Wikia

An Arcanite Bar is a rare metal used in many level 60 recipes. Not only is it a component to making many items, but it is also needed to create Elementium.

This grayish metal looks dull even when tempered, but it holds a keener edge than any other metal on Azeroth. Arcanite is extremely flexible and can be worked into a springy armor that turns aside the mightiest blows. Only weapons, armor, and shields normally made of metal can be fashioned from arcanite; a warblade can be made of arcanite, but a tauren totem cannot.^[1]

Source

This item is created by Alchemists using the Transmute: Arcanite ability which requires a skill level of 275 and a [Philosopher's Stone]. The recipe can be learned from Alchemist Pestlezugg in Gadgetzan. NOTE! Transmuting Arcanite won't trigger shared 20-hour-transmute cooldown.

Materials required
	1x [Arcane Crystal]		1x [Thorium Bar]

Arcanite Bar as an ingredient

Blacksmithing

Engineering

Arcanite Bar as a quest objective

The Tier 3 armor quests at Light's Hope Chapel in the Eastern Plaguelands (Only available after completing [60] Echoes of War.) Please note that the following have been removed from game as of patch 3.0.2.