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Knowledge of corrosion protection systems for steel structures

Date:2016-10-24 22:06:44 Visits:

Corrosion protection measures of 1 steel structure

(1) weathering steel: corrosion resistance is better than the general structure of steel called weathering steel, generally containing phosphorus, copper, nickel, chromium, titanium and other metals, the metal surface to form a protective layer, in order to improve the corrosion resistance. The low temperature impact toughness is better than that of the general structure. Standard for "welding structure with weathering steel" (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 prevent the purpose of corrosion. The advantage of this method is that it has long service life, high industrialization degree and stable quality. So it is widely used in outdoor steel structures, which are more severe and difficult to maintain. Such as a large number of transmission tower, communication tower, etc.. In recent years, a large number of steel structure in the light of the pressure plate and so on. More also use hot-dip zinc corrosion resistance. First process of hot dip galvanizing is pickling, then cleaning. These two processes are not completely to prevent corrosion and leave hidden dangers. So it must be dealt with thoroughly. For the steel structure designer, it should avoid the design of the components with the phase fitting surface, so as to avoid the gap in the joint surface of the pickling is not completely or acid cleaning. 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 the two ends of the seal will cause the expansion of the air inside the tube to make the end of the board burst, resulting in a safety accident. 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. The method can not be in the inner wall of the tubular member, so that the two ends of the tubular member must be airtight sealed so that the inner wall can not be corroded. The advantage of this process is that it has a strong adaptability to the size of the component, and the shape and size of the component is almost unrestricted. Large to such as the Gezhouba Dam lock is also used in this method of construction. Another advantage is that the thermal effects of this process are localized, subject to constraints, and thus will 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: the coating method is generally not as good as long-term corrosion protection method (but the current anti-corrosion of fluorocarbon coatings, or even up to 50 years). So for indoor steel structure or relatively easy to maintain the outdoor steel structure more. It is a low cost, but the cost of maintaining a high cost 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. The choice of coating should be taken into consideration in the surrounding environment. Different coatings have different tolerance to different corrosion conditions. General primer (layer) coating and topcoat (layer) of. Primer containing powder, low 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. Whether there are compatible or not between the different paint, before and after the selection of different paint to pay attention to their compatibility. The construction of the coating should have the appropriate temperature (5~38 degrees Celsius) and humidity (relative humidity is not more than 85%). To reduce construction environment of dust coating, surface cannot have a dew. The coating shall within 4 hours after rain. Coating is generally done 4~5 times. The total thickness of the dry film outdoor project is 150 mu m, indoor project is 125 mu m, the allowable deviation is 25 mu m. In the sea or sea or in a strong corrosive atmosphere, the total thickness of the dry film can be thickened to 200~220 M.

(5) cathodic protection: the corrosion of steel on the surface of the steel structure with a more active metal instead of steel. Commonly used in underwater or underground structures.