Corrosion Behavior Evaluation of Coated Steel Using Fiber Bragg Grating Sensors

Abstract

Coatings, either soft or hard, are commonly used to protect steel against corrosion for longer service life. With coatings, assessing the corrosion behavior and status of the substrate is challenging without destructive analysis. In this paper, fiber Bragg (FBG) grating sensors were proposed to nondestructively evaluate the corrosion behavior of steel coated with two popular coatings, including the polymeric and wire arc sprayed Al-Zn coating. Laboratory accelerated corrosion tests demonstrated that the embedded FBG sensors inside both the soft and hard coatings can effectively quantify the corrosion rate, monitor the corrosion progress, and detect the coating damages and crack propagation of coated steel in real time. The laboratory electrochemical corrosion test on the wire arc sprayed Al-Zn coating validated the proposed embedded FBG sensor method with a good agreement in comparison. The proposed sensing platform provides an alternative nondestructive real-time corrosion assessment approach for coated steel in the field.

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“…These changes could be induced by deformation, induced by corrosion, or could be down to a coating failure type that involves deformation of the coating; for example, osmotic blistering. Therefore these sensors could potentially be used to measure and determine corrosion related strains as well as coating issues, such as delamination [ 65 ]. As changes in strain occur in the coating, due to corrosion or failure, the Braggs grating wavelength changes and the corrosion rate can be calculated [ 65 ].…”

“…Therefore these sensors could potentially be used to measure and determine corrosion related strains as well as coating issues, such as delamination [ 65 ]. As changes in strain occur in the coating, due to corrosion or failure, the Braggs grating wavelength changes and the corrosion rate can be calculated [ 65 ]. The effect of strain on a Braggs grating is shown in Figure 15 .…”

“…Many companies have developed this technology and there has been some implementation success in the civil industry using integrated FBGs to monitor static building structures [ 63 ]. There has also been some success in embedding these sensors into coatings (polymeric and metallic) on top of steel [ 65 , 66 ]. These studies showed that results from FBGs could give readings that correlated with electrochemical tests carried out simultaneously.…”

“…These studies showed that results from FBGs could give readings that correlated with electrochemical tests carried out simultaneously. Furthermore, FBGs have been deployed into concrete rebar structures to measure corrosion [ 65 ] and it was reported that the FBG method was within 1% of the calculated electrochemical corrosion rate [ 65 ] (for a metallic coating). An example of a Braggs grating detecting the formation of a blister in a coated product is shown in Figure 16 .…”

“…It has also been shown that the Bragg fibre is capable of surviving thermal metal coating deposition so it is expected to be able to survive application of a paint system [ 66 ]. Finally as they are a well-developed sensor technique they are available commercially at high quality and it has been suggested that measurement of crack initiation and corrosion rate under polymeric coating is possible [ 65 ].…”