A typical calculating lifetime of Hot-Dip Galvanising coating is set to 20 years on average, but this is based on many variables like humidity, temperature, environmental impact etc.
If you require to calculate the coating lifetime for your localization, please ask a question to
Galvanising Association
or
visit their website
for more details.
For more details please refer to:
Finishes (Plating)
Galvanizing is durable
Corrosion Rates in UK & Ireland - Corrosion Map