An Australian Cessna 210 lost a wing due to failure directly attributable to corrosion:
https://www.atsb.gov.au/publications...ir/ao-2019-026
There have been other structural failures in Cessna and Pipers where corrosion of primary structure was a factor. In the case of Cessnas, the "SID" inspections are pretty thorough in defining what inspections should be done. Whether mandatory or not, a GA airplane owner would be foolish to dismiss these inspections as not necessary. The Cessna SIDs, in particular, are really well written, and obviously based on a true understanding of the vulnerable areas of the structure of the legacy planes based on decades of experience.