Car repair paint and its color adjustment

1. Composition of sedan repair paint

Car repair paint literally refers to the paint used to repair the original car body paint from scratch. It can only be done manually by workers, and spraying is necessary at low temperatures (below 60 degrees Celsius). Repair paint needs to have two functions: maintenance function and beautiful function. These two functions cannot be completed independently by a single product. Therefore, high-quality repair paint brands generally have a series of products to combine, which mainly include:

(1) Putty: used to fill defects in sheet metal

(2) Primer: Used for rust prevention, promoting adhesion between paint layers, and increasing paint film thickness

(3) Topcoat: used to improve appearance quality and increase weather resistance

Considering that the entire car cannot withstand high-temperature baking, the coating conditions in general car repair factories are poor. For car repair and refurbishment coatings, self drying primer, putty, center coating, self drying resin paint, evaporative dry nitrocellulose paint, and perchloroethylene paint are often used

Nitro paint is easy to apply, quick to dry, and can be polished, making it an ideal top coat for car repair. However, nitro paint generally has poor weather resistance, and in the south, it can cause severe loss of gloss and discoloration after being used in a summer. However, nitro paint modified with high-quality resins (acrylic resin and silicone resin) has good weather resistance. However, its solid content is low, and it needs to be sprayed 3-4 times to reach the required surface coating thickness, which is expensive, resulting in higher repair costs

Alkyd paint has excellent weather resistance. Generally, it can reach a thickness of over 40um by spraying two coats, and the gloss and fullness of the coating are good. Its disadvantage is that it is dry and slow, requiring 16-24 hours for each coat to self dry. The construction cycle is long, and a clean coating environment is required. Other alkyd paints have poor moisture and heat resistance, are prone to foaming, and have poor decorative appearance, making them unsuitable as top coats for sedans

Nowadays, most finished coatings are made with double-layer paint, which is a metal or pearl layer followed by a clear coat, while the rest are essentially two component pure color paints. Two component paints were first introduced by Akzo Nobel Company's Xinjin Company in the 1960s, Its fundamental mechanism is to use acrylic chains containing hydroxyl functional groups (- OH) to react with (- NCO) groups in cyanate esters to solidify into a network structure of polyurethane polymers. This two component polyurethane paint combines the advantages of nitro paint and alkyd paint, with fast drying, good gloss and fullness. It can reach a thickness of over 40um after 1-2 coats, and has excellent weather resistance, chemical resistance, and moisture heat resistance, which is quickly selected by various paint manufacturers. Metal paint, Pearl paint uses modified butyl acetate cellulose resin as the carrier and is coated with a clear two component varnish 2. Differences between car repair paint and original factory paint

The paint used for the original paint of sedans is different from that used for general car repair paint. The original paint of sedans is the paint used for joint coating before leaving the factory. Car factories have specific requirements for the paint used for their entire vehicle, so most car factories have formulated special supply agreements with paint companies. However, for unprocessed metal bodies, due to the lack of other plastic accessories and the fact that the spraying operation is carried out in a temperature controlled environment on the coating production line, high-temperature baking paint is generally used

Car repair paint is a solution to the exterior coating of a car. Due to accidental damage or years of aging (such as coating cracking, discoloration, loss of gloss, powdering, etc.), it needs to be repaired or repainted from scratch for various miscellaneous situations, commonly known as repair paint. Specifically, it is different from the coating production line of a general factory, with no single operation. The painted model, shape, and color are all different, Most operations cannot be carried out according to the regular sequence of processes, and the maximum baking temperature cannot exceed 60 degrees Celsius, otherwise plastic accessories will be damaged. Therefore, repairing cars requires the use of different paint categories, and repairing cars needs to be carried out in repair factories. However, the equipment in repair factories varies, making it difficult to compare with car manufacturers Car repair coating can be divided into partial repair coating and whole vehicle repair coating according to the amount of repair work. The former only applies to the damaged part or object of the coating

Damaged parts shall be repainted after being corrected by sheet metal workers; The latter is due to aging of the coating or the need to change the color for the entire vehicle to be repainted from scratch

The process requirements for sedan repair painting are variable, so it requires operators to have high painting skills, especially in color matching during partial repair painting, so that the appearance, luster, and color of the repair surface and the original coating are fundamentally consistent. It is necessary to consider the color of the sedan, the texture of the topcoat, and the condition of the topcoat, as well as many potential factors that may cause color changes, Some of them are beyond the control of painters at the moment, so operators need to have rich practical experience and high operational skills

3. Color calibration of sedan repair paint

There are three main factors that affect the appearance of a car: the color of the car, the texture of the topcoat, and the condition of the topcoat. Especially, color is the basis for judging the quality

(1) Factors that affect the color of sedans: There are mainly three concepts for defining and describing color: brightness, and color: brightness refers to the degree of brightness of the color; Color is the color seen by the human eye; Chromaticity refers to the intensity and concentration of a color, including intensity, concentration, saturation, grayscale, etc In fact, different light sources have different effects on the paint, causing the color of the paint to change. This is because the content of various colorful light in the light source is different. For example, a certain paint contains blue components that may not be visible in sunlight, but are very noticeable under mercury lamps. Due to the different content of blue light in sunlight and mercury lamps, the repair paint may match well with the color of the car when viewed under workshop lighting, But under sunlight, it is not good enough. The color distribution under workshop lighting conditions is closely related to the type of lighting used in the workshop. For example, incandescent lighting can cause the paint color to turn red; The difference in fluorescent powder in fluorescent lamps causes the paint color to turn yellow or blue; Both cold white light and soft white light can alter the color presented by the paint Sometimes the pigment in the repair paint formula is not completely the same as that used by the original car manufacturer's topcoat formula. In this case, even if the repair paint matches the original topcoat well in sunlight or simulated sunlight, it may not be the same when viewed under another light source

