What 550 g/m2 Hot-Dip Galvanizing Actually Means

The Number

The specification used on Hongda beam products is a zinc coating of 550 g/m2, which corresponds to a thickness of around 80 microns. The gram figure is a mass of zinc per square metre of surface; the micron figure is the same coating expressed as a depth.

Why Guardrail Needs It

Barrier sits exposed at the roadside for its whole service life with no opportunity for recoating. The zinc layer is the only thing between the steel and the weather, which is why the coating weight is written into tender documents rather than left to the supplier.

Hot-Dip, Not Spray

Hot-dip galvanizing immerses the formed section in molten zinc, so the coating covers the whole section including the inside of formed corrugations. Posts can also be supplied spray-coated, but hot-dip is the finish specified on the beam products.

Passivation

After galvanizing, the passivation ratio is controlled precisely so the galvanized surface resists corrosion. This step is applied across posts, terminals, curved sections and buffers as well as beam.

Where Coatings Fail

Cut and drilled points made on site leave bare steel outside the galvanized layer. Inspect these before handover and treat any exposed steel, or the corrosion starts at the fixings rather than across the face of the beam.

The Environmental Side

Hot-dip galvanizing produces harmful wastewater. Hongda runs its own wastewater treatment station and environmental treatment equipment on site, alongside a dedicated wastewater treatment workshop.