Borderlands 2 introduces a telltale yellow Armor bar for Armored foes, generally making it much easier to tell when you should use Fire weapons versus Corrosive ammo. However many Health targets also have armored parts.
Notably there are Spiderants and Hyperion Soldiers like Engineers. Engineers appear to be almost completely covered with armor. Are they weak to corrosion or flame? For Spiderants I know Fire works well on their unarmored thorax but Corrosive works, with reduced damage, on the armored parts (just like it worked in Borderlands 1).
With Hyperion I've had a harder time telling; in the first playthrough it seems both Acid and Fire work servicably, but in the second playthrough elemental effects are more pronounced, so I'd really like to know which element I should use against them.
Are "armored" looking enemies with red health bars still weak to flame (ignoring elemental enemies of course)?