Rusting

Visited HMS Warrior at Portsmouth recently ... ship was not in dry dock, but was still floating in the sea (built 1860, so that's over 140 years in salt water!)
On enquiring, was told that wrought iron "does not rust". On further investigation have found that whilst it does indeed rust, it does so very slowly.
Since wrought iron is simply cast iron that has been reheated, folded and beaten, why should this change the chemical reactivity in relation to rusting? ... any ideas?

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dunno, maybe a passivating skin formed on top?

Thanks for the reply. Not sure I understand what you mean by a passivity skin - not likely to be an oxidised layer as normal casting would also produce this.
Could it be the laminating from the "wroughting" process ... the layers each "protect" the next as they corrode? sort of like an onion that rots from the outside ..as one layer rots/corrodes it acts sacrificially thus protecting the layer beneath???
Is this what you mean?

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