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    Home > Coatings News > Paints and Coatings Market > Coating process: coating process of refrigerated container

    Coating process: coating process of refrigerated container

    • Last Update: 2020-04-03
    • Source: Internet
    • Author: User
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    Core tips: 1

    Preface Refrigerated containers are divided into steel refrigerators and aluminum refrigerators according to their materials

    Here we mainly focus on the steel freezer and describe the requirements of its coating process

    Coating process flow of refrigerated container: 2

    The pretreatment of corten (low alloy high strength) steel plate is the same as that of most dry containers

    All corten steel plates must be pretreated first to remove oxide, rust and impurities on the surface

    In different production lines, there are two kinds of pretreatment processes, one is the same as the dry goods cabinet, after abrasive polishing Shenyang steel structure fireproof coating construction expert punde Building Fire Engineering Co., Ltd Recommended introduction: since its establishment, Shenyang punde Construction Fire Engineering Co., Ltd

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    According to its material, refrigerated containers are divided into steel refrigerators and aluminum refrigerators

    Here we mainly focus on the steel freezer and describe the requirements of its coating process

    Coating process flow of refrigerated container: 2

    Pretreatment of corten (low alloy high strength) steel plate is the same as that of most dry containers

    All corten steel plates must be pretreated first to remove oxide, rust and impurities on the surface

    In different production lines, there are two pretreatment processes

    One is the same as the dry goods cabinet

    After abrasive jetting treatment, the surface degreasing level reaches Sa2.5 of iso8501-1; the surface cleanliness reaches level 2 of iso8502-3; after the surface roughness is controlled at 20 ~ 50 / IM, zinc primer is sprayed immediately, and the dry film thickness of zinc primer is generally controlled at about LMM

    The dry film should not be too thick to avoid air holes in the future welding; the other is that the corten steel plate, after abrasive jetting, will not be sprayed with zinc primer, and will directly enter the molding and part assembly, and the surface spray treatment will be carried out after the second treatment after the final assembly

    This process requires a lot of baskets for the equipment of the factory

    It is not allowed to smear oil on the surface of the treated plate due to the negligence in the processing process

    The advantage is to ensure that the welding quality is not affected by the paint coating

    Secondly, it can save paint relatively

    3

    After degreasing treatment of stainless steel plate and spraying foaming coating of stainless steel plate (usually MGSS steel) through uncoiling, shearing, molding, transportation and other processes, there are many oil stains and impurities on the surface, which must be removed before coating

    Generally, there are two methods of treatment: one is flame cleaning

    After the top and side plates are installed, oxyacetylene gas is used to clean the surface of the parts; the other is spray oil removal with basket warm water vapor

    Both of the above methods need good equipment

    The commonly used standards and methods for the inspection of the treated stainless steel surface are: flame cleaning: the standard is inktest44 steam cleaning: the plate after degreasing treatment by dripping method shall be sprayed with foaming paint on the inner surface immediately

    The main function of spraying foaming coating is to increase the adhesion between stainless steel plate and insulating material

    The insulation of refrigerated container mainly depends on the inner insulation material

    If there is delamination and gap between the outer plate and the insulation layer, the insulation will be affected, and the strength of the box will be affected

    The foaming paint is usually polyurethane paint

    Because of its technical requirements, it is imported products in various freezer factories at present

    The spray dry film thickness of the foaming paint is usually 15-25pm

    If it is too thick, it is easy to cause delamination due to the temperature and high pressure of the basket in the subsequent foaming process

    4

    The secondary treatment is carried out after the completion of the general assembly

    Because most of the top and side plates of the freezer are made of stainless steel plates, the abrasives used in the secondary treatment are different from those used in the dry container

    It usually uses a kind of abrasive called "Brown steel jade" which is used to make the sand wheel as the spray abrasive

    This kind of abrasive has two advantages

    One is to use this kind of abrasive with edges and corners, and the secondary surface quality of its treatment can reach grade SA3

    It can completely meet the spraying requirements of metal zinc; secondly, in view of the light proportion of the abrasive, it will not produce too much roughness when spraying stainless steel plate, and it is hard and durable

    Compared with the ordinary steel abrasive, the damage to the plate is correspondingly small

    In the secondary treatment, in addition to the sanding treatment of the thermal area and the damaged part in the assembly process, the stainless steel surface also needs to be cleaned

    Because the surface of stainless steel plate is very smooth, in order to make a good adhesion between the plate and the coating, the sand is usually swept to a density of 10-30%

    4.1 for the parts of corten steel sprayed with metal zinc and zinc primer, according to the manufacturing requirements of the owners of the refrigerators, zinc primer shall be sprayed after the secondary surface treatment, and some parts shall also be sprayed with metal zinc

    The position of spraying metal zinc depends on the requirements of each cabinet owner, usually the exposed gooseneck plate, bottom beam, front and rear frames, etc

    The surface treatment before spraying is required to be better than that of basket

    The derusting level must be above Sa2.5, the cleanliness is level 1, the roughness is 30-6mm, and the spraying thickness of zinc is about 30-4 (the spraying of Cambodian M

    metal zinc can not form the coating film like the coating, but many of them show the "dew point" shape

