POLYUREA-BASED PROTECTIVE COATING TECHNOLOGY FOR CORROSION PREVENTION IN CONSTRUCTION AND INFRASTRUCTURE PROJECTS

Tran Ngọc Anh – Chairman of Newtec Group Joint Stock Company

1. General introduction

Vietnam is characterized by a tropical hot and humid climate, with a coastline stretching over 3,260 kilometers from North to South. These environmental conditions create an aggressive setting that significantly accelerates the corrosion of metallic structures as well as the degradation of reinforced concrete structures (RCCs).

According to data from the Vietnam Association of Corrosion Science and Metal Protection, corrosion-related losses in the country are estimated to account for no less than 5% of the GDP. This translates into an annual economic loss of approximately 20–25 billion USD due to corrosion—a remarkably high figure. On a global scale, corrosion incurs similarly severe consequences; in the United States alone, the annual cost of corrosion damage amounts to several hundred billion USD.

Given this context, corrosion protection of metal structures and RCCs plays a crucial role in extending the service life of constructions and thereby preserving economic value. Various methods can be employed to mitigate corrosion, including:

• Selection of appropriate structural steel materials with high corrosion resistance suited to the operational environment;
• Application of methods to alter the corrosivity of the surrounding medium, including the use of corrosion inhibitors;
• Selection and application of high-performance protective coatings with superior mechanical durability and extended service life;
• Implementation of cathodic protection systems;
• Enhancement of the performance properties of concrete, increasing the thickness of the protective concrete cover, or applying protective coatings to the reinforcement in RCCs, especially in coastal atmospheric environments or chemically aggressive and chloride-rich settings.

In practice, the use of protective coatings remains one of the most widespread and essential methods for corrosion prevention of metallic materials. In specific cases—such as underground steel pipelines and storage tanks—protective coatings are often combined with cathodic protection. For above-ground pipelines and tanks, coatings are typically used in conjunction with corrosion inhibitors. For reinforced concrete, corrosion mitigation may involve increasing the thickness of the protective concrete cover, improving the quality and durability of concrete, or applying composite protective coatings.

Therefore, the selection of appropriate corrosion protection measures should be carefully considered during the initial design phase of a construction project. In other words, the choice of protective coating materials is critically important, as it directly influences both the longevity and the investment efficiency of the structure.

2. Conditions for the occurrence of corrosion and degradation of metals

The primary agents causing metals corrosion are water and oxygen.

Steel equipment and pipelines (Fe-C alloys) that come into contact with water (or steam) and oxygen are prone to the following chemical reactions:

3Fe + 4H₂O  = Fe₃O₄ (rust) + 4H₂↑
3Fe + 2O₂  = Fe₃O₄ (rust)

Additionally, redox (oxidation-reduction) reactions occur in electrolytic environments (such as low-resistivity soils, acidic or alkaline solutions, and salt-contaminated media) and create Fe₃O₄nH₂O (rust). These electrochemical processes generate corrosion currents, resulting in accelerated corrosion rates.

In some specific cases, corrosion can occur even in the absence of oxygen, particularly sulfide corrosion. This form of degradation involves sulfur compounds produced by microorganisms that decompose organic impurities in the environment.

3. Conditions for the corrosion and degradation of reinforced concrete structures (RRCs)

Corrosion of reinforcement steel in concrete primarily occurs in the presence of chloride ions: Water vapor, oxygen, and chloride ions from the external environment penetrate into the concrete cover surrounding the reinforcement. Free chloride ions diffuse through the concrete matrix in accordance with Fick’s Second Law of Diffusion (Fick II). The rate of diffusion increases with higher temperature gradients, atmospheric pressure differences, humidity levels, and chloride concentrations. Conversely, concrete with higher impermeability will significantly reduce the diffusion of chloride ions. When the concentration of chloride ions in the concrete reaches approximately 0.6 to 0.8 kg/m³, the passive protective film on the surface of the reinforcement is destroyed. This allows oxygen and water vapor to quickly react with the exposed steel, initiating the corrosion reactions previously described in Section 2: Conditions for the Corrosion and Degradation of Metals. Once corrosion begins, the rust (iron oxide) that forms has a volume 4 to 6 times greater than that of the original steel, leading to internal stresses that cause cracking and spalling of the concrete cover. Corrosion and degradation of RCCs in coastal atmospheric environments in Vietnam are highly prevalent and represent a serious concern. Most structures in these regions show visible signs of corrosion within 15 to 20 years of service. Many buildings and infrastructure projects experience severe structural deterioration after 30 years, posing significant risks to safety and integrity.

