Monitoring of Atmospheric Corrosion in a Mass Rapid Transit (MRT) Tunnel

A study has been conducted to measure uniform corrosion due to the tunnel environment in the mass rapid transit North East Line (NEL) in Singapore. The study was aimed at investigating the corrosivity of the atmospheric environment in the NEL to enhance understanding on the maintenance of metallic components in a tunnel. The corrosivity levels at the buffer areas of ten stations along the NEL were monitored over a period of two years. The measurements were based on physical metal coupons as well as real-time monitoring systems using electrical resistance sensors. The corrosivity levels measured at different exposure sites showed differences, but were generally low and could be generally categorised as G1 according to ISA standard 71.04:2013. The reason for the low corrosivity levels was likely to be due to the relatively mild temperature and low (<60%) average relative humidity.