Nondestructive corrosion detection using fiber optic photoacoustic ultrasound generator Xiaotian Zou a , Tyler Schmitt b , David Perloff c , Nan Wu b , Tzu-Yang Yu c , Xingwei Wang a,b,⇑ a Department of Biomedical Engineering and Biotechnology, University of Massachusetts, Lowell, MA 01854-2827, United States b Department of Electrical and Computer Engineering, University of Massachusetts, Lowell, MA 01854-2827, United States c Department of Civil and Environmental Engineering, University of Massachusetts, Lowell, MA 01854-2827, United States article info Article history: Received 1 October 2013 Received in revised form 27 October 2014 Accepted 5 November 2014 Available online 20 November 2014 Keywords: Corrosion detection Fiber optic Nondestructive Ultrasonics abstract Ultrasonic technologies have been widely used in nondestructive and noninvasive testing applications in industry. In this paper, a study on novel nondestructive corrosion detection mechanism with fiber optic photoacoustic ultrasound generator is conducted. The pre- sented corrosion detection mechanism features compact device size (ideal for embedded optical fiber applications), non-contact approach, stable performance, and high spatial res- olution. The principle of ultrasonic corrosion detection is introduced in the first section. The experimental procedure for simulation and acceleration of the sample corrosion by using the electrochemical process is also presented. Three steel reinforced rebar samples were prepared with different corrosion rates. The rebar samples were characterized to demonstrate that our mechanism is an effective tool in detecting the corrosion level of steel rebar samples. Published by Elsevier Ltd. 1. Introduction Rebar corrosion has proven to be the culprit in a signif- icant portion of reinforced concrete structural failures [1]. Rebars, which form a supportive lattice in concrete, are meant to handle the tensile demands on the structures in which they are implemented. Without their additional strength, concrete structures become vulnerable to these tensile loads, and the chances of catastrophic failure increase dramatically [2]. The corrosion process has a drastic economic toll, the Federal Highway Administration has reported that the cost of rebar corrosion related repairs average about $286 bil- lion per year [3]. In addition to monetary and infrastruc- ture concerns, the resulting detriment to human security must be addressed. Many structural failures, especially those of buildings and bridges, pose significant safety threats that cannot be ignored [4]. The corrosion process is typically attributed to the use of deicing salts in snow hazards and salt water corrosion near the shores. The surrounding concrete can protect rebars from corrosion with a high alkaline environment, but the inevitable formation of micro-cracks from strain provides multiple points of entry for corrosive materials. Chloride ions are notoriously aggressive corrosives of refined steel products, like rebars [4,5]. The best way to mitigate safety, economic, and infra- structure concerns is the early detection of this process and the swift repair of affected rebars. Tests and measure- ments must also be done nondestructively in order to be cost-effective. There are multiple nondestructive tech- niques that are used to estimate the extent of corrosion in practice today. Some methods, such as open circuit potential, surface potential, and concrete resistivity measurements, attempt to detect indications of the http://dx.doi.org/10.1016/j.measurement.2014.11.004 0263-2241/Published by Elsevier Ltd. ⇑ Corresponding author at: Department of Electrical and Computer Engineering, University of Massachusetts, Lowell, MA 01854-2827, United States. E-mail address: Xingwei_Wang@uml.edu (X. Wang). Measurement 62 (2015) 74–80 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement