Anti corrosion technology of the hottest plastic p

Plastic powder flame spraying anti-corrosion technology

Abstract: This paper aims at the current domestic thermal spraying technology, which is mainly used for parts repair and pre protective coating. The spray gun has a single powder feeding structure and spraying function, which can not meet the needs of large-scale component thermal spraying anti-corrosion field construction. Shaanxi Zhongke Surface Engineering Co., Ltd. has specially developed "plastic powder flame spraying" and "ceramic powder flame spraying" for thermal spraying anti-corrosion coating. The spray gun adopts a multi-functional powder supply structure, which can use the powder bucket on the gun to supply powder, and can also use a large capacity powder feeder to supply powder. Different nozzles can be changed according to different powders, From then on, it ensures that the new flame spraying equipment is "reliable, practical, efficient and multi-functional spraying" in the construction of large projects, and meets the requirements of thermal spraying anti-corrosion coating in the field spraying construction of large components

key words: thermal spraying corrosion prevention; Plastic powder; Flame spraying; Ceramic powder flame spraying

I. overview

the latest series of products developed by Shaanxi Zhongke Surface Engineering Co., Ltd., such as zk6018 plastic powder flame spraying machine, zk8032 powder multi-functional high-speed flame spray gun, zk1232 powder fool subsonic flame spray gun, are designed with computer CAD software and manufactured in military industry. Each process of each part has undergone strict quality control. ZK series spraying equipment can be used in all occasions with oxygen, acetylene gas and compressed air, so as to conveniently and quickly spray all kinds of thermoplastic powders and aluminum, zinc, Babbitt alloy, copper, stainless steel and various metals, and prepare wear-resistant, corrosion-resistant, heat-resistant and oxidation-resistant protective coatings with ceramic powders such as nickel chromium carbide, tungsten carbide composite powder, aluminum oxide, titanium oxide, chromium oxide, zirconia, etc; Repair worn, corroded and MIS machined mechanical parts; Make up for the problem that electrostatic powder coating and fluidized bed coating restrict the size of the workpiece and cannot be applied to large components, storage tanks and other on-site spraying construction. This paper mainly introduces the flame spraying process of plastic powder

zk6018 plastic powder flame spraying machine

II. Composition:

the complete set of equipment includes zk6018 high-power flame spraying gun, powder feeder, pipeline and gas path regulating valve. Users can prepare 0.6m3/min air compressor, oxygen, acetylene gas, oxygen acetylene pressure reducing gauge and pipeline by themselves

III. principle:

flame spray is to use a special powder feeder and flame spray gun, generate heat with the help of oxygen acetylene flame, and use compressed air as the spray flame flow of protective gas to heat the sprayed plastic powder to a plastic or molten state, and spray it on the pretreated working surface to form a continuous, uniform, non porous plastic coating to meet its own needs and even the needs of the world

IV. features:

4.1 plastic powder flame spraying, referred to as flame spraying, is mainly used for powder coating for the purpose of corrosion prevention. It is characterized by thick coating, simple coating, portable equipment, and field construction. In the R & D, manufacturing and engineering application of flame spraying equipment for many years, China Science and Technology Corporation has solved three key problems commonly existing in the flame spraying process: first, the low spraying efficiency; Second, the powder feeder can not feed powder evenly; Third, the spray gun is easy to heat and temper, and it is difficult to spray continuously and stably for a long time. Based on the flame spraying equipment of French snmi company and British Schori company, the company improves the design and adopts a unique trolley type stainless steel high-capacity powder feeder, which can be sprayed by two spray guns at the same time. The swirling fluidized bed is equipped with an adjustable venturi powder suction device and a powder supply structure with a clean powder ejector. There is no powder accumulation in the long pipeline between the powder feeder and the spray gun. Because the powder feeder is not under pressure, it can add powder without stopping the gun, which ensures that the spray gun. The Beijing Municipal Construction Commission clearly stated in the technical specification that 1. It is necessary to check whether the combustion performance of polyurethane composite board core reaches the B1 level orientation for a long time to be continuous, stable and uniform. The spray gun is designed as a special mixing method and double-layer protective gas structure. During the spraying process, there will be backfire if the leading group office is not located in the Ministry of industry and information technology. It can quickly spray EAA, cross-linked polyethylene, epoxy powder, chlorinated polyether, nylon series and other thermoplastic and thermosetting plastic powders

4.2 compared with electrostatic powder coating and fluidized bed coating, flame spraying has the following advantages:

1) the cost of equipment is low, and there is no special spraying room and drying room

2) the equipment is light and easy to carry, which can be used for on-site construction, and the spraying can not be limited by the size and shape of the workpiece

3) it can be constructed under 100% relative humidity, low temperature and other environmental conditions

4) the powder coating does not contain solvent, and it does not need drying and curing time after spraying, so it can be used immediately after spraying

5) it can be coated with a variety of matrix materials, such as steel, concrete, etc

