Scale Armor is made from Scales, which are from Iguanas . It is the same as iron, but with a secret bonus! If the entire set is worn, you are given fire protection for each piece of armor. This fire resistance extends to resistance against lava, enabling a player to swim in lava. However, it does take durability damage so take precaution. You can also buy a set from the Koa villagers.
As you can clearly see, the durability has taken a very slight reduction, but the health is intact as stated above.