CN107099247A - Composite silane film for metal surface and preparation method - Google Patents

Abstract

The invention discloses a composite silane film for metal surface, which comprises a silane layer of a double hydrolysis head group and a fluorine-containing silane layer of a monohydrolysis head group. The method of the invention can carry out anti-corrosion and anti-scaling, solves the problem that existing metals are prone to local corrosion and scaling in harsh working conditions such as seawater, sewage and chemical media, and has high compactness and superior anti-corrosion effect.

Description

Composite silane film for metal surface and preparation method thereof

technical field

The invention belongs to the field of chemical materials, in particular to a metal anti-corrosion and anti-fouling film, in particular to a preparation method for a composite silane self-assembled film used to resist seawater corrosion on the surface of stainless steel.

Background technique

With the development of modern industry, people put forward higher requirements for the anti-corrosion and anti-scale of metal surface. Among them, stainless steel with good corrosion resistance and plasticity is widely used, such as pipelines, sea water pumps, valves, fasteners, propellers, instrument housings, etc. The reason why stainless steel has good corrosion resistance is that the Cr and Ni passivation films on its surface have self-healing properties. However, under harsh conditions, such as seawater, the self-healing performance of the surface passivation film is inhibited under long-term immersion, which will cause localized corrosion and easy scaling. Traditional stainless steel surface protection treatment technologies such as chromate treatment will cause health problems, and phosphate treatment will cause eutrophication of water bodies, which no longer meet the requirements of the state to protect the marine ecological environment.

Silane is a surface treatment agent that is environmentally friendly, has good film-forming properties, and excellent corrosion resistance, and is called an organic passivation film. The mechanism of action of silane is that silane is hydrolyzed to form silanol, which can self-assemble on the metal surface to form a film, and the formed film can effectively block the corrosion of the metal by the corrosive medium. At present, the silane film protection process has attracted more and more attention, and is gradually replacing the chromate and phosphate treatment processes. However, the single silane film has disadvantages such as poor compactness, so it is necessary to design and adjust the preparation process of the silane film to further improve the compactness and anti-corrosion performance of the silane film. Adhami et al [AdhamiS, Atapour M, Allafchian A R.Corrosion protection of copper by silane sol–gelcoatings[J].Journal of Sol-Gel Science and Technology,2015,74(3):800-809.] in 3.5% NaCl The corrosion protection of tetraethoxysilane (TEOS), 3-trimethoxysilyl-1-propanethiol (TPS) and TEOS+TPS silane films on copper was studied in solution. Compared with copper substrate and single TEOS and TPS coating, the mixed TEOS+TPS mixed silane film has increased thickness and the best corrosion resistance. Wait[ MP, Ramallo-López J M, Benítez G, et al. Optimization of the surface properties of nanostructured Ni-W alloys on steel by a mixed silane layer.[J].Physical Chemistry Chemical Physics,2015,17(21):14201-14207. ] A mixed film of tetraethoxysilane (TEOS) and octadecyltrichlorosilane (OTS) was prepared on the steel surface by two-step method of galvanostatic pulse electrodeposition. The hybrid silane film improves the hydrophobicity of the steel surface and enhances the anti-corrosion behavior of the surface. However, the performance and preparation methods of the existing composite membranes still need to be further improved and improved, in order to solve the problems that the existing metals are prone to localized corrosion and scaling in harsh working conditions such as seawater, sewage and chemical media.

Contents of the invention

The purpose of the present invention is to provide a composite silane film for metal surfaces and its preparation method, which can be used for anti-corrosion and anti-scaling, and solve the problem that existing metals are prone to localized corrosion and scaling in harsh working conditions such as seawater, sewage and chemical media. .

The concrete technical scheme that the present invention takes is as follows:

The invention provides a composite silane film for metal surface, comprising a silane layer of a double hydrolysis head group and a fluorine-containing silane layer of a monohydrolysis head group.

Further preferably, the film thickness of the composite silane film of the present invention is less than 200nm; there is no special requirement on the thickness of the silane layer of the double hydrolysis head group and the fluorine-containing silane layer of the monohydrolysis head group, preferably the silane layer of the double hydrolysis head group Or/and the thickness of the fluorine-containing silane layer of the monohydrolyzed head group is 80-120 nm, and the film thickness of the composite silane film is less than 200 nm.

