Originally Posted by CliftonGK1
Most non-stainless steel alloys will rust heavily within 12 hours given the OP's listed conditions (high humidity and/or rain.) Especially if there's rough pitting/scoring from being cut, and quicker if there's any mild acidity to the exposed surfaces. "Instantly" is a bit of a stretch for visibility, but the rusting does begin in that short a time. It just usually takes a few hours before it's visible.
My stepdad who has been welding for over 35 years agrees with you, Clifton. I can attest to the high humidity of a Chicago summer.
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