Research and development of four types of mainstream water-based anti-corrosion coatings

Traditional industrial coatings contain a large number of organic solvents, solvents in the construction and drying process are mostly waved out, which not only seriously pollutes the environment and harms human health, but also a great waste of resources. According to the data, steel products and their facilities in the coating process volatile VOC total of about 20% to 25% of the global VOC, has become one of the main sources of air pollution. Therefore, the use of water-based coatings instead of solvent-based coatings for industrial anti-corrosion coating is of great practical significance for China to build a harmonious society and achieve sustainable
of
.
water-based coatings are either water as solvents or as dispersing media. It has the characteristics of non-toxic, tasteless, low price, abundant resources, can greatly reduce the pollution of the atmosphere caused by the evaporation of organic solvents in coatings, and water as a solvent, can greatly improve the safety of coatings in the storage, transportation and construction process. At present, water-based anti-corrosion coatings have been successfully used in building decoration, automobile manufacturing, ship and container manufacturing, railway locomotives, aerospace, transportation bridges and wood coating.
water-based anti-corrosion coatings mainly include water-based inorganic zinc-rich coatings, water-based epoxy coatings, water-based acrylic coatings and water-based polyurethane coatings four categories.
1
water-based inorganic zinc-rich coatings
water-based inorganic zinc-rich coatings are generally divided into self-curing inorganic zinc-rich and post-curing inorganic zinc-rich two categories. At present, the market is widely used is water-based self-curing inorganic zinc-rich coatings. Water-based inorganic zinc-rich coatings are mainly based on inorganic silicates (including Li4SiO4, Na4SiO4, K4SiO4, (NH4) 4SiO4, etc.) as the base solution, zinc powder as anti-corrosion pigment, in order to improve the construction of water-based inorganic zinc-rich coating film, corrosion resistance, need to be appropriately added to the corresponding additives, such as flow leveling agents, corrosion inhibitors.
water-based inorganic zinc-rich anti-corrosion coating mainly has the following characteristics:
(1) drying speed, at 20 degrees C and 75% of the relative humidity, about 1h finger drying.
(2) coating has good electrostectronic conductivity and excellent welding performance.
(3) excellent corrosion resistance, long-term resistance to pH range of 5.5 to 10.5 chemical corrosion, in the ocean atmosphere environment, water-based inorganic zinc-rich coatings can be used for up to 25a.
(4) can withstand temperatures of up to 400 degrees Celsius for a long time.
(5) clean and environmentally friendly, water as a thinner and cleaning agent, volatile organic matter for 0, environmentally friendly.
(6) water-based inorganic zinc-rich coating is also its shortcomings, mainly manifested in the dry film contains a large number of zinc powder, resulting in porous coating;
water-based inorganic zinc-rich coatings are suitable for long-lasting corrosion protection of steel structures such as marine platforms, ships, containers, large steel components, pipelines, and various chemical tank linings in various environments such as ocean platforms, ships, containers, etc.
2
water-based epoxy coating
water-based epoxy coating is mainly water-dispersed epoxy coating, composed of hydrophobic epoxy resin and hydrophobic curing agent two components.
the process of filming is divided into two stages:
first, the evaporation of water to reach the table dry,
, the polymerization of epoxy resin and curing agent cross-linking process.
water-based epoxy coating itself contains water, which can be used together with moisture on the surface of the wet substrate to form a component of the water-based epoxy coating.
water-based epoxy coating system has the following characteristics:
(1) in steel, concrete, aluminum and other substrate surface has excellent adhesion, coating film with high hardness, good wear resistance, corrosion resistance and excellent chemical resistance and so on.
(2) Low volatile organic matter content, will not cause air pollution, its water as a dispersion medium, low-cost, odorless, non-combustible, storage, transport and use of the process of safety greatly improved.
(3) fast-drying, at 20 degrees C and 75% relative humidity, generally 2h can reach finger drying, the minimum curing temperature of 15 degrees C.
