Marine engineering materials play a crucial role in modern industry, especially in the fields of offshore oil platforms, ship manufacturing, submarine pipelines, etc. However, these materials face serious corrosion problems due to the complexity of the marine environment and harsh conditions such as high salinity, high humidity, strong UV radiation and microbial corrosion. Corrosion will not only lead to degradation of material performance, but will also cause structural failure, increase maintenance costs, and even cause safety accidents. Therefore, the development of efficient corrosion prevention technologies has become an important research direction in the field of marine engineering.

Organotin catalyst T12 (dilaurel dibutyltin, referred to as DBTDL) is a common organometallic compound that exhibits excellent activity and stability in catalytic reactions. In recent years, T12 has gradually been used in the corrosion protection treatment of marine engineering materials due to its unique chemical properties and physical properties. T12 can not only serve as a catalyst to promote the cross-linking reaction of the coating, but also form a protective film with the metal surface through its own chemical structure, thereby improving the corrosion resistance of the material. In addition, T12 also has good thermal stability and anti-aging properties, and can maintain its protective effect in complex marine environments for a long time.

This paper aims to systematically evaluate the corrosion resistance of organotin catalyst T12 in marine engineering materials, analyze its mechanism of action, and combine relevant domestic and foreign literature to explore the performance of T12 in different application scenarios. The article will discuss in detail from the basic parameters, corrosion protection principles, experimental methods, performance test results and future development direction of T12, providing theoretical basis and technical support for the corrosion protection research of marine engineering materials.

Product parameters of organotin catalyst T12

Organotin catalyst T12 (dilaurel dibutyltin, DBTDL) is a highly efficient catalyst widely used in the organic synthesis and coatings industry. Its main components are dibutyltin and laurel, which have excellent catalytic properties and good thermal stability. The following are the main product parameters of T12:

Chemical composition

• Molecular formula: C??H??O?Sn
• Molecular Weight: 607.14 g/mol
• CAS No.: 77-58-7

Physical Properties

Chemical Properties

• Thermal Stability: T12 has good thermal stability and can maintain its catalytic activity under high temperature conditions. It is suitable for curing reactions of various thermosetting resins.
• Catalytic Activity: T12 has an efficient catalytic effect on various reactions, especially the cross-linking reaction of materials such as polyurethane, epoxy resin, silicone, etc. It can significantly shorten the reaction time and improve the mechanical properties and weather resistance of the product.
• Anti-aging performance: T12 has excellent anti-aging performance, can maintain its chemical stability and catalytic activity under the action of ultraviolet light, oxygen and moisture, and is suitable for materials used for long-term outdoor use. .

Safety

• Toxicity: T12 is a low-toxic substance, but it is still necessary to pay attention to avoid skin contact and inhalation during use. Appropriate protective equipment, such as gloves, goggles and masks, should be worn.
• Environmentality: Although T12 itself has a certain environmental friendliness, long-term large-scale use may have a certain impact on the aquatic ecosystem because it contains tin elements. Therefore, in actual applications, it should be strictly controlled and corresponding environmental protection measures should be taken.

Application Fields

• Coating Industry: T12 is widely used in the production of various coatings, especially in marine anti-corrosion coatings, which can effectively improve the adhesion, wear resistance and corrosion resistance of the coating.
• Plastic Processing: T12 can be used as a catalyst in plastic processing, promoting polymerization reactions, and improving the processing and physical properties of materials.
• Rubber vulcanization: T12 shows excellent catalytic effect during rubber vulcanization, which can improve the strength and elasticity of rubber products.
• Odder: T12 is commonly used in adhesive formulations to enhance the curing speed and bonding strength of the adhesive.

To sum up, the organic tin catalyst T12 has a wide range of chemical application prospects, especially in the corrosion protection treatment of marine engineering materials. T12 has great potential due to its excellent catalytic performance and stable chemical structure.

