Kia Picanto 3 years old, brake failed

Hello, I would like to briefly describe my problem. About a year ago I bought a private checkbook Kia Picanto, who was only 2 years and 4 months old. In September 08 the 3 year warranty was extinguished. Now I was at the TÜV and would not have expected that I could not get the TÜV badge. The brakes were tested and it turned out that the brake at the rear right was no longer working. The man from the Tüv was also very surprised because the car was only 27,000 kilometers down and is just a little over 3 years old. He then said that it might come from the salt and that the whole thing just had to be made “accessible”, so a little greased and then the whole thing would run again, I should not let myself be mentioned, because you would like to tell young girls something else… For this reason I immediately drove to a Kia-contract dealer and told them the problem. Have you any idea if I could let the whole thing run on Kulanz? The guarantee has just expired for 5 months and I also bought myself an extra well-kept young car so that as a student I don’t have to pay for the workshop every few months… and now something like that… Suppose I don’t get a Kulanz anymore, would it be cheaper to run the whole thing over a Kia workshop and e.g. over ATU? I’m talking about every answer.