[outofsalt]

"By the mid-19th century steam engines had been fitted in some wooden ships of the line. But the Royal Navy was shocked when, in 1858, the French started building La Gloire. This was the first armour-hulled ship. However, because French industry could not make an iron hull, the Gloire had to be built of wood protected by 11 cm (4.5 in) of iron. Iron cladding the wooden British fleet was the simplest way of responding to this French challenge. However, Sir John Pakingham, the First Lord of the Admiralty, supported the idea of a completely iron hull. So, the Warrior was ordered in June 1859."

Iron rusted so copper sheathing the iron was tried, however galvanic interaction between the metals was even worse. They then tried wooden planking between the iron and the copper. The link above is very informative.

[Ruy Dias de Bivar]

My understanding was that 1700s sailing ships were cased in copper to prevent damage caused by the Teredo worms.

Also, British ships off the Vancouver isles had to post guards as the native Indians would swim out and pry off the copper plates to use in some of their art and rituals.

[MuttTheHoople]

When some observer first saw the CSS Virginia sink a Union sail ship, remarked that every navy in the world was now obsolete.

Probably the same thought when the German ME-262 first flew up to attack the B-17's.