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| The performance characteristics of organic and inorganic zinc rich coatings |
Paint as a simple and economical and effective means of anti-corrosion has been thousands of years of history. Since the industrial revolution, iron and steel and other metal materials mass production, in order to reduce the problem of metal corrosion, people have taken many measures, but so far, the most effective and the most economical, the most economical. At present, as the steel structure anticorrosion and shop primer is the most common, the most important still is zinc rich primer. The development of modern industrial technology not only provides a better technical material conditions for the development of anti-corrosion coatings for steel structures, but also offers a wider market.
Zinc rich coatings
Zinc rich coating in the coating system is mainly in the form of zinc rich primer for all kinds of steel structure corrosion, due to its formula rich in a large number of electrochemical antirust pigment, zinc powder, therefore is called zinc rich coatings. Zinc rich paint film is hard, good adhesion, corrosion resistance strong, with excellent anti-corrosion properties and oxidation corrosion resistance, and excellent cathodic protection effect and electrostatic guiding role and performance of welded without adverse effects, and the use of most of the coating supporting, has become of iron, steel and other ferrous metal anti-corrosion field is most common, the most important of the primer, in the atmosphere and ocean in the field of corrosion had almost no compete with rivals. Only to be coated material in acid corrosion medium environment, because these media can penetrate into react with zinc powder easily generated hydrogen, had no choice but to use other anti rust primer. Zinc rich primer on the production and application can be divided into two categories, namely with silicate inorganic adhesive inorganic zinc rich primer and with epoxy resin as the bonding agent of organic zinc rich primer. When used in the field of anti-corrosion, they must meet the requirements of the following supporting: due to zinc primer to steel with close contact in order to play its role in electrochemical protection and so on the substrate surface pretreatment requirements strictly, is the bottom coating material must be sandblasted to ensure the quality of construction. II zinc rich primer coating is usually thin and subject to the influence of external environment medium, therefore generally not used alone, must match with appropriate intermediate paint and paint, and achieve the specified film thickness. Because of the zinc rich primer with good corrosion resistance and weldability. Therefore, it is widely used to shop primer, also known as steel pretreatment processing primer or maintenance primer. Coated with maintenance primer for steel and steel structure in the pretreatment, cutting and welding and no rusting, steel structure parts installed without sand, just water cleared the dirt on the coated surface of the object can be directly under the primer or top coat paint.
The requirements of zinc powder
Zinc powder is the most important electrochemical antirust pigment, and other metal compared to have the following characteristics: lighter than iron, good ductility, made of aluminum alloy with iron. The most important is the electrochemical activity and the standard electrode potential is -0.76 V, -0.44 V iron has a lively, full of "self sacrifice". Zinc is melting and processing purification into fine particles of high purity zinc powder, as an important anti rust pigment for anticorrosive coatings, in the erosion of the film, zinc powder as the anode will first from corrosion, steel material as the cathode under protection. Due to the zinc powder as sacrificial anode formation of oxidation products of coating to the closure effect, thus strengthening the protective effect of the coating on the substrate. The zinc in the protection of substrate from erosion process is gradually consumed, but the speed is very slow. Its resistance to the formation of corrosion products and the coating and substrate potential difference decreases, when the film is damaged, and exposed new metal zinc and potential difference will immediately increases, resulting in a new round of strong cathodic protection effect, so zinc rich paint will not rust from the coating damage to Zhou Wai diffusion. In order to ensure in zinc rich primer zinc can steel with closely to conductive and sacrificial anode effect, quality assurance of zinc rich primer, zinc rich coatings containing zinc content (percentage of the total mass of the membrane, the international has been stipulated. Such as standard of American steel structure coating association the SSPC - paint 20 "in specific provision: inorganic zinc rich paint not less than 74%, organic zinc rich paint not less than 77%. The zinc content than inorganic zinc rich paint containing zinc content is due to the relatively poor conductive inorganic zinc rich paint organic zinc rich paint. Many more single coating long-acting anti the content of zinc powder in corrosion inorganic zinc rich coating products in water soluble paint Zhongda 75%, solvent type coating reached 82%. The use of different coating requirements of zinc rich primer thickness are different, then the powder particle size and the morphology of different requirements |
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