Construction methods · Steel erection

Corrosion protection of steel bridges: coatings and weathering steel

Steel bridges live or die by their corrosion protection. Multi-coat paint systems (zinc-rich primer, epoxy, polyurethane) are applied in the shop and touched up on site; metallising adds a sprayed zinc or aluminium layer; weathering steel forms its own patina where the climate lets it dry. The choice sets the maintenance cycle for decades.

How bridges get built · Steel erection · Corrosion protection of steel bridges: coatings and weathering steel

Also called: bridge painting, weathering steel, metallising, duplex coating

How it is done

Blast to Sa 2.5, apply the shop system in a controlled environment, protect splices with masked areas for site coating.
Weathering steel: detail to avoid water traps and salt, keep the patina from staining the substructure, do not use it in marine or de-icing salt spray zones without care.
Metallise where the environment is severe; seal and topcoat.

Where it fits

All steel bridges; weathering steel for rural dry climates; metallising for marine sites.

Where it does not

Weathering steel in the Gulf splash zone or under leaking joints; site-only coating of large areas.

Plant, pace and money

PlantBlasting and coating facilities, inspection instruments.

ProductivityShop-driven.

CostCoatings USD 40-80 per m2; 3-6 % of the steel cost; repainting every 20-30 years.

Risks and controls

What goes wrong

Coating failure at edges and splices, patina not forming in humid marine air, salt contamination under the coating.

Quality assurance

Blast profile and salt tests, dry film thickness, holiday tests, inspection at handover.

Examples

Korean coastal steel bridges are metallised; US rural steel bridges use weathering steel; the game's marine-grade durability option includes coatings.