Figure 1. Electrochemical corrosion mechanism of steel in concrete in the presence of chloride ions

Corrosion of RCCs constructed in submerged environments (such as seawater, brackish water, or freshwater) often occurs through chemical reactions between the mineral components of concrete (cement paste and aggregates) and magnesium salts (Mg²⁺) or sulfate salts present in the surrounding water. Additionally, alkali-silica reactions may take place, leading to leaching and degradation of the concrete matrix. In some cases, microbial-induced corrosion can also occur, further accelerating structural deterioration.

Corrosion of RCCs in industrial facilities and water supply and drainage infrastructure is currently a widespread and economically damaging issue in Vietnam. This is largely due to the rapid development of industry and urbanization across the country. The main cause lies in the direct exposure of reinforced concrete structures (such as tanks, pipelines, and floor slabs) to highly aggressive corrosive agents found in industrial environments and wastewater. Common corrosive agents include sulfur dioxide (SO₂), hydrogen sulfide (H₂S), carbon dioxide (CO₂), polyaluminum chloride (PAC), chlorine-based chemicals, and industrial detergents… When RCCs come into contact with these substances, chemical corrosion occurs primarily through acid-base neutralization reactions, which degrade the alkalinity of the concrete. This results in chemical decomposition and rapid deterioration of the structure. Numerous industrial and water infrastructure facilities in Vietnam have experienced severe corrosion and structural degradation within just 5 to 7 years of operation if appropriate corrosion protection measures are not implemented. As for steel storage tanks used in metallurgical and chemical industries, even when they are protected against corrosion from the beginning, the protective coatings typically require replacement every 3 to 4 years, due to the extreme conditions of operation.

4. Examples of corroded and damaged construction and infrastructure projects in Vietnam

Figure 2	Figure 3

Project: 1.5 km long D1400 circulating water pipeline – Uong Bi Thermal Power Plant

Investor: Uong Bi Thermal Power Plant

Damage Status: After 30 years of operation, the surface of the 2mm-thick steel pipe suffered severe corrosion, with many areas perforated.

Cause of Corrosion: Exposure to brackish water containing high chloride ion content.

Solution: Removal of rust, patching of perforations, followed by application of a 2mm thick polyurea anti-corrosion coating.

Figure 4	Figure 5

Project: 1.5 km long D800 wastewater pipeline – Bàu Bàng Industrial Park

Investor: Becamex Corporation

Damage Status: After 15 years of operation, the concrete pipe surface experienced severe corrosion, with multiple perforations and water leakage.

Cause of Corrosion: Wastewater containing decomposed organic substances, which generated highly corrosive compounds such as hydrogen sulfide (H₂S).

Solution: Cleaning of the concrete surface, patching of perforations, followed by the application of a 2.5 mm thick polyurea anti-corrosion coating.

Figure 6	Figure 7

Project: Wastewater Treatment Tank – Units A & B

Facility: Bình Hưng Wastewater Treatment Plant

Investor: Ho Chi Minh City Center for Technical Infrastructure Management

Damage Condition: After more than 10 years of operation, the submerged concrete surfaces were severely corroded, with exposed aggregate and corroded reinforcement steel. The tank exhibited significant water leakage.

Corrosive Agent: Chemical substances introduced into the tank during the wastewater treatment process, which caused aggressive chemical degradation of the concrete structure.

Solution: Cleaning of the concrete surface and patching of damaged areas, followed by the application of a 2 mm thick polyurea coating to provide corrosion protection and waterproofing.

Figure 8	Figure 9

Project: Water Pumping Station
Investor: Tan Hiep Water Treatment Plant – Ho Chi Minh City

Damage Condition: After 25 years of operation, the reinforced concrete floor and beams experienced severe corrosion, including spalling, surface delamination, and cracking of concrete beams.

Corrosive Agent: Chlorine-based chemicals introduced into the water supply for disinfection prior to the distribution of treated water caused chemical corrosion.

Solution: Cleaning of the concrete surfaces, patching of damaged areas, structural steel reinforcement, and application of a 3 mm thick polyurea coating for corrosion protection and waterproofing.

5. Polyurea coating technology for corrosion protection

Underground pipelines are typically designed and installed with a minimum service life of over 50 years, and for Category I infrastructure, the required service life may exceed 100 years. Maintenance and repair of underground pipelines are often extremely costly and, in some cases, infeasible due to factors such as right-of-way restrictions, deep subsurface installation, or difficulty in disassembly and replacement. As a result, any damage caused by corrosion is highly undesirable and may lead to significant economic losses for the owner or operator.

