How to identify cor ten (weathering steel) in the field 1

[frogit22]

I am looking at an existing pedestrian bridge.

How do I know if the bridge is constructed using weathering steel or if it is just rusting?

Overall the level of corrosion does not appear alarming.

A secondary question is if it is weathering steel and I need to do some repairs, what are the durability issues with drilling holes or welding the existing weathering steel. Would I be compelled to use weathering steel for any steel repairs or supplementary structural members?

thanks,
Garry

 

[PEinc]

Thanks. I hope it's just my monitor and not my eyes!