Artificial salt mist atmosphere accelerated corrosion test method

Abstract

The invention relates to an artificial salt mist atmosphere accelerated corrosion test method which comprises the following steps: 1) preparing a test solution which comprises Na2S2O8 with the mass fraction of 1%-2% and a NaCl solution with the mass fraction of 5% + / -0.5%; 2) continuously spraying; and 3) sample post-treatment and evaluation. According to the method, Na2S2O8 is introduced into a neutral salt spray test and can be decomposed in water to generate H2O2 with a relatively strong depolarization effect, so that on one hand, a good corrosion acceleration effect can be achieved, and on the other hand, the intergranular corrosion degree of the aluminum alloy material can be investigated; the salt spray corrosion resistance and intergranular corrosion resistance of the aluminum alloy material can be synchronously compared and evaluated through one test, the method is simple, the workload of related tests can be effectively reduced, and the test efficiency is improved. The method has simulation performance, acceleration performance and reproducibility, can rapidly evaluate salt spray corrosion and simplified corrosion behaviors of high-corrosion-resistance materials such as aluminum alloy, and provides a basis for reasonable material selection, corrosion prevention method optimization and the like.

Description

Technical Field

[0001] The invention belongs to the field of atmospheric corrosion simulation, and in particular relates to an accelerated corrosion test method in an artificial salt spray atmosphere. Background Art

[0002] As a corrosion resistance evaluation method, the salt spray test is relatively simple to operate, the test equipment is easy to maintain, and the test process is easy to control, so it has high practicality. Compared with other corrosion test methods, the salt spray test has low cost and can be completed in a shorter time. It is economical and efficient and suitable for enterprises and research institutions of all sizes. At the same time, the test results of the salt spray test have high reliability and repeatability, and can provide accurate evaluation of the corrosion resistance of materials or coatings, which is suitable for various materials and coatings.

[0003] At present, the mature test methods in the field of salt spray testing are divided into four categories according to the ambient temperature and salt spray concentration: neutral salt spray test, acetic acid salt spray test, copper accelerated acetic acid salt spray test, and alternating salt spray test. The neutral salt spray test is most widely applicable, but its disadvantage is that the test cycle is long and the reliability is poor due to the weak corrosiveness of the medium. The acetic acid salt spray test is mainly applicable to copper-nickel-chromium plating, nickel-chromium plating and aluminum anodized film. The copper accelerated acetic acid salt spray test has good consistency with the atmospheric exposure test results for some coatings, but its scope of application is narrow. The alternating salt spray test is suitable for the evaluation of the ability of equipment used in marine environments or offshore areas to withstand salt spray corrosion, but it has high requirements for equipment and complex operation. In summary, at present, the neutral salt spray test is generally used to evaluate the corrosion resistance of aluminum alloy materials, but it has the problems of long test cycle and poor reliability.

[0004] In addition, for aluminum alloy materials, in addition to considering their corrosion resistance in actual engineering applications, most application scenarios also need to fully consider their intergranular corrosion. The test method generally refers to GB / T 7998 "Determination Method for Intergranular Corrosion of Aluminum Alloys". 2000, 7000 series high-strength aluminum alloys and 5000 series high-magnesium (≥7%) aluminum alloys are sensitive to stress corrosion. However, the current neutral salt spray test cannot simulate the intergranular corrosion scenario. Summary of the invention

[0005] The purpose of the present invention is to provide an accelerated corrosion test method in an artificial salt spray atmosphere to solve the technical problems of the existing neutral salt spray test having a long test cycle, poor reliability and inability to simulate intergranular corrosion scenarios.

[0006] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0007] An artificial salt spray atmosphere accelerated corrosion test method comprises the following steps: preparing a test solution, wherein the test solution comprises a Na2S2O8 solution; continuously spraying; and post-processing and evaluating the sample, including evaluation of salt spray corrosion resistance and intergranular corrosion degree.

[0008] Preferably, the test solution comprises Na2S2O8 with a mass fraction of 1% to 2% and NaCl solution with a mass fraction of 5%±0.5%.

[0009] Preferably, the test solution is an acidic solution.

[0010] Preferably, the test solution comprises 1% by mass of Na2S2O8 and 5% by mass of NaCl acidic solution.

[0011] Preferably, the pH value of the acidic solution is 4-6.

