Process for forming an anodized film on the inner surface of an aluminum tube

Abstract

The application discloses an aluminum pipe inner cavity anti-etching and anti-biofilm anodic oxidation film process and belongs to the anodic oxidation film process field. In the application, Si is selectively dissolved in the pipe inner cavity by electrochemical jet flow, and a film hole structure is generated in situ. Gradient pulse anodic oxidation is carried out to introduce nano fluorinated graphene to reduce the pore size. Finally, nano silver and PTFE fluorosilane composite emulsion are filled into the film hole structure and solidified by a negative pressure-ultrasonic-positive pressure three-stage method to form a fluorine-silicon crosslinking network. The aluminum pipe inner cavity film layer has high film base bonding force, and the process is chromium-free and nickel-free. The anti-etching and anti-biofilm performance is good, and the application is suitable for harsh working conditions such as marine heat exchange and medical high-temperature sterilization.

Description

Technical Field

[0001] This invention discloses an anodizing film process, and more particularly relates to an anodizing film process for an anti-corrosion and anti-biofilm formation in the inner cavity of an aluminum tube. Background Technology

[0002] Existing technologies for anodizing the outer surface of aluminum tubes have the following drawbacks regarding the inner cavity:

[0003] The high-silicon second phase (Si≥10%) and the stagnant liquid inside the aluminum tube generate high temperatures, leading to large pores in the oxide film. High-temperature concentration damages the oxide film structure, causing salt spray corrosion to extend along the Si / Al interface. Biofilms (mainly Pseudomonas and sulfate-reducing bacteria) preferentially colonize within the membrane pores, resulting in film cracking after 120℃ steam sterilization. Uneven electric field distribution within the cavity makes it prone to burn-out at the top and bottom with traditional DC power supplies, resulting in film thickness variations of <8μm. Conventional sealing methods using Ni-F and zeolite are insufficient to reduce surface energy, leading to bacterial contact angles <70° and poor adhesion resistance. Therefore, an anodizing process is urgently needed to simultaneously address the three major contradictions: efficient cooling of the aluminum tube cavity and consistent controllable tank temperature, high-silicon-induced defects, uniform film formation within the cavity, and controllable oxidation production temperature with resistance to biofilm formation. Summary of the Invention

[0004] The purpose of this invention is to provide an anodizing film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an anodizing film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity, comprising pretreatment of the substrate, followed by processing of the pretreated substrate, including the following steps:

[0006] S1, internal cavity electrochemical treatment, employs anodized components, with an anode connection to an aluminum tube, powered by a DC pulse power supply with a 40% duty cycle, a frequency of 100Hz, and a current density of 0.8Adm. -2 ;

[0007] Electrolyte formulation: 3 g / L CuCl2, 0.5 mol / L HCl, 0.1 g / L surfactant FC-4430, temperature 25℃;

[0008] S2, gradient pulse anodizing, with an alloy conductive cathode and a fixed aluminum tube anode;

[0009] Electrolyte formulation: 140 g / L sulfuric acid, 25 g / L tartaric acid, and 4 g / L aluminum sulfate; composite additives: 6 g / L oxalic acid, 10 g / L sulfosalicylic acid, 0.7 g / L cerium sulfate, 0.2 g / L nano-fluorinated graphene, and 10 g / L nano-silver.

[0010] The power supply waveform uses a trapezoidal pulse with a rising edge of 858.36ms, a falling edge of 858.36ms, a duty cycle of 50%, and a frequency of 50Hz.

[0011] S3, membrane pore structure sealing, the lumen is filled with -0.09MPa negative pressure and soaked in sealing liquid for 5min, followed by 40kHz ultrasonic vibration for 10min, and 0.5MPa positive pressure pulse 3 times, each pulse for 30s;

[0012] Sealing solution formulation: 36 g / L PTFE emulsion with a particle size of 200 nm, 2 g / L perfluorodecyltriethoxysilane PFDS, 1 g / L silane coupling agent KH-560, temperature 90℃;

[0013] The suspended aluminum tubes were cured in a vertical tube oven at 380℃, with protection provided by nitrogen.

