Ford India — Regarding my car roof getting rusted if its own

Address:

H-46, Green Park Extension, New Delhi -1)

Dear Sir,
I have purchased Ford Eco sport in 2017, now I realised the paint is getting chipped from different locations of roof, so raised a complaint with customer care Ford india the reply was unsatisfactory.
They said since the warranty has expired so you have to bear the cost.
My concern is do all Ford car roof get rusting, hopefully not then why my car has this special feature of rusting of its own.
It looks the dealer or company has given me defective car.
Request you to kindly take appropriate action to get it resolved else will go to social media and start posting the roof pictures.