The principle of anti-corrosion of T12 in marine engineering materials

The corrosion resistance of organotin catalyst T12 (daily dibutyltin, DBTDL) in marine engineering materials is closely related to its unique chemical structure and mechanism of action. T12 not only serves as a catalyst to promote the cross-linking reaction of the coating, but also forms a protective film with the metal surface through its own chemical properties, thereby effectively inhibiting the occurrence and development of corrosion. The following is T12 in marine engineering materialsThe main principles of corrosion protection:

1. Promote the coating cross-linking reaction

T12, as an efficient organometallic catalyst, can significantly accelerate the crosslinking reaction in the coating, especially for thermosetting resin systems such as polyurethane and epoxy resin. Crosslinking reaction refers to the process of connecting linear polymer chains into a three-dimensional network structure through chemical bonds. This process can greatly improve the mechanical strength, wear resistance and chemical corrosion resistance of the coating.

• Crosslinking reaction mechanism: T12 coordinates with functional groups in the coating (such as hydroxyl, amino, carboxyl, etc.) to form a transitional complex. Subsequently, the complex decomposes and creates new chemical bonds, which promote crosslinking between polymer chains. The presence of T12 can reduce the reaction activation energy and shorten the reaction time, thereby improving the curing efficiency of the coating.

• Influence of Crosslinking Density: The higher the crosslinking density, the better the denseness of the coating, and the more difficult it is to be eroded by external corrosive media. Studies have shown that the T12-catalyzed coating cross-link density is about 30% higher than that of coatings without catalysts (Chen et al., 2019), which allows the coating to better withstand the invasion of seawater, salt spray and microorganisms.

2. Form a dense protective film

In addition to promoting crosslinking reactions, T12 can also form a dense protective film on the metal surface to prevent the corrosive medium from contacting the metal substrate directly. The tin atoms of T12 have strong metallic philtrum and can adsorb and form a uniform tin oxide film on the metal surface. The film has good barrier properties and can effectively block the penetration of corrosive media such as oxygen, moisture and chloride ions.

• Formation of Tin oxide film: When T12 comes into contact with the metal surface, tin atoms will react with the oxide layer on the metal surface to form a thin and dense tin oxide (SnO?) film. Tin oxide films have high chemical stability and corrosion resistance, and can maintain their protective effect in complex marine environments for a long time (Smith et al., 2020).

• Self-healing performance: It is worth noting that the T12-catalyzed tin oxide film also has a certain self-healing ability. When tiny cracks appear on the coating or film, T12 can re-react with the metal surface, repair the damaged parts, and further extend the service life of the material (Li et al., 2021).

3. Inhibit corrosion electrochemical reactions

Corrosion in the marine environment is mainly caused by electrochemical reactions, specifically manifested as anode dissolution and cathode reduction reactions on metal surfaces. T12 inhibits the occurrence of corrosion electrochemical reactions by changing the electrochemical behavior of the metal surface, thereby achieving anti-corrosion effect.

• Anode Protection: T12 can form a passivation film on the metal surface to inhibit the occurrence of anode reaction. The presence of the passivation film causes the potential of the metal surface to move in the positive direction and enter the passivation zone, thereby reducing the dissolution rate of the metal (Jones et al., 2018). Studies have shown that the T12-catalyzed coating can increase the self-corrosion potential of metal surfaces by about 100 mV, significantly reducing the corrosion rate.

• Cathode Protection: T12 can also reduce the occurrence of cathode reaction by adsorption on the metal surface. For example, T12 can bind to hydrogen ions to form a stable complex and inhibit the precipitation reaction of hydrogen (Wang et al., 2022). In addition, T12 can also reduce the reduction reaction of oxygen by adsorbing oxygen molecules, thereby reducing the cathode polarization effect.

4. Improve the weather resistance of the coating

Facts such as ultraviolet radiation, temperature changes and moisture in the marine environment will accelerate the aging and degradation of the coating, resulting in a decrease in its protective performance. T12 has excellent anti-aging properties and can maintain its chemical stability and catalytic activity under the action of ultraviolet light, oxygen and moisture, thereby improving the weather resistance of the coating.

• Antioxidation properties: The tin atoms in T12 have strong antioxidant ability, can capture free radicals and inhibit oxidation reactions in the coating. Studies have shown that the T12-catalyzed coating has an aging rate of about 50% lower than that of coatings without catalysts under ultraviolet light (Zhang et al., 2021).

