Armor Pen directly negates Armor, and Flat Pen is applied before Scalar Pen (e.g. 50 Armor affected by 10 Armor Pen is effectively 40 Armor, 50 Armor affected by 40% Armor Pen is effectively 30 Armor, and 50 Armor affected by both 10 Armor Pen and 40% Armor Pen is effectively 24 Armor ((50 - 10) * (1.0 - 0.4))
Armor Pen cannot reduce armor below zero.
Armor Penetration can refer to:
Ignores a percentage of enemy Armor when determining Physical Damage.
Hard Cap: 100%
The Sharpest Edge is the only item with Scalar Armor Penetration.
Ignores a flat amount of enemy Armor when determining Physical Damage.
Items with Flat Armor Penetration: