Evaluation method for hydrogen content increment after coating steel is subjected to environmental action

Abstract

The invention provides a method for evaluating hydrogen content increment of steel with a plating layer after environmental action, and belongs to the field of high-strength steel electroplating process evaluation. The method comprises the following steps: bundling a steel mesh with a certain coating thickness on a to-be-electroplated window of a hydrogen meter probe, putting the probe bundled with the steel mesh into a to-be-tested solution, solvent or environment, taking down the steel mesh after a certain test time, and measuring the HP value of the probe; when the hydrogen measuring instrument probe wound with the steel mesh with the coating is exposed or soaked in atmosphere, solution and solvent, the interaction between the steel with the coating and the atmosphere, solution and solvent can be simulated, the hydrogen peak HP value under different conditions is transversely compared, the increase amount of the hydrogen ion content after the steel with the coating is subjected to the action of different environments can be obtained, and the hydrogen ion content of the steel with the coating is calculated. And semi-quantitative evaluation of the hydrogen ion content increment is realized.

Description

Technical Field

[0001] This invention belongs to the field of evaluation of high-strength steel electroplating processes, and relates to a method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors. In particular, it relates to a method for evaluating the increase in hydrogen content of the base metal when the coating is removed by chemical methods, based on the stripping solution and stripping method. It also relates to a method for evaluating the increase in hydrogen content of the base metal after coated steel is exposed to or immersed in an atmosphere, solution, or solvent. Background Technology

[0002] In the aerospace industry, steel is widely used in aerospace products due to its high specific strength, good fatigue and processing properties, and low cost. Under certain load conditions, steel parts are far superior to other commonly used materials in terms of small size and good stability. High-strength steel has high tensile strength, but it is highly sensitive to hydrogen embrittlement. Accidents caused by hydrogen embrittlement fracture are often sudden and catastrophic. Therefore, the most important principle when surface protecting high-strength steel is that the protective process must have low hydrogen embrittlement performance. This requires good low hydrogen embrittlement performance throughout the entire electroplating process and in subsequent use and storage processes, so that the substrate absorbs as few hydrogen ions as possible.

[0003] To facilitate the assessment of the impact of electroplating processes on the hydrogen embrittlement properties of high-strength steel, hydrogen permeability testing using a hydrogen detector is often employed according to relevant specifications. The principle is as follows: The hydrogen detector utilizes an iron-cased electron tube as a probe for electroplating. During electroplating, some hydrogen atoms permeate through the plating layer and tube wall into the electron tube, reducing the vacuum level inside the tube. This change in vacuum caused by hydrogen permeation is converted into a current signal. The hydrogen embrittlement tendency test results can be obtained from the curve recorded by the hydrogen detector during the electroplating test. After probe electroplating, the tube is baked in an oven. When the hydrogen diffusion of the plating layer and tube wall reaches equilibrium, a hydrogen peak (HP) appears. Subsequently, hydrogen diffuses outward through the tube wall and plating layer. The rate of decrease in the hydrogen voltage-current curve is directly related to the hydrogen permeability of the plating layer; therefore, the time required for the curve to drop from the highest point HP to 1 / 2 HP is defined as the λ value (in seconds). HP represents the amount of hydrogen absorbed by the coating and the substrate. The smaller the HP value, the lower the risk of hydrogen embrittlement of the coating. λ represents the hydrogen permeability of the coating. The smaller the λ value, the lower the risk of hydrogen embrittlement of the coating.

[0004] However, after high-strength steel is electroplated, the coating can absorb hydrogen and cause hydrogen embrittlement when the coated steel is removed or comes into contact with other solutions or environments. Examples include immersing steel with a cadmium coating in hydrochloric acid solution to remove the coating, and storing steel with a cadmium coating for extended periods in a marine atmosphere. There is no convenient testing method for the increased hydrogen ion content in coated high-strength steel after exposure to stripping solutions or other environmental factors. The hydrogen embrittlement test bar method can only provide a qualitative assessment, and the processing and testing costs of the test bars are high, with a long testing cycle (200 hours). While the inert gas melting method can provide a quantitative assessment, it requires cutting and processing the sample, specialized equipment, and is also expensive.

[0005] This invention expands the application field of hydrogen analyzers and provides a simple, low-cost, and short-testing method for evaluating the increase in hydrogen ion content of coated steel after environmental exposure. It does not require separate sample processing and can obtain semi-quantitative results in about 2 hours. Summary of the Invention

[0006] The purpose of this invention is to provide a method for evaluating the increase in hydrogen content of coated steel after exposure to environmental conditions. This method is particularly useful for evaluating the increase in base metal content caused by stripping solutions, in order to meet the experimental requirements such as process formulation screening. It can also be used to evaluate the increase in hydrogen content of base metal caused by coated steel after exposure to atmospheres, solutions, solvents, or immersion, in order to assess the impact of the environment on hydrogen embrittlement of coated steel.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors includes the following steps:

[0009] 1) Instrument and probe preparation:

[0010] Preheat the hydrogen analyzer for 24 hours. Turn on the oven 30 minutes before the test and check the oven temperature, as well as the zero point and full scale of the dial instrument. Before the test, use an auxiliary heater to heat the probe of the hydrogen analyzer until the indicator light goes out. After the probe cools down, weigh it and check the standard reference point value (SRP value). The SRP value should be less than 0.2. Shield the probe with tape, ensuring that only the window to be electroplated is exposed. Use a sandblasting device with dry alumina abrasive to sandblast the probe surface. After removing the tape, weigh it to ensure the sandblasting effect. Ensure that the surface of the window to be electroplated is not touched during the tape removal process. Use a soft brush to remove the abrasive. Visually check the cleanliness of the surface of the window to be electroplated and weigh it to check the amount of sandblasting removed. Compared with the weight after sandblasting, the weight removed should be greater than 40mg.

[0011] 2) Probe calibration:

[0012] The probe was subjected to cathode hydrogen charging for 180 s using a standard solution (a mixed aqueous solution of 50 g / L NaCN and 50 g / L NaOH) (current density: 21 A / Ft). 2 Then wash with water and acetone, blot dry with filter paper, and bake the probe in an oven. The hydrogen analyzer automatically records the curve of hydrogen pressure current changing with time and displays the hydrogen peak value HPc and the hydrogen permeability λc value. The calibration ends when the curve decays to 1 / 2 HPc, and the HPc and λc values ​​are recorded. The accuracy of the probe measurement value is determined based on the HPc and λc values.

[0013] 3) Hydrogen embrittlement performance test:

[0014] Insert the probe into the cable socket, wrap the probe base and cable threads with PTFE tape, and tighten the nuts. Secure a steel mesh with a certain coating thickness to the probe's electroplating window, ensuring the mesh is tightly fitted and completely covers the window. The coating thickness should be the typical or maximum thickness of the process being tested. The steel mesh should be made of 304 stainless steel with a mesh size of 20-40. Alternatively, stainless steel wire can be used to secure the mesh to the probe, ensuring the binding is outside the electroplating window and that the binding material does not react with the test solution or scratch the probe's protective layer.

[0015] Place the probe, secured with a steel mesh, into the solution, solvent, or environment to be tested. After a certain testing time, remove the probe, remove the steel mesh, wash it with cold water and acetone, blot it dry with filter paper, and measure and record the probe's HP value. The testing time is determined based on the solution, solvent, or environment being tested.

[0016] By comparing the peak hydrogen (HP) values ​​under different conditions, we can determine the increase in hydrogen ion content in coated steel after exposure to different environments, thus achieving a semi-quantitative assessment of the increase in hydrogen ion content.

[0017] 4) Baking and retesting:

[0018] After the test is completed, place the probe in an oven to bake. After baking, test the remaining test conditions according to steps 1)-3).

[0019] The core technology of this invention is to expand the application field of hydrogen analyzers by winding a coated steel mesh around the probe and exposing or immersing it in an atmosphere, solution, or solvent. The hydrogen peak value (HP) in the probe is then measured, allowing for a semi-quantitative assessment of the increase in hydrogen ion content. Using a 20-40 mesh 304 stainless steel mesh with a coating around the probe simulates the effect of coated steel. If the mesh size is too small, it is too fine, which is detrimental to both electroplating and simulating the interaction between the atmosphere, solution, solvent, and substrate. If the mesh size is too large, it is too coarse, also hindering the simulation of the interaction between the atmosphere, solution, solvent, and coating. Using 304 stainless steel avoids errors caused by steel mesh corrosion.