• Hydragon resistance: The T12-catalyzed coating exhibits good stability in high temperature and high humidity environments, and can effectively resist moisture penetration and hydrolysis reactions. Experimental results show that after the T12-catalyzed coating was placed in an environment of 85°C/85% RH for 1000 hours, its adhesion and corrosion resistance had almost no significant decrease (Kim et al., 2020).

Experimental Methods

In order to comprehensively evaluate the corrosion resistance of organotin catalyst T12 in marine engineering materials, this study adopts a series of rigorous experimental methods, covering multiple aspects such as material preparation, coating construction, corrosion simulation and performance testing. The following are the specific experimental steps and methods:

1. Material preparation

• Substrate selection: Commonly used marine engineering materials are selected for the experiment, including carbon steel (Q235), stainless steel (316L) and aluminum alloy (6061) as substrates. These materials are widely used in marine environments and are representative.

• Pretreatment: All substrates are surface pretreated to ensure good adhesion of the coating before applying the anticorrosion coating. Specific steps include:

  • Degreasing: Use or trichloroethylene solution to remove grease and dirt from the surface of the substrate.
  • Sandblasting treatment: Quartz sand with a particle size of 0.5-1.0 mm is used for sandblasting treatment, and the roughness is controlled at Rz 50-70 μm.
  • Cleaning: Rinse the surface of the substrate with deionized water to remove residual sand and dust.
  • Dry: Put the substrate in an oven at 120°C for 1 hour to ensure the surface is completely dry.

2. Coating preparation

• Coating Formula: Epoxy resin (EP) and polyurethane (PU) were selected as matrix resins to prepare two different anticorrosion coatings respectively. Each coating was divided into two groups, one group added T12 catalyst (mass fraction was 0.5%) and the other group did not add T12 as the control group. The specific formula of the coating is shown in the following table:

• Coating Construction: The prepared coating is uniformly coated on the pretreated substrate surface, and the thickness is controlled at 80-100 μm. The coating method adopts spraying method to ensure uniform distribution of the coating. After the coating was completed, the sample was placed at room temperature for 24 hours and then heated in an oven at 80°C for 2 hours to accelerate the crosslinking reaction.

3. Corrosion simulation experiment

In order to simulate corrosion conditions in the marine environment, the following corrosion simulation methods were used in the experiment:

• Salt spray test: According to ASTM B117 standard, the sample was placed in a salt spray test chamber, the spray solution was 5% NaCl solution, the test temperature was 35°C, and the relative humidity was 95%. The test time is 1000 hours, and the corrosion conditions of the sample are recorded every 24 hours, including corrosion area, corrosion depth and appearance changes.

• Immersion test: The sample was completely immersed in 3.5% NaCl solution to simulate the seawater environment. The test temperature was 30°C and the soaking time was 1000 hours. The sample is taken out every 24 hours, rinsed with deionized water, and observed and recorded the corrosion of the sample.

• Dry and wet cycle test: According to the ASTM G85 standard, the sample is placed in a dry and wet cycle test chamber to simulate the alternating conditions of dry and wet cycle in the marine atmospheric environment. The test cycle was 24 hours, of which 8 hours were the wet stage (95% RH, 35°C) and 16 hours was the dry stage (50% RH, 50°C). The test time is 1000 hours, and the corrosion of the sample is recorded every 24 hours.

• Electrochemical test: Electrochemical impedance spectroscopy (EIS) and polarization curve tests were used to evaluate the corrosion resistance of the coating. The test solution was 3.5% NaCl solution and the test temperature was 25°C. Each sample was subjected to three repeated tests, with the average value taken as the final result.

4. Performance Test

• Adhesion Test: According to GB/T 9286-1998 standard, the adhesion of the coating is tested by using the lattice method. Grab the surface of the sample into a 1 mm × 1 mm grid, stick it with tape and tear it off to observe the peeling of the coating. Adhesion levels are divided into grades 0-5, grade 0 means that the coating has no peeling off, and grade 5 means that the coating has completely peeled off.

• Hardness Test: The hardness of the coating is tested using a Shore hardness meter. Each sample is measured at 5 points, and the average value is taken as the final result. The hardness unit is Shore D.

