Corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe and preparation method thereof

Abstract

The invention discloses a corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe and a preparation method thereof. The surface of the stainless steel pipe is provided with a composite oxide layer containing CeCrO3 and Cr2O3. The preparation method of the stainless steel pipe comprises the steps that the stainless steel pipe containing Cr is subjected to pre-pickling, and a steel pipe with an oxide skin removed is obtained; the steel pipe is immersed in a pickling solution containing CeO2 nanoparticles, and current is continuously applied to the pickling solution; and the steel pipe is taken out and passivated with inorganic acid, and then the stainless steel pipe with the Ce-Cr composite oxide layer on the surface is obtained. CeO2 nanoparticles are added into the stainless steel seamless tube pickling solution, then Ce in the pickling solution is combined with Cr on the surface of the stainless steel seamless tube by utilizing the synergistic effect of an electrochemical replacement reaction and chemical oxidation and utilizing the high specific surface area and oxidation-reduction activity of the CeO2 nanoparticles, formation of a Ce-Cr composite oxide layer is promoted, and therefore the corrosion resistance of the stainless steel seamless tube is improved, and the corrosion resistance of the stainless steel seamless tube is improved. And the corrosion resistance of the stainless steel pipe in a high-temperature and high-Cl-environment is improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a corrosion-resistant stainless steel pipe, in particular to a corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe and a method for preparing the same. Background Art

[0002] The surface protection of traditional stainless steel pipes mainly uses pickling passivation process, which removes surface impurities and builds a Cr-based surface on the metal matrix through chemical corrosion of a mixed solution of nitric acid and hydrofluoric acid. 2 O 3 The chromium-based oxide layer is mainly composed of chromium. This chromium-based oxide can effectively isolate the substrate from the contact with the corrosive medium under normal conditions through physical barrier effect and self-repair function. However, under working conditions with a temperature exceeding 150°C or a medium environment with a high Cl- concentration, Cl- ions will preferentially adsorb on the defects of the oxide layer due to their strong penetrability, causing local dissolution of the passivation film, and then inducing local corrosion phenomena such as pitting corrosion and crevice corrosion, which may eventually develop into stress corrosion cracking. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe to solve the problem that the chromium-based oxide layer on the surface of the existing stainless steel pipe is not resistant to Cl- corrosion. Another purpose of the present invention is to propose a method for preparing a corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe to solve the problem of how to prepare a stainless steel pipe with a Ce-Cr composite oxide layer on the surface.

[0004] Technical solution: The corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe of the present invention forms a layer containing CeCrO on the surface of the stainless steel pipe. 3 and Cr 2 O 3 The composite oxide layer of the stainless steel pipe is 1 and the thickness of the composite oxide layer h 2 Satisfy 0.002%≤h 2 / h 1 ≤0.025%.

[0005] Preferably, h 1 2-5mm, h 2 It is 100-500nm.

[0006] Another aspect of the present invention discloses a method for preparing the above-mentioned corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe, comprising the following steps:

[0007] (1) Pre-pickling a Cr-containing stainless steel pipe to obtain a steel pipe with oxide scale removed;

[0008] (2) Immerse the descaled steel pipe in a solution containing CeO 2in the pickling solution of the nanoparticles, and continuously apply an electric current to the pickling solution;

[0009] (3) Take out the steel pipe from the pickling solution containing CeO 2 nanoparticles, and obtain a stainless steel pipe with a Ce-Cr composite oxide layer on the surface after passivation with inorganic acid.

[0010] In the present invention, by adding CeO 2 nanoparticles to the pickling solution, utilizing its high specific surface area and redox activity, and then through electrochemical replacement and passivation treatment, Ce in the pickling solution is combined with Cr on the surface of the stainless steel seamless pipe to form CeCrO 3 and Cr 2 O 3 composite oxide layer to enhance the corrosion resistance of the stainless steel pipe.

[0011] Preferably, in step (1), the mass fraction of Cr in the stainless steel pipe containing Cr is at least 15%.

