Comparison
GP vs HDGI: Pre-Galvanised vs Hot-Dip Galvanised Solar Structures
GP and HDGI both protect steel with zinc, but they differ in coating mass, edge protection and typical service life — which decides where each is the right choice.
| Specification | Pre-Galvanised (GP) | Hot-Dip Galvanised (HDGI) |
|---|---|---|
| Process | Zinc applied to coil before forming (in-line) | Whole fabricated member dipped in molten zinc after cutting/welding |
| Coating mass (typical) | Lower (e.g. Z120–Z275) | Higher (thicker zinc layer, ~70–85 microns typical) |
| Cut edges & welds | Exposed at cuts/holes | Fully covered, including edges and welds |
| Best suited to | Rooftop, sheltered, high-volume | Ground-mount, coastal, high-humidity, long-life |
| Relative cost | Lower | Higher |
| Indicative service life | Good in mild environments | Longest, up to ~25 years by environment |
Frequently asked questions
- When should I choose HDGI over GP?
- Choose HDGI for ground-mount, coastal or high-humidity sites and wherever maximum, edge-to-edge corrosion protection and the longest service life are required.
- Is GP acceptable for rooftop solar?
- Yes — GP is commonly used for sheltered rooftop mounting where speed and cost matter and the environment is mild.
Not sure which to choose?
We will recommend based on your site and load case.