SLK – rust inside on bonnet !!!

A friend of mine drives a SLK year 1999, 110,000 km, accident-free with original paint. When you open the hood, you can see the inside left under the edge of the hood at the height of the headlight on a length of approx. 15 cm the paint swells or rusts and bursts from the inside! He drove the car to the MB branch, the master said that it is already the 3rd SLK that has this problem. He measured the paint thickness and confirmed that it is all accident-free. Nevertheless, the Mercedes does not compensate the damage because the car is already over 8 years old. Really bad, because it is obviously a mistake of the manufacturer. The master dismissed the rust as a “pure cosmetic problem”. I suspect however that it is only a question of time until the rust eats through the surface. Do not want to know what the hood looks like in 5 years. Mercedes does not even want to replace a smart repair. What should the 8-year limit? Builds MB cars that should last only 8 years Bin very much over SLK is considered to be stainless. Who can say anything about this or who has had similar experiences?