The combination of Hong Kong’s humid subtropical climate and its location near the South China Sea accelerates metal corrosion, which poses a threat to the durability and safety of buildings. To tackle this problem, researchers at PolyU’s Department of Civil and Environmental Engineering (CEE) have developed a real-time monitoring system that tracks atmospheric corrosion in steel components and structures, to improve maintenance strategies and protect the structural integrity of buildings.

Understanding corrosion patterns

Professor Chung Kwok-fai, Professor of the CEE and Director of the Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch), and his team have conducted air exposure studies at seven Hong Kong locations since 2010. Their results show that carbon steel corrodes at a rate of 30 to 40 micrometres each year, whereas the zinc and galvanised steel used outdoors corrode more slowly at 3 micrometres per year. Buildings around Victoria Harbour are more vulnerable to year-round air deterioration, making effective upkeep essential.

Guided by Professor Chung, CEE PhD student Mr Yuen Ka-fai spearheaded the creation of a real-time corrosion monitoring system. Between 2020 and 2024, he collected about 40,000 datasets annually from seven buildings across Hong Kong. The system uses advanced electrochemistry, remote sensing, and AI-supported data analytics to evaluate the effects of corrosive chemicals such as chlorine, sulphur dioxide, and nitrogen oxide, as well as climate factors like temperature and humidity. It provides more accurate results than traditional models, allowing for effective long-term corrosion monitoring and evaluation.

Validation in key projects

The Hong Kong Construction Industry Council and Hong Kong Council of Social Service invited the research centre to implement the new system at InnoCell in the Hong Kong Science Park and the Nam Cheong 220 social housing project. 

InnoCell was the first building in Hong Kong to use modular integrated construction (MiC). Real-time results from the system revealed that its indoor steel corrosion rates are one-third those of outdoor rates, highlighting the importance of tailored protection strategies. Nam Cheong 220, Hong Kong’s first structural steel social housing project to use MiC technology, demonstrated similar corrosion conditions to typical buildings. The findings validate the suitability of MiC for reuse and relocation and emphasise the need for effective maintenance strategies for both indoor and outdoor steel components.

Professor Chung Kwok-fai noted: “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 costs, thereby contributing to the sustainable development of society.”
 

The system enables real-time monitoring of atmospheric corrosion, helping engineers and professionals assess its impact on building structures and develop effective maintenance strategies.