Corruption in Path of Terraria works much like other games. Corrupting an item will prevent it from being modified further by currency shards and has a chance to break the item you use it on.
50% = Nothing Happens
25% = Item downgrades to a rare , that is from the same base type as the unique, and rolls new affixes
25% = Item receives a new "Corruption Implicit" Affix that is an additional affix on the item. Now totaling 5 affixes possible. Implicit added is randomly rolled and is weighted. So the higher weight affixes roll more commonly.
50% = Nothing Happens
50% = Item receives a new "Corruption Implicit" Affix that is an additional affix on the item. Now totaling 5 affixes possible. Implicit added is randomly rolled and is weighted. So the higher weight affixes roll more commonly.
Corruption Implicits - To be expanded upon later