Not 100% correct. Since most steels today contain significant recycled content some alloys have impurities that accelerate rust as several auto manufacturers discovered some years back when they bought the cheapest stock they could find. They used to call the stuff "pre-rusted steel" as even multiple coatings failed to prevent premature rust. Galvanic action plays a role and these alloys rot extra quickly.
I am curious about this- I know that since Nucor introduced the EAF (electric arc furnace) and continuous casting to the USA in 65, the process testing has gotten way better than in the old days- they monitor, in real time, alloy contents.
It is true that, in the old Bessemer process, usually only 10% of the charge was recycled, but way back then it could have contained wrought as well as alloy steel.
Currently, A36 does have lower standards of whats in it than, say 1018 does, and its true that 40 years ago, when I used to buy cold rolled if I wanted sharp corners, it would not have been A36. So there is often more copper, for example, in A36, than there used to be. Does copper content make steel rust easier?
But back then, I paid a premium for 1018 or 1020 cold rolled square or flat bar.
I imagine, if I was willing to pay for it, and wait for shipping, I could still get real 1018.
However, my memory says it rusted EASIER than hot rolled did, as hot rolled had an oxide coating.
In short, I think good steel used to be cheaper, so more places stocked it, and now, since even crappy A36 is more than 80 cents a pound, nobody bothers to stock or buy better steel.
I still dont see how magic steel of my childhood could have rusted less, though.
As Neil Young says, Rust Never Sleeps.
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