We had our house built just 10 years ago. The bathtub drain has a lot of corrosion on it and in it. Very gross. We bought a new drain to replace it BUT the old one is so bad that when we tried to unscrew it at the "cross-bar" section that we were using pliers and a screwdriver on, the cross bars broke. Anyone have a suggestion on how to get this old one out now? The guy at Lowe's said would be easy to replace. HA! This is the only drain in the house that has this corrosion problem. Any ideas what may have caused it and remedies on how to prevent it?