[0014] Preferably, the substrate pretreatment includes ultrasonic alkaline washing to saponify the rolling oil, high-pressure rinsing of the inner cavity with deionized water, acid neutralization to remove alkaline film and metal impurities, and drying.

[0015] Preferably, in step S2, the nano-fluorinated graphene has a sheet diameter of 200-500 nm and a thickness of 1-3 layers.

[0016] Preferably, in step S2, the current density is applied in a stepped manner: 2.0 Adm for 0-5 min. -2 ; 5-10 min using 2.6 Adm -2 ; 10-30 min using 3.2 Adm -2 ; 30-35 min using 2.8 Adm -2 .

[0017] Preferably, the anodizing process components include:

[0018] Alloy conductive wire, used as a cathode for conducting electricity;

[0019] A ring structure is fitted on the outside of the alloy conductive wire, and multiple acid and alkali resistant insulating impellers are provided.

[0020] The electrolyte is driven to rise by aeration gas. As the electrolyte flows with the aeration gas, it can drive the acid and alkali resistant insulated impeller to rotate, pushing the aeration gas to continue flowing in the inner cavity of the aluminum tube.

[0021] The aeration system is connected to the inner cavity of the aluminum pipe through the outlet of the aeration pump.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] In the inner cavity of the tube, Si is selectively dissolved by electrochemical jet to generate a membrane pore structure in situ; then, nano-fluorinated graphene is introduced by gradient pulse anodic oxidation to reduce the pore size; finally, a three-stage method of negative pressure-ultrasound-positive pressure is used to inject nano-silver PTFE fluorosilane composite emulsion into the membrane pore structure and solidify it to form a fluorine-silicon cross-linked network.

[0024] The resulting aluminum tube inner cavity membrane layer has high bonding strength, the process is chromium-free and nickel-free, and it has good corrosion resistance and biofilm resistance, making it suitable for harsh working conditions such as marine heat exchange and medical high-temperature sterilization.

[0025] When using only aeration gas to drive the acid- and alkali-resistant insulated impeller, the problem of easy backflow obstruction and stagnation of electrolyte in the inner cavity of aluminum tube, which affects the formation and adhesion of oxide film, is solved. To address this, the electrolyte is used to drive the rotation of the acid- and alkali-resistant insulated impeller as it flows with the airflow. The aeration gas drives the acid- and alkali-resistant insulated impeller, which in turn promotes the formation of a continuous circulation of liquid in the inner cavity of the aluminum tube. This ensures that the temperature of the electrolyte in the inner cavity is consistent with the temperature of the bath solution, ultimately resulting in the formation of a uniform and dense oxide film. Attached Figure Description

[0026] Figure 1 Charts showing data from salt spray corrosion resistance experiments;

[0027] Figure 2 Charts showing experimental data on anti-biofilm activity;

[0028] Figure 3 Charts showing experimental data on film thickness and adhesion;

[0029] Figure 4 To create charts for experimental data;

[0030] Figure 5 SEM images of the surface morphology of the aluminum tube before and after filling the inner cavity with PTFE;

[0031] Figure 6 This is a simplified structural diagram of the anodizing process components;

[0032] Figure 7 This is a simplified structural diagram of a ring-shaped structure. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. In this description, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] An anodizing film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity involves pretreatment of the substrate, which includes ultrasonic alkaline washing and saponification of rolling oil, high-pressure rinsing of the inner cavity with deionized water, acid neutralization to remove alkaline film and metal impurities, and drying. The specific steps are as follows:

[0035] Insert titanium alloy conductive pins into the 5mm area at both ends of the aluminum tube, and cover with a PEEK sheath to ensure that only the tube opening contacts the metal of the clamp, thus avoiding the shielding of the electric field in the inner cavity. At 60°C, use a solution of 25g / L Na2CO3, 25g / L Na3PO4, and 0.5g / L anionic surfactant to perform an ultrasonic alkaline wash at 40kHz for 180s, maintaining the pH at 11.5±0.2. Saponify the rolling oil until all bubbles in the inner cavity are completely precipitated. Rinse the inner cavity with 0.4MPa deionized water for 60s to remove surface debris. Soak in 10vol% HNO3 thiourea corrosion inhibitor for 30s for acid neutralization. Dry with hot air at 110°C for 180s, and maintain the tube wall at ≥80°C for 60s for rapid dehydration to avoid watermarks and corrosion spots.

[0036] The pretreated substrate is then processed, including the following steps:

[0037] S1, internal cavity electrochemical treatment, powered by DC pulse, duty cycle 40%, frequency 100Hz, current density 0.8Adm -2 ;

[0038] like Figure 6 and Figure 7 As shown, the anodizing process components include:

[0039] The anodizing process components include:

[0040] Alloy conductive wires are used as cathode conductors. Alloy conductive wires can be made of carbon, lead / titanium alloys, or aluminum alloys.

[0041] A ring structure is fitted onto the outside of the alloy cable, and multiple acid and alkali resistant insulating impellers are installed.

[0042] The electrolyte is driven upward by aeration gas. As the electrolyte flows with the aeration gas, it drives the rotation of an acid- and alkali-resistant insulated impeller, propelling the aeration gas to continue flowing within the aluminum tube. However, using only aeration gas to drive the impeller can lead to problems such as obstructed backflow and stagnant temperature rise in the electrolyte within the tube, which negatively impacts oxide film formation and adhesion. Therefore, this method utilizes the electrolyte's movement with the airflow to rotate the acid- and alkali-resistant insulated impeller. The aeration gas then drives the impeller, creating a continuous circulation of liquid within the aluminum tube. This ensures that the electrolyte temperature within the tube matches the bath temperature, ultimately resulting in a uniformly adhered and dense oxide film.

[0043] The aeration system is connected to the inner cavity of the aluminum pipe through the outlet of the aeration pump.

[0044] like Figure 7 As shown, during use, the flexible movable shaft is inserted into the aluminum tube to be anodized, and the inner cavity of the tube is pre-positioned by the annular ring structure; the aeration pump injects gas N2 into the inner cavity of the aluminum tube, and the electrolyte flows from bottom to top to fill the inner cavity of the aluminum tube. For irregular parts such as bent tubes, it can ensure complete coverage of electrolyte, and the annular ring structure can prevent the flexible movable shaft from directly contacting the inner cavity surface and causing a short circuit. The flexible movable shaft can be adapted to the inner cavity of various irregular parts. The anode uses wires and clamps to fix the aluminum tube and energize the aluminum tube.

[0045] Electrolyte formulation: 3 g / L CuCl2, 0.5 mol / L HCl, 0.1 g / L surfactant FC-4430, temperature 25℃;

[0046] A membrane pore structure is formed on the inner cavity surface through oxidation-reduction, providing a three-dimensional framework for subsequent fluorine storage, buffering, and wear reduction. Si has a higher work function than Al, and the local potential difference is approximately 0.15V. Cu 2+ +e - →Cu 0 Preferential reduction occurs on the surface of Si particles; Cu 0 H forms a micro galvanic cell with Si. + The process involves reduction on the Cu surface, H atoms penetrating into the Si / Al interface, and Si particles fragmenting and falling off. The jet shearing immediately removes the detached Si fragments, leaving behind inverted cone-shaped pits with a diameter of 80µm, a depth of 60µm, and a distance of 150µm between the pit shoulders. Microscopically, the pit walls exhibit high-index crystal planes {210} / {311}, increasing the surface energy γ, which becomes the preferred nucleation site for the α-Al2O3 barrier layer during S2 anodizing.

[0047] S2, gradient pulse anodizing, with an alloy cable as the cathode and an aluminum tube as the anode;

[0048] Electrolyte formulation: 140 g / L sulfuric acid, 25 g / L tartaric acid, and 4 g / L aluminum sulfate; composite additives: 6 g / L oxalic acid, 10 g / L sulfosalicylic acid, 0.7 g / L cerium sulfate, 0.2 g / L nano-fluorinated graphene, and 10 g / L nano-silver.

[0049] The power supply waveform uses a trapezoidal pulse with a rising edge of 858.36ms, a falling edge of 858.36ms, a duty cycle of 50%, and a frequency of 50Hz.

[0050] In step S2, the nano-fluorinated graphene has a sheet diameter of 300 nm and a thickness of 3 layers. The current density is applied in a stepped manner: 2.0 Adm for 0-5 min. -2 ; 5-10 min using 2.6 Adm -2 ; 10-30 min using 3.2 Adm -2 ; 30-35 min using 2.8 Adm -2 Different thicknesses but equally dense α-Al₂O₃ barrier layers and nanoporous membrane structures were grown at the shoulder, wall, and bottom of the membrane pore structure, respectively, forming a gradient membrane. The radius of curvature at the pore shoulder was the smallest, and the electric field strength E≈1.2×10⁻⁶. 9 V / m, the first breakdown, the bottom of the hole E≈0.7×109V / m, breakdown hysteresis, within 858ms of the trapezoidal wave zero current plateau, the electrolyte is forcibly replaced 2.5 times by the high-speed jet, carrying away 60% of the Joule heat, inhibiting ablation cracks, the barrier layer α-Al2O3 lattice constant 4.76Å, mismatch with the {111} plane of the substrate 1.8%, the lowest interfacial energy, preferential vertical epitaxial growth; the edge bands of the nano-fluorinated graphene F-Gn sheets in the membrane pore structure layer have -F and -COOH, which are electrostatically adsorbed on the pore wall under a positive bias of 1.2V, blocking the chemical dissolution of Al2O3 by H2SO4, reducing the pore size of the membrane pore structure and increasing the density; fluorine-doped F - Replace O 2- It forms an Al-OF bond with a bond energy of 674 kJ / mol, which is greater than the 512 kJ / mol of Al-O, thus improving thermal stability at 130℃.

[0051] S3, membrane pore structure sealing, the cavity is filled with sealing fluid under negative pressure of -0.09MPa for 5min, followed by ultrasonic vibration at 40kHz for 10min, and 3 pulses of positive pressure of 0.5MPa for 30s each;

[0052] Sealing solution formulation: 36 g / L PTFE emulsion with a particle size of 200 nm, 2 g / L perfluorodecyltriethoxysilane PFDS, 1 g / L silane coupling agent KH-560, temperature 90℃;

[0053] The suspended aluminum tubes were cured using a vertical tube oven at 380℃, with protection provided by nitrogen (N2).

[0054] The formed membrane pore structure is filled with PTFE and then sealed. Under negative pressure infusion, the residual gas inside the membrane pore structure expands, the bubbles burst and are extracted, increasing the vacuum level of the membrane pore structure. PTFE particles are then injected into the membrane pore structure using a 40kHz ultrasonic cavitation microjets. Figure 5 As shown, the surface morphology before and after PTFE filling was observed. After PTFE composite treatment, the surface morphology of the film layer became smooth and flat, and the surface smoothness was improved. Then, the PTFE particles were tightly packed by positive pressure pulse, and the relative density was increased.

[0055] The aluminum tube is vertically suspended inside the vertical tube oven, ensuring that the molten PTFE is leveled by gravity. The aluminum tube wall is heated rapidly in a non-contact manner by a medium-frequency induction coil wound around the outer wall of the furnace. Nitrogen gas is released uniformly from bottom to top through a nitrogen gas tube in the center of the tube to prevent the PTFE from oxidizing at high temperature and to remove the volatile PFDS hydrolysis byproducts ethanol and water in time.

[0056] Curing temperature rise curve: 25→200℃, with a temperature rise of 3℃ / min to remove residual moisture and low molecular weight alcohol;

[0057] 200→327℃, 2℃ / min, to allow PFDS to be completely hydrolyzed and condensed with Al-OH to form -Si-O-Al-covalent bonds;

[0058] 327→380℃, 1℃ / min, PTFE particles melt, melt viscosity drops to 10 2 Pa·s spreads and penetrates the membrane pore structure under the action of capillary and nitrogen gas flow;

[0059] Hold at 380℃ for 20 minutes, then begin cooling; the furnace chamber is ventilated to 10m³. 3 Nitrogen gas is circulated at a rate of 4℃ / min to reduce the temperature below 200℃, in order to prevent PTFE from crystallizing too quickly in the 325-315℃ range and producing large spherulites.

[0060] When PTFE melts, its melting point is 327°C. Its volume shrinkage is just compensated by the melt flow. At the same time, PFDS hydrolyzes to form a -Si-(CH2)8-CF3 hydrophobic film with a water contact angle of 125°.

[0061] The formation mechanism of the fluorine-silicon crosslinking network involves the hydrolysis of perfluorodecyltriethoxysilane in PFDS at 200-250℃ to generate C. 10 F 21 -C2H4-Si(OH)3:

[0062] Nitrogen gas carries away the ethanol;

[0063] C 10 F21 -C2H4-Si(OH)3 condenses with Al-OH on the α-Al2O3 surface:

[0064] and self-condensation:

[0065] ;

[0066] The PTFE molecular chain (-CF2-CF2-)n is anchored to the -OH group on the α-Al2O3 surface via hydrogen bonds, with a stripping energy of 0.8 Jm. -2 It is superior to traditional zeolite sealing.

[0067] The -CF3 end of PFDS is exposed on the outermost layer, with a surface energy γ=6mN / m and a bacterial adhesion free energy ΔG_adh>0, achieving thermodynamic repulsion against biofilm.

[0068] A controlled experiment was designed to verify the effects of membrane pore structure-membrane pore structure coupling and PTFE / PFDS composite sealing technology on corrosion resistance, biofilm resistance, and adhesion compared to traditional anodizing. The groups included the following:

[0069] Control group A: Traditional DC anodizing

[0070] Electrolyte: 160g / L H2SO4, no additives;

[0071] Power supply: DC2Adam -2 30 minutes;

[0072] Sealing: zeolite for 20 minutes;

[0073] Control group B: Traditional pulse anodizing;

[0074] Electrolyte: Same as A;

[0075] Power supply: 50Hz rectangular wave, 50% duty cycle, 3Adam -2 30 minutes;

[0076] Sealing: Ni-F, 25℃, 10min;

[0077] Experimental Group C: The process of this embodiment;

[0078] The test samples were 50cm sections of aluminum tubes obtained from each group of processes.

[0079] The experimental platform, equipment, and key parameter charts are as follows:

[0080] ;

[0081] Test method:

[0082] Salt spray corrosion resistance

[0083] Cycle: 2000h, every 48h take out clean water to rinse with salt, dry and weigh;

[0084] Specification: Corrosion weight loss ≤ 0.02 gm -2 Record the time of the first white rust formation;

[0085] Parallel samples: n=5, take the mean plus the standard deviation;

[0086] Anti-biofilm

[0087] Pretreatment: Sterilize at 121°C for 30 minutes three times to form an aged film;

[0088] Bacterial solution: P. aeruginosa 10 7 CFUm / L, 37°C for 24 hours of continuous soaking;

[0089] Staining: SYTO-9 live bacteria green, PI dead bacteria red, confocal microscope 10× objective lens;

[0090] Quantitative: ImageJ calculates the coverage area percentage; ≤3% is considered acceptable.

[0091] Parallel samples: n=3, average of 5 fields of view for each tube;

[0092] Film thickness

[0093] Eddy current method: 8 points axially spirally distributed per tube, with a range ≤2µm

[0094] CT scan: Membrane pore structure filling rate ≥95%, bubble rate ≤1%;

[0095] bonding force

[0096] Tensile test: 20mm glue column bonding, peeling at 1mm / min, record the maximum tensile force, tensile force ≥30MPa is qualified;

[0097] like Figure 4 The experimental data processing charts shown are presented. A one-way ANOVA was used with a significance level of α=0.05. The LSD-t test was used to compare the differences between groups and to give the mean, standard deviation, and p-value. The results showed that the experiment had a highly significant effect on salt spray corrosion resistance and biofilm resistance.

