Water Tables are available in aluminum or Corten steel.
Aluminum has the advantage that it is lighter and these tables are available in various colours. Aluminum is powder coated and has a very long lifetime.
Corten steel requires no maintenance and does not need to be painted or coated. The steel begins to rust under the influence of moisture and oxygen. This should be avoided with regular steel, but with Corten steel the rust-coloured and very dense oxide skin shields the deeper lying material from oxygen, which slows down oxidation considerably.