Corrosion-resistant environment-friendly phosphating solution for phosphating oil casing coupling as well as preparation and use methods thereof

Abstract

The invention belongs to the technical field of metal material surface treatment, and particularly relates to a corrosion-resistant environment-friendly phosphating solution for phosphating an oil casing coupling as well as a preparation method and a use method of the corrosion-resistant environment-friendly phosphating solution. The invention relates to a corrosion-resistant environment-friendly phosphating solution for phosphating an oil casing coupling, which is prepared from the following components in parts by weight: 700 to 900 parts of water, 130 to 150 parts of phosphoric acid, 200 to 300 parts of zinc oxide, 125 to 150 parts of nitric acid, 15 to 25 parts of a composite accelerator containing metallic nickel, 0.2 to 0.6 part of an activating agent and 0.1 to 0.7 part of a buffer solution. The citric acid-sodium citrate buffer solution is added into the oil casing coupling phosphating solution, and the phosphating solution can well maintain the stability of free acidity in the solution during phosphating, so that a formed phosphating film is moderate in thick grain fineness and uniform in film formation, a surface conditioning procedure is replaced, the production cost is saved, and the production efficiency is improved. In addition, residues generated in the phosphorization process can be better avoided, and the requirement for green and sustainable industrial production is met.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material surface treatment, and particularly relates to a corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings and a preparation and use method thereof. Background Art

[0002] At the oil field site, the oil casing is usually connected into a pipe string in the form of a coupling for use in the well. The quality of the coupling phosphate coating directly affects the number of times the oil casing is broken out and its performance. A phosphate coating with good corrosion resistance can significantly improve the corrosion resistance of the entire oil casing coupling, but a phosphate coating with poor corrosion resistance will cause it to fail prematurely.

[0003] The requirements for the corrosion resistance of oil casing couplings are increasing day by day, and people are committed to optimizing and improving the composition ratio of phosphating solution, such as adding nitrate and molybdate auxiliary accelerators to the phosphating solution, in order to further improve the corrosion resistance of the phosphating film. However, these auxiliary accelerators will cause environmental pollution. With the increasing environmental protection requirements, it is imperative to reduce the pollution of phosphating solution.

[0004] Patent 20101026821.0, applied for on August 26, 2010, involves a surface treatment technology for preventing oil casing from sticking. It adopts a manual immersion phosphating process, and the implementation process is: pre-degreasing, degreasing, water washing, distillation washing, pickling, water washing, distilled water washing, surface conditioning, phosphating, water washing, distilled water washing, and rust prevention. Although the number of oil casings damaged by thread wear and sticking during use is greatly reduced, it does not involve environmental issues caused by waste phosphating liquid. Patent 202010664038.4, applied for on July 10, 2020, involves a phosphating liquid and a phosphating process for improving the quality of finished products using it. It adopts a primary phosphating treatment and a secondary surface conditioning treatment to improve the process quality of the phosphating film and improve the yield rate. However, the effect of the stability of the free acidity (PH) in the phosphating liquid on the quality of the phosphating film is not qualitatively considered, and the secondary surface conditioning is relatively cumbersome for industrial production and has high labor costs. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a corrosion-resistant and environmentally friendly phosphating solution for phosphating oil casing couplings and a preparation and use method thereof. By adding citric acid-sodium citrate buffer to the phosphating solution for oil casing couplings, the corrosion resistance of the phosphating film of the oil casing couplings is improved, and at the same time, the pollution of the phosphating solution to the environment will not be aggravated.

[0006] The technical solution of the present invention is: a corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings, which is made of the following components by weight: 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution.

[0007] The pH value of the buffer solution is in the range of 3 to 8; the specific components of the buffer solution are water and any two of disodium hydrogen phosphate, citric acid, sodium citrate, and citric acid.

[0008] The activator is any one of plant-type methyl silicone oil, S-polydimethylsiloxane, lauric acid ester, and polyethylene glycol octylphenyl ether.

[0009] The free acidity in the phosphating solution ranges from 2.0 to 6.0.

[0010] The composite accelerator containing metallic nickel is any one of zinc nitrate, succinic acid and mercaptoacetic acid containing metallic nickel.

[0011] A method for preparing the above-mentioned corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings comprises the following steps: S1: By weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution; S2: Heat and stir the phosphating solution in S1, the heating temperature range is 80~95℃, the heating time is 20~30min, and the free acidity in the phosphating solution is controlled in the range of 2.0~6.0 during the stirring process.

