How can corrosion resistance be improved in steel fabrication?

2025-03-27 15:05:27

Inside the steel box girder of the Hong Kong-Zhuhai-Macao Bridge, the nano-composite coating is resisting the attack of salt spray in the South China Sea; the gradient protection system of wind power pile foundation in Bohai Bay realizes 20 years of zero maintenance; the intelligent monitoring system of a railroad steel bridge on the Tibetan Plateau warns of the risk of corrosion in real time ... These innovative practices signify that the anti-corrosion technology of Steel Structure has shifted from passive protection to the intelligent era of active defense.

I. Material gene optimization innovation

Breakthrough in weathering steel alloy design

Through Cr-Cu-Ni-Mo multi-dimensional micro-alloying technology, a new type of weathering steel in the simulated marine atmospheric environment, the corrosion rate down to 0.015mm/a (traditional steel 0.08mm/a). The impedance value of the dense rust layer formed on its surface reaches 3×10⁴Ω-cm², and in the application of the steel bridge of Sichuan-Tibet Railway, the service life without painting breaks through 30 years.

Stainless steel composite steel plate revolution

Explosive rolling process prepared 304/Q345B composite plate, interface shear strength ≥ 210MPa, pitting corrosion resistance equivalent PREN value of 25.6. A coastal chemical plant pipeline corridor applications show that the cost of pure stainless steel program than the 45% reduction in Cl- corrosion resistance to enhance the ability of 3 times.

Second, surface modification technology upgrade

Cold spray metal ceramic coating

The use of high-pressure gas-accelerated Al-SiC powder (particle size 5-25μm), the steel surface to form a 0.8mm thick gradient coating. The salt spray test of guardrail of a cross-sea bridge in Qingdao after treatment reaches 5000 hours without red rust, and the abrasion and corrosion resistance is upgraded by 60% compared with the traditional hot-dip zinc.

Laser cladding functional layer

Using Co-based alloy powder as raw material, 0.5mm thick amorphous coating is applied on the surface of steel components, with porosity<0.3%. The electrochemical test of an offshore platform pile leg after treatment shows that the self-corrosion potential is positively shifted by 380mV, and the corrosion current density is reduced to 1.2×10-⁷A/cm².

Third, intelligent protective coating system

Graphene modified coating breakthrough

The epoxy coating with 0.5wt% graphene oxide added has an impedance modulus value of 10¹⁰Ω-cm² (10⁸Ω-cm² for traditional coatings) under simulated seawater immersion conditions. The application data of a ship steel structure in Zhuhai shows that the coating life is extended to 15 years and the maintenance cost is reduced by 70%.

Self-healing microcapsule technology

Urea-formaldehyde resin microcapsules (particle size 50-150μm) containing corrosion inhibitors are doped into the primer, automatically releasing the repair agent when the coating is broken. Laboratory simulation shows that a dense passivation film is formed in the scratched area within 48 hours, and the corrosion extension inhibition rate reaches 92%.

IV. Cathodic protection system evolution

Flexible anode distributed protection

Adopting mixed metal oxide (MMO) ribbon anode, together with intelligent constant potential meter, the uniformity of current distribution is increased to 95%. After application in a submarine pipeline project, the protection potential is stabilized at -0.85 to -1.05V (CSE), and the design life is up to 40 years.

Photoelectric coupling cathodic protection

Utilizing photovoltaic system to drive titanium-based MMO anode, continuous protection is realized in grid-free area. The measured data of steel structure of an island in South China Sea shows that the output current density of the system is stable at 10mA/m², and the maintenance cycle is 5 times longer than that of traditional sacrificial anode program.