Automotive coatings refer to coatings painted on the body and parts of various vehicles such as cars, which can be divided into original body paints, automotive refinish paints, auto parts coatings and other automotive coatings according to application scenarios. Automotive coatings, like general coatings, are composed of film-forming substances (resins), additives, pigments, and solvents.
As an important component of automotive coatings, especially pigments used for automotive topcoats, pigments play a particularly important role in the high decoration and high durability of automotive coatings, so the inorganic pigments used in automotive coatings have excellent performance and high requirements for weather resistance and light resistance.
At present, the inorganic pigments commonly used in automotive coatings often have these performance characteristics.
Environmental protection and non-toxic: With the strengthening of people's health awareness and environmental protection laws and regulations, pigments containing lead, chromium, cadmium and other elements such as lead, chromium and cadmium red are no longer available in China's automotive coatings. Consumers continue to put forward higher requirements for the environmental performance and safety of automotive coatings, and the transformation from traditional solvent-based coatings to water-based coatings is an inevitable trend in market development.
Excellent chemical stability and color performance: In addition to the fastness to various chemicals such as acid and alkali resistance and solvent resistance, pigments for automotive coatings also need to have good fastness to sun and rain, ultraviolet rays and sulfur dioxide when used outdoors for a long time under various climatic conditions, that is, they have excellent outdoor durability of gloss retention, color retention and chalking resistance. In addition to the color itself, the strength of the pigment's hiding power also affects the pigment's tinting strength. Hiding power is the ability of colored paints to disguise the surface of an object. The thickness of the coating film and the concentration of pigments also play a significant role in the ability of the coating film to absorb and scatter light. In addition, the color stability of pigments is also very important, and the color indicators such as the main color, hue, and tinting strength of different batches and even different brands of pigments should be within the allowable color difference.
Application performance: In grinding, dispersing and painting, the pigments used in automotive coatings should have a good dispersion, flocculation resistance and storage stability, and the resulting color paste should have a good fluidity to meet the process design requirements of computer automatic color matching in the production and manufacturing of automotive coatings of modern enterprises in China.
In terms of the specific application of automotive coatings, the commonly used inorganic pigments mainly include titanium dioxide and color mixed miscible inorganic pigments. Color miscible inorganic pigments are a class of inorganic pigments with excellent chemical stability. Miscible pigments can be regarded as solid solutions of metal oxides, and the composition of different oxides can produce different colors, such as titanium nickel yellow, titanium chromium brown, cobalt blue, cobalt blue, cobalt chromium blue and copper chrome black, manganese iron black, etc. These pigments are characterized by good resistance to high temperatures, acids, alkalis, light and weathering.
In highly decorative coatings such as automotive coatings, inorganic pigments can be mixed with titanium dioxide and organic pigments with strong tinting strength, especially rutile miscible pigments such as titanium nickel yellow and titanium chromium brown to replace toxic inorganic lead chromate pigments and cadmium pigments. There is also bismuth yellow pigment, which is close to lemon yellow in hue, environmentally friendly and non-toxic, bright and clean in color, and is also commonly used in automotive coatings. The manganese iron black and copper-chrome black pigments are often used in high-temperature coating applications such as automobile exhaust pipes, which have significant thermal stability and very strong tinting strength under extremely harsh production conditions. In addition, in the "three electric" coating of new energy vehicles, pigments such as cobalt blue, cobalt chrome blue, and cobalt green have good salt spray resistance and weather resistance, as well as electrolyte corrosion resistance, and will usher in major development opportunities driven by market demand.