[0012] Preferably, in step (1), the preparation method of the stainless steel pipe containing Cr is as follows:

[0013] S1. Heat the solid round steel of 0Cr18Ni9 to 1050 - 1200 °C, hold for 40 - 60 min, and then perform piercing to form a pipe;

[0014] S2. Grind the pipe, then perform cold rolling, degreasing and pickling treatments, and then obtain a stainless steel pipe containing Cr after solution annealing and straightening.

[0015] Preferably, in step (1), the method of pre-pickling is: Immerse the stainless steel pipe containing Cr in a pre-pickling solution at 40 - 60 °C for 10 - 30 minutes to remove the oxide scale on the surface. The ratio of the pre-pickling solution is 20 vol% nitric acid, 5 vol% hydrofluoric acid, and 75 vol% water.

[0016] Preferably, in step (2), the pickling solution containing CeO 2 nanoparticles includes the following components: 10 - 20 wt% nitric acid, 3 - 8 wt% hydrofluoric acid, 1 - 3 wt% CeO 2 nanoparticles, 0.5 - 1 wt% dispersant, and the balance is water.

[0017] Further preferably, the temperature of the pickling solution containing CeO 2 nanoparticles is 40 - 60 °C, the dispersant is polyethylene glycol, and the particle size of the CeO 2 nanoparticles does not exceed 100 nm.

[0018] Preferably, in step (2), the current density is 5 - 10 mA / cm 2, with a duration of 5 - 15 min.

[0019] Preferably, in step (3), the method of inorganic acid passivation is: immersing the steel pipe in a nitric acid aqueous solution with a volume fraction of 4 - 6% at 40 - 60 °C for 20 - 40 min for passivation treatment.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0021] By adding CeO 2 nanoparticles to the pickling solution of stainless steel seamless pipes, and then utilizing the synergistic effect of electrochemical displacement reaction and chemical oxidation, and at the same time using the high specific surface area and redox activity of CeO 2 nanoparticles, Ce in the pickling solution combines with Cr on the surface of the stainless steel seamless pipe, promoting the formation of a Ce - Cr composite oxide layer that is denser and more stable than the traditional Cr 2 O 3 layer, which can effectively block the penetration of corrosion media such as Cl - and O 2 , etc., and improves the corrosion resistance of stainless steel pipes in high - temperature and high - Cl - environments. Description of the drawings

[0022] Figure 1 is a schematic diagram of the composite oxide layer of CeCrO 3 and Cr 2 O 3 . Detailed implementation manners

[0023] The technical solutions of the present invention will be further described below with reference to the drawings.

[0024] Example 1: A corrosion - resistant Ce - Cr composite oxide layer stainless steel pipe, which has a composite oxide layer containing CeCrO 3 and Cr 2 O 3 with a thickness of 100 nm on its surface, and the wall thickness of the stainless steel pipe is 2 mm.

[0025] The preparation method of the above - mentioned corrosion - resistant Ce - Cr composite oxide layer stainless steel pipe is as follows:

[0026] (1) Heating a solid round steel with a material of 0Cr18Ni9 (304) and a Cr mass fraction of 18.2% to 1150 °C, holding for 50 minutes, and then performing piercing to obtain a steel pipe blank;

[0027] (2) Conduct crack inspection and grinding on the steel pipe blank; cold roll the ground steel pipe, then degrease and pickle it. The pickling solution is formulated as 15 vol% nitric acid, 3 vol% hydrofluoric acid, 82 vol% water, at a temperature of 50 °C, and the pickling time is 30 minutes;

[0028] (3) Place the pickled steel pipe (wall thickness 2 mm) in a furnace at 1050 °C for solution annealing for 60 min, water cool it, then straighten it and pre-pickle to remove the surface scale of the steel pipe. The pre-pickling solution is formulated as 20 vol% nitric acid, 5 vol% hydrofluoric acid, 75 vol% water, at a temperature of 50 °C, and the pickling time is 20 minutes;

[0029] (4) Then immerse the steel pipe with scale removed in a pickling solution containing CeO 2 nanoparticles at 50 °C, and continuously apply a current with a current density of 5 mA / cm 2 for 10 min; the pickling solution containing CeO 2 nanoparticles includes the following components (by mass percentage): 15% nitric acid, 5% hydrofluoric acid, 1% CeO 2 nanoparticles, 0.5% dispersant (polyethylene glycol), and the balance is deionized water. The average particle size of the CeO 2 nanoparticles is 30 nm.

