How thick of a metal shielding do you need against mains voltage induction

I will be placing an arduino to read a current on the main electrical line after the master breaker of my house using a non-invasive current transformer.

The master breaker is rated 50Amps(?). assuming the full 50A is on that line how thick of metal should i use to protect against the inductions that will be generated on that line.

To measure the line current, use a current transformer as described in this tutorial.

The Arduino can be mounted some distance away from the breaker panel, and it is unlikely you will need shielding.