Boat owners and fishing enthusiasts love galvanised trailer gear—for good reason. Compared to bare or black steel, hot dip galvanised steel is known to take longer to rust in highly corrosive environments (like saltwater). However, some Australians are concerned that traditional galvanising weakens steel—particularly in the context of trailer suspension. This is what we’re diving into today.
Outline of Topics:
- What is Galvanised Steel?
- How is Steel Galvanised?
- Does Galvanising Make Steel Weaker?
This is part of the Couplemate™ Technical Hub unit on Trailer Hardware.
What is Galvanised Steel?
Galvanised steel is just regular steel with a zinc (Zn) coating that is resistant to corrosion. The best way to think about galvanising is that it prolongs steel usefulness in corrosive environments.
AS 2312.2 covers the extent of what hot dip galvanising coating should provide in terms of corrosion resistance. However, what’s important for most people to understand is:
- Galvanising doesn’t stop rust forever—it delays it.
- The length of time rust is delayed for heavily depends on the steel itself.
It’s useful to know that there are other types of protective zinc coatings (such as Dacromet or ElectroGal). Moreover, depending on component application, these alternative coatings can be better than hot dip Gal. You can read more about that here.
How is Steel Galvanised?
Put simply, steel gets galvanised by being dipped into a molten zinc mixture—typically at 450°C (840°F).
While submersed, the zinc penetrates and chemically bonds with the steel to form layers of metallic zinc and zinc-iron alloy. It’s the depth of these layers that provide corrosion resistance.
As we’ve outlined above, the effectiveness heavily depends on the steel itself—not all steel will react the same way. Manufacturers have a responsibility to ensure the steel have mechanical properties that are: a) suitable for the intended application, and b) compatible with the galvanising process.
The chemistry of the steel affects the formation of the galvanized coating and can affect the thickness of the galvanized coating, appearance of the article, relative smoothness of the galvanized coating, and the galvanized coating’s ability to withstand mechanical damage.
– Galvanizing Association of Australia (Advisory Note 35)
Does Galvanising Affect Steel Properties (e.g. Strength)?
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