Iirc steel rust was one of the factors contributing to the collapse of the Morandi Bridge in Italy. And because corroded elements were covered in concrete, could not be inspected with naked eye until concrete started cracking, which was too late.
The "same" cables on the "near" pylon #11 (the one that collapsed was #9) had been replaced in years 1992-1996 because of severe corrosion.
Everyone was expecting that the same replacement would have been soon made on the pylons #9 and #10 but the inspections (circa 1991) that were made (boring holes to visually inspect the cables in a few points) and, although these inspections (obviously) showed some relevant corrosion it was underestimated, and anyway no correction measures were taken in a timely manner (please read as in the next 25 years).
That the bridge was overloaded (by traffic as much as 4-5 times the amount it was designed for originally) and that it needed interventions was a known fact and starting 2006-2009 there were several projects about demolishing and rebuilding it that were never finalized/approved.
A new inspection made in 2015 evidenced the very poor state of the cables, the results of this inspection were once again underestimated or even falsified.
A project was made for replacing/reinforcing the cables in 2017 (20+ years after the works on #11 and 2 years after latest inspection) and the bid for it was published only a few months before the bridge collapsed in 2018.
It was a story of incompetence, sloppyness and greed.