I will be putting up a natural stone counter top in the patio (2 inch thick natural stone tread, 5 1/2 ft long, 2 ft wide, which is the 250-300 lb weight range. This counter top will be supported on front, left, right by a cinder/concrete block wall.

I was thinking of using flat steel per other posts on this forum. However it seems that regular steel will rust and stainless steel flat bar is very very expensive.

Can anyone suggest a solution for this? Can i prep the regular steel flat bar, to essentially make it last longer before rusting?

And how many such steel bars would I need to support the stone top. Currently the overhang on the near edge of the wall is 4-5 inches and the overhange on the far side of the
counter top and the overhang there will be 9-11 inches range.

Thanks
Raj