[0012] Preferably, the test temperature of the continuous spraying is 35±1°C.

[0013] Preferably, the test temperature of the continuous spraying is 35°C.

[0014] Preferably, the salt mist deposition rate of the continuous spray is 1.0-2.0 mL / 80 cm 2 / h.

[0015] Preferably, the test cycle of the continuous spraying is 12h, 24h, 48h, 96h, 168h, or 240h.

[0016] Preferably, the salt spray corrosion resistance evaluation includes judging, comparing and evaluating through indicators such as appearance after the test, appearance after removing corrosion products, number and distribution of pitting defects, time when corrosion begins to appear, and corrosion weight loss.

[0017] Preferably, the evaluation of the degree of intergranular corrosion includes judging, comparing and evaluating indicators such as the distribution of intergranular corrosion and the maximum depth of intergranular corrosion through metallographic examination.

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

[0019] A method for accelerating corrosion test in artificial salt spray atmosphere includes the following steps: 1) preparing a test solution, wherein the test solution includes a Na2S2O8 solution with a mass fraction of 1% to 2% and a NaCl solution with a mass fraction of 5%±0.5%; 2) continuous spraying; 3) post-treatment and evaluation of the sample. The method introduces sodium persulfate (Na2S2O8) into the neutral salt spray test, and utilizes the fact that it can decompose in water to generate H2O2 with a strong depolarizing effect. On the one hand, it can have a good accelerated corrosion effect, and on the other hand, it can examine the intergranular corrosion degree of aluminum alloy materials. The salt spray corrosion resistance and intergranular corrosion resistance of aluminum alloy materials can be compared and evaluated simultaneously through one test. The method is simple, can effectively reduce the workload of related tests, and improve the test efficiency. The present invention has simulation, acceleration and reproducibility, can quickly evaluate the salt spray corrosion and streamlined corrosion behavior of highly corrosion-resistant materials such as aluminum alloys, and compare and evaluate the corrosion resistance of different types of aluminum alloy materials, providing a basis for reasonable material selection, optimization of anti-corrosion methods, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a macroscopic morphology diagram of the aluminum alloy material sample after the test of Example 1 of the present invention;

[0021] Figure 2 This is a macroscopic morphology diagram of the aluminum alloy material of the comparative example of the present invention after testing;

[0022] Figure 3 This is a microscopic morphology diagram of the aluminum alloy material sample after the test of Example 1 of the present invention;

[0023] Figure 4 This is a microscopic morphology diagram of the aluminum alloy material sample after the test of the comparative example of the present invention;

[0024] Figure 5 The weight loss curves of the aluminum alloy material samples of Example 1 of the present invention and the comparative example after removing the corrosion products are shown. DETAILED DESCRIPTION

[0025] The specific implementation methods of the present invention are described in detail below with reference to examples, but the implementation examples do not limit the present invention in any form. For those skilled in the art, any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principle of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

[0026] Example 1

[0027] Sample preparation: 5052 aluminum alloy plate, size 30mm*40mm*4mm, the surface is smoothed with sandpaper, after cleaning, the sample is dried and weighed with an accuracy of ±1mg.

[0028] Test process: Dissolve chemically pure Na2S2O8 and NaCl in distilled water or deionized water to prepare a solution with a mass fraction of 1% Na2S2O8 and a mass fraction of 5% NaCl, and adjust the pH to between 4 and 6. Set the temperature of the salt spray test chamber to 35±1℃, and the salt spray deposition rate to 1.0~2.0mL / 80cm 2 / h. Place the sample in the salt spray test chamber, the angle can be adjusted between 1530° to ensure uniformity of falling mist and continuous spraying. The test time is 240h.

[0029] Sample post-processing: After the test, observe the macroscopic morphology of the sample visually or with a magnifying glass, observe the microscopic morphology of the sample with a scanning electron microscope, and measure the sample test weight loss by removing the surface corrosion products. The method used to remove the surface corrosion products is: soak the sample in nitric acid (HNO3, ρ = 1.42g / ml) solution at room temperature for 1 to 5 minutes. The specific soaking time is determined according to the removal of the surface corrosion products of the sample, until it is completely removed.

[0030] Comparative Example (Neutral Salt Spray Test)

[0031] The sample preparation was the same as in Example 1.

