The fence posts of a fence made from COLORBOND® steel have a different metallic coating underneath the paint to that used in the rest of the fence, which mean they are suitable for concrete immersion. You should not allow the concrete to contact the rails or infill sheets of the fence as this can detrimentally affect the performance of COLORBOND® steel. For the design of concrete footings, we recommend contacting your chosen supplier of fencing made from COLORBOND® steel.