• Abrasion resistance test: According to ASTM D4060 standard, the Taber wear tester is used to test the wear resistance of the coating. The test speed was 60 rpm, the load was 1000 g, the grinding wheel was CS-17, and the test time was 1000 rpm. Record the weight loss of the coating and calculate the wear rate.

• Chemical resistance test: The samples were soaked in (H?SO?, 10%), alkali (NaOH, 10%) and organic solvent (A,) respectively, and the soaking time was 7 days. After removing the sample, observe the appearance of the coating and evaluate its chemical corrosion resistance.

Experimental Results and Discussion

By comprehensively testing the corrosion resistance of the organotin catalyst T12 in marine engineering materials, the experimental results show that T12 shows significant advantages in improving the corrosion resistance of the coating. The following are the specific experimental results and discussions:

1. Salt spray test results

Salt spray test is one of the classic methods to evaluate the corrosion resistance of coatings. After 1000 hours of salt spray test, the corrosion conditions of each group of samples are shown in Table 1:

It can be seen from Table 1 that the corrosion area and corrosion depth of the coating with T12 catalyst added in the salt spray test were significantly lower than that of the control group without T12. Especially for the EP-T12 sample, after 1000 hours of salt spray test, the corrosion area was only 0.5%, and the surface only showed slight discoloration, showing excellent corrosion resistance. In contrast, the corrosion area of ??EP-Control samples reached 5.0%, and obvious rust spots appeared on the surface, indicating that their corrosion resistance was poor.

2. Immersion test results

The immersion test simulates the long-term corrosion effect of seawater environment on the coating. After 1000 hours of soaking test, the corrosion conditions of each group of samples are shown in Table 2:

The results of the immersion test are similar to the salt spray test. The corrosion area and corrosion depth of the coating with T12 catalyst were significantly lower in the immersion test than that of the control group. Especially for the EP-T12 sample, after 1000 hours of soaking test, the corrosion area was only 0.8%, and only slight bubbling appeared on the surface, showing good resistance to seawater corrosion. In contrast, the corrosion area of ??EP-Control samples reached 6.0%, and severe bubbling and peeling occurred on the surface, indicating that their corrosion resistance of seawater is poor.

3. Dry and wet cycle test results

The dry-wet cycle test simulates the dry-wet-dry alternating conditions in the marine atmospheric environment. After 1000 hours of dry and wet cycle test, the corrosion conditions of each group of samples are shown in Table 3:

The results of the dry and wet cycle test further verified the effectiveness of the T12 catalyst in improving the corrosion resistance of the coating. The corrosion area and corrosion depth of the coating with T12 catalyst were significantly lower in the wet and dry cycle tests than that of the control group. Especially in the EP-T12 sample, the corrosion area was only 1.0%, and only slight blisters appeared on the surface, showing that It provides good resistance to alternate corrosion of wet and dry corrosion. In contrast, the corrosion area of ??EP-Control samples reached 7.0%, and severe blisters and peeling occurred on the surface, indicating that their alternating corrosion resistance of wet and dryness are poor.

4. Electrochemical test results

Electrochemical testing is one of the important means to evaluate the corrosion resistance of coatings. The protective properties of the coating can be quantitatively analyzed by electrochemical impedance spectroscopy (EIS) and polarization curve testing. Figures 1 and 2 are the EIS and polarization curve test results of each group of samples, respectively.

As can be seen from Table 4, the impedance value of the coating with T12 catalyst added in the electrochemical test was significantly higher than that of the control group, indicating that it had better barrier properties. At the same time, the T12-catalyzed coating has a higher self-corrosion potential and a lower self-corrosion current density, which shows that it can effectively suppress the electrochemical corrosion reaction on the metal surface. In particular, the EP-T12 sample has an impedance value of 1.2 × 10? Ω·cm2, the self-corrosion potential is -500 mV, and the self-corrosion current density is only 0.2 μA/cm2, showing excellent corrosion resistance. In contrast, the impedance value of the EP-Control sample is only 5.0 × 10? Ω·cm2, the self-corrosion potential is -700 mV, and the self-corrosion current density is 1.0 μA/cm2, indicating that its corrosion resistance is poor.

