Do you guys think this is fine at 1d8, or should it be 1d10 to make up for its situational usage?

Crush Steel

Transmutation cantrip

• Casting Time: 1 action
• Range: 30 feet
• Components: V, S, M (a wad of crushed tinfoil)
• Duration: Instantaneous
• Classes: Sorcerer, Wizard ___ You motion at a creature within range that is wearing metal or armor or made of metal and cause its armor to debt inwards. The target must succeed on a Constitution saving throw or take 1d8 bludgeoning damage and suffer a -2 penalty to its AC until the start of your next turn. On success it takes half as much damage and does not suffer a penalty to its AC.

This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).