Corrosion situation and protection methods of marine equipment in my country

With the rapid development of marine industry, the number of marine-based infrastructure is increasing day by day, and the corresponding problem of marine anti-corrosion is also emerging. Because the salt content of sea water is very high and the conductivity is very good, the more active metals with different livelyness will accelerate corrosion when they come into contact. The concentration of chlorine ions in seawater is about 3%, which has the highest corrosion rate of

. In addition, the microorganisms, dissolved oxygen, PH, temperature and other factors in seawater all affect the corrosion of marine equipment to some extent.
China's annual economic losses caused by corrosion are about 3% to 5% of GDP, the total corrosion losses in 2014 exceeded 2.1 trillion yuan, of which marine corrosion has accounted for one-third of the annual corrosion situation.
above shows that the phenomenon of marine corrosion equipment in China has become more and more serious. To this end, our country has also carried out a number of studies, the results of which are shown below.
China's current main corrosion protection methods and their cost ratio
from the above chart cost ratio we can see that China has invested more money in coating protection methods, that is to say, coating protection is the most important corrosion protection methods. This is because coating protection avoids direct contact between the substation surface and corrosive environments such as air and water, thus achieving corrosion purposes.
preparation of water-based epoxy materials
Water-based epoxy coatings do not contain volatile organic matter, with green, environmental protection, low toxicity and so on, is the future trend of coating development. The first thing to do to make a water-based epoxy coating is to solve the problem of how to disperse the oil-soluble epoxy resin in water, that is, the hydration technology of epoxy resin. Epoxy resin is insoluble in water, and its water-based methods are mechanical, chemically modified, and emulsified.
Michine method
is to directly grind solid epoxy resin into micron-grade epoxy resin powder, and then at high speed dispersion to add emulsion aqueous solution, the final epoxy resin particles can be evenly dispersed in water to form a water-based epoxy emulsion.
: The process is simple. The amount of emulsifying agent is less.
: large size of epoxy particles in emulsion, irregular shape, poor stability, easy coagulation, film-forming performance is also poor.
Chemical modified method
chemical modified method, also known as self-emulsification method, introduces some hydro-hydroploric groups into the molecular chain of epoxy resin, so that epoxy resin obtains the properties of self-emulsification. When the modified epoxy resin is dispersed with water, the hydrophobic epoxy resin molecular chain will gather into particles, hydrophobic groups distributed on the surface of these particles, due to the interaction between charges, under certain dynamic and thermodynamic conditions, can form a stable hydroreoxygen emulsion.
: small size of epoxy emulsion particles (up to the nanoscale), wide size distribution, high emulsion stability.
a plus emulsification method
plus emulsification method is a high-speed dispersion of epoxy resin and emulsion evenly mixed, and then slowly add water to the system, so that the whole system gradually from the oil-packed water type to the water-packed oil type, and then form a stable water-based epoxy emulsion.
characteristics of water-based epoxy coatings
water-based epoxy coatings maintain solvent-based epoxy coatings with strong adhesion, excellent performance, corrosion resistance and other advantages. The specific features are as follows:
Green: water-based epoxy resin replaces organic solvents with water, contains or contains a small amount of air harmful pollutants (HAP) and volatile organic compounds (VOCs), and does not pollute the environment.
Safety: Because the water-based epoxy resin system does not contain or contain a small amount of volatile organic solvents, so in the production and construction process will not endanger human health, will not occur combustion, explosion accidents, storage, transportation, construction process is more convenient.
easy to clean: water-based epoxy coating appliances cleaning is relatively simple, water can basically be flushed clean, both economical and convenient. The application equipment of solvent-based epoxy coating must be cleaned with organic solvent, and the cleaning work is in danger of solvent poisoning and explosion.
: Water-based epoxy coatings are more resistant to a variety of oils than solvent-based epoxy coatings.
re-coating is good: water-based epoxy coating after a long time to re-coat, its coating film still has good performance.
water-based epoxy coating also has some shortcomings and defects, which become the limitation of water-based epoxy coating application. First, water-based epoxy coating film is more difficult to dry, water polarity, with high thermal capacity and high boiling point, therefore, water in epoxy resin coating volatilization rate is relatively low, especially in high humidity and low temperature environment, water evaporation is slower; The addition of active agents will produce foam, but also lead to the presence of organic volatile substances in the coating;
the current marine equipment corrosion is becoming more and more serious, the development of water-based coatings can protect the outer layer of marine equipment, but also to greatly reduce maintenance costs. Because of its green, environmentally friendly and non-toxic nature, water-based epoxy coatings are the best choice for marine equipment to ensure marine industry and fisheries. Although water-based epoxy coatings in the development and construction process is facing many difficulties, but the coating hydration is the trend of global coating industry development, the future application of water-based epoxy resin will be more popular.
.