Method for measuring corrosion rate of high alloy steel

Abstract

The invention provides a high alloy steel corrosion rate determination method, and belongs to the technical field of corrosion detection. The method comprises the following steps: acquiring specification parameters of a high-alloy steel original sample, and preparing the high-alloy steel initial sample; pickling the high alloy steel initial sample by using a first pickling solution, and obtaining a first pickled sample after surface floating rust is completely dissolved; washing the first pickling sample with clear water, if an oxide layer exists on the surface of the washed first pickling sample, pickling the first pickling sample with a second pickling solution, and obtaining a second pickling sample after the oxide layer is completely dissolved; sequentially cleaning the second pickling sample with absolute ethyl alcohol, and drying to obtain a tested sample; collecting the specification parameters of the tested sample and calculating the weight loss ratio by combining the specification parameters of the high alloy steel original sample; and representing the corrosion rate of the high alloy steel by using the weight loss ratio. Through the synergistic effect of the first pickling solution and the second pickling solution, an oxide layer on the surface of the high alloy steel is efficiently removed in stages, and meanwhile the over-corrosion problem of a base body is avoided.

Description

Technical Field

[0001] This invention relates to the field of corrosion detection technology, and in particular to a method for determining the corrosion rate of high alloy steel. Background Technology

[0002] High-alloy steel, as an important metallic material, typically achieves its performance optimization by adding various alloying elements such as C, Si, Mn, P, S, Cr, Ni, Mo, and Ti to the iron matrix. When the total alloying element content exceeds 10%, the material is defined as high-alloy steel. These materials, due to the addition of elements such as Cr and Ni, exhibit significantly improved tensile strength, toughness, and corrosion resistance, making them widely used in engineering fields operating under harsh environments. In corrosion performance evaluation, accelerated corrosion tests such as salt spray tests and immersion tests require calculation of the corrosion rate using the weight loss method.

[0003] Currently, mature technical solutions have been developed for pickling corrosion products of low-alloy steel and stainless steel. For low-alloy steel, a pickling solution composed of hydrochloric acid and hexamethylenetetramine is commonly used to effectively remove corrosion products; while for stainless steel, a mixed pickling system of nitric acid and hydrofluoric acid is often used. However, these existing technologies are difficult to apply to high-alloy steel: on the one hand, the Cr and Ni enriched oxide layer formed on the surface of high-alloy steel has special chemical stability, and its dense structure exhibits significant inertness to inorganic acids such as sulfuric acid and hydrochloric acid, making it impossible for traditional low-alloy steel pickling methods to completely remove the oxide layer; on the other hand, although stainless steel pickling solutions have the ability to dissolve Cr and Ni-containing substances, the Cr and Ni content in the rust layer of high-alloy steel is significantly lower than that of stainless steel, and the use of a nitric acid-hydrofluoric acid system can easily cause over-corrosion of the substrate, resulting in errors in the measurement of corrosion rate. This technological gap poses a serious challenge to the accurate measurement of the corrosion rate of high-alloy steel.

[0004] There is an urgent need for a method to determine the corrosion rate of high alloy steel. Summary of the Invention

[0005] In view of this, the present invention provides a method for determining the corrosion rate of high alloy steel, which removes the Cr and Ni enriched oxide layer formed on the surface of high alloy steel by combined pickling with a first pickling solution and a second pickling solution, without over-corroding the substrate, and obtains an accurate corrosion rate.

[0006] Therefore, the present invention provides the following technical solution: A method for determining the corrosion rate of high alloy steel, comprising: Collect the specifications and parameters of the original high-alloy steel sample and prepare the initial high-alloy steel sample. The high-alloy steel initial sample was pickled using the first pickling solution, and the first pickled sample was obtained after the surface rust was completely dissolved. The first pickled sample is rinsed with clean water. If an oxide layer is present on the surface of the first pickled sample after rinsing, the first pickled sample is pickled with the second pickling solution. The second pickled sample is obtained after the oxide layer is completely dissolved. The second pickled sample was sequentially cleaned with anhydrous ethanol and dried to obtain the test sample. The weight loss rate was calculated by collecting the specifications of the test specimens after the test and combining them with the specifications of the original high-alloy steel specimens. The weight loss rate is used to characterize the corrosion rate of high alloy steel.

[0007] Furthermore, the method for preparing the first pickling solution includes: S1. Slowly pour 100-150 mL of concentrated hydrochloric acid into distilled water and stir until well mixed. Add 5-10g of hexamethylenetetramine to S2; S3 was mixed with distilled water to prepare a 1000ml solution, which was used as the first pickling solution.

