Galvanised steel or aluminium: which material for an outdoor sign in Benin?
Sea air, the rainy season, the harmattan: the climate often decides the material before the budget does. Here is how we weigh it up on our projects in Cotonou and across the sub-region.
On a port site, a badly specified sign rusts within eighteen months. On an urban road inland, the same sign lasts ten years. The material is not chosen from a catalogue — it is chosen on site.
Climate before budget
The sea air in Cotonou is laden with chlorides. Within two kilometres of the coast, any unprotected steel component will pit. Hot-dip galvanising remains an option, provided it is paired with a lacquer coat and the welds are retreated after assembly — something many installers leave out.
A weld reworked on site without touching up the protective coating cancels out the benefit of galvanising.
Galvanised steel: when thickness wins
For structures carrying significant loads — gantries, twin-post supports, structural frames — steel remains the rational choice. Its mechanical strength allows smaller sections for the same load, and the material cost stays lower.
Aluminium: light weight and height
At greater heights, aluminium changes the calculation: less load on the anchoring, so lighter foundations and faster installation. The higher material cost is often recovered on the civil engineering.
Total cost over five years
Compare the full spend: material, treatment, transport, installation, annual maintenance and partial replacement. On our recent coastal projects, lacquered aluminium works out 12% cheaper over five years despite an initial investment 20% higher.
Our decision framework
Distance from the coast, installation height, wind loading, access for maintenance, expected service life: five criteria, one judgement. We work through it with you during the on-site survey.
Twelve years of manufacturing and installation in Benin and across the sub-region.
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