Thanks to the coloring, the car acquires not only a beautiful appearance, but also receives protection against corrosion. An important factor that ensures reliable quality painting of the machine is the thorough preparation of its surface. This process consists in removing damaged layers and cleaning the surface of rust, oil and grease.
This is necessary so that when applying a new layer it is well kept, which is possible only on a cleaned surface. On old paint will quickly and easily peel off. To clean the car of old layers, rust and grease, paint is washed off chemically, in addition, mechanical and hot methods are used.
The most straightforward method is mechanical or manual cleaning using metal cleaning brushes, steel scrapers, large sandpaper, grinding stones, etc. Depending on the complexity of the work, one or another tool is used. It should be noted that this method is quite time-consuming, and if possible it should be replaced with other cleaning methods. For example, washing off old paint.
The most productive mechanical method is sandblasting the surface of the car. Nevertheless, this method gives good results in relation to rust, and the removal of old paint by this method is not very effective, especially when it remains sufficiently elastic.
Cleaning the surface of the car from old layers of paint is also done by firing, for this they use a blowtorch. The method is quite effective, especially where it is necessary to get rid of thick layers from vast areas. With this method, the paint partially burns out under the influence of high temperature and becomes so soft that it can easily be removed manually with brushes or a scraper.
Nevertheless, this method of cleaning using a flame is very time-consuming. It is difficult and sometimes impossible to use when repairing a car to remove old paint from the casing, as well as plastic parts, since these elements can be damaged.
The best way is to wash the paint or a chemical method using a variety of pastes, solvents. The result is a saving of time and labor with low material costs. Removing old layers by washing is a process of chemical exposure to the surface of a car, with the swelling and dissolution of the paint. To implement this method, alkaline washes and a paint thinner are used.
In repair shops, alkalis are mainly used to remove old layers from the metal surface of car parts and assemblies. The paint is washed off by immersing the elements of the car in a container filled with a solution of caustic soda, heated to a temperature of + 60-70 degrees. Removing old paint from a car body can be done by applying a 30 percent caustic soda solution with a washcloth. After 12 hours, the paint is destroyed and washed off easily with warm water. However, to remove many layers, this procedure has to be repeated several times. This method requires a large consumption of soda.
More effectively, the paint is washed off using pastes, which are weak alkaline solutions, mixed to a viscous state together with mineral and organic substances.
The paste is applied three times to the surface with a brush, making a two-hour exposure after each application, and then washing it off with a stream of water from a hose. The paste helps to “raise” oil and nitrocellulose varnishes, enamels and paints well.
The paint is also washed with various liquid and paste solvents based on organic substances. After applying the solution, the softened layers are removed with a spatula.