[0012] A method for using the above-mentioned corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings is characterized by comprising the following steps: S11: Remove rust and oil stains on the surface of the coupling of the oil casing to be phosphated; S22: by weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metal nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution, and after heating and stirring, the oil casing coupling treated in step S1 is directly placed in the phosphating tank for phosphating treatment. The temperature range of the phosphating solution during the phosphating treatment is 80-95° C., and the total acidity range of the phosphating solution is 50-58 points; S33: Put the phosphating treated oil casing coupling into a cleaning tank, a hot water tank, and an anti-rust tank in turn for cleaning, and then dry the phosphating coupling to obtain the finished product for storage.

[0013] In step S11, rust and oil stains on the surface of the oil casing coupling are removed. The specific process is: the oil casing coupling is sequentially subjected to pre-degreasing, degreasing, hot water washing, water washing, pickling, neutralization, and cleaning treatments.

[0014] The steel grade of the oil casing coupling is ≤140ksi.

[0015] The thickness of the phosphating film on the surface of the oil casing coupling after the phosphating treatment in step S22 is 20-30 μm.

[0016] The technical effects of the present invention are as follows: 1. Compared with the existing phosphating solution, the strength of the free acidity is mainly determined by the concentration of H+ hydrolyzed by dihydrogen phosphate, and the free acidity determines the stability of the film quality of the phosphating film, and in the phosphating reaction, water is needed to timely adjust the acidity of the phosphating solution to keep it within an appropriate range, the procedure is complicated and the stability is poor. The present invention adds citric acid-sodium citrate buffer to the phosphating solution of the oil casing coupling. During phosphating, the phosphating solution can better maintain the stability of the free acidity in the solution, so that the formed phosphating film has moderate thickness and grain fineness, uniform film formation, and can replace 1. It replaces the surface adjustment process, saves production costs, and can better avoid the residues generated in the phosphating process, which meets the needs of green and sustainable industrial production; 2. The present invention can stably control the complexing ability of the citric acid-sodium citrate buffer added to the phosphating solution, which plays a role in refining the phosphate grains. Citric acid is an organic compound, which is easy to complex with metals to form a dense organic protective film, which can inhibit metal corrosion, further improve the corrosion resistance of the phosphating film, meet the actual corrosion protection needs of the oil casing at the oil field site, and will not aggravate the pollution of the phosphating solution to the environment.

[0017] The following is a further description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a phosphating microstructure diagram of an oil casing coupling according to an embodiment of the present invention.

[0019] Figure 2 This is a cross-sectional microstructure diagram of the phosphate film of the present invention.

[0020] Figure 3 This is a diagram of the thickness of the phosphating film of the embodiment of the present invention.

[0021] Figure 4 It is a phosphating make-up curve diagram of the oil casing coupling according to the embodiment of the present invention.

[0022] Figure 5 It is a phosphating make-up curve diagram of the existing oil casing coupling according to the embodiment of the present invention. Implementation

[0023] Example 1 A corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings is prepared from the following components by weight: 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution.

[0024] The pH value of the buffer solution is in the range of 3 to 8; the specific components of the buffer solution are water and any two of disodium hydrogen phosphate, citric acid, sodium citrate, and citric acid.

[0025] The activator is any one of plant-type methyl silicone oil, S-polydimethylsiloxane, lauric acid ester, and polyethylene glycol octylphenyl ether.

[0026] The free acidity in the phosphating solution ranges from 2.0 to 6.0.

[0027] The composite accelerator containing metallic nickel is any one of zinc nitrate, succinic acid and mercaptoacetic acid containing metallic nickel.

[0028] Compared with the existing phosphating solution, the strength of the free acidity is mainly determined by the concentration of H+ hydrolyzed by dihydrogen phosphate, and the free acidity determines the stability of the film quality of the phosphating film. In addition, water is needed to timely adjust the acidity of the phosphating solution during the phosphating reaction to keep it within an appropriate range, which has a complex procedure and poor stability. The present invention adds citric acid-sodium citrate buffer to the phosphating solution for the oil casing coupling. During the phosphating process, the phosphating solution can better maintain the stability of the free acidity in the solution, so that the formed phosphating film has moderate thickness and grain fineness, and the film is uniform, and the surface adjustment process is replaced. , saving production costs, and better avoiding the residues generated in the phosphating process, meeting the needs of green and sustainable industrial production; the present invention can stably control the complexing ability of the citric acid-sodium citrate buffer added to the phosphating solution, thereby playing a role in refining phosphate grains; citric acid is an organic compound, which is easy to complex with metals to form a dense organic protective film, which can inhibit metal corrosion, further improve the corrosion resistance of the phosphating film, meet the actual corrosion protection needs of oil casing at the oil field site, and will not aggravate the pollution of the phosphating solution to the environment.

