Coating process II of PVF in steel drum for the ho

2022-08-07
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Inner coating of steel barrel for food -- coating process of PVF (II)

general differentiation and mechanical methods for surface treatment of steel barrel:

1 Chemical method

general treatment process: degreasing → water washing → derusting → water washing → phosphating → water washing → drying. Generally, for cold rolled sheet, emphasis should be placed on oil removal to ensure that the oil stain is completely removed; For hot rolled plates, oil and rust removal are indispensable. After phosphating, the phosphating film shall not be too thin or too thick. The main disadvantages of chemical methods are: large site occupation; Difficult sewage treatment; Some deoiling agents and phosphating agents need to be used at a certain temperature for obvious effect. The surface treatment agent produced by Sino Japanese joint venture Shenyang pakase fine Co., Ltd. is of good quality, and now it has supporting assembly line production equipment

2. Mechanical methods

there are many mechanical treatment methods, which can replace several steps such as oil removal, rust removal and phosphating. The surface color of the object after coating is soft and beautiful. Main disadvantages: large noise, dust and serious environmental pollution; High energy consumption; The treated workpiece must be sprayed immediately to avoid rusting again. There are many surface treatment methods, and the conditions and equipment of each unit are diverse. Since the PVDF coating has no special requirements for surface treatment, it is generally applicable to the effective methods of painting

II. Spraying process

1 Spraying equipment and environment

① spraying tools: high pressure airless spraying method and air spraying method can be used for PVF coating construction. There are two types of spraying: mechanical spraying and manual spraying. However, in Nike, Adidas, Chanel, 3star, Anta and other domestic and foreign first-line brands, the manual spraying equipment is simple, but the film thickness is not easy to be uniform; Mechanical spraying can realize full-automatic or semi-automatic operation. The coating is easy to be uniform and the efficiency is high. Spray guns, including a800n gun produced by Beijing rec spray measurement and Control Technology Co., Ltd. and a series of spray guns produced by nuoxin Co., Ltd. in the United States, have been applied by many manufacturers with good spraying effect and ideal stability, which are more suitable for the construction characteristics and process requirements of PVF coating. In the air spraying method, the equipment is simple, the spray gun is easy to adjust and flexible. However, the paint wastes a lot, and the high-pressure air is easy to carry water and oil. Especially in humid areas in the south, oil removal and drying devices must be installed. The high-pressure airless spraying method directly pressurizes the coating, eliminating moisture and oil pollution. However, the requirements for coating characteristics (such as viscosity, fineness, etc.) are quite strict, and adjustment requires certain technology. When the viscosity of the coating is high, high pressure airless spraying is more appropriate. A thick film can be obtained by one spraying

② the spray room

is similar to the ordinary spray room, but a paint recovery device shall be attached as far as possible. PVF coating is different from ordinary paint. PVF coating volatilizes very slowly at room temperature, and its surface will not harden or crust when exposed to air. The scattered coating can be recovered and reused

③ washing

pvf coating is different from ordinary paint. It will not stick to hands and will not solidify at room temperature. Therefore, vessels, tools, skin, clothes and workpieces that need to be repainted with this coating provide infinite development space, which can be easily wiped or wiped with soapy water and alcohol

④ fixture

when designing the fixture, it is necessary to consider two characteristics, especially the large-scale transaction of profile steel and the PVDF coating: first, there is no viscosity, so the "wet" barrel parts are often collided. What should be done in this situation? First, confirm whether the materials at this position can be treated with rust prevention and exposed to the bottom; Second, the plasticized "dry" coating will soften again under high temperature, so when a barrel needs to be coated twice, do not put the coated side on the shelf for baking

⑤ the construction site

shall be protected from dust. Mud dust and metal powder with a slightly larger weight are easy to touch the bottom when they fall on the "wet" coating, affecting the protection performance. (to be continued)

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