Have you ever asked yourself why the armor of a medieval knight didn`t rust? After all, the armor was not made from stainless steel but from iron and normal steel. And today, iron and steel immediately start to rust when you keep them in the rain or simply in a moist place. So how exactly did medieval knights stop their iron and steel armor from rusting?
Chainmail that wasn`t needed for longer periods of time was stored in oiled leather bags so that the oil created a film on the rings and prevented them from rusting. It was not necessary to oil chainmail that was worn regularly since the movement caused the rings to rub against each other so that the mail cleaned itself from any surface rust before it could do damage. Plate armor had to be oiled and polished after it was used to prevent surface rust, which would eventually bite into the material and weaken the armor.
Let`s take a closer look!
Preventing chainmail from rusting
We basically have to look at two types of medieval armor, chainmail and plate armor, when talking about how a knight prevented his armor from rusting. Since the maintenance of these two types of armor was quite different, I will talk about them separately. And I will start by talking about chainmail.
Shirts of chainmail (so-called Hauberks) were an effective and popular type of armor, not only in the Middle Ages but also in Antiquity. As such they were not only worn by medieval knights, but were also worn by generations of Roman legionaries.
But the individual rings that made up a shirt of chainmail were made from iron or steel wire. And as soon as iron or steel (when it isn`t stainless steel) comes in contact with water, it starts to rust.
So how did knights prevent their Hauberks (shirts of chainmail) from rusting and becoming useless?
When a knight didn`t wear his shirt of chainmail for a longer period of time he usually stored it in an oily leather bag so that the oil coated the rings. That protected the rings from getting in contact with water and from starting to rust. That was only necessary when the chainmail wasn`t moved regularly. When chainmail was worn regularly it had one big advantage over plate armor.
Surface rust started to form as soon as the metal of the chainmail came in contact with water (or sweat). And when the surface rust was not quickly removed, then the rust worked itself deep into the metal. That either created weak points that reduce the effectiveness of the armor or even turned the shirt of chainmail into a worthless piece of rusty scrap metal.
But when chainmail was worn, then the individual rings rubbed against each other and scraped the surface rust off each other as soon as it formed. So as long as chainmail was worn regularly, it immediately cleaned itself from any forming surface rust before the rust could damage the mail!
That made the maintenance of mail armor extremely easy, especially when the knight was away at war and wore his Hauberk regularly. That kind of simple maintenance was actually one of the 5 reasons why chainmail was so popular for so long!
Contrary to chainmail, plate armor could not self-clean itself from rust but had to be carefully maintained.
Preventing plate armor from rusting
Just like chainmail, plate armor also rusted quickly when it came into contact with water or sweat. But unlike chainmail, plate armor could not self-clean and rub off the surface rust itself. Instead, plate armor had to be carefully maintained and polished regularly.
Just like chainmail that was not moved over longer periods of time, plate armor was also regularly oiled so that the oil created a protective film on the plates. That had to be done regularly to prevent the oil film from becoming patchy. When that happened or the plate armor was not immediately maintained after it was used, then surface rust formed.
In order to prevent rust, the individual parts of medieval plate armor were rubbed over with an oily rag. That created a protective oil film on the surface of the plates which protected them from rusting. In case rust had already formed, it was immediately removed by grinding and polishing the affected plates.
When the surface rust was not removed, then it would eventually bite deep into the metal and create weak spots in the armor. That obviously drastically reduced the effectiveness of the armor.
However, there was another way to protect plate armor from rusting.
The cheap, mass-produced plate armor that was pretty common among regular soldiers and low-ranking men-at-arms during the Late Middle Ages was often painted. Painting the plate armor prevented it from rusting immediately, but also had other advantages.
Unlike that kind of cheap and mass-produced armor, the plate armor worn by knights was always polished. The mirror-bright plate armor was even generally associated with the knightly class.
I hope you enjoyed our trip to the Middle Ages. Do you want to find out more about medieval armor? Then I would like to recommend you my article here on the effectiveness of medieval swords against armor.
Take care of yourself because you deserve it. You really do.
Until next time
David S. Bachrach: Warfare in Tenth-Century Germany (Woodbridge 2012).
Malte Prietzel: Krieg im Mittelalter (Darmstadt 2006).
Alan Williams: The knight and the blast furnace (2003).