[0030] (5) Then take out the stainless steel pipe and immerse it in a 5% nitric acid aqueous solution at 50 °C for passivation for 30 minutes to form a CeCrO 3 / Cr 2 O 3 composite oxide layer on the surface of the stainless steel pipe;

[0031] (6) Inspection, testing and warehousing: Inspect the prepared stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer, and after passing the corrosion resistance test, pack it and store it in the warehouse.

[0032] Example 2: The preparation method of the stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer is as follows:

[0033] (1) Heat a solid round steel with a material of 022Cr17Ni12Mo2 (316L) and a Cr mass fraction of 16.8% to 1200 °C, hold it for 40 minutes, and then perforate it to obtain a steel pipe blank;

[0034] (2) Conduct crack inspection and grinding on the steel pipe blank; cold roll the ground steel pipe, then degrease and pickle it. The pickling solution is formulated as 15 vol% nitric acid, 3 vol% hydrofluoric acid, 82 vol% water, at a temperature of 50 °C, and the pickling time is 40 minutes;

[0035] (3) Place the pickled steel pipe (wall thickness: 4 mm) in an annealing furnace at 1000 °C for 70 minutes for solution annealing, then straighten it after water cooling, and perform pre-pickling to remove the surface scale of the steel pipe. The composition of the pre-pickling solution is 20 vol% nitric acid, 5 vol% hydrofluoric acid, 75 vol% water, at a temperature of 50 °C, and the pickling time is 20 minutes;

[0036] (4) Then immerse the steel pipe with the scale removed in a pickling solution containing CeO 2 nanoparticles at 60 °C, and continuously apply a current with a current density of 8 mA / cm 2 for 15 minutes; the pickling solution containing CeO 2 nanoparticles includes the following components (by mass percentage): 12% nitric acid, 8% hydrofluoric acid, 2% CeO 2 nanoparticles, 0.8% polyethylene glycol, and the balance is deionized water. The average particle size of the CeO 2 nanoparticles is 40 nm.

[0037] (5) Then take out the stainless steel pipe and immerse it in a 4% (by volume) nitric acid aqueous solution at 60 °C (the volume of nitric acid in the solution accounts for 4% of the total volume) for passivation for 40 minutes to form a CeCrO 3 / Cr 2 O 3 composite oxide layer with a thickness of 300 nm on the surface of the stainless steel pipe;

[0038] (6) Inspection, testing and warehousing: Inspect the prepared stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer, and after passing the corrosion resistance test, pack it and store it in the warehouse.

[0039] Example 3: The preparation method of the stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer is as follows:

[0040] (1) Heat a solid round steel with a material of 022Cr22Ni5Mo3N (2205) and a Cr mass fraction of 22.8% to 1100 °C, hold it for 60 minutes, and then perform piercing to obtain a steel pipe blank;

[0041] (2) Conduct crack inspection and grinding on the steel pipe blank; cold roll the ground steel pipe, then degrease and pickle it. The composition of the pickling solution is 15 vol% nitric acid, 3 vol% hydrofluoric acid, 82 vol% water, at a temperature of 50 °C, and the pickling time is 50 minutes;

[0042] (3) Place the pickled steel pipe (wall thickness: 5 mm) in an annealing furnace at 1100 °C for 50 minutes for solution annealing, then straighten it after water cooling, and perform pre-pickling to remove the surface scale of the steel pipe. The composition of the pre-pickling solution is 20 vol% nitric acid, 5 vol% hydrofluoric acid, 75 vol% water, at a temperature of 60 °C, and the pickling time is 10 minutes;

[0043] (4) Then immerse the steel pipe with the scale removed in an acid pickling solution containing CeO 2 nanoparticles at 40 °C, and continuously apply a current with a current density of 10 mA / cm 2 for 5 min; the acid pickling solution containing CeO 2 nanoparticles includes the following components (by mass percentage): 17% nitric acid, 3% hydrofluoric acid, 3% CeO 2 nanoparticles, 1% polyethylene glycol, and the balance is deionized water. The average particle size of the CeO 2 nanoparticles is 50 nm.

