One problem related to frame rust has been reported for the 2009 Hyundai Sonata. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Hyundai Sonata based on all problems reported for the 2009 Sonata.
The 2009 Sonata has excessive rust on the front frame that holds up the engine and transmission. I do not live at the beach, and is only on the passenger side of the vehicle. It has never been in an accident. It was found by a mechanic during routine maintenance. Chunks of frame were falling off as we were inspecting the rust. It is being replaced due to eminent, catastrophic failure. The mechanic said the only time he has ever seen this is on 20-25 year old beach cars.