[0020] The principle of this invention is as follows: When a hydrogen detector probe wrapped with a coated steel mesh is exposed or immersed in an atmosphere, solution, or solvent, it can simulate the interaction between the coated steel and the atmosphere, solution, or solvent. At this time, the coating and the probe window will interact with the atmosphere, solution, and solvent. If hydrogen ions are generated, they will penetrate into the probe window and diffuse into the probe's interior. When the probe is baked in an oven, and the hydrogen diffusion between the window wall and the interior of the vacuum tube reaches equilibrium, a hydrogen peak value (HP) will appear. By comparing the hydrogen peak value HP, the increase in hydrogen ion content after the coated steel is subjected to environmental influences (interactions with different atmospheres, solutions, and solvents) can be compared.

[0021] The beneficial effects of this invention are as follows:

[0022] 1) The test method of the present invention is simple and quick, and can be used to evaluate the increase in the hydrogen content of the substrate metal in the stripping solution when the coating is removed by chemical method.

[0023] 2) This invention can be used to evaluate the increase in hydrogen content of the base metal after coating steel is subjected to various environments such as atmospheres, solutions, and solvents, or after immersion. This invention is practical and can effectively identify and evaluate the increase in hydrogen content of the base metal caused by different stripping solutions, storage under different temperatures and humidity conditions, or immersion in different solutions and solvents. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which provide a further detailed description of the technical solution of the present invention. However, the present invention is not limited to these embodiments.

[0025] Example 1: Evaluation of the increase in hydrogen content in steel with cadmium plating by cadmium stripping solution

[0026] I. Evaluation method for ammonium nitrate cadmium removal solution, including the following steps:

[0027] 1) Instrument and probe preparation:

[0028] Preheat the hydrogen analyzer for 24 hours. Turn on the oven 30 minutes before the test and check the oven temperature, as well as the zero point and full scale of the dial instrument. Before the test, use an auxiliary heater to heat the probe of the hydrogen analyzer until the indicator light goes out. After the probe cools down, weigh it and check the standard reference point value (SRP value). The SRP value should be less than 0.2. Shield the probe with tape, ensuring that only the window to be electroplated is exposed. Use a sandblasting device with dry alumina abrasive to sandblast the probe surface. After removing the tape, weigh it to ensure the sandblasting effect. Ensure that the surface of the window to be electroplated is not touched during the tape removal process. Use a soft brush to remove the abrasive. Visually check the cleanliness of the surface of the window to be electroplated and weigh it to check the amount of sandblasting removed. Compared with the weight after sandblasting, the weight removed should be greater than 40mg.

[0029] 2) Probe calibration

[0030] The probe was subjected to cathode hydrogen charging for 180 s using a standard solution (a mixed aqueous solution of 50 g / L NaCN and 50 g / L NaOH) (current density: 21 A / Ft). 2 Then wash with water and acetone, blot dry with filter paper, and bake the probe in an oven. The hydrogen analyzer automatically records the curve of hydrogen pressure current changing with time and displays the hydrogen peak value HPc and the hydrogen permeability λc value. The calibration ends when the curve decays to 1 / 2 HPc, and the HPc and λc values ​​are recorded. The accuracy of the probe measurement value is determined based on the HPc and λc values.

[0031] 3) Hydrogen embrittlement performance test

[0032] Insert the probe into the cable socket, wrap the probe base and cable threads with PTFE tape, and tighten the nuts. Secure a steel mesh with an approximately 15μm thick cadmium plating layer to the probe's electroplating window, ensuring the mesh is tightly fitted and completely covers the window. The plating thickness should be the typical or maximum thickness of the process being tested. The steel mesh should be made of 304 stainless steel with a mesh size of 20-40. Alternatively, stainless steel wire can be used to secure the mesh to the probe, ensuring the binding is outside the electroplating window, and that the binding material does not react with the test solution or scratch the probe's protective layer.

