1. Material and appearance

Common materials:

Steel bridge: low carbon steel, galvanised steel (anti-rust), stainless steel (high corrosion resistance).

Aluminium alloy bridge: light weight, oxidation resistance, suitable for corrosive environment.

Others: copper alloy (special occasions, such as electromagnetic shielding).

Surface treatment:

Hot-dip galvanising, electro-galvanising, spraying (to enhance corrosion resistance and aesthetics).

Colour: Usually original metal colour (silver grey), can be customised after spraying (e.g. RAL colour card).

2. Mechanical properties

Strength:

Steel bridge has high compressive/bending strength (high load carrying capacity), aluminium alloy bridge has lower strength but light weight.

Load rating: need to comply with the standard (e.g. CECS 31:2017), common light, medium and heavy three levels.

Rigidity: channel bridge has high rigidity, ladder bridge has good ventilation but slightly lower rigidity.

Ductility: aluminium alloy bridge is better than steel, easier to process and form.

3. Thermal performance

Temperature resistance range:

Galvanised steel: -30°C ~ 300°C (long-term use).

Aluminium alloy: -50°C ~ 200°C (better performance in low temperature).

Plastic spray coating may limit high temperature suitability (generally ≤ 120°C).

Coefficient of thermal expansion:

Steel: Approx. 12 × 10-⁶ /K.

Aluminium alloy: approx. 23 × 10-⁶ /K (subject to expansion joint design).

4. Electrical properties

Conductivity: The metal bridge itself conducts electricity and needs to be grounded to prevent static electricity/lightning strike.

Electromagnetic shielding: steel bridge shielding effect is better than aluminium alloy, suitable for sensitive signal lines.

5. Corrosion resistance

Galvanised steel: zinc layer protects the substrate, suitable for general industrial environment.

Stainless steel (e.g. 304/316): acid and alkali resistance, salt spray, suitable for chemical and coastal areas.

Aluminium alloy: natural oxide film to prevent rust, but avoid strong alkali environment.

6. Weight

Steel bridge: heavier (density about 7.85 g/cm³), need to strengthen the support structure.

Aluminium alloy bridge: density about 2.7 g/cm³, weight only 1/3 of steel, suitable for high altitude or large span installation.

7. Structure form

Channel bridge: fully closed, dustproof, anti-interference, strong physical protection.

Ladder type bridge: open, good heat dissipation, easy for cable maintenance.

Tray type bridge: perforated at the bottom, taking into account the protection and ventilation.

8. Installation and maintenance

Connection method: bolt fixing, snap type (common for aluminium alloy bridge).

Seismic resistance: metal bridges need to pass the seismic design (such as adding anti-seismic bracket).

Lifespan: galvanised steel about 15-20 years, stainless steel/aluminium alloy up to 30 years or more.

Application Scenario Selection

Industrial plant: Heavy duty steel bridge.

Data centre: galvanised steel or aluminium alloy (shielding required).

Outdoor/humid environment: stainless steel or hot-dip galvanised bridge.

Clean room: sprayed aluminium alloy bridge (dustproof and beautiful).