Automobile repair base treatment method For the treatment of various automobile repair bases, various suitable methods should be adopted according to the actual situation on site. According to the practical experience and the base layer before painting of various car repairs that are often encountered, the following treatment methods can be roughly adopted.
(1) Local paint film slight scratch (collision) damage treatment method
For the scars on the local paint film due to slight scraping, squeezing, bumping or bumping, as long as the color layer of the paint film is not exposed to the bottom, but only white marks appear on the skin, you can directly apply a little sand wax with a wool polisher When the white mark is polished to the same color , then use light wax to repair the light. If the white marks cannot restore the color of the original paint after polishing with sand wax, it proves that the scars have penetrated the coating of the finish paint or finish paint. Soak in warm water) Grind the scars until they are very smooth and smooth, wash off the abrasive stains, wipe off the water marks, dry the water effectively, and then use putty to scrape it flat, and then touch up the paint.
(2) Treatment method for severe bruising of local paint film
If the partial coating of a car or bus is cracked, crystal grained or delaminated due to collision or collision, the damaged coating needs to be carefully cleaned first. When the base material of the bumped or bumped part is deformed, a sheet metal worker should be asked to knock the deformed part flat with tools such as a backing plate and a wooden hammer, and then use the following methods to deal with it.
① Treatment of cracked parts
Cracking parts are usually divided into two phenomena: paint film cracking and putty layer cracking (cracking), as shown in the figure. For the treatment of the cracked part of the paint film, first use a scraper blade or a paper cutter blade to cut out the edge around the part of the cracked paint film, and then use the blade to cut off the cracked paint film inside the edge in sequence, and then use a 180 or finer Use emery cloth to smooth the bottom layer of the excised part repeatedly. If the base layer of the excised part is exposed to the base material, the part needs to be polished until the metallic luster is completely exposed. However, special attention should be paid when grinding, and the abrasive cloth should not be ground on the surface of the paint film other than the cut part , so as to prevent sand marks after the touch-up paint, which will affect the quality of the touch-up paint. For safe grinding, first tear the emery cloth into strips of 30-40 mm wide or small pieces of suitable length and width, wrap them on the pads of the index finger and middle finger of the right hand, and use the pads of two fingers to press the emery cloth for grinding. If conditions permit, use scotch tape to stick the paper (waste newspaper, etc.) close to the edge of the cracked paint film, and cover the surrounding intact paint film to prevent abrasion.
For the cracks caused by the collision of the putty layer, the edge can be cut out with a blade first, and then the cracked putty layer can be cleaned with a spatula in turn. Then use a blade to cut the surrounding edges into a slope shape, and carefully polish the cut edges with emery cloth , without flying edges, sharp angles or burrs, so as to scrape the putty and enhance the adhesion of the putty. If the putty layer is thick , after the edge is cut out, the cracked coating can be cleaned first, and then the edge can be ground into a slope shape with a Grinder, and the rough edge can be smoothed, and then the bottom layer can be polished and the floating dust can be blown off. Re-spray primer or directly apply putty to make up.
②Treatment of grain lines
Crystal texture coating mainly occurs on the surface of old and new coatings of cars, such as refurbished cars, recolored cars, etc., due to the difference between the two coatings or the improper treatment of the base layer when the new paint is applied (too smooth or oily) The adhesion of the new coating is poor, and the surface paint film has crystal grains in case of collision or vibration, while the bottom (old paint) paint film is intact. In such a situation, first use a blade to cut off the crystal pattern on the surface layer, and the cut part should be as large as possible to prevent gaps. After the paint touch-up, the coating is heated (exposed to the sun, etc.) to cause gas accumulation in the gaps to generate stress and cause bubbling . For the old paint layer with a good bottom layer, it can be polished repeatedly with a fine emery cloth until it shows a uniform sand pattern, so as to enhance the adhesion between the new coating and the old layer . It is easy to cause poor adhesion of the new coating, so that after the surface layer is heated, voids are easily generated inside (the surface paint film is lightly tapped to make a hollow sound), which seriously affects the quality of the touch-up paint. If there is oil stain (greasy feeling) on the surface of the old paint on the bottom layer after the crystal pattern paint film is removed , it is necessary to clean the oil stain with thinner or clean gasoline first, and then polish it . Rework due to quality problems.
③Treatment of delaminated parts
Delamination parts are often caused by severe collisions. After severe collisions, not only the coating falls off, but also the base material is often deformed. When encountering this situation, you should first cooperate with the automobile sheet metal workers to knock the deformed substrate parts to restore the original shape with special tools, and then use a steel shovel to remove the delaminated parts (mainly thick putty layer) and clean them. Remove the loose or gapped coatings all around, and then use a Grinder or a steel spatula with a coarse abrasive cloth to treat the base layer until all the metal luster is exposed, wash off the floating dust with a detergent, and then re-spray Primer or directly scrape putty.