The silane of the dihydrolyzed head group in the present invention means that both ends of the silane molecule contain hydrolyzable groups, such as chlorine, methoxy, ethoxy, methoxyethoxy, acetoxy, etc., preferably bis -One of [γ-(triethoxysilyl)propyl]-tetrasulfide, 1,2-bis(triethoxysilyl)ethane, tetraethoxysilane, tetramethoxysilane or several, within the preferred range, can make the composite silane film obtain better compactness.

The monohydrolyzed head group fluorosilane in the present invention means that one end of the silane molecule contains a hydrolyzable group, preferably tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyl One or more of trimethoxysilane, heptadecylfluorodecyltriethoxysilane, 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane, within the preferred range, can obtain complex silane The film has better hydrophobicity and corrosion resistance.

The present invention also provides a preparation method for the composite silane film, comprising the steps of:

(1) Configure a silane solution of a dihydrolyzed head group with a volume percentage of 4% to 12%, and let it stand for hydrolysis for more than 48 hours;

(2) Coat the silane solution of the double hydrolyzed head group after standing hydrolysis in step (1) on the metal surface for 10 to 40 minutes, then wash with an organic solvent to remove the excess silane of the double hydrolyzed head group, dry at room temperature and then Thermal curing treatment at 50-150°C for 20-60 minutes to form a silane layer of double hydrolyzed headgroups;

(3) Prepare a monohydrolyzed head group fluorosilane solution with a molar concentration of 1-15 mmol/L, and let it stand for hydrolysis for 5-30 minutes;

(4) Then apply the monohydrolyzed head group fluorosilane solution after standing hydrolysis in step (3) on the surface of the silane layer of the double hydrolyzed head group for 5 to 30 minutes, then take it out and clean it with an organic solvent to remove the excess monohydrolyzed head group Fluoro-based silane, heat-cured at 80-150°C for 30-60 minutes to form a fluorine-containing silane layer of monohydrolyzed head group.

Wherein the dihydrolyzed head group silane and monohydrolyzed head group fluorosilane are as described above.

As a preference, the volume percentage of the dihydrolyzed head group silane solution described in the method of the present invention is 5%-10%, and the pH is 5-7.

As a preference, the molar concentration of the monohydrolyzed head group fluorosilane solution in the method of the present invention is 2-10 mmol/L.

As a preference, the organic solvent used for cleaning in the present invention is not particularly limited, and in terms of cost, one or more of isopropanol, absolute ethanol or acetone is preferred.

As a preference, the solvents used in the double hydrolysis head group silane solution and the monohydrolysis head group fluorosilane solution described in the method of the present invention are selected from ethanol, methanol, isopropanol, n-propanol, butylpropanol, isooctane, toluene , n-hexane or heptane, etc. or one or more of them.

The coating method used in the present invention can be a method commonly used in the industry, including but not limited to one or more of liquid phase dipping, spray gun spraying or aseptic cotton brushing.

In the present invention, before coating the silane solution of the double hydrolyzed head group, the metal surface can be cleaned first, and the cleaning method can include common chemical cleaning, electrochemical cleaning or ultrasonic cleaning.

Beneficial effects of the present invention:

(a) The introduction of the double-head silane of the present invention makes the composite membrane of the present invention have high compactness and excellent anti-corrosion effect;

(b) Since the outer layer contains fluorine, the hydrophobicity and antifouling properties of the coating are further improved, compared with the mixed films of tetraethoxysilane (TEOS) and octadecyltrichlorosilane (OTS) reported in the literature, The static contact angle is increased by 10-30°, and the anti-corrosion and anti-fouling properties are significantly increased;

(c) The preparation method of the present invention is simple and easy for large-scale production.

Description of drawings

Fig. 1 Static contact angles of stainless steel surfaces modified with different silanes.

Fig. 2 Pitting corrosion test diagram of silane-modified stainless steel ferric chloride.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited.

Example 1:

(1) 304 stainless steel surface chemical pretreatment method

Cut 304 stainless steel into a rectangular substrate of 1×2 cm ² , neutralize the substrate with 0.01M HCl solution to remove iron filings on the surface, and treat the surface of stainless steel with 1 mol/L NaOH solution for 1 hour to hydroxylate the surface of the stainless steel. Rinse with deionized water and dry for later use.

(2) Silanization of metal surface

Add 1,2-bis(triethoxysilyl)ethane to the ethanol-water mixture with a volume ratio of 23:7, so that the volume of 1,2-bis(triethoxysilyl)ethane The percentage is 7%. The 1,2-bis(triethoxysilyl)ethane/ethanol solution should be hydrolyzed for 48 hours before use. Immerse the pretreated 304 stainless steel in the silane solution for 30 minutes, take it out, wash it with isopropanol, absolute ethanol, and acetone to remove excess 1,2-bis(triethoxysilyl)ethane, and dry it at room temperature Then thermal curing treatment was performed at 65° C. for 30 minutes. Add 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane to the isooctane solution to make a mole fraction of 2.0mmol/L. The 1H,1H,2H,2H-perfluorodecyltrichlorosilane/isooctane solution needs to be hydrolyzed for 15 minutes before use. Immerse the 304 stainless steel treated with 1,2-bis(triethoxysilyl)ethane in the silane solution for 10 minutes, take it out and ultrasonically clean it in acetone, carbon tetrachloride and isopropanol solutions to remove excess surface The FDTS molecules were heat-cured at 120°C for 1 hour.

(3) Coating performance comparison

The two test methods adopted in this embodiment are as follows:

The static water contact angle (WCA) adopts the DropMeter A100P model contact angle tester to test the static contact angle of ultrapure water on the surface of the material respectively.

For accelerated corrosion, refer to GB/T 17897-201635, configure 6% FeCl ₃ solution, control the temperature at 40°C, fix the position of the sample, soak the stainless steel for 1 hour and take it out. According to GB/T 16545-2015, the corrosion products on the sample were removed, and after drying, the mass of the sample was accurately weighed with an electronic balance, accurate to 0.1mg36. Three parallel groups were set up, and new pitting solution was required for each experiment, and the number of pitting corrosion on the stainless steel surface was counted visually, and the pitting density was calculated. Test the corrosion weight loss rate before and after pitting corrosion, its calculation formula (2):

ω＝(W1－W2)/(S t) (2)

Among them: W1 is the weight of the experiment before the experiment, mg; W2 is the weight of the sample after removing the corrosion products after the experiment, mg; S is the area of the sample, cm ² ; t is the soaking time, h.

The test results are as follows:

Figure 1 shows the contact angles of different silane-modified 304 stainless steel surfaces. Fig. 2 is a pitting test diagram of silane-modified stainless steel ferric chloride. In Figure 1 and Figure 2, M is the surface of stainless steel; M-B is the surface of stainless steel coated with 1,2-bis(triethoxysilyl)ethane; M-F is the surface of stainless steel coated with 1H,1H,2H,2H-perfluorodecyl Trichlorosilane stainless steel surface; for M-BF, the first layer is 1,2-bis(triethoxysilyl)ethane, and the second layer is 1H,1H,2H,2H-perfluorodecyltrichlorosilane coating A composite film coating with an average thickness of 80nm.

Figure 1 The static contact angle test results show that the contact angle of M is 63°±0.3°, the contact angle of MF is 109°±4.3°, the contact angle of MB is 34°±2.6°, and the contact angle of M-BF is 120° °±0.9°. Among them, the Si-OCH ₃ at both ends of the double-headed silane is hydrolyzed to form Si-OH. When a film is formed on the metal surface, the Si-OH at the other end is hydrophilic, resulting in a decrease in the contact angle of MB. The contact angle of M-BF is larger than that of MF, and the composite silane film shows stronger hydrophobicity. 120° is the limit value of the contact angle of fluorine on the flat surface, which shows that the distribution of fluorine on the surface of the composite silane film is very dense, which can effectively improve the corrosion resistance and anti-fouling properties of the coating; while the performance of the MF silane film is slightly worse.

Fig. 2 is a pitting test diagram of silane-modified stainless steel ferric chloride. Different numbers of pitting pits (white dots) appeared on the surface of the samples after the test. The results of the accelerated corrosion test show that M-BF has the best corrosion resistance. The pitting density of M-BF per square centimeter per hour is 1, which is much smaller than that of M. The pitting densities of MF and MB are respectively for 4 and 5. The order of the corrosion weight loss rate from large to small is M>MB>MF>M-BF, where the corrosion weight loss rate of M is (12.5±1.5) mg cm ² h, while the corrosion weight loss rate of M-BF is only It is (3.4±0.9) mg·cm ² ·h, 72.8% less than M. The corrosion weight loss rates of MF and MB were (8.7±0.3) mg·cm ² ·h and (9.6±2.0) mg·cm ² ·h, respectively, which were 30.4% and 23.2% lower than M. The order of pitting density from high to low is consistent with the corrosion weight loss rate.

