 1 y=60.74-0.21x 0.99 0.21 8.96 Example 2 Stabilized weathering steel 2 y=72.24-0.28x 0.99 0.28 7.63 Example 3 Stabilized weathering steel 3 y=84.66-0.31x 0.98 0.31 6.54 Comparative Example 1 Untreated weathering steel 3 y=108.27-0.37x 0.98 0.37 6.54 Comparative Example 2 Carbon Steel 4 y=225.69-0.57x 0.98 0.57 1.35 Comparative Example 3 Carbon Steel 5 y=344.46-0.89x 0.99 0.89 0.48

[0031] The corrosion weight gain curve of Example 1 is as follows Figure 1 As shown in the figure, at the beginning of the third month during the test, when the sample was about to enter the stable state, due to the bad weather of thunderstorms and strong winds, the corrosion layer on the surface of the sample fell off, and the weight dropped sharply. Then, under the effect of the self-repair of the rust layer on the surface of the sample, the weight gradually increased and returned to the state of constant weight gain or the late stage of fluctuation. The surface condition after being in the stable state is shown in the figure. Figure 4 As shown, Figure 2 and Figure 3 The corrosion weight gain rate curve and corrosion weight loss rate curve are respectively. It can be seen that based on the conventionally recognized rust layer stabilized state of weathering steel, the corrosion weight gain curve is highly similar to the widely used corrosion weight loss rate curve, which proves that this method is reliable. At the same time, this method also omits the rust removal step, avoids the adverse effects of under-pickling or over-pickling on the results, and greatly reduces the workload.

[0032] The method of this embodiment is simple and easy to implement. It only requires the use of a balance, without the need for special inspection of chemical composition and corrosion resistance, without the use of large-scale precision instruments, and without the need for scanning, XRD and other testing costs. It is especially suitable for construction parties with tight scientific research funds or in remote areas. After the method of this embodiment determines that the rust layer of weathering steel is in a stabilized state, the weathering steel product can be shipped out of the factory.

[0033] In addition, it is not difficult to see from the above table that after the three weathering steels with different weathering indices in Examples 1-3 are subjected to the same rust layer stabilization treatment, the fitting results in the continuous weight loss stage are also different, and the weight loss slope -b is negatively correlated with the weathering index. Example 3 and Comparative Example 1 use the same weathering steel. It can be seen that the weight loss slope -b of Example 1 after rust layer stabilization treatment is also smaller than that of Comparative Example 1. The comparison of the three comparative examples also conforms to the law that the weight loss slope -b is negatively correlated with the weathering index. It can be seen that the weight loss slope -b can be used to evaluate the corrosion resistance of the material itself.

[0034] Inspired by the contents recorded in the present invention, it is easy to think that the present invention can be used not only for weathering steel, but also for other materials with similar corrosion principles. Similarly, the adaptability of materials in different environments can also be evaluated and compared by this method. For example, multiple samples of the same material are placed in Xinjiang and Sichuan for atmospheric exposure experiments. The smaller the weight loss slope -b, the better the environmental adaptability.

[0035] In addition, this embodiment is a research exploration, so it takes a long time to carry out. Generally, if there is no shedding of the corrosion layer, it takes about 3-4 months to obtain weighing results that continue to decrease for more than three times.

[0036] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0037] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for evaluating the stabilization state of weathering steel rust layer, It is characterized in that include: After the rust layer of the weathering steel is stabilized, the weathering steel sample is subjected to an atmospheric exposure test. The sample is weighed and the weighing results are recorded at regular intervals. During the weighing, the weathering steel sample is ensured to be dry and the surface rust layer is intact. When the weighing results show a continuous downward trend for three or more consecutive times, the rust layer of the weathering steel is determined to be in a stabilized state. If the rust layer on the surface of the weathering steel sample is found to be damaged or falling off during weighing, the atmospheric exposure test needs to be continued after the weighing record to wait for the rust layer on the surface of the weathering steel sample to self-repair. After the weighing result gradually increases, and then the weighing result shows a continuous downward trend for three or more consecutive times, it is determined that the rust layer of the weathering steel is in a stable state; After recording the weighing results, a corrosion weight gain curve of the weathering steel sample is drawn. The curve includes at least two consecutive stages: a continuous weight gain stage and a continuous weight loss stage. The corrosion weight gain shows a continuous increasing trend in the continuous weight gain stage, and the corrosion weight gain shows a continuous decreasing trend in the continuous weight loss stage. The continuous weightlessness stage is the stabilization state. The continuous weightlessness stage part of the curve is fitted with the function y=a+bx, and the confidence level of the fitting is not less than 0.95; In the first three weeks after the atmospheric exposure experiment began, the test specimens were weighed every three days, and starting from the fourth week, the test specimens were weighed every 7-10 days.

2. A method for evaluating the stabilization state of weathering steel rust layer according to claim 1, Features: There is a constant or fluctuating weight gain stage between the continuous weight gain stage and the continuous weight loss stage; the continuous weight gain stage consists of a rapid weight gain stage and a slow weight gain stage. During the rapid weight gain stage, the slope of the curve is the largest, and during the slow weight gain stage, the slope of the curve gradually decreases.

3. A method for evaluating the stabilization state of weathering steel rust layer according to claim 1 or 2, Features: The weathering steel sample is ensured to be dry. If the weathering steel sample is found to be damp, or there is humid weather during the atmospheric exposure experiment, it is slowly blown dry with hot air to ensure that the weathering steel sample is dry.

4. A method for evaluating the stabilization state of weathering steel rust layer according to claim 1, Features: If there is severe weather during the atmospheric exposure test that can easily cause the rust layer on the surface of the weathering steel sample to be damaged or fall off, check and confirm the condition of the rust layer on the surface of the weathering steel sample.

5. An application of the evaluation method according to any one of claims 1 to 4, Features: Once it is determined that the rust layer of the weathering steel has reached a stabilized state, the weathering steel product can be shipped from the factory.

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