Does anyone have any (Practical) advice on what I should do to stop my shed colorbond walls rusting?




Details:
**Built around 7 years ago.
**25Km from the coast.
**Concrete slab went down first, then shed built around it.
**Filled in the gaps between the slab and wall sheets with a cement / mortar mix to prevent vermin entering. (I think this is where the issue is)
**Lined the shed with timber ply sheets and fibreglass insulation.
**Rust is random around the shed, even in parts where there is no scoria.

Is there really a magic cure available or are they all BS?

Thanks
G.