Embodiment 2-7 is as shown in table 1, and other is with embodiment 1.

Table 1 embodiment 2-7 described method and result

The above content is only a basic description of the concept of the present invention, and any equivalent transformation made according to the technical solution of the present invention shall fall within the scope of protection of the present invention.

Claims (10)

1. A composite silane film for metal surfaces, characterized in that it comprises a silane layer of a double hydrolysis head group and a fluorine-containing silane layer of a monohydrolysis head group. 2. the composite silane film for metal surface according to claim 1, is characterized in that, the film thickness of described composite silane film is less than 200nm, preferably the silane layer of double hydrolysis head group or/and the monohydrolysis head group The thickness of the fluorine-containing silane layer is 80-120nm, and the film thickness of the composite silane film is less than 200nm. 3. the composite silane film for metal surface according to claim 1, is characterized in that, the silane of double hydrolysis head group refers to that silane molecule two ends contain hydrolyzable group, preferably two-[gamma-(triethyl One or more of oxysilane)propyl]-tetrasulfide, 1,2-bis(triethoxysilyl)ethane, tetraethoxysilane or tetramethoxysilane. 4. The composite silane film for metal surfaces according to claim 1, wherein the monohydrolysis head group fluorosilane refers to a hydrolyzable group at one end of the silane molecule, preferably tridecafluorooctyltrimethoxysilane , Tridecafluorooctyltriethoxysilane, Heptadecafluorodecyltrimethoxysilane, Heptadecafluorodecyltriethoxysilane or 1H,1H,2H,2H-perfluorodecyltrichlorosilane one or several. 5. A preparation method for a composite silane membrane, characterized in that, comprises the steps: (1) Configure a silane solution of a dihydrolyzed head group with a volume percentage of 4% to 12%, and let it stand for hydrolysis for more than 48 hours; (2) Coat the silane solution of the double hydrolyzed head group after standing hydrolysis in step (1) on the metal surface for 10 to 40 minutes, then wash with an organic solvent to remove the excess silane of the double hydrolyzed head group, dry at room temperature and then Thermal curing treatment at 50-150°C for 20-60 minutes to form a silane layer of double hydrolyzed headgroups; (3) Prepare a monohydrolyzed head group fluorosilane solution with a molar concentration of 1-15 mmol/L, and let it stand for hydrolysis for 5-30 minutes; (4) Then apply the monohydrolyzed head group fluorosilane solution after standing hydrolysis in step (3) on the surface of the silane layer of the double hydrolyzed head group for 5 to 30 minutes, then take it out and clean it with an organic solvent to remove the excess monohydrolyzed head group Fluoro-based silane, heat-cured at 80-150°C for 30-60 minutes to form a fluorine-containing silane layer of monohydrolyzed head group. 6. The preparation method of the composite silane film according to claim 5, characterized in that, the volume percent of the double hydrolysis head group silane solution is 5% to 10%, and the pH is 5 to 7; the monohydrolysis The molar concentration of the head group fluorosilane solution is 2-10 mmol/L. 7. the preparation method of composite silane film according to claim 5 is characterized in that, the used solvent of described double hydrolysis head group silane solution and monohydrolysis head group fluorosilane solution is selected ethanol, methyl alcohol, Virahol, normal One or more of propanol, butylpropanol, isooctane, toluene, n-hexane or heptane, etc. 8. The preparation method of the composite silane film according to claim 5, characterized in that, before coating the silane solution of the double hydrolysis head group, the metal surface is cleaned earlier. 9. The preparation method of the composite silane membrane according to claim 5, characterized in that the coating method is one or more of liquid phase dipping, spray gun spraying or sterile cotton brushing. 10. the preparation method of composite silane membrane according to claim 5 is characterized in that, the silane of double hydrolysis head group refers to that silane molecule two ends contain hydrolyzable group, preferably two-[gamma-(triethoxy One or more of silicon)propyl]-tetrasulfide, 1,2-bis(triethoxysilyl)ethane, tetraethoxysilane or tetramethoxysilane; monohydrolyzed head group fluorine Silane means that one end of the silane molecule contains a hydrolyzable group, preferably tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyl One or more of triethoxysilane or 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane.