Why the yellow leather 20 head is gray and black These coatings assume special functions.

a wide variety of coatings on aircraft, but generally speaking, can be classified into three uses: corrosion prevention, decoration, special functions. In particular, the "decoration" function of aviation coating is not limited to the completion of the final coating of the aircraft, the above picture of such a yellow bare metal is also to talk about decorative effect - the aircraft paint must be uniform color, uniform appearance, delicate appearance, color flat and moderate;
the author's previous article has said that the appearance of the 20 yellow leather machine mainly uses zinc-yellow acrylic polyurethane primer, which is a very versatile foundation
septic coating
. However, in many parts, the most obvious such as the head of the J-20, the pneumatic wing (duck wing, wing, full tail, etc.) edge, the use of a large number of gray paint. There are two reasons for this, first, these parts are hit by air currents and raindrops, friction, impact of the most violent places, especially in high-speed and high-mobility state, and second, some parts have special requirements, such as the radar cover outside the paint must be able to make electromagnetic waves in and out of the smooth and low loss.these parts, it is often necessary to use a variety of special functions at the same time special coating combination, in order to meet the design requirements. In the case of radar covers, for example, it requires anti-static coatings to dissipate static electricity from the surface to avoid electronic interference, lightning damage, or sparks (so anti-static coatings are also widely used inside aircraft fuel tanks to prevent fuel fires and explosions).
Anti-static coatings used in the modern aviation industry, mainly rely on the distribution of conductive pigments to achieve charge conduction - so its final performance and decorative function is closely related to the performance, uneven spraying, unreasonable curing, will inevitably lead to anti-static paint coating performance is not qualified.. Because of the performance of the radar, the color change of the radar cover is more careful; For example, a mechanical scanning radar/black radar cover combination is used on the J10A/S platform, and a phased array radar is used on the J10B/C platform, which turns gray.
And as the plane crosses the rain zone, the head and wing edge of the aircraft will form a large number of high-speed flushing effect with raindrops - for the J-20, such as the unprecedented emphasis on high-speed capabilities of the fourth-generation fighter aircraft, the chances of encountering supersonic raindrops washed is quite low. Therefore, the radar cover and the front edge of the wing must be sprayed with a certain thickness, by the polymer elastic system of wear-resistant coatings - usually using polyurethane elastomer coatings, it can use its own elastic absorption of the impact kinetic energy of water droplets, thereby reducing or eliminating the erosion of water droplets.
For example, some of China's second- and third-generation fighter aircraft, a complete radar cover coating system is roughly composed of the following three parts, first, on the surface of the glass and steel radar cover sprayed a colorless or slightly yellow epoxy polyurethane varnish, and then sprayed 2-4 green or white anti-corrosion coating, and finally sprayed 2-3 black polyurethane anti-static coating.And for this model, because it is now the most cutting-edge model in the study, and related aspects of the performance requirements are also the height never involved before, so it in radar and other electronic antenna cover and wing edge of the special coating combination, itself ahead of all the current stage of the domestic public information and related standards.
In fact, only if the development of the equivalent of 20 successful, the new standard norms in this regard can be established, so although from the general technical law, the radar cover and wing front edge on the 20 should be the use of anti-rain erosion and anti-static function, including multi-layer coating design, but more specific information, will have to wait for the future release of relevant domestic information.