What causes the combustion in the rear section of the exhaust pipe of Nissan paladin No.6 cylinder, and how to solve it? high mark

The exhaust temperature of automobile engine is about 800 degrees Celsius at the cylinder outlet and 200 degrees Celsius at the exhaust pipe outlet, so many exhaust pipes are oxidized and rusted by heat. When the engine works normally, the temperature of the exhaust pipe gradually decreases, but even in the rear section of the exhaust pipe, the surface temperature will exceed 50 degrees Celsius, which is normal for scalding hands. Don't worry.