[0044] (5) Then take out the stainless steel pipe and immerse it in a 6% (by volume fraction) nitric acid aqueous solution at 40 °C for passivation for 20 minutes to form a CeCrO 3 / Cr 2 O 3 composite oxide layer with a thickness of 500 nm on the surface of the stainless steel pipe;

[0045] (6) Inspection, testing and warehousing: Inspect the prepared stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer, and after passing the corrosion resistance test, pack it and store it in the warehouse.

[0046] Example 4: The preparation method of the stainless steel pipe with a corrosion-resistant Ce-Cr composite oxide layer is as follows:

[0047] (1) Heat the solid round steel of 022Cr17Ni12Mo2 (316L) with a Cr mass fraction of 16.8% to 1150 °C, hold for 50 minutes, and then perform piercing to obtain a steel pipe blank;

[0048] (2) Conduct crack inspection and grinding on the steel pipe blank; cold roll the ground steel pipe, and then perform degreasing and pickling. The ratio of the pickling solution is 15 vol% nitric acid, 3 vol% hydrofluoric acid, 82 vol% water, the temperature is 50 °C, and the pickling time is 35 minutes;

[0049] (3) Place the pickled steel pipe (wall thickness of 3 mm) at 1050 °C for 50 min for solution annealing, water-cool it, then straighten it and perform pre-pickling to remove the surface scale of the steel pipe. The ratio of the pre-pickling solution is 20 vol% nitric acid, 5 vol% hydrofluoric acid, 75 vol% water, the temperature is 40 °C, and the pickling time is 30 minutes;

[0050] (4) Then immerse the steel pipe with the scale removed in an acid pickling solution containing CeO 2 nanoparticles at 50 °C, and continuously apply a current with a current density of 9 mA / cm 2 for 13 min; the acid pickling solution containing CeO 2The pickling solution for the nanoparticles comprises the following components (by mass percentage): nitric acid 20%, hydrofluoric acid 4%, CeO 2 nanoparticles 2%, polyethylene glycol 0.7%, and the balance being deionized water. The average particle size of the CeO 2 nanoparticles is 60 nm.

[0051] (5) Then, take out the stainless steel tube and immerse it in a 6% (by volume) nitric acid aqueous solution at 60 °C for passivation for 20 minutes to form a CeCrO 3 / Cr 2 O 3 composite oxide layer with a thickness of 400 nm on the surface of the stainless steel tube;

[0052] (6) Inspection, testing and warehousing: Inspect the prepared corrosion-resistant Ce-Cr composite oxide layer stainless steel tube, and after passing the corrosion resistance test, pack it and put it into storage.

[0053] Comparative Example 1: The rest are the same as in Example 1, except that:

[0054] Replace hydrofluoric acid in the pickling solution containing CeO 2 nanoparticles with phosphoric acid.

[0055] Comparative Example 2: The rest are the same as in Example 1, except that:

[0056] Replace hydrofluoric acid in the pickling solution containing CeO 2 nanoparticles with sulfuric acid.

[0057] Comparative Example 3: The rest are the same as in Example 1, except that:

[0058] Replace hydrofluoric acid in the pickling solution containing CeO 2 nanoparticles with nitric acid.

[0059] Comparative Example 4: The rest are the same as in Example 1, except that:

[0060] Replace nitric acid in the pickling solution containing CeO 2 nanoparticles with hydrofluoric acid.

[0061] Comparative Example 5: The rest are the same as in Example 1, except that:

[0062] Replace nitric acid in the pickling solution containing CeO 2 nanoparticles with phosphoric acid.

[0063] Comparative Example 6: The rest are the same as in Example 1, except that:

[0064] Replace nitric acid in the pickling solution containing CeO 2 nanoparticles with sulfuric acid.

[0065] Comparative Example 7: The rest is the same as in Example 1, except that:

[0066] The CeO 2 nanoparticles were replaced with La 2 O 3 nanoparticles.

[0067] Comparative Example 8: The rest is the same as in Example 1, except that:

[0068] The CeO 2 nanoparticles were replaced with Sm 2 O 3 nanoparticles.

[0069] Comparative Example 8: The rest is the same as in Example 1, except that:

[0070] CeO 2 nanoparticles were not added.

