China Sets World Record with 537-Day Deep-Sea Material Corrosion Test

China has achieved a world-first deep-sea milestone, completing a 537-day material corrosion test at approximately 11,000 meters in the Mariana Trench — the longest continuous deep-sea in-situ corrosion experiment ever conducted globally. The breakthrough, announced on May 23, 2026, was carried out by the 725th Research Institute of China State Shipbuilding Corporation (CSSC) and reported by CCTV News.

Context: The Hidden Enemy of the Deep

Corrosion is the primary threat to deep-sea equipment. At depths of 11,000 meters, hydrostatic pressure exceeds 100 megapascals — more than 1,000 times standard atmospheric pressure — combined with low temperatures, high salinity, and aggressive chemical species. These extreme conditions rapidly degrade materials, making long-duration testing essential for designing reliable underwater infrastructure.

In-situ testing — conducting experiments directly in the deep-sea environment without retrieving samples — preserves authentic physical and chemical conditions, yielding the most reliable data. The 537-day test represents a nearly threefold extension over China’s previous record of 184 days, which was completed on May 3, 2025, and tested 30 types of protective coatings, 4 types of sacrificial anodes, and 22 types of structural metal materials.

Key Developments

According to IT Home, the CSSC 725th Research Institute overcame significant technical challenges to achieve the record, including ultra-high-pressure dynamic sealing, deep-sea intelligent in-situ sensing, and long-term stable energy supply. The test evaluated a wide range of engineering materials and protective coatings for corrosion resistance in the extreme deep-sea environment.

Liao Zhiqian, Deputy Director of CSSC 725th Research Institute and Executive Deputy Director of the National Key Laboratory for Marine Corrosion and Protection, explained the scope of the experiment:

“The deep-sea in-situ corrosion test framework primarily carries test samples and in-situ monitoring devices. We have ferrous and non-ferrous metals among metal materials, functional materials including coatings, sacrificial anode materials, and non-metallic buoyancy materials — a very wide variety.”

Liao noted that the team developed five or six new types of coatings during this test, laying the foundation for future coating systems across various ocean depths.

CCTV reporter Li Ning, who examined the retrieved materials, observed: “The test materials that spent 537 days in the deep sea show significant differences between different coatings — some are very well preserved, while others have rusted. This has accumulated very valuable data for our subsequent research.”

Analysis: Strategic Implications

The data from this test fills a critical global gap: real-world, long-duration corrosion performance data from 11,000-meter depth was previously unavailable. As China Youth Net reported, Liao Zhiqian emphasized that the retrieved data can optimize corrosion allowance design for deep-sea equipment, “ending the dilemma of either wasteful over-thickness or risky under-thickness.”

The findings have direct applications for:

• Deep-sea resource development: More reliable equipment design for underwater oil and gas production and deep-sea mining operations
• Scientific infrastructure: Longer-duration underwater observation stations and research platforms
• Defense applications: Corrosion-resistant materials for submarines and naval installations operating at extreme depths

Sun Mingxian, Deputy Chief Engineer and Researcher at CSSC 725th Research Institute, highlighted that the institute’s independently developed 10,000-meter-class deep-sea simulation test device — a high-pressure autoclave that replicates deep-sea conditions — is already being used by multiple Chinese research institutions including the Ningbo Institute of Materials Technology, Northeastern University, University of Science and Technology Beijing, and Tianjin University for materials screening and development.

Broader Context: China’s Deep-Sea Ambitions

This achievement is the latest in a series of rapid advances in China’s deep-sea exploration capabilities. The country’s manned submersible Fendouzhe (Striver) reached 10,000 meters in the Challenger Deep in November 2020, making China the second nation after the United States to achieve manned dives to that depth. As of early 2025, Fendouzhe had completed 329 dives, 25 of which exceeded 10,000 meters — ranking first globally in number of deep dives and personnel involved.

China’s deep-sea push parallels its ambitions in space exploration, with both programs demonstrating the country’s growing technological capabilities and strategic focus on frontier science.

What’s Next

The data from the 537-day test will inform the next generation of deep-sea equipment design, including longer-duration underwater observation stations and resource extraction platforms. The deep-sea simulation device at CSSC 725th Research Institute will continue to support materials research, enabling faster screening and development of new protective materials without requiring repeated deep-sea deployments.

As China’s deep-sea exploration capabilities continue to expand — with routine manned operations at 10,000-meter depths now established — the country is positioning itself at the forefront of a global race for deep-sea resources and technology.