For steel storage tanks or RCCs that come into contact with chemicals or corrosive agents, the application of a protective anti-corrosion coating is mandatory. One of the most effective preventive measures is for end users, and particularly design engineers, to carefully select the most suitable coating system and specifically, the priming and structural lining layers. These coatings must offer: superior mechanical strength, high chemical resistance, excellent impermeability, maximum service life and durability…

Anti-corrosion coatings are generally required to meet the following performance criteria:

• High impermeability to water, oxygen, and chloride vapor;
• Excellent electrical insulation and electrochemical resistance;
• Strong adhesion to steel or concrete surfaces;
• High mechanical strength, as well as UV and chemical resistance;
• Good impact resistance;
• Scratch and abrasion resistance, to protect against damage during handling, testing, transportation, installation, and operational use;
• Resistance to substrate movement and thermal stress;
• High crack-bridging capability and elongation at break, allowing the coating to accommodate structural movements without failure.

Now, various protective coating systems are employed globally to safeguard underground pipelines, steel structures, and storage tanks. These include:

• Bituminous coatings: Among the earliest coating materials used, bitumen-based coatings are known for their low cost. However, they suffer from low durability, poor impact resistance, and are highly susceptible to scratching during installation. They also contain toxic solvents, making them environmentally and occupationally hazardous. As a result, their use has been significantly limited worldwide in recent years.
• Polyester/Vinyl ester resins reinforced with fiberglass (FRP composites): These materials are widely used due to their ease of application. However, they exhibit poor impact resistance, are brittle, prone to cracking, cannot withstand thermal shock, and have very low UV resistance. Moreover, the resins used are highly toxic. In exposed environments, their service life typically does not exceed 5 years.
• Epoxy coatings: These are commonly used and relatively easy to apply. Their limitations include brittleness, low impact resistance, proneness to cracking, and inability to tolerate thermal shock. The typical service life of epoxy coatings is less than 10 years.
• Polyethylene jacketing: This method involves wrapping polyethylene sheets around the external surface of pipelines, resulting in numerous seams. The jacketing is vulnerable to damage during installation. It softens at 80 °C (176 °F) and melts at around 100–110 °C (212–230 °F). Additionally, it cannot be applied to the internal surfaces of pipelines, thus limiting its application.
• Polyurea coatings: Polyurea is a next-generation protective coating, developed by advancing polyurethane chemistry, a technology that originated over 80 years ago. Polyurea has been used worldwide for over 30 years in industries such as oil and gas, water and wastewater, civil construction, and hydropower. In Vietnam, polyurea has been applied for nearly 20 years in pipeline protection, water storage tanks, and roof waterproofing. Polyurea is widely regarded as a “perfect coating material” of the 21st century due to its superior performance over all other coating systems. Its service life is exceptional across multiple environments:
  • Over 50 years when submerged in water or soil
  • More than 20 years in exposed conditions
  • At least 15 years in marine environments
  • Over 8 years in chemical industrial environments

Polyurea coatings offer numerous advantages over conventional protective coating systems, including:

• Rapid curing time: Polyurea cures within 5 to 120 seconds, depending on the formulation and user requirements. Surfaces can be placed into immediate contact with water within 60 seconds after spraying. This allows for high productivity, minimizes downtime, and reduces economic losses due to interrupted operations during repair or maintenance.
• Excellent adhesion to a wide range of substrates, including steel, concrete, wood, and plastics, with a seamless, joint-free membrane once applied.
• Superior impact resistance, ranking as the highest among all coating systems.
• Outstanding chemical and corrosion resistance, making polyurea ideal for harsh and aggressive environments.
• High crack-bridging ability, capable of spanning cracks up to 5 mm, maintaining membrane integrity.
• Exceptional tensile elongation, with values of over 350%, and a tensile strength ratio approaching 1/10 of structural steel, ensuring flexibility and durability under stress.
• Reduced hydraulic losses due to the smooth internal surface of coated pipelines, improving flow efficiency.
• Long-term cost efficiency, owing to its minimal degradation from abrasion and chemical attack, resulting in extended service life and reduced maintenance costs.
• Zero VOC (Volatile Organic Compounds) content, making polyurea safe for human contact and suitable for potable water and food-related applications.
• In industrial or wastewater pipeline applications—where materials are often exposed to aggressive substances such as chlorides, alkalis, and acids… polyurea demonstrates superior chemical resistance and provides a longer service life than any traditional coating system.

Several durability tests have been conducted on polyurea materials manufactured by the Polyurea and Paint Factory of Newtec Group Joint Stock Company, under the witness and supervision of numerous experts in the construction sector, as well as technical officers from the Department of Technology Management and the Drainage Management Division of the Department of Technical Infrastructure – Ministry of Construction, and various project investors.

(Factory address: CN2-12, Yen Duong Industrial Cluster, Y Yen District, Nam Dinh Province, Vietnam)

Figure 10. Spraying polyurea onto a lightweight concrete wall to test impact resistance.	Figure 11. When struck with a hammer, the concrete wall was broken, but the polyurea coating remained intact.

