There are some good photos and history of a 2.4 m diameter turbine with corroded magnets at the Build Your Own Wind Turbine site in Ireland. A paint job on some corroded magnets in 2009 and we get to see how effective this was.
Here is a paint job they did in 2009. Jump to 2011 and the turbine is revisited.
The alternator is pulled apart and this is what it looks like:
Not too bad really considering what it looked like in 2009. I would probably have replaced them but they are very expensive. There is another story here.
And a discussion on the Fieldlines Board covering the issue of neo magnet corrosion.
Finally some photos on facebook here. Not all completely on the magnet topic.