Are the complete contact areas of your discs clean and shiny?

When I purchased an '08 XC70, the tech who checked it out noted that the pads did not make proper contact with the discs - there was a hardened layer of rust on the discs, a shiny dark color. The discs should be bare metal.

Since this was a safety issue, the selling dealer (a Lincoln dealer) replaced the front discs, turned the rear discs and put all new pads in as this condition cannot be properly repaired otherwise.

When I test drove the car, and when I drove it 15 miles to my Volvo dealer I did not notice a problem.

Did the car sit for a while before the grinding started?

Our low mileage '12 XC70 will grind upon the first brake application if it has sat for a week - it is quiet thereafter. Discs can rust up fast.