Figure 12. Spraying polyurea onto a fiber cement sheet to test the durability of the polyurea membrane.	Figure 13. When a car runs over an uncoated fiber cement sheet, it shatters completely. However, the sheet coated with polyurea retains its original shape.

Figure 14. Concrete specimens coated with polyurea were immersed in a 10% H₂SO₄ solution. After 120 days, samples were extracted to measure sulfate penetration in accordance with JIS A7502-2:2015	Figure 15. The result achieved was above 2.5 MPa, ensuring a strong bond between the polyurea coating and the concrete surface.
Figure 16. Sulfate penetration measurement using the EPMA method. Performed on the JEOL JXA-8200 machine at Kochi University of Technology – Japan	Figure 17. Results: No sulfate penetration into the polyurea coating was detected. The coating meets Type D – corrosion-resistant standard for underground drilling pipes according to JIS A7502-2:2015.
Figure 18. R&D – Polyurea and Paint Factory – NEWTEC GROUP	Figure 19. Cross-section of the sample for measuring sulfate penetration according to JIS A7502-2:2015 at Kochi University of Technology – Japan

Note: Various polyurea coating durability test methods and demonstrations are regularly updated and available for viewing on the official YouTube channel: www.youtube.com/@newtec-group or on the company’s website: https://newtecoat.com/

6. Selected projects utilizing polyurea coatings for corrosion protection and waterproofing implemented by Newtec Group in Vietnam

Over the past years, Newtec Group Joint Stock Company has successfully implemented corrosion protection and waterproofing solutions for numerous large-scale and nationally significant projects in Vietnam. For projects with strict anti-corrosion requirements, high-performance polyurea-based coating materials have been applied. All polyurea products used are subjected to rigorous quality testing and evaluation at specialized laboratories licensed by the Ministry of Construction. Newtec Group’s application and construction processes consistently meet the technical specifications, quality standards, and project timelines as required by investors and regulatory authorities.

Figure 20	Figure 21

Supply of materials and equipment for polyurea coating technology to protect against corrosion for D800 & D1200 concrete pipes at Ha Thanh Concrete Plant

Project: Underground drainage system of To Lich River – Main contractor: TEKKEN Japan

Project: Construction of Yen Xa wastewater treatment system – Hanoi City

The VTV24h channel reported on the news segment: “Installation of the wastewater collection pipeline system along the To Lich River | VTV24.”

Figure 22	Figure 23

Polyurea coating for corrosion protection of 1.5 km long D800 concrete pipeline
Project: Wastewater collection pipeline system – Bau Bang Industrial Park – Binh Duong Province
Investor: Becamex Group

Figure 24	Figure 25

Polyurea coating for corrosion protection of wastewater treatment tanks A-B
Project: Binh Hung Wastewater Treatment Plant
Investor: Technical Infrastructure Management Center – Ho Chi Minh City

Figure 26	Figure 27

Polyurea coating for corrosion protection of the tungsten tank
Project: Nui Phao Mineral Processing Plant
Investor: Masan Group

Figure 28	Figure 29

Polyurea-based waterproofing for the roof of the Government Office Headquarters
Project: Government Office Headquarters
Investor: Government Office

Figure 30. Polyurea spray waterproofing for the roof Vinschool – Ocean Park 3 (9,000 m²)	Figure 31. Polyurea spray waterproofing for wave pool Vinhomes Ocean Park 2–3 (20,000 m²)
Investor: Vingroup

Note: And many other projects using polyurea coating are regularly updated on YouTube: www.youtube.com/@newtec-group or official website: www.newtecgroup.com.vn

7. Conclusion

The selection of an appropriate anti-corrosion coating is one of the most effective methods to protect structural components operating in highly aggressive environments. Specifically, choosing a protective coating system for underground pipelines, steel structures, or chemical-exposed tanks is critically important to ensure both technical performance and economic efficiency, as well as to extend the lifespan of the infrastructure. Among currently available technologies, polyurea-based coatings represent the optimal solution for long-term corrosion protection. Thanks to their exceptionally high durability in corrosive environments, polyurea significantly minimizes losses due to corrosion, offering substantial economic value to both investors and society at large.

The adoption of high-performance polyurea coatings for waterproofing and corrosion protection in construction and infrastructure projects is becoming a global trend, including in Vietnam. While polyurea materials may have a higher initial cost—approximately 1.2 times that of conventional coating systems—and require specialized hot-spray equipment operated by trained technicians, their long-term performance and cost-effectiveness justify the investment.

NEWTEC GROUP is proud to be a domestic manufacturer of polyurea and a leading provider of next-generation coating solutions and services in Vietnam. We are continuously improving our technologies and enhancing quality management systems to deliver high-performance waterproofing and anti-corrosion coatings, ensuring maximum durability and economic efficiency for every project we serve.