Shiny Steelix!? Nice Score Man!
Here's what I reccomend you use.
Steelix @ Leftovers ( Gradual HP Recovery works well when tanking, and he has no source for instant recovery other than using Rest, which will either make him absent for 3 turns, waste a moveslot for Sleep Talk, or waste an item slot making him be able to only have to take one turn using it )
Role: Tank ( Played better than a wall on him, due to him having a workable attack stat )
Trait: Sturdy ( You already have it ^^ )
EVs: 160 HP (Bulk ) / 96 Atk (Attacking Power, better Curse boost ) / 252 SDef ( So he can take sp atks )
Sassy Nature (+SDef, -Spd)
- Curse ( No Ev's in Def, this makes up for it, extra attack, and Speed drop supports Gyro Ball.
- Earthquake ( STAB And covers 5 types, Heck Yes! )
- Gyro Ball ( Powerful STAB, Supported by Curse and his Speed lowering Nature. )
- Rock Blast ( A Competitor with Stone Edge, but it can reach a higher total power, and breaks subs.