Steel bar corrosion monitoring with long-period fiber grating sensors coated with nano iron/silica particles and polyurethane

Abstract

In this article, a recently proposed long-period fiber grating sensor coated with a thin layer of polyurethane and nano iron/silica particles is further developed and applied to monitor the corrosion process of deformed steel bars. Once calibrated, one coated long-period fiber grating sensor and one uncoated long-period fiber grating sensor for environmental compensation were attached to each of three steel bar samples that were tested in 3.5 wt% NaCl solution for 512 h. The resonant wavelength in long-period fiber grating spectra increased exponentially with immersion time due to corrosion of iron particles and thus reduction in coating thickness. The mass loss rate of steel bar #1 at the completion of corrosion tests (512 h of corrosion time) was correlated with that of sparse iron particles on long-period fiber grating sensor #1 after 130.5 h of immersion. The corrosion rates of long-period fiber grating sensors #2 and #3 were evaluated at 130.5 h and then used as a prediction of the corrosion rates of steel bars #2 and #3. The predicted corrosion rates by the long-period fiber grating sensors #2 and #3 were finally compared with those by potentiodynamic tests. The maximum mass loss prediction error by the long-period fiber grating sensors #2 and #3 is 26%. The coefficients of variation of three corrosion rate measurements are 0.049 by the long-period fiber grating sensors and 0.115 by the potentiodynamic tests, indicating more consistent and reliable measurements with the proposed technology.

A Recent Progress of Steel Bar Corrosion Diagnostic Techniques in RC Structures

“…Preliminary results by Coelho et al [96] show that Fe-coated LPFG has great potential to realize early-warning corrosion under a severely corroded conditions of coastal and offshore projects. A recent work by Huang et al [97] proposed an LPFG sensor coated with a thin layer of polyurethane and nano iron/silica particles to monitor the corrosion process of deformed steel bar, which shows the wide application in LPFG sensors using coating technology. The better durability and wide application in different RC structures, by using the LPFG sensors, needs to be further investigated.…”

Recent Progress in Fabrications and Applications of Heating-Induced Long Period Fiber Gratings

“…SLPFG sensor coated with a layer of polyurethane and iron/silica nanoparticles was developed to detect the corrosion process of deformed steel bars. However, the experimental results show that the corrosion sensitivity would decrease significantly with the extension of the service time [72]. Then, a sensor based on SLPFG written in SMF by a transverse focused CO 2 laser was demonstrated to monitor the corrosion process of carbon steel in a 3.5 wt% NaCl solution.…”

“…Various heating-induced LPFGs in conventional fiber [12,13,22,28,35,46,47], photonic crystal fiber (PCF) [14,15,16,29,48], and photonic bandgap fiber (PBF) [27,30,31] could then be successfully written. LPFG-based devices have recently attracted great attention and found versatile applications, such as in all-fiber orbital angular momentum (OAM) mode converters [11,13,14,17,49,50,51,52,53,54,55,56], and strain [48,57,58,59,60,61,62,63,64], pressure [16,29,30,65,66], torsion [16,19,38,46] and biochemical sensors [67,68,69,70,71,72,73].…”

Feasibility of Distributed Fiber Optic Sensor for Corrosion Monitoring of Steel Bars in Reinforced Concrete

“…Compared with the traditional electric corrosion sensors, fiber optic sensors carry numerous advantages such as high sensitivity, high precision, immunity to electromagnetic interference, etc. [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Fiber optic sensors can be categorized into point sensors and distributed sensors, in terms of their sensing length.…”

“…The sensor was placed near the steel bar and the wavelength shift of the FBG sensor due to corrosion of the twin bars was used to detect corrosion of the steel bar. Another paradigm was to coat responsive materials on the cladding of the LPFG [ 15 , 16 , 17 ]. Corrosion of the coating material caused shift of the resonant wavelength of the LPFG; the wavelength shift was used to evaluate corrosion-induced mass loss of steel bar [ 15 ].…”