My 2m high fence posts with 2 x 2 m approx wood panels have rotted at the base where they were put in concrete foundations about 1 foot in diam probably 25 years ago. I don't particularly want to dig all the concrete out which could take a week. Is it a good idea to clean out the 3" x 3" holes in the existing foundations and set new steel fence spikes in them with concrete then attach to new fence posts. Or will the standard spikes from the sheds just rust away in a few years, especially if the length needs to be trimmed, exposing bare steel. These seem to be painted rather than galvanised. Appearence is not an issue as they won't be visible.
thanks for any advice
john