Dear all; In Australia, we have numerous wrought iron rail bridges that are +100yrs old. Some of these bridges have a couple of issues with corrosion of the original material post modification. The configuration in question is a sandwich of 2 x 18mm mild steel outer, added with 1 x 6mm original wrought iron inner. For further reference, the inner is a I beam web and the outers are web stiffeners that were added to provide additonal strength to the member. Other than RT, what portable alternative methods / new technologies are available for the detection of gross corrosion / wall loss (>25%) of the inner web in a timely manner?????? Note, access is not a problem and survey of outer web stiffeners is also not a problem.