A zinc primer is a spray-on coating that goes on before the powder-coating finish.  Zinc-rich primers are unique from regular primers because they contain zinc which has highly sacrificial anodic properties.  High concentrations of zinc dust act sacrificially when in direct contact with steel by providing cathodic protection and galvanizing properties.  Simply put, the zinc primer provides a secondary layer of protection.  This is an extra measure to help prevent any corrosion that the typical powder coating (without a zinc primer) may not provide during ordinary conditions over time.  However, because zinc primer is a spray-on coating, it can be scratched or nicked just like paint.
The process of hot-dip galvanizing results in a metallurgical bond between zinc and steel.  It is the process of coating steel with zinc by immersing the steel in a bath of molten zinc.  The result of this process protects the steel from corrosion. Galvanized steel is widely used in applications where corrosion resistance is needed without the cost of stainless steel, and is considered superior in terms of cost and life-cycle.  It is a more robust measure compared to the zinc primer.  The galvanized coating could potentially be deeply scratched or nicked to expose a base layer of steel but this is much less likely to happen.
We recommend regularly inspecting your goals for nicks and scratches in the paint and sanding and repainting the area when necessary. This will help prevent rust and prolong the life of your goals. Rust is not a condition of the warranty. The best rust protection is early detection.