To answer that question, you really need to understand the process of galvanization. It is our belief that anyone who buys steel for outdoor use and does not pay the extra cost for galvanization is making a poor long-term decision.
Galvanizing provides a rust resistant finish for metal products. Products with a galvanized finish are much less likely to show rust, except where the galvanized coat wears off in use. In areas where products will be exposed to salt water (sea air) serious thought should be given to using products that have a galvanized base. Otherwise, it will be necessary to repaint as much as every year. Because the galvanizing process involves total immersion of the material, it is a complete process; all surfaces are coated. Galvanizing provides both outside and inside protection for hollow structures.
Steel can be further protected from the elements by adding powder-coating. This combines the advantage of the durability of galvanizing with the attractive appearance of powder-coating.
Economic Benefits: Because duplex systems (combining galvanizing with powder-coating) greatly extend the service life of a product, maintenance costs are significantly decreased. Additionally, a product lasts longer before it must be replaced, thus decreasing the life-cycle cost. The cost of a product, which has been protected by galvanizing and painting, is lower over the entire life of the product than most single system methods of corrosion protection.
Synergistic Effect: Combining galvanizing with powder-coat finishes provides corrosion protection 1.5 to 2.5 times longer than the sum of the lifetimes of zinc and paint used individually. For example, if a galvanized coating is expected to last 40 years and a paint system is expected to last 10 years, galvanizing and paint together should last 75 years with needed maintenance, or 1.5 times the sum of both systems.