How does steel fabrication deal with high humidity environments?

2025-03-26 15:54:02

In harsh environments with humidity >85% such as coastal and tropical rainforests, Steel Structure processing faces challenges such as accelerated corrosion, welding defects and coating failures. Through material science innovation, process innovation and environmental control technology integration, modern steel structure processing enterprises have formed a whole-process anti-humidity technology system from raw material treatment to finished product protection.

I. Material pretreatment technology upgrade

Nanoscale passivation treatment

The steel structure processing workshop introduces plasma activation equipment to generate a 5-10nm thick chromium oxide passivation layer on the surface of the steel plate, which reduces the free energy of the metal surface to 28mJ/m² (60% lower than the traditional process). The practice of a shipyard proved that this technology extends the initial corrosion time of steel in high humidity environment from 72 hours to 600 hours. Together with the vacuum-packed storage system, the raw material inventory cycle can be extended to 12 months without rusting.

Environmentally sensitive primer pre-coating

A water-based epoxy zinc-rich pre-coat primer (82% zinc content) is used to form a 15μm dense layer by electrostatic spraying. The coating activates the corrosion inhibition component when the humidity is >90%, and the application in the processing of steel box girders of a cross-sea bridge shows that the corrosion rate of the welded heat-affected zone is controlled to be below 0.02mm/year.

Second, the dynamic environmental control system

Workshop microclimate control

Steel structure processing workshop configuration intelligent dehumidification cluster, through the rotor dehumidifier and solution dehumidifier linkage, the relative humidity will be controlled stably at 45 ± 5%. The measured data of a Southeast Asian factory shows that the system can still maintain the humidity of welding area at 48% when the external humidity is 95%, and the power consumption is reduced by 35% compared with the traditional program.

Localized environmental isolation technology

Key processing areas (such as welding stations) to set up a double-layer air curtain isolation device, the use of 0.5m / s laminar wind speed to form a humidity gradient difference. The application of a nuclear power equipment manufacturing project has proved that this technology can control the dew point temperature of the welding area at -15℃, avoiding the risk of hydrogen cracking.

Third, anti-humidity welding process system

Low hydrogen welding material innovation

Developing JQ-SJ101G flux containing rare earth elements, the diffusion hydrogen content of the molten metal is reduced to below 3mL/100g (ISO 3690 standard). Together with the intelligent oven management system, the exposure time of welding rod from 350℃ holding tank to welding is shortened to<30 seconds, and the qualified rate of welds in the processing of conduit racks of an offshore platform is increased to 99.8%.

Pulse gas shielded technology

Adopting double-pulse MAG welding process, the shielding gas coverage is increased to 98% through 0.5Hz low-frequency pulse to form the molten pool oscillation. Comparative tests conducted in a humidity environment of 85% show that the weld porosity is reduced from 1.2% to 0.3%, and the mechanical properties fully meet the AWS D1.1 standard.

IV. Intelligent Moisture-Resistant Coating System

Moisture-responsive top coat

Applying polyurethane topcoat containing modified graphene, the nanopores in the coating automatically close to form a dense barrier when the ambient humidity is >75%. A tropical oil refinery steel processing measurements show that the coating in the humidity of 95% conditions still maintain > 1 × 10¹²Ω-cm surface resistance, effectively preventing electrochemical corrosion.

Self-healing closed layer technology

Microencapsulated corrosion inhibitor (particle size 50-80μm) is implanted in the coating system, which automatically releases the repairing substance when microcracks occur in the coating. After 2000 hours of wet heat cycle test (40℃/95%RH), the self-repair rate of coating scratches reaches 92%, and the anticorrosion life is extended to more than 15 years.