[0098] like Figure 1 As shown, group C exhibits significantly better corrosion resistance than groups A and B. Group C utilizes trapezoidal pulses and F-Gn to reduce the pore size of the membrane, and the α-Al₂O₃ dense layer in the pore shoulder region thickens, blocking corrosion channels. F... - Replace O 2- Al-OF bonds are formed, improving the thermodynamic stability of the barrier layer; the water contact angle is 112° after PTFE / PFDS sealing, and Cl... -Adsorption free energy ΔG>0, electrochemical impedance Rp increases;

[0099] like Figure 2 As shown, group C exhibits significantly better anti-biofilm performance than groups A and B. The membrane pore structure diameter of group C is 35 nm, which is smaller than the diameter of bacterial flagella. This microscopic morphology creates a repulsive effect, preventing bacteria from anchoring. The membrane pore structure is filled with PTFE, reducing surface roughness and decreasing the area available for colony implantation. The -(CH2)8-CF3 terminus reduces the Lifshitz-vanderWaals attraction, resulting in a positive thermodynamic repulsion between bacteria and the surface. The F / Si crosslinking network remains intact after steaming at 130°C, maintaining hydrophobicity.

[0100] like Figure 3 As shown, group C has better film thickness and bonding strength than groups A and B, and the Al-OF and Si-O-Al covalent bonds have higher thermal and chemical stability.

[0101] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0102] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An anodizing film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity, characterized in that: The substrate is pretreated before processing, and then the pretreated substrate is processed, including the following steps: S1, internal cavity electrochemical treatment, employs anodized components, with an anode connection to an aluminum tube, powered by a DC pulse power supply with a 40% duty cycle, a frequency of 100Hz, and a current density of 0.8Adm. -2 ; Electrolyte formulation: 3 g / L CuCl2, 0.5 mol / L HCl, 0.1 g / L surfactant FC-4430, temperature 25℃; S2, gradient pulse anodizing, with an alloy conductive wire as the cathode and an aluminum tube as the anode; Electrolyte formulation: 140 g / L sulfuric acid, 25 g / L tartaric acid, and 4 g / L aluminum sulfate; composite additives: 6 g / L oxalic acid, 10 g / L sulfosalicylic acid, 0.7 g / L cerium sulfate, 0.2 g / L nano-fluorinated graphene, and 10 g / L nano-silver. The power supply waveform uses a trapezoidal pulse with a rising edge of 858.36ms, a falling edge of 858.36ms, a duty cycle of 50%, and a frequency of 50Hz. S3, membrane pore structure sealing, the lumen is filled with -0.09MPa negative pressure and soaked in sealing liquid for 5min, followed by 40kHz ultrasonic vibration for 10min, and 0.5MPa positive pressure pulse 3 times, each pulse for 30s; Sealing solution formulation: 36 g / L PTFE emulsion with a particle size of 200 nm, 2 g / L perfluorodecyltriethoxysilane PFDS, 1 g / L silane coupling agent KH-560, temperature 90℃; The suspended aluminum tubes were cured in a vertical tube oven at 380℃, with protection provided by nitrogen.

2. The anodic oxidation film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity according to claim 1, characterized in that: The substrate pretreatment includes ultrasonic alkaline washing to saponify the rolling oil, high-pressure rinsing of the inner cavity with deionized water, acid neutralization to remove alkaline film and metal impurities, and drying.

3. The anodic oxidation film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity according to claim 2, characterized in that: In step S2, the nano-fluorinated graphene has a sheet diameter of 200-500 nm and a thickness of 1-3 layers.

4. The anodic oxidation film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity according to claim 3, characterized in that: In step S2, the current density is applied in a stepped manner: 2.0 Adm for 0-5 min. -2 ; 5-10 min using 2.6 Adm -2 ; 10-30 min using 3.2 Adm -2 ; 30-35 min using 2.8 Adm -2 .

5. The anodic oxidation film process for corrosion-resistant and biofilm-resistant aluminum tube inner cavity according to claim 4, characterized in that: The anodizing process components include: Alloy conductive wire, used as a cathode for conducting electricity; A ring structure is fitted on the outside of the alloy conductive wire, and multiple acid and alkali resistant insulating impellers are provided. The electrolyte is driven to rise by aeration gas. As the electrolyte flows with the aeration gas, it can drive the acid and alkali resistant insulated impeller to rotate, pushing the aeration gas to continue flowing in the inner cavity of the aluminum tube. The aeration system is connected to the inner cavity of the aluminum pipe through the outlet of the aeration pump.

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