(2) Identifying the color of the original brand sedan: The first step in color matching is to obtain the original color based on the paint code of the sedan manufacturer, in order to reduce the difference between the repair paint formula and the paint formula used by the original sedan manufacturer. Almost all brand sedan paint codes can be found on various sedan trademark paint code location maps. A repair color compilation can be purchased on the market, This type of book includes color cards and pigment materials for brands and models. The first step is to find the paint code of the car manufacturer, which is located around the paint code. For safety reasons, it is best to compare the color card with the color of the car itself, as some cars may have already been painted with other colors

(3) Confirmation of the original paint surface paint type

1) Visual inspection method. If the skin arrangement near the exterior line of the car body is rough, or if the paint surface conflicts and presents" Polishing arrangement", It is clarified that the original paint used was a polishing type

2) Solvent method. Use a white cloth dipped in nitrocellulose paint release agent (banana water) to investigate the degree of dissolution of the paint film. If the paint film dissolves and leaves marks on the cloth, it is self drying paint; If not dissolved, it may be baking paint or two component paint. Acrylic polyurethane paint does not dissolve as easily as self drying paint, but sometimes solvents can penetrate and weaken the surface gloss

3) Heating method. First, use fine sandpaper dipped in water to polish the paint film to lose its luster, and then use an infrared lamp to heat it. If the passivation surface appears shiny from the beginning, it indicates that it is acrylic spray paint

4) Hardness testing method. The hardness of the paint film varies after various types of paint become dry. Generally speaking, the hardness of the paint film of two component paint and baking paint is higher than that of self drying paint. The most commonly used method to confirm the hardness and thickness of the paint film is to use an electromagnetic thickness gauge or a mechanical thickness gauge

(4) Repair paint color calibration: The process of confirming the relationship between paint and car color using graphical methods based on brightness, color, and chromaticity, in order to calibrate the color. Color calibration only has meaning when comparing the car itself. By grasping and applying color calibration methods, differences in brightness, color, and chromaticity can be distinguished

Table 4-1 Color Calibration Table for Suitable Metal Bright Paint

Side light brightness □ Shallow □ Deep

Sedan color

Side light color □ Bluish □ Green

Sedan color □偏紅 □偏黃

Color: light yellow

Editor's code: Transforming beauty into a transformer. Total engineering cost

402 white 336.0 336.0

452 Yellow 49.0 385.0

451 Light Yellow 13.5 398.5

457 Yellow or Red 9.0 407.5

405 Black 11.5 419.0

465 adhesive 3.71 790.5

485 Balancer 184.5 975.0

Color calibration is beneficial for understanding the paint formula, including those color matching materials. However, it is necessary to note that the colors produced may not be completely the same as the actual colors of the car, as all car topcoats will gradually change over time, some becoming lighter and some becoming darker. For example, yellow color fades quickly, and if it fades to beige, the pigment should be mixed lighter and lighter; If it fades into a green color composed of blue and yellow, then the pigment should be slightly blue and generally darker

Due to the rapid development of scientific skills, especially the development of electronic computer skills, it has also been applied in painting skills to a certain extent. By using computer paint mixing, extremely messy paint mixing operations are modified to be very formal, and the operation is very simple and accurate

(1) The fundamental principle of computer paint mixing: In the homework of computer paint mixing, the computer is actually a large material library of paint formulas,

We have stored standardized formulas for various types of paints. All types of paints are symbolized by numbers, not only for multi color paints, but also for single color paints. The number of types of paints reaches a thousand specifications, fully satisfying the application of car manufacturing and car repair

After the repaired car arrives at the repair shop, some car body topcoats are coated with paint grades in certain areas. If the repair shop has the same grade of paint, it can be directly selected; If it is not available, you can input this label into the computer. The components and components of each single color paint composed of this label can be displayed on the fluorescent screen. By assigning them according to their components and components, you can obtain the required label of the paint

(2) The operation process of computer paint mixing: The first step is to confirm the type of paint color of the repaired sedan topcoat. There are generally two methods: for modern high-end sedans

Some of the car's topcoats have paint number markings, find their paint number markings; Some can find specifications for the types of materials used for the topcoat from the repair manual; If there is no record, the final solution is to use a color label for measurement

Color label card is a specially printed paint color card. It is a standardized color card designed according to the type of color and different shades of the same type. The card is marked with its digital number, and each color card number is a symbol of a type of paint

A purple paint with different shades, 301A5, the lightest shade, and 301H1, the darkest. There is a circular hole in the center of each square color

When determining the top paint of a car, the first step is to measure the color card that is similar to the top paint of the car. Then, lay the color card flat on the exterior of the car body, reveal the paint nature of the car body through the circular holes in the color card, and find the square that is most similar to or even the same color as the color card. This determines that the top paint of the car is the color represented by the number of that square

If the measured number of car topcoat is 301A5 and there is no ready-made color paint in stock, input this code into the computer. The formula of 301A5 displayed on the computer's fluorescent screen is 956, which is 179.9g; 744 is 1.5g; 957 is 71.8g; 666 is 81.5g; 333mL is

153.4g. Based on the above formula, use an electronic scale to measure the weight of each component, measure the required amount according to the weight, and place it in a certain distribution container

Mix evenly with manual machinery, adjust to the required concentration according to the construction requirements, and the distribution of paint is now complete

The use of computer paint mixing can make the assignment of car topcoats simple and accurate. It is necessary to strictly ensure the quality of various digital color paints purchased

In addition, although there are many types of paint specifications used, the quantity of each specification is relatively small, as repair and care are different from batch production

Article source: Qingyuan Automotive Repair Paint http://www.jinliangxincai.com