After the first ironclads proved themselves, it wasn't long before iron and then steel replaced wood as the primary material for ship construction.

Ship construction, and sailing, had not changed fundmentally from the time of the caravel until the height of sailing technology in the great tea clippers, but ironclads coupled with better engines and propulsion would soon bring about a revolution of sorts in both shipbuilding and the life of the sailor.

The very first ironclad was the French warship Gloire, completed in 1860. She was clad amidships at the waterline with iron plate to deflect enemy cannon shot. She was quickly followed by the Invincible in 1862, another French ironclad with two large steam engines, giving her a top speed without sail of over 14 knots. The British countered with the construction of the HMS Warrior, and the ironclad frigate Royal Oak, both formidable warships for their time. Soon, the Americans got into the act, and immediately got the chance to test their ships in the now famous battle between the Merrimac and the Monitor. In all truth both these ships were unwieldy, but they hammered at each other for hours without either ship being sunk despite multiple hits. Not to be left out, the Russians got into the act with the Pervenetz in 1863. These early ironclads are the forebears of almost all military ships since, and are very important in the history of transportation because they proved that the ships could carry the weight of their iron hulls, and this eventually led to steel ships, with the strength of steel making much larger ships viable. Naturally, improved steam engine technology and the steam screw (which was not exposed to enemy fire like the earlier side wheels) are what made it possible to achieve respectable nautical speeds carrying the extra weight of iron.

As steel production technology evolved, and steel became less brittle and less liable to shatter when struck by an enemy shell, it replaced iron for ironclads, first as an outer shell over wrought iron, and eventually as nickel steel with no iron. The last of the ships to be called ironclads were actually steel-clads. This technology advanced very rapidly throughout the second half of the 19th Century. Iron or steel clad hulls can also be referred to as composite hulls. Composite hulls did not last long. As engineers, ships architects, and naval strategists sought ways to sink the new ironclad ships, ramming ships saw their first serious consideration since the days of the galleys and triremes. Naturally, ships designed for ramming require a strong frame, and it didn’t take a huge leap of the imagination to try iron as a framing material, first as reinforcement, and eventually as the main structural component, and by the time steel replaced iron for armor plate, the concept of whole steel hulls, frame and all, did not seem the least bit extraordinary. This whole process only took a few decades starting about 1860.

There were a few all-iron hulls built, but they had three serious drawbacks. The hammering needed in iron hull construction tended to magnetize the hulls, and create serious deviation in navigation with magnetic compasses. Attraction of lightning was also a problem, and iron was very susceptible to rust in the marine environment. Iron and steel frames were used inside wood hulls in some cases, like the famous tea clipper Cutty Sark. Soon numerous all steel ships were being built, and the rest, as they say, is History.