Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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48 NOVEMBER 2018 W W W.MATERIALSPERFORMANCE.COM CM CORROSION MANAGEMENT T This article presents findings of a three-year corrosion monitoring study of the world's largest reinforced con- crete tidal power plant in South Korea using 19 sets of commercially avail- able corrosion sensors. The collected data indicated that the sea side of the plant is a more aggressive corroding environment for reinforcing steel than the lake side. Periodic collection of macro-cell corrosion current and con- crete resistance data along with sen- sor temperature is recommended to monitor the corrosion state of marine concrete structures. Diffusion of a critical concentration of chloride ions at embedded sensors should be de- tected by noticeable differences be- tween collected data sets. T h e Ko re a Wa t e r R e s o u r c e s C o r p . (K-water) built Si-Hwa tidal power plant in the middle of an 11.2-km (7.0-mi) long manmade seawall that divides Si-Hwa Lake and the Yellow Sea in South Korea. The plant began operating in 2011 after seven years of construction with a capacity of 254 MW/h and an annual power generation of 552.7 GWh, which is the largest of its kind in the world. Figure 1 shows an aerial view of the power plant. More information about the plant can be found elsewhere. 1 Due to the harsh marine exposure con- ditions combined with a 30-ft (9-m) tidal variation, K-water was concerned about the long-term structural integrity of the structure. It developed two types of high- performance concrete mixes containing blast furnace slag and specified a clear cover of 135 mm (5.3 in) to ensure a life of 100 years. Impressed current cathodic pre- vention systems for the turbines and the surrounding reinforced concrete structure were also installed. In addition, the com- pany developed a corrosion monitoring program during the design stage to deter- mine in advance when timely maintenance actions are required. As a result, 19 sets of commercially available corrosion sensors were installed during construction and the monitoring data were collected at every quarter from November 2012 until October 2015. This article presents the adopted cor- rosion monitoring methodology and its major findings. Corrosion Monitoring System At each sensor location, three types of c o r r o s i o n m o n i t o r i n g s e n s o r s w e r e installed within a radius of 230 mm (9 in). 1 Figure 2 shows schematic drawings of the sensor installation. The first corrosion sen- sor is a multifunctional, multi-probe type that consists of four short carbon steel probes fixed at different heights on a plas- tic ring base containing a noble metal. The probes are intended to be macro-anodes and the metal ring a macro-cathode. This configuration monitors progressive corro- sion activities in terms of corrosion poten- Corrosion Monitoring of World's Largest Tidal Power Plant Seun G -Kyoun G l ee, SK Lee & Associates, Inc., Fairfax, Virginia, USA Bon G -Seo K Jan G , Jeon G - h wan a hn, and Ki-Cheol Ki M , Korea Water Resources Corp., Daejeon, Republic of Korea

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