Many years ago, I designed a set of tamper proof screws that would protect electric meters from being illegally tampered.
Basically,once inserted and over tightened, the screw head sheared off leaving a fairly smooth surface.
I suspect that Screwfix has something similar now.
Nothing new in all this, it was the way that things like sea mines and such were disabled from being rendered harmless by bomb disposal teams.
One of the techniques to fool this is still on the British Secret list.
If you want to rust something- washing soda is the thing. My father was a sapper in the Royal Engineers
And the preacher for next week's service will be nailed to the church door at the end of this service.
Norman