Oxidation is a 
Vladof Repkit
Its special effect is Blood Iron - Reloads a percentage of ammo equal to the percentage of health healed on use.
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How to Unlock The Legendary Oxidation Repkit
Repkits
Legendary Loot
Overview
How To Unlock
Unlock Location:
- Progress through the (Murders and Acquisitions) DLC until reaching the Final Boss BETAMAXXX.
Farm Method:
- Defeat BETAMAXXX to get a chance at the Oxidation.
- After use the Encore Machine nearby to reset the fight.
- Repeatedly defeat BETAMAXXX until the Oxidation drops.