Pre-industrial armoured ships

There are recorded incidents of armour having been employed in naval warfare prior to the introduction of the ironclad warship in both Europe and in East Asia, in the form of wooden ships or ships of composite construction (wooden planking on iron frames) armoured with thick metal plates. The Europeans made ships with metal ribs as rams, and there are also documents about armoured ships, some of them equipped with naval artillery. In East Asia there are records about metal armoured warships combined with naval artillery from the 16th century. However, in every single case of both European and Far Eastern vessels evidence of iron armour is either unclear, ambiguous or disputed.

Ship armour is to be distinguished from the practice of hull sheathing for preservational reasons, namely the protection against marine wood-boring worms. Greek merchantmen were fitted with lead sheets for that purpose by the 5th century BCE. A notable Roman example were the excavated Nemi Ships with an underwater hull covered by a thin layer of lead. The practice was resumed by the Spanish and Portuguese in the Age of Exploration, while the British Royal Navy began to copper their war ships in the 1760s.

The huge Syracusia, built by the Greek tyrant Hiero II of Syracuse around 240 BCE, featured bronze-clad mast-tops for marines and an iron palisade on its fighting deck against enemy boarding attempts. Its hull was sheathed with lead plates fixed with bronze nails. Roman naval cataphract warships were protected on their sides by a layer of tarred and lead sheathing. Although this does not provide much protection from ramming, it does provide protection from damage while at sea for lengthy periods of time.

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Wikipedia