[0029] A method for preparing the above-mentioned corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings comprises the following steps: S1: By weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution; S2: Heat and stir the phosphating solution in S1, the heating temperature range is 80~95℃, the heating time is 20~30min, and the free acidity in the phosphating solution is controlled in the range of 2.0~6.0 during the stirring process.

[0030] A method for using the above-mentioned corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings is characterized by comprising the following steps: S11: Remove rust and oil stains on the surface of the coupling of the oil casing to be phosphated; S22: by weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metal nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution, and after heating and stirring, the oil casing coupling treated in step S1 is directly placed in the phosphating tank for phosphating treatment. The temperature range of the phosphating solution during the phosphating treatment is 80-95° C., and the total acidity range of the phosphating solution is 50-58 points; S33: Put the phosphating treated oil casing coupling into a cleaning tank, a hot water tank, and an anti-rust tank in turn for cleaning, and then dry the phosphating coupling to obtain the finished product for storage.

[0031] In step S11, rust and oil stains on the surface of the oil casing coupling are removed. The specific process is: the oil casing coupling is sequentially subjected to pre-degreasing, degreasing, hot water washing, water washing, pickling, neutralization, and cleaning treatments.

[0032] The steel grade of the oil casing coupling is ≤140ksi.

[0033] The thickness of the phosphating film on the surface of the oil casing coupling after the phosphating treatment in step S22 is 20-30 μm. Example

[0034] Taking P110 steel grade Φ139.7mm×9.17mm special threaded casing as an example, the corrosion-resistant and environmentally friendly phosphating liquid for phosphating the oil casing coupling as in Example 1 and its preparation and use method are used, and the specific process is as follows: Step 1: pre-treat the processed P110 steel grade casing coupling before phosphating, perform pre-degreasing, degreasing, hot water washing, water washing, pickling, neutralization, and cleaning treatments to remove rust and oil stains on the surface of the coupling; Step 2: Mix 18 parts of citric acid and 2 parts of sodium citrate by weight, and then stir continuously for 10 minutes to fully dissolve to obtain a citric acid-sodium citrate buffer solution for standby use, heat the buffer solution to 90° C., and then add 700 parts of water, 130 parts of phosphoric acid, 200 parts of zinc oxide, 125 parts of nitric acid, 15 parts of a composite accelerator containing metallic nickel, and 0.2 parts of S-polydimethylsiloxane to fully dissolve to form a phosphating solution; Step 3: Place the pre-treated oil casing coupling directly into the phosphating tank for phosphating treatment for 10 to 15 minutes. Place the phosphated oil casing coupling in the cleaning tank, hot water tank, and anti-rust tank in turn for cleaning, and then dry the phosphated coupling to obtain the finished product for storage.

[0035] The performance of the coupling after phosphating was tested, and the thickness was measured by CM8829 coating thickness gauge. According to QB / T3284 standard, the copper sulfate detection solution was used to evaluate the corrosion resistance of the phosphating coupling, as shown in Table 1. The microstructure of the phosphating sample was observed by scanning electron microscope, as shown in Table 1. Figure 1~Figure 3 As shown in the figure, the phosphate grains are small and the phosphate film is dense. The Φ139.7mm×9.17mm special threaded casing was tested for make-up and make-down. Figure 4 , Figure 5 As shown, after three times of putting on and two times of unloading the casing, the existing phosphating anaerobic adhesive is powdered and falls off, and the phosphating film is not affected. However, after repeated putting on and unloading, the phosphating film gradually falls off. After the phosphating of the present invention, its anti-sticking ability and the putting on curve are significantly enhanced and no signs of falling off appear.

[0036] Table 1 Phosphate coating performance test Phosphate coating type Phosphating solution of the present invention Existing phosphating solution Film thickness / μm 15.3 10.8 Corrosion resistance / s ＞180 160 Example

[0037] Taking 125V steel grade Φ139.7mm×12.7mm special threaded casing as an example, the corrosion-resistant and environmentally friendly phosphating liquid for phosphating the oil casing coupling as in Example 1 and its preparation and use method are used, and the specific process is as follows: Step 1: pre-treat the processed 125V steel grade casing coupling before phosphating, perform pre-degreasing, degreasing, hot water washing, water washing, pickling, neutralization, and cleaning treatments to remove rust and oil stains on the surface of the coupling; Step 2: Mix 16 parts of disodium hydrogen phosphate and 4 parts of sodium citrate, and then stir continuously for 15 minutes to fully dissolve to obtain a citric acid-sodium citrate buffer for standby use, heat the buffer solution to 90° C., and then add 800 parts of water, 150 parts of phosphoric acid, 210 parts of zinc oxide, 150 parts of nitric acid, 12 parts of a composite accelerator containing metallic nickel, and 0.2 parts of methyl silicone oil to fully dissolve to form a phosphating solution; Step 3: Place the pre-treated oil casing coupling directly into the phosphating tank for phosphating treatment for 10 to 15 minutes. Place the phosphated oil casing coupling in the cleaning tank, hot water tank, and anti-rust tank in turn for cleaning, and then dry the phosphated coupling to obtain the finished product for storage.

