Protection method of the hottest metal surface coa

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Protection method of metal surface coating

the surface of metal contacting corrosive medium is isolated from the metal surface by coating, plating, lining and other methods, so as to achieve the purpose of protecting all kinds of extruded pipe braided pipe protection or decoration, which is the most important and widely used protection method in anti-corrosion methods. The metal surface covering layer can be divided into metal covering layer protective layer and non-metal covering protective layer

a. metal surface coating

the metal surface covering layer can be divided into protective layers such as plating layer, enamel welding layer, lining layer, bimetal layer, etc

coating includes spray coating, chemical coating, infiltrated coating, electroplated coating, dip coating, etc., such as spraying aluminum on the steel surface, zinc to prevent atmospheric and seawater corrosion, and spraying alloy on the steel surface to improve heat resistance, corrosion resistance and wear resistance. Chemical nickel plating and other metals are used on the steel surface to improve the corrosion resistance, while siliconizing and carburizing on the steel surface to improve the hardness, etc. Electroplating is widely used for rust prevention and decorative effect on the surface of steel products. Electroplating is also widely used for corrosion prevention and wear resistance, from daily life products to precision instruments and meters. The most common ones are precious metal plating, non-ferrous metal plating, such as lead, zinc, copper, nickel, chromium, etc. The most common hot-dip coatings are zinc and tin coatings. The potential of zinc is extremely negative, which can effectively prevent the corrosion of steel. Even if there are pores locally, it can also play the role of screen protection. Brush plating is a kind of electroplating layer with special function developed in recent years

8. required sample size: 100mm × The most commonly used 100mm enameling layer is lead enameling or lead alloy, which is used for the bottom layer of composite lining or anti-corrosion protective layer. In the past, lead lining was a commonly used protective method. At present, with the development of synthetic materials and the use of new protection methods, lead lining and lead lining are only used in the protection of individual production system equipment

the common protection methods of lining layer include steel surface lining with lead, stainless steel lining and so on. The steel lining with lead equipment is widely used in the corrosion prevention of sulfuric acid production equipment. In addition to corrosion protection, stainless steel lining can also replace stainless steel equipment with 2 ~ 3mm stainless steel lining layer, so as to save stainless steel and reduce equipment cost

bimetallic layer is the development direction in the future. When rolling steel plates or products, the metal composite of two different materials will protect the matrix material

b. non metallic cover

there are three kinds of non-metallic covering protective layers: coating, mastic protective layer and lining protective layer. Generally, the thickness of the coating is less than 1mm, the thickness of the mastic protective layer is between the lining layer and the coating, and the thickness of the lining layer can range from 1 ~ 2mm to hundreds of mm

among the non-metallic coatings, there are enamel inorganic coatings, such as enamel, glass lining, and plastic spraying layers (flame spraying or normal temperature spraying followed by heat treatment and sintering). The protective layer of various solvent based coatings is the most widely used method of rust prevention, and there are thousands of coating brands in China. In order to improve the strength and impermeability of solvent based coatings, glass cloth reinforcement and flake glass filler have been used in recent years to improve the coating effect and greatly prolong the service life. Plastic coating and inorganic enamel protective layer are commonly used for the inner wall protection of various chemical equipment, and can be used in strong corrosive media. Enamel equipment is also used in the occasions of heat conduction (jacket heating and cooling). Solvent based coatings are suitable for atmospheric, seawater and places with weak corrosion due to their thin coating and microporosity. The solvent-free synthetic resin coating developed in recent years has a thick film, which is suitable for some places with strong corrosivity

the daub protective layer has been used in China as early as the 1950s. For example, the first impermeable graphite tube cooler made by Tianjin Chemical Plant adopts impregnated graphite tube to bond with steel flower plate, and the flower plate is protected by phenolic daub. At that time, the rubber protective layer of the lining of hydrochloric acid railway tank car was easy to swell and damage in the by-product hydrochloric acid containing benzene. It also included that the effective solution in other places had been coated with phenolic mastic protective layer for protection. In recent years, with the development of science and technology, there are examples of using mastic to protect the surface of concrete tanks in chemical plants. Its engineering cost is lower than that of FRP lining, but it is not widely used along the

there are many kinds of non-metallic lining protective layers, such as FRP lining, rubber lining, brick lining, composite lining, etc., which are bonded. Lining plastic is commonly used at present. Each kind of lining has different materials and methods, such as rubber lining and natural rubber plate lining. After the rubber plate is pasted, it should be steam vulcanized. Synthetic rubber plates such as butyl rubber can be pasted at room temperature without treatment. Nitrile polyvinyl chloride adhesive board can be pasted on the concrete surface. The brick board lining can be made of inorganic adhesive and four kinds of thermosetting synthetic resin mastic such as phenolic, furan, epoxy and unsaturated polyester, or mutually modified mastic lining ceramic board, diabase board, stainless graphite board, etc. it can resist the corrosion of various media and is the most widely used protection method

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