You need a toxin or electricity Riven for this build and use [Stormbringer] or [Infected Clip] to build corrosive. If you don't have a decent Riven just replace it with [Infected Clip].
The aim of this build is raw damage with appropriate damage multipliers for armoured targets. Corrosive does +75% to Ferrite and Cold does +25% to Alloy and +50 to Shields.
Able to kill 120 Corrupted Heavy Gunner in 5-6 shots primary fire. Secondary fire is stronger with [High Voltage] instead of Stormbriger but it makes Primary fire slightly weaker.