Corrosive Weapon Fusion
(from Starfinder Core Rulebook)
The corrosive fusion weaves the destructive power of acid into the weapon’s form. Half the weapon’s damage type is replaced with acid damage. You can activate or deactivate the corrosive fusion as a swift action. If the weapon already deals two types of damage, replace one of them with acid (you decide which damage type is replaced each time you activate the corrosive fusion). You can add this fusion only to a weapon that does not already deal acid damage. This fusion never causes a weapon that normally targets KAC to target EAC.