(3) Treatment of newly replaced substrates
The newly replaced base material mainly refers to the steel plate base material, aluminum base material, glass fiber reinforced plastic base material, etc. that have been repaired and replaced after various automobiles have been severely damaged .
①Steel base material treatment method
If there is oil stain (the surface of the steel plate is coated with protective oil during storage), if there is no rust, you can use cotton gauze dipped in gasoline or a towel dipped in detergent to clean the oil stain repeatedly, and then use clean cotton gauze or towel to wipe off the remaining traces carefully. Clean (until there is no impurity on the surface of the hand or paper wipe). After these tasks are done, use a Grinder or No. 80 emery cloth to repeatedly grind off the oxide layer on the surface of the steel plate until the metallic luster is completely revealed, and then wipe off the floating dust with a detergent. When there is rust and no oil, such as a slight rust layer (rust layer caused by rain or moisture), it can be removed directly with a sander or emery cloth in turn. due to long-term
The thick rust layer caused by rain should be removed with a steel spatula until it is basically clean, and then the rust in the numb eyes should be removed repeatedly with a wire brush, and then polished with emery cloth to wipe off the floating rust . Corroded thick steel plates are mainly used to replace the surface of ordinary passenger cars or trucks. If conditions permit, try to use pickling (30% hydrochloric acid aqueous solution) or degreasing and derusting clear. After cleaning, rinse the residual liquid with tap water, and immediately spray primer protection after drying the water to prevent rust. After the primer is dry, replace it, which can greatly reduce labor intensity and improve the quality of treatment. The "two-in-one" treatment agent for oil and rust removal is available in chemical stores all over the country.
For the steel plate after replacement, if there are welds or residual high solder spots, it needs to be ground with a Grinder first, and the welding dust (white solder powder) on both sides of the weld should be removed repeatedly with a wire brush to prevent paint High solder joints .
②Aluminum base treatment method
Aluminum substrates are mainly used in the body parts of high-end luxury passenger cars. For example, the sides of the body are mostly made of aluminum plates and aluminum strips, and the warehouses (cargo bodies) and doors on both sides are mostly made of thin aluminum plates. Light, thereby reducing the weight of the vehicle body. For the base layer where the aluminum material is to be replaced, such as the aluminum plate, use a sander to pad 80~100 emery cloth, and perform rough treatment repeatedly, that is, to effectively grind off the oxide layer on the surface, and there must be no missing grinding phenomenon, so as to prevent the oxide layer from being too smooth and affecting the coating . The ability of the layer to bond to the substrate. For parts that are not easy to be ground by the Grinder, such as corners, you should handle them with abrasive cloth to ensure the quality of rough treatment. For the replaced aluminum strips, since the aluminum strips are bonded with a scoop of cement, the bottom edge of each aluminum strip is easy to seep out the residual glue. The residual glue should be scraped off one by one with a blade first, and then use a wire brush (Do not use a Grinder to prevent the edges from being abraded ), and perform rough treatment repeatedly along the direction of the aluminum strip. After the rough treatment, use No. 120 emery cloth to smooth the surface along the direction of the aluminum strip, wipe off the floating powder, and then spray the primer again.
③ FRP substrate treatment method
FRP substrates are mainly used for the front and rear panels of high-end luxury buses, as well as the bumpers and front covers of various buses. For the treatment of FRP substrates, because FRP parts have a layer of wax on the surface when they are molded and demolded (release agent, so as to facilitate smooth demoulding after molding), this layer of wax has an impact on the coating quality of the coating. If it is too large, it will affect the adhesion of the coating to the substrate, and if it is serious, it will easily cause coating peeling (the paint film is brittle and easy to peel), so it is necessary to effectively remove the wax. There are several ways to remove wax:
Grind the wax layer repeatedly with a polisher until it is rough and evenly ground without leakage.
Roughen by hand with 80-grit emery cloth.
First use a wire brush to brush the wax layer repeatedly, and then polish it smooth with emery cloth.
For the replacement of the front mask workpiece, the workpiece can be placed flat on the workbench, first use the grinding wheel to grind the wax layer thoroughly, and then polish it smooth with emery cloth .
When processing the FRP base, care should be taken not to use electric Grinders or sharp steel shovels, blades and other tools to prevent grinding or cutting through the base. For small pieces of FRP, do not soak them in strong solvents such as benzene solvents to prevent workpieces.
