I just bought a new battery and it is already getting corroded. Tonight it wouldn’t start until I cleaned the corrosion off the connection. What might be going on?

An over-charging alternator can cause the battery to vent more corrosive gas. The alternator shouldn’t produce than about 14 1/2 volts dc. Check your repair manual for the exact figure. Some alternators have their charging (output) voltage controlled by the engine computer. Some of the auto parts stores will do a battery and alternator check in the parking lot. The alternator, or battery, doesn’t have to be removed from the car to have the check done.
Before you put the battery cable terminals back on, put Vaseline on the battery post and terminals. This will keep the battery acid off the connections.

As noted, over charging can be the problem. It would be a good idea to make sure the battery and cables are totally clean and shinny as well.

I just read yesterday on this page about a volvo doing the same thing . over charging .