In the marine environment, anti-corrosion paint is a special coating that is used on metal structures such as docks, platforms, and pipelines. It can react chemically with the metal surface to form a tightly adherent protective film. This protective film can effectively block seawater, oxygen, etc. from corroding the metal, thus extending the service life of the metal structure. It can also extend the service life of the anti-corrosion paint itself, and ensure its safety and functionality in the marine environment.
What are the main causes of coastal corrosion?
The coast is corroded. This electrochemical process is complicated. Seawater is a highly conductive electrolyte. It dissolves the metal anode, which is corrosion, and creates an ideal environment for the cathode reaction including oxygen reduction. Chloride ions are very corrosive. It can destroy the passivation film on the metal surface and accelerate the corrosion rate.
In addition to the sea water itself, the ocean atmosphere is also severe. Salt spray particles are carried by sea breeze, and the salt spray particles settle on the metal surface, thereby forming a thin liquid film. This also constitutes a corrosion battery. The tidal range and splash zones are often the most violent locations due to the alternation of wet and dry conditions and sufficient oxygen supply. Knowing these basics turns out to be the starting point for choosing protection methods.
How to choose a coating protection system for steel structures
Coatings are widely used in anti-corrosion methods. Coatings use physical barriers to isolate metals from corrosive media. In coastal environments, the coating system must have excellent weather resistance, adhesion, resistance to chloride ion penetration and wear resistance. Generally, a matching system such as "primer – intermediate paint – topcoat" is used.
The paint commonly used for primers is zinc-rich primer, which uses zinc to act as a sacrificial anode and provide cathodic protection. Epoxy mica paint is commonly used as an intermediate paint, which can increase the thickness of the coating and block corrosion factors. Polyurethane or fluorocarbon topcoats are often used as topcoats. These two topcoats can provide outstanding weather resistance and aesthetics. Surface treatment before construction, such as sandblasting to Sa2.5 level, is extremely critical and will directly affect the life of the coating.
How to implement cathodic protection technology
For the metal structure, cathodic protection measures are carried out on the metal structure by means of making its configuration assume the negative electrode state under electrochemical conditions, thereby inhibiting the dissolution reaction of the anode position of the metal structure. There are two main methods of cathodic protection, one is the sacrificial anode method, and the other is the method of applying external current type. The sacrificial anode method connects metals with more active properties, such as aluminum and zinc alloy blocks, to the protected structural parts to protect the steel structure through its own corrosion conditions.
According to the law of impressed current, protective current is applied to the structure, and with the help of DC power supply and auxiliary anode, they act on the targeted structure. This method is suitable for large and complex marine projects, such as long-distance submarine pipelines and large port facilities. The implementation of this method requires a stable power supply and continuous monitoring and maintenance. However, its protection range is wide and its lifespan is long. Provide global procurement services for weak current intelligent products!
What are the applications of composite materials in corrosion protection?
Fiber-reinforced polymer composite materials, also known as FRP, have excellent corrosion resistance and have become a material that can effectively replace steel or be used to reinforce steel in coastal environments. In particular, FRP materials are completely non-conductive, eliminating electrochemical corrosion from the source, and are high in strength and light in weight.
Among some commonly seen applications, there are instances where FRP bars are used to replace steel bars in concrete structures, and they are also used to make corrosion-resistant grilles, guardrails, pipes and ship parts. In addition, FRP sheets or fabrics are often used to reinforce concrete beams and columns that have suffered corrosion. Although its initial cost is relatively high, it has the characteristics of free maintenance and long life, which is often more economical throughout its life cycle.
Routine procedures for monitoring and maintaining corrosion
To achieve effective corrosion prevention and control, it is absolutely impossible to do without systematic monitoring and full maintenance. Conventional monitoring methods include regular visual inspections, coating thickness measurement, potential measurement of phenomena (for cathodic protection systems), and the use of ultrasonic thickness measurement to examine the specific wall thickness loss of components.
Based on the data obtained from monitoring, a preventive maintenance plan needs to be formulated. This plan includes timely repair of damaged areas of the coating, replacement of consumed sacrificial anodes, adjustment of the output of the impressed current system, partial replacement or reinforcement of severely corroded areas, and the establishment of a complete corrosion management file, which serves as the basis for subsequent maintenance decisions and life assessment.
Future development trends of coastal protection technology
As time goes by, the development of technology will focus more on intelligence, environmental protection and long life. Intelligence is specifically demonstrated where sensors and Internet of Things technology are integrated. It has the ability to realize real-time online monitoring and early warning of corrosion status, thus promoting the transformation of protection from regular maintenance to predictive maintenance.
In accordance with environmental requirements, research and development needs to be carried out to obtain products such as water-based coatings and high-solid coatings with low VOC emission characteristics. At the same time, corrosion inhibitors with more outstanding environmental characteristics must be developed. In the field of materials, at this time, self-healing coatings have become a hot spot of research, new corrosion-resistant alloys have also become a hot spot of research, and nano-modified coatings have also become a hot spot of research. The goal of these studies is to further improve the reliability of the protection system, further enhance the durability of the protection system, reduce the maintenance cost of the entire life cycle, and reduce the environmental burden throughout the life cycle, and ultimately achieve the above effects.
In view of the coastal engineering project you are currently carrying out, when faced with weighing the initial investment and long-term maintenance costs, do you prefer to choose traditional and mature protection solutions, or are you willing to try to use new smart monitoring technologies that are promising but may be more expensive? Welcome to share your views and practical experience in the comment area. .
Leave a Reply