The surface finish on gate hardware is not just cosmetic — it determines how long the product lasts in the field. Here is a direct comparison of the two most common industrial finishes.
Why Surface Finish Matters for Gate Hardware
Gate hardware — hinges, latches, rollers, brackets, and gear racks — is permanently exposed to rain, UV radiation, humidity, and in coastal areas, salt-laden air. A poor surface finish will rust within months, leading to product failures, warranty claims, and damage to your brand reputation. Choosing between hot-dip galvanizing (HDG) and powder coating is one of the most consequential decisions in the specification process.
Hot-Dip Galvanizing (HDG)
Hot-dip galvanizing is a metallurgical process in which clean steel is immersed in a bath of molten zinc at approximately 450°C. The zinc reacts with the steel surface to form a series of zinc-iron alloy layers, topped by a pure zinc outer layer. The result is a coating that is metallurgically bonded to the steel — not simply adhered to the surface.
Key Properties
- Coating thickness: Typically 45–85 microns on structural steel, governed by ISO 1461.
- Corrosion protection: In a moderate industrial environment, HDG typically provides 20–70 years of protection before first maintenance is required.
- Self-healing: Zinc is anodic to steel. If the coating is scratched or cut, the surrounding zinc sacrificially protects the exposed steel, preventing rust from spreading.
- Interior coverage: Molten zinc penetrates hollow sections, coating the interior surfaces of tubes and box sections — something powder coating cannot achieve.
Limitations
HDG produces a spangled silver-grey finish that cannot be colour-specified. The coating surface is also rougher than powder coat, which some architects and specifiers find aesthetically unacceptable for visible applications. Additionally, very thin steel sections (below 3 mm) can distort during the galvanizing process due to thermal stress.
Powder Coating
Powder coating is an electrostatic dry finishing process. Finely ground pigment and resin particles are electrostatically charged and sprayed onto a grounded steel substrate. The coated part is then cured in an oven at 180–200°C, causing the powder to flow and form a hard, smooth film.
Key Properties
- Coating thickness: Typically 60–80 microns in a single coat.
- Colour range: Virtually unlimited — any RAL or custom colour can be matched. Gloss, matte, satin, and textured finishes are all available.
- Surface quality: Smooth, uniform finish suitable for architectural and decorative applications.
- Chemical resistance: Good resistance to most solvents and mild chemicals.
Limitations
Powder coating is a surface-applied film. Unlike HDG, it does not bond metallurgically with the steel. If the coating is chipped or scratched — common during installation or in high-traffic environments — bare steel is exposed and rust will develop at the damage site. Without a zinc primer undercoat, rust can spread laterally under the coating (a phenomenon known as undercutting). Powder coating also does not protect interior surfaces of hollow sections.
HDG + Powder Coat: The Best of Both Worlds
For premium gate hardware, the industry best practice is to apply both finishes in sequence: hot-dip galvanize first, then powder coat over the galvanized surface. This "duplex system" provides the corrosion protection of zinc with the colour and aesthetic quality of powder coat. The two coatings also interact synergistically — the zinc layer acts as a barrier against undercutting if the powder coat is damaged.
The expected service life of a duplex system is typically 1.5–2.3× the sum of the individual coating lifespans, according to ISO 14713.
Which Finish Should You Specify?
| Application | Recommended Finish |
|---|
| Coastal or marine environment | HDG + powder coat (duplex) |
| Industrial or chemical environment | HDG |
| Residential, colour-matched fencing | Powder coat (with zinc primer) |
| Commercial security fencing | HDG or HDG + powder coat |
| Automated gate components (rollers, racks) | Zinc plating or HDG |
| Interior or covered applications | Powder coat |
HST offers HDG, powder coat, and duplex finishing options across its full range of gate hardware. All HDG products comply with ISO 1461. Contact us to discuss finish specifications for your next order.