[roy snook]

Here is a picture of some of the flat panels after machining. I have left cut Zintec steel sheet outside for over a year and the ingress of corrosion on the edges is negligable. The material can be dipped after machining to protect against corrosion until the final surface (colour) is applied. It is true you do need to be very careful when machining to ensure accuracy of the finished panels but this is not difficult to achieve. .