The technology of powder coating can be called revolutionary. Powder painting allows you to paint any metal objects that abound in the household plot and the country house. How to learn to paint using this technology?
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What is a powder painting
Powder painting is a process of applying solid components of dispersion composition with special film-forming resins and targeted additives.
The field of application of the powder coating technology is extensive and includes a list of products to be dyed. As an example, we call the need to cover the inner surface of pipes for the oil-producing and processing industries. Thus, the application of painting technology is necessary under the following conditions:
• increased internal pressure in the pipes
• high temperature of the working medium
• the presence of aggressive media.
Powder painting of metal is capable in this case to exclude unfavorable factors and to ensure the operability and functioning.
Types of powder paints
Depending on the film-forming component, the powder paints are divided into the following types:
• thermoplastic
• thermosetting.
Powdered thermoplastic paints are made using film-forming agents. The coating is formed without chemical reactions and transformations, but is produced by melting the molten paint. The process of thermal fusion and cooling of particles forms a partially soluble film. Therefore, the composition of the film is identical to the composition of the starting material for painting. The paints of the thermoplastic group are composed of:
• polyamide
• polyethylene
• polyvinyl chloride
• polyvinyl butyral.
Powder paints based on polyvinyl butyral are used as a protective film for electrical insulation works, protective and decorative functions for internal use.
Powder based paints based on polyvinyl chloride are used for external use, due to the high resistance of the coating.
Thermosetting powder paints consist of hard resins with a high molecular weight and a binder component. The main resins that make up the thermoset paint are: epoxy, polyester and acrylic.
The composition of the resins is applied to the object or equipment by electrostatic spraying. Heated to the operating temperature and applied resin mixture after a certain time hardens, forming a stable film - polymer network. The chemically transformed and cured layer is not further deformed even after repeated heat exposure. The most demanded is the powder painting of metal (doors, grates, fences).
Powder coating technology
The technology of powder coating consists of a chain:
• preparation of the surface for staining
• preparation of the working composition of the paint
• application of powder paint
• polymerization
• recovery.
The preparation of the surface for painting involves the manual removal of all kinds of impurities, as well as the degreasing and phosphating process to improve the adhesion of the paint. Removal of impurities from the working surface requires a correctly selected treatment method, as well as a composition that depends on:
• material of the processing surface
• degree of pollution.
Therefore, ubiquitous methods of degreasing, abrasive cleaning with etching, as well as application of a conversion layer are widely used. When painting using powder paint, you need to think through the preparatory stage. For cleaning and degreasing the surface it is recommended to make:
• Phosphating using zinc or iron phosphates
• Rinsing the surface with subsequent fixing and drying.
Then follows the process of preparing the working staff. The main advantage of powder paint is its readiness for use and application. The paint is supplied by the manufacturer in the form of a ready mix. Therefore, there is no need to dilute the paint or add catalysts that provide certain characteristics.
Such advantage allows to avoid mistakes in the preparation of the working staff and guarantees the original quality of the painting.
The application of powder paint to the surface can be done using a special powder painting chamber, and in the case of powder painting at home using hand tools.
Equipment for powder painting
professional equipment
Technologically, powder paints are applied to products and parts by electrostatic spraying or by immersion in a fluidized layer of powder paint. It is possible to use flame spraying. Special equipment is used for these purposes.
To obtain a conversion layer and bake powder paint, polymerization ovens are used. The polymerization furnace is a closed chamber, the working volume of which is adjusted to the temperature at which the polymerization takes place.
Depending on the amount of work intended for multi-stage powder coating, there are professional complexes. The complex of equipment allows to paint metal products in overall dimensions 0,8х2,7х7,0 m. Such complexes are distinguished by significant working sizes and volumes:
• painting chamber
• Polymerization ovens.
Such equipment is intended for large-sized products, namely: gates, trusses, facade systems, fences, profiled sheets.
With significant volumes of large-sized parts and products, a transport system is used, with which the painting process is significantly automated. Products easily move from one point to another on hanging rails.
Powder painting is made by electrostatic method with the technology of applying several layers (primer + anticorrosion coating + varnish).
The wide-scale services of professional systems for powder coating do not compare with the small-scale handicraft "Do it yourself", so for painting in the latter use a hand gun for powder painting.
hand-held equipment
It is necessary to distinguish between the spray gun electrostatic and tribostatic.
The electrostatic gun consists of the following parts:
• high-voltage cascade, which converts a low signal at the input to a high
• the electrode holder that creates the electrostatic field
• the deflector forming the working torch of paint.
The types of electrode holder and deflectors are selected depending on the type of paint and the speed of application.
Tribostatic gun sprayer allows you to paint a product with a complex shape with a uniform finish layer.
Unlike an electrostatic device that uses a corona charge, a tribostatic gun does not contain any conversion elements.
Paint powder is placed in the tank, located on the spray gun body.
How to create an aggregate for powder painting on the basis of a hair dryer for drying hair at home will graciously show the video.
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