(4) but its chemical resistance is still slightly worse than the solution dosage form epoxy coating, the service life is also shorter than the general solvent-based epoxy coating.
now commercialized water-based epoxy anti-corrosion coatings are:
water-based iron epoxy red primer, water-based zinc epoxy phosphate primer, water-based epoxy zinc-rich primer and water-based epoxy cloud iron intermediate paint.
3
Water-based acrylic coating
water-based acrylic coating refers to the main acrylic co-polymer as the base material, water as a dispersant, and then add pigment fillers, additives and other ingredients made, acrylic co-polymer by methyl acrylates, acrylates and acrylic synthesis, it is divided into water-based, water-soluble and water-soluble acrylic paint according to the state of the resin in water. Because the relative molecular mass of acrylic polymer water dispersion is higher than that of solvent-based polymers, a harder paint film can be obtained after drying. This resin is in a long chain of three-dimensional mesh form, by selecting different monoliths and monolith ratios, can meet different requirements for use.
water-based acrylic anticorrosive coating system has the following characteristics:
(1) water-based acrylic paint has good weather resistance, UV resistance, water resistance, not yellowing. After 45min up to hard dry, after 2h can be re-coated, can be used at as low as 5 degrees C.
(2) water-based acrylic paint can be matched with water-based epoxy or acrylic primer, medium paint, can also be used on solvent-based coating, forming a composite coating system.
(3) excellent corrosion resistance, good color preservation, water as a thinner and cleaning agent, non-combustible and safe.
(4) water-based acrylic coating also has a large hardness, solvent resistance and other problems.
water-based acrylic anticorrosive coatings can be made into light and semi-gloss types and can be used as primers, finishes and closed paints for concrete surfaces. Can be built on the surface of steel, concrete and other substrates, the coating has good adhesion, weather resistance, low temperature resistance, preservation of color and so on. Water-based acrylic coatings are widely used in the construction industry, automobiles and other fields, has become a large anti-corrosion coating system.
4
-based polyurethane coating
water-based polyurethane coating is based on water-based polyurethane resin, water, pigments, additives and other preparations. Water-based polyurethane resins can be divided into polyurethane aqueous solutions by particle size and appearance (particle size <0.001 m, transparent appearance), polyurethane water dispersions (particle size: 0.001-0.1 m, translucent appearance), polyurethane emulsions (particle size >0.1 m, appearance turbidity) water-soluble three.
water-based polyurethanes can be divided into polyether type, polyester type and polyether type, polyester hybrid type according to synthetic monomer. According to the choice of diocyanate, water-based polyurethane can be divided into aromatic and adipose groups, or specifically divided into TDI type, HDI type, MDI type and so on. The whole synthesis process of water-based polyurethane can be divided into two stages. The first stage is pre-gradual polymerization, i.e. water-based polyurethane pre-polymer with a relative molecular mass of 1000 magnitude is produced by gradual polymerization of low-polymer glycol, chain-expanding agent, water-based monomer and isocyanate through solution;
water-based polyurethane anti-corrosion coating has the following characteristics:
(1) particle size is less than 0.1nm, with good dispersion stability.
(2) low production costs, safe non-combustion, non-pollution of the environment, not easy to damage the surface of the coating, easy to operate and modification.
(3) have good adhesion to wood, fiberboard, plastic film, metal, glass and leather.
(4) water-based polyurethane coatings still exist into the film for a long time, the paint film caused by hydrophosphatlic group water resistance is poor, paint film easy to produce bubbles, higher raw material costs and other shortcomings.
water-based polyurethane anti-corrosion coatings are mainly used as anti-corrosion paint, widely used in railway locomotives, bridges, automobiles, wood furniture, architectural decoration and other coatings. With the continuous improvement of environmental protection, human health and the quality requirements of coatings, the comprehensive use of a variety of modified methods and the development of new modified methods has become the main direction of water-based polyurethane coating research. In addition, how to improve the water-resistant, anti-static and antibacterial properties of water-based polyurethane coatings will also become a new direction of future research.
the development of water-based coatings can not only greatly alleviate the consumption of petroleum resources, but also can greatly reduce VOC emissions, which in the environment is deteriorating and oil resources are becoming increasingly tight today has a very important economic and social significance.