Solar mounting structures are outdoor installations exposed to years of weather, and the fasteners holding them together need to outlast the panels themselves. The two standard choices — Hot-Dip Galvanised (HDG) and Stainless Steel (SS 304/316) — perform very differently depending on your site's environment.
Hot-Dip Galvanised (HDG) Fasteners
HDG fasteners are coated with a thick zinc layer through a hot-dip galvanising process, which acts as a sacrificial barrier — the zinc corrodes before the underlying steel does. This makes HDG a durable, cost-effective choice for inland, semi-urban, and standard rooftop or ground-mount solar installations.
Stainless Steel (SS 304 / SS 316) Fasteners
Stainless steel fasteners resist corrosion through a passive chromium oxide layer rather than a sacrificial coating. SS 304 suits general-purpose inland use; SS 316 adds molybdenum for superior resistance to chlorides, making it the standard choice for coastal, marine, and high-salinity environments.
HDG vs Stainless Steel: Which to Choose
| Factor | HDG | Stainless Steel (304/316) |
|---|---|---|
| Best Environment | Inland, semi-urban, standard rooftop | Coastal, marine, high-humidity, chemical exposure |
| Corrosion Resistance | Good — sacrificial zinc barrier | Excellent — passive oxide layer (316 adds chloride resistance) |
| Cost | More cost-effective at volume | Higher unit cost, longer service life in harsh conditions |
| Typical Sizes | M8–M14 | M8–M14 |
| Supply Format | Assembled sets or individual components | Assembled sets or individual components |
Frequently Asked Questions
Is stainless steel always better than HDG for solar mounting?
Not necessarily — for standard inland installations, HDG offers good corrosion protection at a significantly lower cost. Stainless steel becomes the better choice specifically in coastal or high-corrosion environments where the added cost is justified by longer service life.
Can I mix HDG and stainless steel fasteners in one installation?
Avoid direct contact between dissimilar metals where possible, as it can accelerate galvanic corrosion. Keep the fastener range consistent across a single mounting structure.
Excel Construction Materials stocks both HDG and Stainless Steel (SS 304/316) fastener sets for solar mounting as part of our Solar Structure Items range. Get a quote or WhatsApp us your project's environment and size requirement.