Please try this at home. You all have rusty iron ball laying around, right?

It wouldn't be weird for someone in the south of France to have a rusty pétanque ball.

Now you can be hoisted not just in your own petard, but also in your own pétanque.

This clearly calls for thermite petanque.

Hammer faces would work (def wear goggles!!!). Hit the face of the disposable one with a mixture of hydrogen peroxide, vinegar and salt and wait an hour.

Joining the thread to see where iron balls can be sourced.

Some vendor on AliExpress? Those Lucky Iron Fish?

This might work with old iron dumbbells (or modern iron kettle balls if left unpainted). Your gym might hate you for it though.

Cast iron pan left outside for a day or two.

I'd guess exact form wouldn't matter. Wrap a hammer in foil and beat up something rusty.