PolyU develops real-time system for monitoring atmospheric corrosion on buildings in Hong Kong

Located in a subtropical region facing the South China Sea, during summer Hong Kong experiences high salinity in the warm sea air which corrodes the metal structures of buildings. To address this challenge posed by the humid environment, researchers from the Department of Civil and Environmental Engineering of The Hong Kong Polytechnic University (PolyU) have developed a real-time monitoring system to evaluate the impact of atmospheric corrosion on steel structures and components in buildings. This system has been deployed to monitor the structural corrosion of a newly-built research complex and a housing project. Based on the data collected, targeted protective measures have been proposed to help achieve sustainable building development.

Prof. Kwok-fai CHUNG, Professor of the PolyU Department of Civil and Environmental Engineering and Director of the Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch), along with his team, have been conducting atmospheric exposure tests at seven sites across Hong Kong since 2010. The results indicate that the corrosion rate of carbon steel typically ranges from 30 to 40 µm per year, whereas zinc and galvanised steel used for outdoor construction exhibit corrosion rates of approximately 3 µm per year. The commercial complexes located around Victoria Harbour are particularly vulnerable to year-round atmospheric corrosion, which compromises the durability of buildings and structures and can even pose safety risks.

To assist engineers and professionals in formulating more effective building maintenance strategies, Mr Ka Fai YUEN, PhD student from the PolyU Department of Civil and Environmental Engineering has developed a real-time corrosion monitoring system under the supervision of Prof. Kwok-fai Chung. Between 2020 and 2024, Mr Yuen collected approximately 40,000 real-time corrosion and environmental datasets per year from seven different buildings across Hong Kong. Utilising advanced electrochemistry technology integrated with remote sensing and AI-supported data analytics, the system can evaluate the effects of corrosive chemicals such as chlorine ion, sulphur dioxide and nitrogen oxide, as well as collect climatic data including temperature and humidity on steel members and structures. The system significantly improves upon the accuracy of conventional corrosion prediction models and enables long-term corrosion monitoring and assessment for buildings in Hong Kong.

Led by Prof. Chung, the Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch), has been invited by the Hong Kong Construction Industry Council and Hong Kong Council of Social Service (HKCSS) respectively to apply the system for corrosion monitoring in the InnoCell at Hong Kong Science Park and technical monitoring of Nam Cheong 220, a social housing project coordinated by HKCSS, to validate the effectiveness of the system and provide critical data for developing appropriate building maintenance strategies.

InnoCell is the first building in Hong Kong to adopt a modular integrated construction (MiC) approach. During the two-year monitoring period, the team assessed the corrosion rates of steel structures and their components in both indoor and outdoor environments. The findings revealed that the corrosion rate of steel in indoor environments is only one-third of that in outdoor environments, demonstrating that atmospheric conditions play a significant role in corrosion assessment. Therefore, different levels of corrosion protection should be implemented for indoor and outdoor steel components, with priority given to protecting external steel components to enhance their durability and lifespan.

Nam Cheong 220 is Hong Kong’s first structural steel social housing project to adopt modular integrated construction (MiC) technology. The team’s monitoring results showed that the corrosion condition of this type of building was similar to typical buildings in Hong Kong, with no significant corrosion damage observed. These findings align with the inspection results of the steel components during the building’s deconstruction and relocation process, demonstrating that MiC technology is suitable for repeated use and offers an ideal solution for the reuse and relocation of transitional housing.

Prof. Kwok-fai Chung said, “Hong Kong’s unique tropical climate and marine environment make atmospheric corrosion a critical issue for buildings. The results of this study will help develop more effective building maintenance strategies, prolonging the lifespan of buildings and structures with reduced manpower and lower cost, thereby contributing to the sustainable development of society.”

Mr Ka Fai Yuen said, “PolyU has provided me with invaluable opportunities to apply my knowledge and research findings in practical ways to address societal challenges. These experiences are essential for my future research and personal development.”

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