[0071] The steel pipe samples prepared in Examples 1-4 and Comparative Examples 1-8 were respectively subjected to salt spray test and electrochemical corrosion test. The salt spray test used a 7% sodium chloride brine solution, and the pH value of the solution was adjusted to the neutral range (6.5 - 7.2) as the spraying solution. The test temperature was 35 °C, and the salt spray deposition rate was 2.5 mL / 80 cm 2 ·h. Whether rust appeared on the surface of the steel pipe was observed every 40 h, and the results were as follows:

[0072] Table 1 Test results of the corrosion resistance of different steel pipe samples

[0073]

[0074] In the results of Table 1, the Cl - corrosion resistance of the steel pipe samples in Comparative Examples 1-9 was significantly lower than that of Example 1. Among them, Comparative Examples 1-6 showed that the CeCrO 3 / Cr 2 O 3 composite oxide layer prepared by the synergistic effect of electrochemical replacement and chemical oxidation depends on a specific mixed acid system. Using common inorganic acids that promote oxidation alone or in combination cannot effectively help Ce replace and bind Cr in the stainless steel material, and a Ce-doped chromium-based oxide layer cannot be formed, resulting in no significant improvement in the corrosion resistance of the chromium-based oxide layer. Only the mixed acid system composed of nitric acid and hydrofluoric acid can effectively help Ce electrochemically replace and bind Cr to obtain a composite oxide layer with excellent corrosion resistance. Comparative Examples 7-8 showed that the composite oxide layers formed by the electro-displacement and binding of rare earth elements such as La and Sm with Cr do not have good corrosion resistance and do not improve the corrosion resistance of the chromium-based oxide layer compared to Comparative Example 9.

Claims

1. A corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe, characterized in that: A composite oxide layer containing CeCrO3 and Cr2O3 is formed on the surface of the stainless steel pipe, and the wall thickness h1 of the stainless steel pipe and the thickness h2 of the composite oxide layer satisfy 0.002%≤h2 / h1≤0.025%.

2. The corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 1, characterized in that: h1 is 2-5mm, h2 is 100-500nm.

3. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 1 or 2, characterized in that: The steps include: (1) Pre-pickling a Cr-containing stainless steel pipe to obtain a steel pipe from which oxide scale has been removed; (2) immersing the descaled steel pipe in a pickling solution containing CeO2 nanoparticles, and continuously applying an electric current to the pickling solution; (3) The steel pipe is taken out from the pickling solution containing CeO2 nanoparticles, and is passivated with an inorganic acid to obtain a stainless steel pipe having a Ce-Cr composite oxide layer on the surface.

4. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (1), the mass fraction of Cr in the Cr-containing stainless steel tube is at least 15%.

5. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (1), the preparation method of the Cr-containing stainless steel tube is: S1. Heat the solid round steel made of 0Cr18Ni9 to 1050-1200℃ and keep it warm for 40-60min before punching it to form a pipe; S2. After grinding, the pipe is cold rolled, degreased and pickled, and then solution annealed and straightened to obtain a Cr-containing stainless steel pipe.

6. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (1), the pre-pickling method is: immersing the Cr-containing stainless steel pipe in a pre-pickling solution at 40-60° C. for 10-30 minutes to remove the oxide scale on the surface, and the ratio of the pre-pickling solution is 20 vol% nitric acid, 5 vol% hydrofluoric acid, and 75 vol% water.

7. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (2), the pickling solution containing CeO2 nanoparticles comprises the following components: 10-20wt% nitric acid, 3-8wt% hydrofluoric acid, 1-3wt% CeO2 nanoparticles, 0.5-1wt% dispersant, and the balance is water.

8. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 7, characterized in that: The temperature of the pickling solution containing CeO2 nanoparticles is 40-60°C, the dispersant is polyethylene glycol, and the particle size of the CeO2 nanoparticles does not exceed 100nm.

9. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (2), the current density is 5-10 mA / cm 2 , duration is 5-15min.

10. The method for preparing the corrosion-resistant Ce-Cr composite oxide layer stainless steel pipe according to claim 3, characterized in that: In step (3), the inorganic acid passivation method is: immersing the steel pipe in a nitric acid aqueous solution with a volume fraction of 4-6% at 40-60° C. for passivation treatment for 20-40 minutes.

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