[0008] Furthermore, the method for preparing the second pickling solution includes: S1. Slowly pour 200-300 mL of concentrated hydrochloric acid into distilled water and stir until well mixed. Add 5-10g of hexamethylenetetramine to S2; Add 50-100 mL of hydrogen peroxide solution to S3; S4 was mixed with distilled water to prepare a 1000ml solution, which was used as the second pickling solution.

[0009] Furthermore, the concentrated hydrochloric acid has a mass fraction of 38%.

[0010] Furthermore, the hydrogen peroxide solution has a mass fraction of 30%.

[0011] Further, the preparation of the initial high-alloy steel sample includes: The original high-alloy steel sample was degreased with petroleum ether and cleaned with anhydrous ethanol in sequence to obtain the high-alloy steel sample. After the high-alloy steel sample is subjected to corrosion test, the residual corrosion solution on the sample surface is rinsed off with clean water and then used as the initial high-alloy steel sample.

[0012] Furthermore, the specifications include: Specimen length, specimen width, specimen thickness, and specimen weight.

[0013] Furthermore, the calculation of the weightlessness rate includes:

[0014] In the formula, The rate of weightlessness, ; The original weight of the high-alloy steel sample is in grams. The weight of the sample after the test, in grams; The sample length is in mm; The width of the sample is in mm; The sample thickness is in mm; The test time is in hours (h).

[0015] Advantages and positive effects of the present invention: This invention utilizes the synergistic effect of a first pickling solution and a second pickling solution to remove the dense Cr / Ni-enriched oxide layer on the surface of high-alloy steel in stages. The first pickling solution preferentially dissolves surface rust, while the second pickling solution effectively removes the oxide layer and stops corrosion once a bright iron substrate appears. The combined effect of the two solutions significantly improves the oxide layer removal efficiency while controlling the corrosion rate, thus avoiding the problem of over-corrosion of the substrate caused by single pickling. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for determining the corrosion rate of high alloy steel. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] This invention provides a method for determining the corrosion rate of high alloy steel, comprising: S1. Prepare initial high-alloy steel samples and collect the dimensional parameters of the original high-alloy steel samples; 1) After the original high-alloy steel sample was degreased with petroleum ether and cleaned with anhydrous ethanol, the high-alloy steel sample was obtained. The specifications were collected, including weight, length, width and thickness.

[0021] 2) After the corrosion test is performed on the high alloy steel sample, rinse the surface of the sample with clean water to remove the residual corrosion solution and use it as the initial sample of high alloy steel.

[0022] Corrosion tests include: salt spray test, immersion test, and full immersion test.

[0023] S2. Preparation of pickling solution: 1) Slowly pour 100-150 mL of concentrated hydrochloric acid (38% by mass) into distilled water, stir well, then add 5-10 g of hexamethylenetetramine, and add distilled water to prepare a 1000 mL solution as the first pickling solution.

[0024] 2) Slowly pour 200-300 mL of concentrated hydrochloric acid (38% by mass) into distilled water, stir well, add 5-10 g of hexamethylenetetramine, then add 50-100 mL of hydrogen peroxide solution (30% by mass), and add distilled water to prepare a 1000 mL solution, which is the second pickling solution.

[0025] S3, Pickling Step: 1) Immerse the initial high-alloy steel sample in a sufficient amount of first pickling solution, and obtain the first pickling sample after the surface rust is completely dissolved. 2) Rinse the first pickled sample with clean water. If there is an oxide layer on the surface of the first pickled sample after rinsing, use the second pickling solution to pickle the first pickled sample. Stop the corrosion after the oxide layer is completely dissolved and a bright iron substrate appears, and obtain the second pickled sample. 3) The second pickled sample was successively cleaned with anhydrous ethanol and dried to obtain the test sample.

[0026] S4. Determine the test results: 1) After cooling to room temperature, weigh the test sample with an accuracy of 0.1 mg.

[0027] 2) The weight loss rate is calculated based on weighing, using the following formula:

[0028] In the formula, The rate of weightlessness, ; The original weight of the sample is in grams. The weight of the sample after the test, in grams; The sample length is in mm; The width of the sample is in mm; The sample thickness is in mm; The test time is in hours (h).

[0029] 3) The corrosion rate of high alloy steel is characterized by the weight loss rate.

[0030] Example S1. Prepare the original sample and collect its specifications: 1) After degreasing the high alloy steel sample with petroleum ether, clean it with anhydrous ethanol, weigh it, and measure the length, width, and thickness of the sample.