    Therefore, when determining the thickness of zinc layer, it is usually based on the calculation of the amount of zinc, that is to say, the weight of zinc required is calculated according to the film thickness to determine whether the thickness of zinc layer is reached

    After spraying, the surface of zinc coating is in a rough state, and the adhesion between metal zinc and steel is not firm

    It needs to be coated by subsequent coating to achieve the effect of adhesion to the steel surface

    When some refrigerators do not require spraying metal zinc or parts of a refrigerator other than spraying metal zinc, the spraying of zinc primer shall be carried out according to the matching

    The spraying requirements of zinc primer are generally the same as that of dry cargo cabinet

    The concealed parts and weld beads that are not easy to be painted shall be pre coated, without missing coating, sagging and other problems, and the dry film thickness shall meet the requirements

    4.2

    For the spraying of intermediate (primer) paint, a layer of intermediate paint is usually provided for the paint matching of refrigerated container, whose purpose and function are to connect the adhesion between the top coat and steel

    Meanwhile, the intermediate paint is generally epoxy type, with wear-resistant function

    The spraying part of the middle layer paint is also carried out according to the requirements of the cabinet owner, and the construction requirements are the same as those of the dry goods cabinet

    Generally, the top and side plates of the freezer are stainless steel plates, and the thickness of the dry film is generally 80F% I

    the film thickness of the middle layer paint is only 40wn

    Therefore, after the middle layer paint is sprayed, it gives people the feeling of "blooming" and "exposed bottom"

    It should be said that this is also very normal

    This is because the common middle layer paint is light color, when the dry film is 40pm, and the bottom is dark It is difficult to achieve the ideal covering power when metal plates are used

    As long as the middle layer paint reaches the specified film thickness, even if there is "flower" or "exposed bottom", it should be acceptable

    4.3 after the drying and spraying of the middle layer (bottom) paint, there needs to be a drying process before spraying the finish paint

    Generally, the temperature of the drying room shall be controlled at 30 ~ 50 *; the time shall be 10 ~ 15min, and the specific temperature and time shall be determined according to the situation of each production line

    There are two functions for the drying of the middle layer (bottom) paint: first, it can make the solvent in the coating evaporate quickly, make the paint film dry in a short time, and ensure that there will be no sagging during the subsequent coating spraying; second, it is convenient for the aesthetic inspection of the zinc primer and the middle layer paint before the final finishing coat spraying, and whether there are obvious particles and impurities, or the first two coats of paint If there is any coating defect in the work, once it is found, it can be repaired to ensure the overall aesthetics after finishing

    The correct spraying method of s top coat is very important for the beauty of the whole box of coating

    At present, there are two kinds of external spraying in the manufacture of refrigerators: manual spraying and automatic spraying

    In terms of manual spraying, the method and requirements are similar to those of dry container; in automatic spraying, the side plates that need to be close to the front and rear frames in particular will produce coarse sugar or paint mist due to improper control of the time between manual spraying of the front and rear frames and automatic spraying of the top side plates

    This has a similar problem in the dry container of the automatic spraying line

    This is mainly because the time of manual spraying of front and rear frames and automatic spraying of top and side plates must be well controlled, and there should be no longer interval between them

    The correct method is: when the automatic spraying starts from the top and side plates at one end, the manual spraying means spraying the frame at the beginning and end of the automatic spraying, while when the automatic spraying gradually moves to the other end, the manual spraying also needs to be carried out at the same time

    In this way, the paint mist will not be produced due to the time difference between the two spraying

    The choice of diluent should also be considered when spraying the top coat, for example, the solvent with different volatilization rate should be selected in different seasons to ensure a good film-forming state of the paint film

    Some cabinets are mainly designed for different types of finish

    In order to protect the door adhesive strip from "aging" due to the solvent volatilization in the paint, except that the top coat adopts polyurethane, the other top coats, such as vinyl, acrylic, etc., shall be sprayed with a polyurethane varnish at the contact part of the door adhesive strip to prevent the contact between volatile dry paint and door adhesive

    In general, the top coat of refrigerated containers does not use chemical rubber paint

    5

    The drying box of the finish paint after spraying can not enter the drying room immediately for forced drying, so the surface of the coating will easily produce pinholes or bubbles, especially in the areas with thick spraying of the middle layer paint and zinc primer

    Therefore, it must stay for 15 minutes to make it level and volatilize to touch dry before entering

    The temperature of the drying room is generally controlled at 60 ~ 80 *, which should not be too high, otherwise it will affect the adhesion between the internal insulating material and the steel plate, resulting in delamination, and affect the insulation of the box

    The forced drying time is generally from 10 to 5.2

    After finishing and spraying the face paint, drying in the drying room, and then a series of foaming, labeling, assembly and other processes, the whole box shall be finished integrally, such as the damaged parts in the transportation, the decoration of the door frame edge, etc

    In addition, in case of any defect on the top coat caused by various reasons when spraying the top coat, it shall also be repaired

    6

    The last process of spraying underframe paint is spraying underframe paint

    Generally, the underframe paint is asphalt and bleached asphalt paint

    The spraying requirements of underframe paint are similar to those of dry container

    When spraying the underframe paint, pay attention not to spray the paint mist on the side plate, so as to ensure that the whole box is white without pollution

    So far, the painting of refrigerated containers has been basically completed

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