Corrosion Protection for Bridge Constructions with DST Dehumidifiers

Corrosion damage to steel constructions is a major challenge that can lead to high maintenance costs and shorter lifespans for bridges around the world. By maintaining a relative humidity (RH) below 50%, steel components can be effectively protected against rust.

Traditionally, steel has been protected with corrosion-resistant paint—an approach that is often expensive, requires regular upkeep, and adds extra weight to the structure. An increasingly popular alternative is to use avfuktare that circulate dry air in enclosed spaces, reducing the need for extensive painting. This is especially beneficial for hard-to-access areas, such as steel cables or anchor points in suspension bridges, where dehumidification can replace or complement traditional corrosion-protection methods.

The Challenge

• High Cost and Complexity
  Corrosion-resistant paints are expensive, demanding frequent inspections and repainting.
• Added Weight and Accessibility
  Paint layers on large surfaces can increase a bridge’s weight significantly, and certain sections are very difficult to reach for maintenance.
• Risk of Corrosion
  When humidity rises above 50% RH, the likelihood of rust forming increases dramatically, potentially shortening the entire bridge’s service life.

The Solution

• Dry Air with DST Dehumidifiers
  Circulating dry air within enclosed areas around steel beams and cables dramatically reduces rust formation.
• Minimal Maintenance
  DST dehumidifiers require little upkeep, which lowers the need for repeated painting.
• Versatile Applications
  Even complex structures—such as cable anchors and anchorage rooms—can be protected effectively using the same technology.

References

Seibu Giken DST AB dehumidifiers are, among others,
used on the following bridges:

South Africa: Nelson Mandela-bridge
France: Millau Bridge
Switzerland: Lorraine Bridge
Sweden: Liljeholm Bridge, Sickla Bridge,
Fotö/Hönö Bridge, Vallsundsbron -Östersund
Norway: Triangle link, Flå Bridge, Mjosund bridge,
Langnes Bridge, Nord-Tröndelag, Grong Bridge, NordTröndelag

Liljeholm Bridge (Stockholm, Sweden)

Liljeholm Bridge, consisting of two bascule bridges built many years ago, houses intricate machinery responsible for raising and lowering the bridge deck. This machinery includes a 500-ton counterweight and large gearwheels—all of which must be safeguarded against rust.

• 2001 Installation
  A DST dehumidifier was installed in one of the bascule bridges, and the relative humidity was monitored closely. The results were positive: the moisture level dropped below the critical threshold. Encouraged by this success, another DST dehumidifier was installed in the second bascule bridge.
• Why Dehumidification?
  When relative humidity is kept below 50% RH, steel and iron remain highly resistant to rust. Dehumidification thus provides a long-term, cost-effective alternative to conventional rustproofing methods, which can be time-consuming, expensive, and labor-intensive.

Long-Term Investment
Dehumidification offers a more sustainable and eco-friendly approach to corrosion protection than repeated painting or chemical treatments.

Hong Kong–Zhuhai–Macau Bridge (China)

Spanning approximately 50 km, the Hong Kong–Zhuhai–Macau Bridge is the world’s longest sea-crossing bridge-tunnel system. Construction began on 15 December 2009 and concluded at the end of 2017.

• DST Protection
  Multiple DST dehumidifiers safeguard the bridge’s girders against corrosion. By maintaining low humidity levels, the service life of the structure is extended, and maintenance costs are reduced.
• Complex, Large-Scale Application
  Given the bridge’s vast length and the demanding marine environment, controlling moisture is critical to preserving steel components.

Yavuz Sultan Selim Bridge (Istanbul, Turkey)

Also known as the Third Bosphorus Bridge, the Yavuz Sultan Selim Bridge accommodates both rail and motor vehicle traffic over the Bosphorus Strait.

• World-Record Design
  • Widest suspension bridge globally
  • Longest span incorporating a rail system
  • Highest bridge towers of any suspension bridge in the world
• Revolutionary Dehumidification System
  The bridge’s girders and tension wires are protected by DST dehumidifiers. A recirculating dry-air system ensures that the wire enclosures remain at an optimal humidity level along the entire span, greatly reducing the potential for corrosion and thereby minimizing expensive maintenance interventions.