[0031] 2) After conducting corrosion tests such as salt spray test, immersion test, and full immersion test, remove the sample, rinse the surface of the sample with clean water to remove any residual corrosion solution, and prepare for pickling.

[0032] S2. Preparation of pickling solution: 1) Slowly pour 100-150 mL of concentrated hydrochloric acid (38% by mass) into distilled water, stir well, then add 5-10 g of hexamethylenetetramine, and add distilled water to prepare a 1000 mL solution as the first pickling solution.

[0033] 2) Slowly pour 200-300 mL of concentrated hydrochloric acid (38% by mass) into distilled water, stir well, add 5-10 g of hexamethylenetetramine, then add 50-100 mL of hydrogen peroxide solution (30% by mass), and add distilled water to prepare a 1000 mL solution, which is the second pickling solution.

[0034] S3. Test Procedure: 1) Immerse the sample in sufficient acid first pickling solution. After the surface rust is completely dissolved, take out the sample and rinse it with clean water. 2) For samples that still have a difficult-to-remove oxide layer on the surface after cleaning, put them into a sufficient amount of second pickling solution. After the oxide layer is completely removed and dissolved and a bright iron substrate appears, stop the corrosion and remove the surface corrosion products with a brush.

[0035] 3) After acid washing, the sample is cleaned with anhydrous ethanol, removed and immediately dried with hot air, and then stored in a desiccator.

[0036] S4. Determine the test results: 1) After cooling to room temperature, weigh the sample with an accuracy of 0.1 mg.

[0037] 2) The weight loss rate is calculated based on weighing, using the following formula:

[0038] In the formula, The rate of weightlessness, ; The original weight of the sample is in grams. The weight of the sample after the test, in grams; The sample length is in mm; The width of the sample is in mm; The sample thickness is in mm; The test time is in hours (h).

[0039] In this embodiment, 83.6707g , , 50.14mm, , 120h .

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the corrosion rate of high alloy steel, characterized in that, include: Collect the specifications and parameters of the original high-alloy steel sample and prepare the initial high-alloy steel sample. The high-alloy steel initial sample was pickled using the first pickling solution, and the first pickled sample was obtained after the surface rust was completely dissolved. The first pickled sample is rinsed with clean water. If an oxide layer is present on the surface of the first pickled sample after rinsing, the first pickled sample is pickled with the second pickling solution. The second pickled sample is obtained after the oxide layer is completely dissolved. The second pickled sample was sequentially cleaned with anhydrous ethanol and dried to obtain the test sample. The weight loss rate was calculated by collecting the specifications of the test specimens after the test and combining them with the specifications of the original high-alloy steel specimens. The weight loss rate is used to characterize the corrosion rate of high alloy steel.

2. The method according to claim 1, characterized in that, The method for preparing the first pickling solution includes: S1. Slowly pour 100-150 mL of concentrated hydrochloric acid into distilled water and stir until well mixed. Add 5-10g of hexamethylenetetramine to S2; S3 was mixed with distilled water to prepare a 1000ml solution, which was used as the first pickling solution.

3. The method according to claim 1, characterized in that, The method for preparing the second pickling solution includes: S1. Slowly pour 200-300 mL of concentrated hydrochloric acid into distilled water and stir until well mixed. Add 5-10g of hexamethylenetetramine to S2; Add 50-100 mL of hydrogen peroxide solution to S3; S4 was mixed with distilled water to prepare a 1000ml solution, which was used as the second pickling solution.

4. The method according to claim 2, characterized in that, The concentrated hydrochloric acid has a mass fraction of 38%.

5. The method according to claim 3, characterized in that, The hydrogen peroxide solution has a mass fraction of 30%.

6. The method according to claim 1, characterized in that, The preparation of the initial high-alloy steel sample includes: The original high-alloy steel sample was degreased with petroleum ether and cleaned with anhydrous ethanol in sequence to obtain the high-alloy steel sample. After the high-alloy steel sample is subjected to corrosion test, the residual corrosion solution on the sample surface is rinsed off with clean water and then used as the initial high-alloy steel sample.

7. The method according to claim 1, characterized in that, The specifications include: Specimen length, specimen width, specimen thickness, and specimen weight.

8. The method according to claim 1, characterized in that, The calculation of the weightlessness rate includes: In the formula, The rate of weightlessness, ; The original weight of the high-alloy steel sample is in grams. The weight of the sample after the test, in grams; The sample length is in mm; The width of the sample is in mm; The sample thickness is in mm; The test time is in hours (h).

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