Frame And Members problems of the 2001 Chevrolet Impala

My 2001 Chevrolet Impala makes a very loud banging noise when rotating the steering wheel while stopped or at very low speed, such as when pulling out of a parking space. I had the vehicle inspected by the Chevrolet dealer where the car was purchased new, the inspection revealed faulty sub frame welding. The mechanic also said this was very common with the recent Impala's and after many sub frames were replaced due to missing verticle welds and faulty sub frame welds, the manufacturer{ general motors} began using a less expensive super glue type locking material kit over the faulty welds, with at least the last 5 repairs at this shop completed as such. I have seen many reports of police vehicles {impala's} involved in accidents after control loss, which may be related to the missing and faulty welds. The loud banging noise is metal to metal caused by flexing of the aluminum sub frame at the missing/ faulty welds.