Increasing the anti-corrosion protection of metal surfaces using a composite epoxy coating with BTA-TiO2 nanotubes treated with ultrasound: a review

Concrete with high alkalinity (pH > 12) protects steel from corrosion by forming a passive oxide film on the surface. However, the pH of concrete can decrease over time due to carbonation or the infiltration of aggressive покрытия, ультразвуковые технологии,

1.    Theoretical foundations of steel corrosion

Corrosion of steel, including in concrete, is a complex problem involving a combination of chemical and electrochemical factors leading over time to deterioration and destruction of the steel structure. The following reactions represent the formation of rust after iron dissolves at the anodic sites in the reinforcement [1]:

(Ferrous Hydroxide) (1) 4Fe(0H')₃ (Ferric Hydroxide) (2) .H₂0 (Rust) (3)

substances such as chlorides (Cl^-), sulfates (SO 4 ^2-), and carbon dioxide (CO 2 ), which destroys the protective film and accelerates the corrosion process [2-4].

Fig. 1. Schematic illustration of reinforcing steel corrosion in concrete as an electrochemical process [5]

2.    Problems of using protective epoxy coatings.

Although epoxy coatings are widely used to protect steel in concrete from corrosion, their effectiveness can be limited over time. The main reason is that epoxy coatings can peel or fail due to a variety of factors, including poor or incorrect construction techniques, mechanical stress, and temperature changes. When the coating is damaged, aggressive substances such as water, chloride ions and sulfates easily penetrate into the concrete and attack the steel, leading to corrosion [6-8]. In addition, epoxy coatings can become saturated with aggressive substances over time, especially in conditions of high humidity and temperature. Therefore, epoxy coatings for the protection of steel, including in concrete, must be used in combination with the use of high-strength concrete, corrosion-resistant reinforcement, and regular inspection and repair to ensure the longevity of the coating and the structure as a whole.

3.    Features of BTA-TiO2 nanocompositions.

From an analysis of scientific works in this area, it follows that most studies are focused mainly on improving mechanical properties when using TiO 2 nanoparticles in epoxy coatings [9-11]. However, in recent years, some studies show that the presence of TiO 2 nanotubes in epoxy resin can not only improve the mechanical properties [12-13], but also improve the heat resistance and anticorrosion properties [14-16] compared to micron-sized particles. However, uniform distribution of TiO 2 nanotubes in the resin is an extremely difficult task.

One of the promising applications of TiO 2 nanotubes is their use as a nanocontainer for storing corrosion inhibitors, including Benzotriazole (BTA) [17]. BTA has wide applicability in various fields, including as an effective corrosion inhibitor of various metals and alloys (Fig. 2).

Fig. 2. Schematic representation of loading corrosion inhibitor into TiO 2 nanocontainers

As part of the study [18], TiO 2 nanoparticles were synthesized and loaded with the BTA inhibitor, which was then randomly distributed in a protective coating based on silane-titanium. The controlled release of corrosion inhibitors from TiO 2 nanoparticles was studied, and a higher release rate was observed at low pH. The integration of TiO 2 nanoparticles into a solgel coating has led to an increase in the effectiveness of corrosion protection of metal alloys. Loading BTA into nanocontainers, rather than directly introducing it into the solgel coating avoided interaction with the solgel network and improved the anti-corrosion properties of the coating.

• 4.    Advantages of ultrasonic influence in the creation and application of composite materials.

• 5.    Research and development of a composite material based on BTA-TiO 2 in an epoxy matrix.

At the stage of creating liquid composite materials, volumetric ultrasonic exposure makes it possible to increase the uniformity of filler distribution in the matrix. In the process of applying composite coatings to metal surfaces, the use of ultrasound can bring significant benefits.

First, ultrasound helps improve adhesion between the coating and the metal substrate. By creating high pressure, ultrasound stimulates the coating to penetrate cracks and hard-to-reach areas of the surface, providing a strong and durable connection. Secondly, ultrasound promotes uniform distribution of the coating over the entire surface. Mechanical waves created by ultrasound prevent voids and ensure uniform coverage [19-20].

This work examines the possibility of producing protective epoxy compositions containing BTA-TiO 2 nanotubes using ultrasound using the following technology:

• 1.    Synthesis of TiO 2 nanowires by methods such as hydrothermal reaction, sol-gel and gas phase to achieve the desired size, shape and structure, optimization of factors such as temperature, reaction time, pH and ratio of starting materials;

• 2.    Binding of BTA to TiO 2 nanowires through a chemical reaction or adsorption, the effectiveness of which depends on the type of binding agent, BTA concentration, pH and reaction time;

• 3.    Production of epoxy compositions containing BTA-TiO 2 nanotubes by ultrasonic dispersion of TiO 2 /BTA nanotubes in epoxy resin.

Conclusion

The use of ultrasound in the technology of manufacturing and applying protective compositions with BTA-TiO 2 nanotubes promises significant prospects. This method allows not only to improve the adhesion of applied protective compositions to the metal substrate but also to evenly distribute BTA-TiO 2 nanotubes in the composition, improving the properties of the protective coating, including anti-corrosion properties. Further research and development in this area may lead to new products that are highly protective and environmentally friendly.