[0038] The performance of the coupling after phosphating was tested, and the thickness was measured by using a CM8829 coating thickness gauge. According to the QB / T3284 standard, the copper sulfate detection solution was used to evaluate the corrosion resistance of the phosphating coupling, as shown in Table 2. The microstructure of the phosphating sample was observed by a scanning electron microscope, and the phosphate grains were fine and the phosphating film was relatively dense. The Φ139.7mm×12.7mm special threaded casing was subjected to a make-up and make-up test. After three make-ups and two make-ups of the casing, the existing phosphating anaerobic rubber powdered and fell off, and the phosphating film was not affected. However, after repeated make-ups and make-ups, the phosphating film gradually fell off. After the phosphating of the present invention, its anti-sticking ability and make-up curve were significantly enhanced and no signs of falling off appeared.

[0039] Table 2 Phosphate coating performance test Phosphate coating type Phosphating solution of the present invention Existing phosphating solution Film thickness / μm 12.4 9.65 Corrosion resistance / s ＞165 140 The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A corrosion-resistant and environmentally friendly phosphating liquid for phosphating oil casing couplings, characterized in that: The phosphating solution is made of the following components by weight: 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution.

2. According to claim 1, a corrosion-resistant and environmentally friendly phosphating liquid for phosphating oil casing couplings, characterized in that: The pH value of the buffer solution is in the range of 3 to 8; the specific components of the buffer solution are water and any two of disodium hydrogen phosphate, citric acid, sodium citrate, and citric acid.

3. According to claim 1, a corrosion-resistant and environmentally friendly phosphating liquid for phosphating oil casing couplings, characterized in that: The activator is any one of plant-type methyl silicone oil, S-polydimethylsiloxane, lauric acid ester, and polyethylene glycol octylphenyl ether.

4. According to claim 1, a corrosion-resistant and environmentally friendly phosphating liquid for phosphating oil casing couplings, characterized in that: The free acidity in the phosphating solution ranges from 2.0 to 6.

0.

5. According to claim 1, a corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings, characterized in that: The composite accelerator containing metallic nickel is any one of zinc nitrate, succinic acid and mercaptoacetic acid containing metallic nickel.

6. A method for preparing the corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings as claimed in claim 1, characterized in that: The following steps are involved: S1: By weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metallic nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution; S2: Heat and stir the phosphating solution in S1, the heating temperature range is 80~95℃, the heating time is 20~30min, and the free acidity in the phosphating solution is controlled in the range of 2.0~6.0 during the stirring process.

7. A method for using the corrosion-resistant and environment-friendly phosphating solution for phosphating oil casing couplings as claimed in claim 1, characterized in that: The following steps are involved: S11: Remove rust and oil stains on the surface of the coupling of the oil casing to be phosphated; S22: by weight, 700-900 parts of water, 130-150 parts of phosphoric acid, 200-300 parts of zinc oxide, 125-150 parts of nitric acid, 15-25 parts of a composite accelerator containing metal nickel, 0.2-0.6 parts of an activator, and 0.1-0.7 parts of a buffer solution are mixed in a phosphating tank to form a phosphating solution, and after heating and stirring, the oil casing coupling treated in step S1 is directly placed in the phosphating tank for phosphating treatment. The temperature range of the phosphating solution during the phosphating treatment is 80-95° C., and the total acidity range of the phosphating solution is 50-58 points; S33: Put the phosphating treated oil casing coupling into a cleaning tank, a hot water tank, and an anti-rust tank in turn for cleaning, and then dry the phosphating coupling to obtain the finished product for storage.

8. The method for using the corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings according to claim 7, characterized in that: In step S11, rust and oil stains on the surface of the oil casing coupling are removed. The specific process is: the oil casing coupling is sequentially subjected to pre-degreasing, degreasing, hot water washing, water washing, pickling, neutralization, and cleaning treatments.

9. The method for using the corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings according to claim 7, characterized in that: The steel grade of the oil casing coupling is ≤140ksi.

10. The method for using the corrosion-resistant and environment-friendly phosphating liquid for phosphating oil casing couplings according to claim 7, characterized in that: The thickness of the phosphating film on the surface of the oil casing coupling after the phosphating treatment in step S22 is 20-30 μm.

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