Other Fuel System Tank Assembly problems of the 2006 Chevrolet Equinox

2006 chevy Equinox fuel gauges does not read accurate. When full it reads 3/4 of tank to 1/2. It will then go to almost full as gas goes down. I noticed there are numerous complaints online about this problem from others. This should be a recall item as it is not safe when you don't know how much fuel you have. Gm says its a corrosion problem with the sender in the tank. Shouldn't that be there problem to fix? seems they chose the wrong material to use in the tank if that is the case. I have never owned any other car which has had this problem. Gm says the sending unit needs replaced at a cost of over $500. 00 including labor.