[0033] The probe, secured with a steel mesh, was immersed in ammonium nitrate cadmium removal solution for a certain period until the coating was completely removed. After the coating was completely removed, the probe was removed, the steel mesh was taken off, and the probe was washed with cold water and acetone, dried with filter paper, and the probe's HP value was measured. The probe's HP value was approximately 2.7 in three measurements, which is very low.

[0034] 4) Baking and retesting

[0035] After the test is completed, the probe is then placed in an oven to bake until the baking process automatically ends.

[0036] II. For the hydrochloric acid cadmium removal solution, the same evaluation method as in section I was used, except that in step 3), the probe with the steel mesh secured was immersed in the hydrochloric acid cadmium removal solution for a certain period of time until the coating was completely removed. After the coating was completely removed, the probe was removed, the steel mesh was taken off, and the probe was washed with cold water and acetone, dried with filter paper, and the probe's HP value was measured. The probe's HP value was approximately 478.9 after three measurements, which is a very high HP value.

[0037] The above experiments show that when hydrochloric acid is used as the cadmium stripping solution, the increase in the base hydrogen content of steel with cadmium coating (HP 478.9) is significantly greater than the increase in hydrogen ions when ammonium nitrate is used as the cadmium stripping solution (HP 2.7). To avoid the risk of hydrogen embrittlement, ammonium nitrate should be selected as the cadmium stripping solution.

[0038] Example 2: Evaluation of the effect of air temperature and humidity on the increase in hydrogen content of chromium-plated steel

[0039] I. For dry air at room temperature, the evaluation method includes the following steps:

[0040] 1) Instrument and probe preparation:

[0041] Preheat the hydrogen analyzer for 24 hours. Turn on the oven 30 minutes before the test and check the oven temperature, as well as the zero point and full scale of the dial instrument. Before the test, use an auxiliary heater to heat the probe of the hydrogen analyzer until the indicator light goes out. After the probe cools down, weigh it and check the standard reference point value (SRP value). The SRP value should be less than 0.2. Shield the probe with tape, ensuring that only the window to be electroplated is exposed. Use a sandblasting device with dry alumina abrasive to sandblast the probe surface. After removing the tape, weigh it to ensure the sandblasting effect. Ensure that the surface of the window to be electroplated is not touched during the tape removal process. Use a soft brush to remove the abrasive. Visually check the cleanliness of the surface of the window to be electroplated and weigh it to check the amount of sandblasting removed. Compared with the weight after sandblasting, the weight removed should be greater than 40mg.

[0042] 2) Probe calibration

[0043] The probe was subjected to cathode hydrogen charging for 180 s using a standard solution (a mixed aqueous solution of 50 g / L NaCN and 50 g / L NaOH) (current density: 21 A / Ft). 2 Then wash with water and acetone, blot dry with filter paper, and bake the probe in an oven. The hydrogen analyzer automatically records the curve of hydrogen pressure current changing with time and displays the hydrogen peak value HPc and the hydrogen permeability λc value. The calibration ends when the curve decays to 1 / 2 HPc, and the HPc and λc values ​​are recorded. The accuracy of the probe measurement value is determined based on the HPc and λc values.

[0044] 3) Hydrogen embrittlement performance test

[0045] Insert the probe into the cable socket, wrap the probe base and cable threads with PTFE tape, and tighten the nuts. Secure a steel mesh with an approximately 15μm thick cadmium plating layer to the probe's electroplating window, ensuring the mesh is tightly fitted and completely covers the window. The plating thickness should be the typical or maximum thickness of the process being tested. The steel mesh should be made of 304 stainless steel with a mesh size of 20-40. Alternatively, stainless steel wire can be used to secure the mesh to the probe, ensuring the binding is outside the electroplating window, and that the binding material does not react with the test solution or scratch the probe's protective layer.

[0046] The probe, secured with a steel mesh, was placed in a constant temperature and humidity chamber at 20°C and 20% humidity for 24 hours. After 24 hours, the probe was removed, the steel mesh was taken off, and the probe was washed with cold water and acetone, dried with filter paper, and the probe's HP value was measured. The probe's HP value was approximately 7.1 in three measurements, which is very low.

