Cannot be traded.
You can refine your armor to +7 through Prontera's Refining Expert. -1 time limited-

[iRO Description]
Take this certificate, 1 Elunium and an upgradable Shield, Shoes, Clothing, or Armor to Mighty Hammer in Eden Group or Payon. If he fails on the upgrade when the item is +4, +5, or +6 the item will not break and it will stay at its current upgrade level.
This item is Tradable, and Storagable only.