There is plenty of evidence to show that an outside metal meter box can last decades, but first the steel, including any mounting holes, and the coating must be adequate.
Steel Grade and Thickness
The majority of meter boxes are manufactured from mild steel or galvanised steel and generally are between 1.2mm and 2mm thick. Thicker gauge steel is more resistant to denting and can be more robust to constant handling, such as a meter box located on the outside of a wall in a corner that can receive frequent knocking from a ladder or from gardening equipment.
How Coatings Protect the Metal
A powder coating bond is to a steel surface similar to that of a hard plastic covering which will repel moisture and mild chemicals. Galvanising on the other hand involves submerging the steel in molten zinc. As the zinc solidifies it bonds to the steel at a molecular level to form a sacrificial coating. This means that even if the coating is scratched, it will continue to protect the steel from corrosion. As previously described in the process behind how hot-dip galvanising protects steel, a galvanised coating generally outlasts a powder coated surface when exposed to the elements.
What UV and Damp Do Over Time
In time UV light can start to fade and harden a painted surface, which is prone to cracking. Once moisture has penetrated through any cracks surface rust will start to form quite quickly. This is particularly a problem for meter boxes sited on the south side of a wall and near to downpipes which leak.
Spotting Early Coating Failure
Spotting coating failure early is a matter of visual inspection. You should check the meter box for signs of coating failure twice a year. Coating failure can show itself as bubbling of the paint, rust staining, hairline cracks etc. Early detection and touch-up of coating failure can prevent major problems down the track.
Cleaning and Basic Maintenance
Clean the unit with mild soap and water occasionally, then rinse and dry. Use a zinc-rich primer when touching up bare metal to help stop rust formation.
If you are looking for Metal Meter Box, see https://www.meterbox.co.uk/.
The cost of a few moments to inspect on a regular basis is far less than that to replace a box which has perforated due to rust.