[0047] 4) Baking and retesting

[0048] After the test is completed, the probe is then placed in an oven to bake until the baking process automatically ends.

[0049] II. High temperature and high humidity: The same evaluation method as in section I was used, except that in step 3), the probe with the steel mesh secured was placed in a constant temperature and humidity chamber at 35℃ and 75% humidity for 24 hours. After 24 hours, the probe was removed, the steel mesh was taken off, and the probe was washed with cold water and acetone, dried with filter paper, and the probe's HP value was measured. The probe's HP value was approximately 86.2 in three measurements, which is relatively high.

[0050] The above experiments show that when steel with chromium plating is stored in a high temperature and high humidity environment, the increase in the base hydrogen content (HP 86.2) is significantly greater than the increase in hydrogen ions when stored in a low temperature and dry environment (HP 7.1). To avoid the risk of hydrogen embrittlement, steel with chromium plating should be stored in a low temperature and dry environment.

[0051] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, characterized in that, A steel mesh with a coating is tied to the electroplating window of the hydrogen analyzer probe. The probe with the steel mesh tied is placed in the solution, solvent or environment to be tested. After a certain testing time, the steel mesh is removed and the HP value of the probe is measured. By comparing the size of the peak hydrogen HP value under different conditions, the increase in hydrogen ion content of the coated steel after being subjected to different environmental effects can be obtained.

2. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, as described in claim 1, is characterized in that... Includes the following steps: Step 1, Instrument and probe preparation: Preheat the hydrogen analyzer. Before the test, bake the probe of the hydrogen analyzer until the indicator light goes out and check the standard SRP value of the probe. Shield the probe with tape, leaving only the window to be electroplated exposed. Sandblast the probe surface and then remove the abrasive. Step 2, Probe Calibration: The probe is cathodially charged with hydrogen using a calibration solution, then washed with water and acetone, dried with filter paper, and placed in an oven to bake. The hydrogen analyzer displays the hydrogen peak value HPc and the hydrogen permeability λc value. The calibration ends when the curve decays to 1 / 2 HPc. The HPc and λc values ​​are recorded, and the accuracy of the probe measurement is determined based on the HPc and λc values. Step 3, Hydrogen embrittlement performance test: Place the probe into the cable socket and secure it to the probe's electroplating window with a steel mesh of a certain coating thickness. Place the probe with the steel mesh in the solution, solvent, or environment to be tested. After a certain testing time, remove the probe, remove the steel mesh, wash it with cold water and acetone, blot it dry with filter paper, measure and record the probe's hydrogen peak value. By comparing the peak hydrogen peak values ​​under different conditions, the increase in hydrogen ion content of the coated steel after being subjected to different environmental effects can be obtained, thus achieving a semi-quantitative assessment of the increase in hydrogen ion content. Step 4, Baking and Retesting: After completing the test, bake the probe and then test the remaining test conditions according to steps 1 to 3.

3. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, as described in claim 2, is characterized in that... The SRP value should be less than 0.

2.

4. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, as described in claim 2, is characterized in that... In step 2, the calibration solution is a mixed aqueous solution of 50 g / L NaCN and 50 g / L NaOH.

5. The method for evaluating the increase in hydrogen content of coated steel after environmental exposure, as described in claim 2, is characterized in that... In step 2, the probe is charged with hydrogen at the cathode for 180 seconds, with a current density of 21 A / Ft. 2 .

6. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, as described in claim 2, is characterized in that... In step 3, the thickness of the steel mesh coating is taken as the typical thickness or maximum thickness of the process to be measured.

7. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental factors, as described in claim 2, is characterized in that... In step 3, the steel mesh is made of 304 stainless steel.

8. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental conditions, as described in claim 2, is characterized in that... In step 3, the mesh size of the steel mesh is 20-40.

9. The method for evaluating the increase in hydrogen content of coated steel after exposure to environmental conditions, as described in claim 2, is characterized in that... In step 3, the testing time is determined based on the solution, solvent, or environment being tested.

10. The method for evaluating the increase in hydrogen content of coated steel after environmental exposure, as described in claim 2, is characterized in that... In step 3, the steel mesh binding position should be outside the probe electroplating window.