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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Information on corrosion control and prevention are continually exposed to wet and dry conditions. An initial durability assessment of the structure should be conducted to establish the corrosion risks that can impact a [\Z]K\]ZM I[ _MTT I[ QLMV\QNa \PM [XMKQÅK areas on a structure where corrosion risks are high, says Cheaitani. "During this stage, we determine what type of corro- sion prevention measures are needed— be it cathodic protection for the steel or use of stainless steel reinforcement in the concrete—and we also determine which aspects of a corrosion monitoring system should be incorporated in the structure based on the corrosion assessment risk," he explains. Cheaitani notes that it is important to understand the type of infor- mation needed to monitor corrosion and the type of sensor that will provide the information, and to create an optimum balance of the sensor quantity and type, as well as the number of readings taken, [W \PI\ ZMTM^IV\ LI\I KIV JM MNÅKQMV\Ta collected and interpreted. He emphasizes that effective monitoring is a matter of knowledge, not quantity, and cautions that thousands of readings from too many sensors can generate so much information that managing the data and drawing meaningful conclusions is not feasible. Basically, corrosion sensors are in- stalled in locations where the durability assessment indicates there is a high risk for corrosion, which can differ depending on the individual structure and its environ- ment. If corrosion prevention measures are incorporated into the structure during the construction phase, then applicable sensors are selected to monitor the perfor- mance of these measures as well as detect any corrosion activity. Corrosion preven- tion measures for a concrete bridge can include cathodic protection (CP) of the reinforcing steel, galvanized or stainless steel reinforcement, corrosion inhibitors NACE International, Vol. 51, No. 11 The Web-based user interface displays data collected from the Crusell Bridge's intelligent SHM system in real time. Image courtesy of Savcor Group, Ltd. added into the concrete, and protective coatings applied to the concrete's surface. Corrosion sensors using various elec- trochemical techniques, such as linear polarization resistance (LPR) or the gal- vanostatic pulse method, are normally utilized to measure resistivity of the con- crete and the corrosion rates of embed- ded reinforcing steel in a concrete bridge exposed to water and chlorides. Informa- tion collected from the sensors is used to make an assessment on the level of chlo- ride ingress into the concrete and the corrosion status of the reinforcing steel, and support decisions regarding the need to incorporate additional corrosion con- trol measures. Since corrosion monitoring is typically just one component of a comprehensive SHM program, a structure can contain a multitude of sensors to measure a variety of other factors that affect its overall health. Cheaitani indicates it is common for one structure to have several indi- vidual monitoring systems as part of an overall SHM program, and each use their own unique hardware and software sys- tems. This can create a challenge when trying to combine all the collected data for assessing a structure's health. An intel- ligent structure concept recently devel- oped by Savcor for marine structures Continued on page 16 November 2012 MATERIALS PERFORMANCE 15