Guide 17 · Fastener Reference Guide
Zinc Coatings
Three ways to put zinc on steel — and why the difference matters.
Text version — searchable and screen-reader friendly
AS/NZS 4680 · AS/NZS 1214 (fasteners) 5–25 µm (8–12 µm typical on fasteners) Repair coating to AS/NZS 4680 Appendix AS 1789 · ISO 4042
| Comparison | Hot dip galvanising | Zinc electroplating | Cold galvanising |
|---|---|---|---|
| Corrosion life outdoors | Longest — decades in inland exposure | Short — indoor or sheltered use only | Moderate — as good as the paint system |
| Appearance | Matte grey, often spangled; rough | Bright and smooth; clear, blue, yellow or black | Flat grey; visible brush or spray texture |
| Efef ct on threads | Thick — nuts must be oversize tapped | Negligible | Will clog threads; keep off them |
| Damage tolerance | Alloy layers are hard and abrasion resistant | Thin and easily scratched through | Soft; re-coat when damaged |
| High-strength fasteners | Not used above property class 8.8 | Bake after plating to relieve hydrogen | No heat or acid — no embrittlement risk |
| Best for | Structural steel, outdoor and marine work | Indoor fixings, appliances, general hardware | Site repairs, welds and cut ends on HDG steel |