Take steel structure residential villa for example, at present, the proportion of steel structure construction in domestic cities and towns is very low, while the proportion of steel structure residential buildings in European and American developed countries is as high as 50%, and the market potential is huge. If it can be effectively promoted, the steel structure industry will inevitably get further growth. At the same time, the application of steel structure in Bridges, schools and hospitals is relatively low at the present stage, and the future of these fields also has huge space for development.
As we all know, the corrosion of steel is a natural existence, for the life of steel structure as the main building, the protection of steel is particularly important. Steel corrosion protection technology generally through the following ways: change the corrosion environment; Develop new materials with good corrosion resistance; Coating coating protective layer; Electrochemical protection; Reasonable material selection and design. Comprehensive operability and economic considerations and other factors, coating protective coating method is the most common application, steel structure construction and construction is the most used in the application of protective coating.
"Before 2000, more than 98% of steel structures were coated with solvent-based coatings, and water-based coatings were almost negligible." Secretary General Xu pointed out that "water-based coatings have an absolute advantage in environment-friendly coatings for steel structure protection due to their convenient construction and outstanding cost performance."
The biggest characteristic of water-based coating is safety and environmental protection. Because it does not belong to the category of inflammable, explosive, easy to make drugs and easy to corrode hazardous chemicals, it is safe and convenient in transportation, storage, construction and other links; At the same time, the construction odor is low, VOC emission reduction in more than 80%, by many steel structure enterprises, paint construction personnel's favor. In recent years, with the gradual improvement of people's environmental awareness, the increasing perfection of environmental laws and regulations, especially the implementation of the national top-level strategy of "carbon peak" and "carbon neutral", environment-friendly coatings (water-based coatings, powder coatings, high-solid coatings, UV curing coatings, etc.) have ushered in unprecedented development opportunities.
Current status of waterborne structural coatings for steel
At present, water-based coatings can be applied to steel structure including water-based alkyd coatings, water-based acrylic coatings, water-based epoxy coatings, water-based inorganic zinc-rich coatings and so on. Waterborne alkyd coating: good adhesion, low requirements on the substrate, film rust resistance is good, cost-effective, suitable for use as a metal primer, underside paint; Water-based acrylic coating: the coating is quick to dry, small odor, good adhesion, strong durability, suitable for metal primer, top paint, bottom paint in one; Water-based epoxy coating: high salt spray resistance, excellent corrosion resistance, excellent oil resistance, water resistance, salt resistance, solvent resistance; The film is tough and compact, and has good adhesion to the substrate; Water-based inorganic zinc-rich coating: good quick drying, excellent resistance to salt spray, VOC almost 0.
According to GB/T 30790 "Color paint and varnish protective coating system for corrosion protection of steel structure" standard, corrosion environment is divided into 6 categories, respectively C1, C2, C3, C4, C5-I, C5-M.
Corrosion environment is divided into Marine corrosion factors and atmospheric corrosion factors. Corrosion factors in Marine environment mainly include salt spray in the air, moisture, electrolyte concentration in seawater, oxygen content, microorganisms, etc. Atmospheric corrosion factors mainly include ambient humidity, temperature, acid pollutant concentration, electrolyte particles floating. A good understanding of the corrosion factors of steel can help us select the appropriate protective products to protect the steel structure and prolong the service life.