What are the anti-corrosion measures of steel structure?
(1) weathering steel: corrosion resistance is better than the general structure of steel steel called weathering steel, generally contain phosphorus, copper, nickel, chromium, titanium and other metal, make metal surface formation protective layer, in order to improve corrosion resistance. Its low-temperature impact toughness is better than the general structural steel. Standard for "weathering steel for welded structures" (GB4172-84).
(2): the liquid zinc hot dip galvanized hot-dip galvanized steel rust after immersed in 600 DEG C melting, the steel member is attached to the surface of the zinc coating, zinc layer thickness on the 5mm plate shall not be less than 65 m, the thickness of less than 86 M. so as to the purpose of the corrosion prevention. The advantages of this method are long durability, high industrialization and stable quality. Therefore, it is widely used in outdoor steel structures which are severely corroded and difficult to maintain. Such as a large number of transmission towers, communication towers, etc.. In recent years a large number of steel structure system in the shape of the pressure plate. More also use hot-dip zinc corrosion resistance. First process of hot dip galvanizing is pickling, then cleaning. These two processes are not completely will leave hidden dangers to corrosion. So it must be dealt with thoroughly. For steel structure designers, should avoid the design of a phase with the surface of the component, so as not to fit the surface of the pickling gap is not thorough or acid wash clean. Cause galvanized surface flow yellow water phenomenon. Hot dip galvanizing is done at high temperature. The tubular member should let its both ends open. If both ends closed will cause the tube air expansion and the head plate burst, resulting in safety accidents. If the closed end is zinc liquid circulation is not smooth, easy in the tube stockpile.
(3) thermal spraying aluminum (zinc) composite coating: This is a long-term corrosion protection method and corrosion protection effect of quite hot galvanizing. The specific approach is to make the blasting of steel surface, the surface of the exposed metallic luster and a hair. Then the oxy acetylene flame will continue to send the aluminium (zinc) wire melting, and compressed air is attached to the steel surface to form a honeycomb aluminium (zinc) coating layer (thickness of about 80 m ~ 100 m). The last filled pores with epoxy resin or neoprene paint coating to form a composite coating. This method can not be built in the inner wall of the tubular member, so that both ends of the tubular member must be airtight sealed so that the inner wall will not corrode. The advantage of this technology is that the size adaptability is very strong, and the member shape and size is almost unlimited. Large locks such as Gezhouba Dam are also constructed in this way. Another advantage is that the thermal effects of this process are local, constrained, and thus do not produce thermal deformation. With the hot galvanizing of this method compared to the degree of industrialization is low, sandblasting spray aluminum (zinc) with high labor intensity, quality is also susceptible to emotional changes of the effects of the operator.
(4) coating method: coating method corrosion is generally not as effective as long-term corrosion prevention method (but fluorocarbon coating corrosion protection life can reach up to 50 years). So for indoor steel structure or relatively easy to maintain outdoor steel structure more. It costs once, but maintains higher costs for outdoor use. The first step is the construction method of coating rust. High quality coating depends on thorough cleaning. So the general requirements of high coating sandblasting derusting, exposed metal luster, remove all rust and oil pollution. The coating available manual derusting construction site. Selection of coatings to consider surrounding environment. Different coatings have different tolerance to different corrosion conditions. General primer (layer) coating and topcoat (layer) of. Primer powder containing more, less base material. The film is rough, and steel, strong adhesion, good bonding with paint. Finish is base material, film luster, can protect the primer from atmospheric corrosion, and resistance to weathering. There is a compatibility between different coatings or not, before and after the use of different coatings should pay attention to their compatibility. Coating construction should have appropriate temperature (5 ~ 38 degrees C) and humidity (relative humidity is not greater than 85%). To reduce construction environment of dust coating, surface cannot have a dew. The coating shall within 4 hours after rain. Coating generally do 5 to 4 times. The total thickness of the dry film outdoor engineering is 150 m, indoor engineering is m, allowing a deviation of 25 M. in the sea or sea or in a strong corrosive atmosphere, dry film thickness can be thickened for the total of 200 ~ 220 M.
(5) cathodic protection method: corrosion of steel on steel structure with more active metal instead of steel. Often used in underwater or underground structures
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