How well armoured was the Roman army?

[Caratacus]

Matthew Amt wrote:
However, as much as I've heard about bimetallic corrosion, I've never seen any hint of it, on anyone's armor. Nor on any original pieces, as far as I can see.

The problem is that we are not dealing with simple bimetallic corrosion here. The brass fitments are an alloy of copper and zinc. While copper is a less reactive metal than iron, zinc is more reactive. There are hundreds of examples of fragments of lorica seg that have pieces of iron plate still attached to the brass fitments. This is so because the zinc 'protects' the iron from corrosion (our modern equivalent is 'galvanising'). The copper would cause the iron to corrode more rapidly but the voltage of the copper/iron couple is lower than that of the zinc/iron one - so the latter wins! However, the effect falls off with distance (which is why we rarely get complete plates of the armour). If the Romans had used bronze, rather than brass, fitments then it's very likely that the iron would have corroded much more rapidly as both copper and tin are less reactive than iron. The protection isn't a complete one, of course but after 2,000 years in the ground one would not expect to find pure iron metal.

The question remains (in my mind) as to whether the Romans knew of this difference in behaviour (without, of course, knowing the electrochemical reason behind it) - or whether it was just serendipity!

I remember that a couple of years back there was a TV programme where eight young men were 'trained' to be Roman legionaries, wearing the lorica seg armour (as well as hamata) for a week and roughing it in the countryside. At the end of a week of exposure to the elements, the iron of the lorica seg had a distinct red tinge to it - ALL OVER.

Mike Thomas
(Caratacus)