Application of Anti-corrosion Coatings for Concrete Structures

Corrosion protection technologies for concrete structures include increasing the density of the concrete structure itself, surface treatment of steel bars, cathodic protection, adding corrosion inhibitors, and coating with anti-corrosion coatings

The anti-corrosion coating technology is a widely used, simple and effective auxiliary anti-corrosion measures for concrete structures

Corrosion mechanism of concrete structures such as sewage pools and cooling towers

With the development of China's environmental protection, in recent years, sewage treatment plants in many regions of China have been or are building coatings online coatingol.

Other concrete structures such as thermal power plants and chemical plants, such as desulfurization flues, cooling towers, and electrolytic cells, often require high-performance special anti-corrosion coatings that are resistant to high temperature, wear, and chemical media.

Commonly used anti-corrosion materials for sewage pools and cooling towers

▷ Sewage treatment tank

Traditional protective coatings include epoxy asphalt and coal tar asphalt coatings

▷ Cooling tower

The cooling tower is one of the important components of the thermal power plant.

▷ Desulfurization flue

There are three typical schemes for desulfurization flue coatings: base coat + vinyl glass flake paint 2 × 1mm + top coat; base coat + vinyl glass flake paint 2 × 1mm + FRP layer + top coat; base coat + vinyl Glass flake coating 2×1mm + (wear-resistant glue + glass cloth) 1-2 layers + topcoat

Development trend of anti-corrosion coating technology for concrete structures

The future development trend of coatings for reinforced concrete structures will also follow the principles of high performance and green environmental protection
.
At the same time, the coating technology is developing in a diversified direction to meet the requirements of different corrosive environments, different anti-corrosion parts, and even human landscapes
.

▷ High performance weathering finish

In the surface dry area, the system of epoxy sealant + epoxy micaceous iron paint + acrylic polyurethane topcoat will be used for a long time in occasions with high anti-corrosion and landscape requirements due to its comprehensive excellent performance
.
In the above system, the base coat epoxy paint will gradually transition to high-solid, solvent-free paint, and the weather-resistant topcoat will gradually transition to fluorocarbon paint and polysiloxane paint with better weather resistance
.

▷ Elastomeric Coatings

Compared with steel, the deformation of concrete structure is larger, so the JT/T695 standard stipulates that the coating used for the surface of concrete structure should have good mechanical properties to adapt to the deformation of concrete
.
The coating system is: epoxy resin or polyurethane primer + epoxy resin putty + flexible epoxy resin or flexible polyurethane middle coating + flexible polyurethane top coating
.
The standards for anti-corrosion surface coatings for railway bridge concrete structures, which are being formulated, specify flexible fluorocarbon coatings and their technical indicators
.

▷ Solvent-free, high solids epoxy coating

Solvent-free epoxy coatings are the most widely used solvent-free anti-corrosion coatings
.
Solvent-free epoxy coatings are difficult to construct, and the use of reactive diluents and high-performance low-viscosity curing agents increases the cost.
Therefore, the use of high-solid epoxy coatings (volume solid content of more than 80%) is also an option.
environmental protection program
.
Some parts with harsh corrosive environment and difficult to maintain can be protected by thick-film epoxy coating, epoxy glass flake coating, or epoxy coating + glass cloth
.
Solvent-free coatings or high-solids high-strength coatings cannot be directly used on concrete surfaces due to their high viscosity and poor permeability.
They should be matched with low-viscosity, high-permeability primers, or these high-viscosity coatings should be diluted and primed
.

▷ Vinyl ester glass flake coating

Commercially available vinyl resin is composed of vinyl ester prepolymer solvent in styrene monomer (usually 35%), and vinyl ester prepolymer is composed of epoxy resin and vinyl group-containing acrylic or methacrylic acid.
should be generated
.
By adding catalyst and curing agent, the reaction between styrene and between styrene and vinyl resin is cured to form a film by free radical polymerization
.
The cross-linking and curing of vinyl ester resin will cause volume shrinkage and internal stress, and part of the internal stress can be eliminated by adding glass flakes
.
Vinyl glass flake coatings have good chemical resistance and high temperature resistance ratings
.
At present, vinyl glass flake coatings are mainly used in desulfurization flues, and also have a small amount of applications in sewage pools
.
The actual application effect of the current vinyl glass flake coating is not good.
The coating used for desulfurization flue has a large area of ​​shedding within 1-2 years, which is mainly determined by the quality of the coating and the construction process
.
The quality of glass flake coatings is mainly determined by the treatment of the glass flakes and the dispersion effect in the matrix resin
.

▷ Polyurea coating

Spraying polyurea is an elastomer material formed by the reaction of isocyanate component (referred to as component A) and amino compound component (referred to as component B)
.
Compared with traditional polyurethane elastomer coating spray technology, spray polyurea elastomer technology (SPUA) has many excellent properties and characteristics: fast drying speed, hardening in a few seconds after application; insensitive to moisture, strong adaptability to construction environment ; Facade thick film construction does not sag; has very excellent mechanical properties and medium corrosion resistance
.
The polyurea applied to the concrete surface is not ideal for direct spraying and adhesion to the concrete surface due to its fast curing speed and poor permeability
.
At present, the main application field in China is the waterproof material of the railway.
In addition, it is also used in the fields of sewage pools, bridges, and desulfurization flues, but the use effect is not ideal
.