1. Sheet metal correction, which is the preliminary work of automobile painting, reshapes the place where sheet metal painting is needed;
2. Scraping has also become plastic molding, and there are still some irreparable defects after body sheet metal correction. In order to be more exquisite, sculpture is needed to make up for the defects;
3. Painting in automotive sheet metal: Painting in automotive sheet metal is usually divided into three steps. The first step is the first primer treatment: filling the sand marks and micropores at the bottom of the workpiece to increase the adhesion of the lower coating, which also has the function of defect indication; Step 2, intermediate primer treatment: prepare a well-lubricated working surface for the top coat, complete the last procedure of all primer work, increase the adhesion of the participating layers and have a certain isolation effect to ensure the quality of the top coat; Step three, topcoat: topcoat is divided into single-layer paint and multi-layer paint, which are color fixing layer and decorative maintenance layer respectively.
4. Paint surface treatment of sheet metal and painting: Paint surface treatment is the last working procedure of topcoat, and defects on the paint surface are treated after the paint surface is dried;
5. Stop grinding with fine wax (without silicon) to remove traces of coarse wax, then treat with repairing agent to achieve perfect luster, and then thoroughly clean the halo and scratches with mirror treatment agent to make the vehicle more rounded and shiny.
Extended data:
Automobile painting refers to coating a layer of paint on the surface of the automobile to protect the automobile. Baking varnish is generally used for automobile painting. In the automobile factory, the frame and shell are welded, and the next process is painting. The forms are common paint, metallic paint and pearlescent paint. Automobile painting process: putty scraping, polishing and painting.
Automobile painting includes: ordinary paint; Metallic paint; Pearlescent paint; Varnish; Matte paint.
1, composition of automobile paint. Automobile paint generally has four basic components: film-forming substance (resin), pigment (including car body pigment), solvent and additive.
(1) Film-forming substance is the main component of paint, its function is to keep the pigment bright, firm and durable, and it can be attached to the surface of objects, and it is the substance that determines the type of paint. Generally, it is made of drying oil or semi-drying oil modified natural resin (such as rosin), artificial resin (such as dehydrated malic acid resin) and synthetic resin (such as methyl methacrylate, polyurethane, polystyrene, polyvinyl chloride, etc.). ). Its durability, adhesion, corrosion resistance, wear resistance and toughness are usually adjusted and improved by adding plasticizers and catalysts.
(2) Pigment is one of the two non-volatile substances in the paint, which endows the topcoat with color and durability, and at the same time makes the paint have hiding power, improves strength and adhesion, changes luster, and improves fluidity and painting performance.
(3) Solvent is a volatile component in the paint, and its main function is to fully dissolve the resin in the paint film, so that the paint can be applied normally. High-quality solvent can improve the daubing performance and paint film characteristics of topcoat, enhance gloss and reduce paint reticulation, thus reducing polishing workload and contributing to more accurate color matching. In addition to the existing solvent in the coating, it is also used as a diluent to dilute the coating to make its viscosity suitable for painting requirements.
(4) additives. Great changes have taken place in coating technology in recent ten years, and the use of additives has become more and more common. Although the proportion of additives in coatings does not exceed 5%, they play various important roles. There are curing agents that can accelerate drying and enhance gloss, retarders that can slow drying, and matting agents that can weaken gloss. Some additives have comprehensive functions: reducing wrinkling, accelerating drying, preventing whitening and improving chemical resistance.
2, the division of automobile paint
Automobile paint has experienced three great leaps in history:/kloc-0 alkyd (magnetic) paint in the 1920s; Acrylic (magnetic) paint in the 1960s and clear paint (carbamate) in the 1980s. Therefore, in the 20th century, automotive coatings made great progress. In order to facilitate understanding, we simply divide automobile paints into ordinary paints and transparent paints (mirror varnish).
Generally speaking, the structure of two kinds of paints is the same: metal material-electrolytic paint-primer-colored paint (the structure of ordinary paint). Transparent paint has one more layer than ordinary paint: transparent surface layer, usually polyurethane or urethane transparent paint.
3, the identification of ordinary paint and transparent paint
Method 1: Visually, the gloss of transparent paint is deeper than that of ordinary paint.
Method 2: Test: Use a wet cloth with a little abrasive to grind it in an inconspicuous place on the car body. If there is color on the cloth, it is ordinary paint; On the contrary, it is transparent paint. In the case that it is difficult to visually observe, it is assumed to be transparent paint, and the procedure of nursing transparent paint is followed.
The appearance of transparent coatings actually has two purposes: one is to increase the brightness and reflectivity of coatings; The second is the protective color paint layer. However, it is worth noting that due to the appearance of transparent paint, the thickness of existing paint is much thinner than before, and the paint of some cars is as thin as one thousandth of an inch. The reason is simple: the primary color layer is both an aesthetic layer and a protective layer. Transparent paint is only for aesthetic purposes, so it is unnecessary to apply it very thick.
Transparent paint is characterized by:
(1) Transparent paint is beautiful and has high gloss. But it is easy to scratch. If we clean the car with a slightly harder towel or suede after washing the car, we will find hair scratches.
(2) The transparent paint is made of polyurethane, polyurethane, fluorine and polyester.
(3) Transparent paint generally contains the protection function of reducing ultraviolet radiation (colored paint does not contain this function), so long as the transparent layer is intact, it can effectively delay the aging (fading) of colored paint.
(4) The quality of transparent paint care is generally reflected by "reflection lines". Take a newspaper and put it in front of the car paint. If you can read the newspaper from the reflection of transparent paint, it means that the transparent paint of this car has a deep shadow and a smooth surface like a mirror. But ordinary paint can't achieve this effect.
(5) Transparent paint is more susceptible to environmental pollution than ordinary paint. Sources of harmful substances: carbon black in carbon dioxide released by automobile exhaust; Debris falling from aircraft jet fuel includes acid rain, acid fog and acid snow. Once these sundries fall on the car, together with the moisture in the air, they immediately become acidic solutions and corrode the transparent paint surface. A little heating (ultraviolet rays in the sun) will start a chemical reaction and erode the protective layer of automobile paint. Once or twice is not obvious, but if left unattended for a long time, this chemical reaction will eventually corrode the color layer, primer layer and metal.