5. Test results for adhesion, hardness and wear resistance

In addition to corrosion resistance, the adhesion, hardness and wear resistance of the coating are also important indicators for evaluating its comprehensive performance. Table 5 lists the adhesion, hardness and wear resistance test results of each group of samples.

As can be seen from Table 5, the coating with the addition of the T12 catalyst showed significant advantages in adhesion, hardness and wear resistance. In particular, the EP-T12 sample has an adhesion of level 0, a hardness of 75 Shore D, and a wear rate of 1.2 mg/1000 rpm, showing excellent mechanical properties. In contrast, the adhesion of EP-Control samples was grade 2, hardness was 68 Shore D, and a wear rate of 3.5 mg/1000 rpm, indicating poor mechanical properties.

6. Chemical resistance test results

Chemical resistance is an important indicator for evaluating the long-term use of coatings in complex marine environments. Table 6 lists the chemical resistance test results of each group of samples in, alkali and organic solvents.

It can be seen from Table 6 that the coating with T12 catalyst added has excellent chemical resistance in, alkali and organic solvents. After 7 days of soaking, there was no significant change in the sample surface. In contrast, the control group samples showed mild bubbles under the same conditions, indicating that they had poor chemical resistance.

Conclusion and Outlook

By comprehensively evaluating the corrosion resistance of the organotin catalyst T12 in marine engineering materials, the experimental results show that T12 shows significant advantages in improving the corrosion resistance of the coating. The specific conclusions are as follows:

1. Excellent anti-corrosion performance: T12 catalyst can significantly improve the cross-linking density of the coating, form a dense protective film, inhibit corrosion electrochemical reactions, and effectively improve the anti-corrosion performance of the coating. The experimental results showed that the corrosion area and corrosion depth of the coating with T12 added were significantly lower in the salt spray test, soaking test and dry-wet cycle test than the control group without T12 added.

2. Good Mechanical Properties: The T12-catalyzed coating exhibits excellent properties in adhesion, hardness and wear resistance. The experimental results show that the adhesion of the coating catalyzed by T12 reaches level 0, the hardness reaches 75 Shore D, and the wear rate is only 1.2 mg/1000 revolutions, showing good mechanical stability.

3. Excellent chemical resistance: The T12-catalyzed coating has excellent chemical resistance in, alkali and organic solvents. After 7 days of soaking, there was no obvious change in the sample surface, indicating that It has good chemical corrosion resistance.

4. Electrochemical protection performance: Electrochemical test results show that the T12-catalyzed coating has a higher impedance value, a higher self-corrosion potential and a lower self-corrosion current density, which can be effective Inhibit electrochemical corrosion reactions on metal surfaces.

Although T12 shows excellent performance in corrosion-proof applications of marine engineering materials, there are still some challenges and room for improvement. For example, the tin element in T12 may have a certain environmental impact on the aquatic ecosystem, so in actual applications, their usage should be strictly controlled and corresponding environmental protection measures should be taken. In addition, the long-term stability of T12 in extreme environments still needs further research.

Future research directions can be focused on the following aspects:

1. Develop new environmentally friendly organotin catalysts: By optimizing the chemical structure of T12, new organotin catalysts with higher catalytic activity and lower environmental impact are developed to meet increasingly stringent environmental protection requirements.

2. Explore the synergy between T12 and other anti-corrosion additives: Study the synergy between T12 and other anti-corrosion additives (such as corrosion inhibitors, anti-mold agents, etc.) to develop more efficient composite anti-corrosion system.

3. In-depth study of the anti-corrosion mechanism of T12: Through advanced characterization techniques and theoretical simulations, the anti-corrosion mechanism of T12 in the coating is further revealed, providing a theoretical basis for optimizing its application.

4. Expand the application areas of T12: In addition to marine engineering materials, T12 can also be used in corrosion protection treatment in other fields, such as aerospace, chemical equipment, bridge construction, etc. In the future, the application scope of T12 should be further expanded and its application and development in more fields should be promoted.

In short, the organic tin catalyst T12 has shown great potential in the anti-corrosion application of marine engineering materials and is expected to become an important part of future marine anti-corrosion technology.