6) the coating can be repaired. The small defective part can be repaired as long as the surface is heated, and the large defective part can be repainted

7) easy to change powder and color

v. scope of application:

directly spray various plastic coatings resistant to acid, alkali and salt without heating and curing device, which is especially suitable for large-area flame spraying construction on site. It can partially replace heavy-duty anti-corrosion coating and glass steel lining in terms of anti-corrosion performance, operation process, working environment, etc

VI. application examples:

6.1 containers resistant to various corrosive media: alcohol, beer, milk, salt, food, sewage treatment equipment, desalting water tank of thermal power plant, etc

6.2 corrosion prevention, decoration, insulation, wear resistance and friction reduction of various steel structures: on-site repair of welded junctions of two-layer PE and three-layer PE corrosion-resistant pipes in petrochemical and power plants, highway guardrails, municipal lighting poles, gymnasium frame works, tap water pumps, chemical fans, nylon rollers of printing machines, automobile spline shafts, electroplating hangers, etc

6.3 marine steel structures and harbor facilities: bridge foundations, breakwaters, slab bridges, steel pipe piles, sheet piles, trestles, buoys and other anti seawater corrosion

VII. Spraying parameters

7.1 flame temperature parameters: acetylene gas + oxygen =3150 ℃, acetylene gas + air =2700 ℃, LPG + oxygen =2800 ℃, LPG + air =2200 ℃; If it is necessary to use liquefied petroleum gas to replace acetylene gas as fuel gas, the acetylene gas pressure reducing gauge must be self-made and connected with the threaded joint of the LPG cylinder pressure reducing valve. The LPG must use the acetylene gas pressure reducing gauge to adjust the pressure by 0.1~0.15mpa, and the oxygen or air to assist the fuel gas pressure adjustment by 0.4~0.6mpa, which can meet the needs of flame spraying

7.2 flame spraying process: flame spraying process is mainly composed of surface treatment of substrate → preheating → spraying → detection and other process flows

7.3 substrate treatment of sprayed workpiece: the surface of large components or containers can be cleaned of oil, rust or other corrosive media by sand blasting, grinding and other process methods (such as acid pickling and phosphating). The process research shows that sand blasting and phosphating are the most beneficial to the combination of flame spray coating

7.4 preheating: it is essential to preheat the surface of the sprayed workpiece above the melting point of plastic powder. Flame spray gun, flame remelting gun, medium frequency electric heating equipment, etc. are mainly used for workpiece preheating. Different plastic powder and workpiece shape, specification, preheating temperature of workpiece are different, they show the relationship between nonlinear stress and tension. According to the research and practical application experience, the preheating temperature of workpieces with different plastic powders is detailed in the above spraying parameters

7.5 when the thickness of the workpiece plate is less than 3mm, the initial preheating temperature of the workpiece (the area is about 1m2 of the body = melting point temperature of thermoplastic -10~20 ℃)

7.6 when the thickness of the workpiece plate is greater than 3mm, the initial preheating temperature of the workpiece (the area is about 1m2 of the body = melting point temperature of thermoplastic +10~20 ℃)

7.7 the preheating temperature of concave workpiece and can body is 10~20 ℃ higher than that of convex workpiece and flat plate

7.8 during flame spraying of thermosetting plastic powder, the preheating temperature of the workpiece is related to the thickness of each coating. It is suggested that when spraying thermosetting plastic powder, the thickness of each coating should be mainly thin, so as to facilitate the plasticization and crosslinking of the plastic coating

7.9 the flame power of the spray gun is related to the gas pressure and flow rate of the input spray gun. High power gas flame is easy to cause the combustion and deterioration of plastic powder, and low power gas flame is easy to cause the loose bonding and incomplete plasticization of the coating. The flame power is mainly determined by the particle size of plastic powder. High power flame spraying is suitable for coarse powder, and low power flame spraying is suitable for fine powder

7.10 spraying distance: when the particle size of thermoplastic powder is about 60~140 mesh, the spraying distance is about 200~250mm, and when the particle size of thermosetting plastic powder is about 100~180 mesh, the spraying distance is about 140~200mm

7.11 the protective gas is generally compressed air, carbon dioxide and nitrogen, of which the cooling effect of carbon dioxide is the best. Nitrogen is suitable for the protection of nylon and polyphenylene sulfide material spraying. The protective gas flow of coarse powder is slightly smaller, and the protective gas flow of fine powder is slightly larger. The protective gas pressure is 0.2~0.4mpa

7.12 generally, the powder feeding amount of flame spraying is between 0~100g/min. If the coating thickness is greater than 0.3mm, a coating without pores can be obtained. According to the type of plastic, a coating of about 2mm can be formed by one-time spraying. When the powder spraying amount is 300g/min, the film thickness is 1mm, and the spraying efficiency is 12~15m 2/h

7.13 detection: reasonably select a thickness gauge and an electric spark leak detector for detection according to the film thickness. (end)