Corrosion around alternator cover

[REGS12]

Was pissed off when I spotted corrosion happening close to alternator cover. Removed plastic cover to investigate further & found quite a big patch under cover. It appears to be beneath the finished surface, and spreading.
Rang dealer and they will look at it, but because warranty has expired by two months don't promise anything. Should I be a prick and insist on replacement? What should I reasonably expect?

 

[MATKAT]

Push them

Just had mine replaced, it was 4 months out of warranty. May need a personal call to BMW customer service though. The delear could not get a result for me, but when I approached them direct immediate decision

 

[MIKA]

BMW know this is a problem and have had to replace them by the bucketload, my '55' plate is starting to show signs of corrosion at the plate but I will wait until it is almost out of warranty before getting it replaced.

Do a search, there are loads of threads on this subject.