[0032] Test process: Dissolve chemically pure sodium chloride in distilled water or deionized water to a concentration of 50g / L±5g / L, keep the pH value between 6.5 and 7.2, set the temperature of the salt spray test chamber to 35±2℃, and set the salt spray deposition rate to 1.0~2.0mL / 80cm 2 / h. Place the sample in the salt spray test chamber, the angle can be adjusted between 15-30° to ensure uniformity of falling mist and continuous spraying. The test time is 240h.

[0033] The post-treatment of the sample was the same as in Example 1.

[0034] Results Evaluation

[0035] The macroscopic morphology of the aluminum alloy material sample of Example 1 after the test is as follows: Figure 1 As shown, the macroscopic morphology of the aluminum alloy sample after the test is as follows Figure 2 As shown in the figure, after 240h of neutral salt spray test, the aluminum alloy surface showed local corrosion discoloration and corrosion peeling, and the overall corrosion was relatively light; after 240h of this method test, the aluminum alloy surface showed severe corrosion, peeling and delamination. This shows that the acceleration effect of this experimental method is significantly higher than that of the traditional neutral salt spray test.

[0036] The microscopic morphology of the aluminum alloy material sample of Example 1 after the test is as follows Figure 3 As shown, the microscopic morphology of the aluminum alloy sample after the test is as follows Figure 4As shown in the figure, after 240h neutral salt spray test, only pitting corrosion occurred locally on the aluminum alloy surface after the corrosion products were removed locally, and no obvious corrosion marks were found in other places, indicating a low tendency of intergranular corrosion. After 240h of this method test, the aluminum alloy surface showed serious peeling and cracking of the corrosion product layer, indicating a high tendency of intergranular corrosion. This indicates that this experimental method has a significant accelerating effect and can compare the degree of intergranular corrosion of materials through microscopic corrosion morphology.

[0037] The weight loss curves of the aluminum alloy material samples of Example 1 and the comparative example after removing the corrosion products are as follows: Figure 5 As shown, 14# is a neutral salt spray test, and 9# is the artificial salt spray atmosphere accelerated corrosion test method described in this application. It can be seen that in different test cycles, compared with the neutral salt spray test, the corrosion weight loss of this method is increased by nearly 1 times, indicating that the system has a good acceleration effect.

[0038] Embodiments 2 to 7

[0039] The specific steps of Examples 2 to 7 are the same as those of Example 1, except that the raw material ratios of the test solutions are different, as shown in Table 1.

[0040] Table 1 Different raw material ratios

[0041]

[0042] The test results are consistent with those of the aforementioned embodiment 1, and are superior to the prior art.

[0043] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. An artificial salt spray atmosphere accelerated corrosion test method, characterized in that: The steps include: Prepare a test solution, the test solution comprising 1% to 2% by mass of Na2S2O8 and 5% ± 0.5% by mass of NaCl solution; Continuous spray; Post-processing and evaluation of samples, including evaluation of salt spray corrosion resistance and intergranular corrosion degree.

2. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The test solution is an acidic solution.

3. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The test solution is an acidic solution of Na2S2O8 with a mass fraction of 1% and NaCl with a mass fraction of 5%.

4. The artificial salt spray atmosphere accelerated corrosion test method according to claim 3, characterized in that: The pH value of the acidic solution is 4-6.

5. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The test temperature of the continuous spraying is 35±1°C.

6. The artificial salt spray atmosphere accelerated corrosion test method according to claim 5, characterized in that: The test temperature of the continuous spray was 35°C.

7. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The salt mist deposition rate of the continuous spray is 1.0-2.0 mL / 80 cm 2 / h.

8. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The test cycles of the continuous spraying are 12h, 24h, 48h, 96h, 168h and 240h.

9. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The salt spray corrosion resistance evaluation includes judging, comparing and evaluating through indicators such as appearance after the test, appearance after removing corrosion products, number and distribution of pitting defects, time when corrosion begins to appear, and corrosion weight loss.

10. The artificial salt spray atmosphere accelerated corrosion test method according to claim 1, characterized in that: The evaluation of the degree of intergranular corrosion includes judging, comparing and evaluating indicators such as the distribution of intergranular corrosion and the maximum depth of intergranular corrosion through metallographic inspection.

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