Corrosion in pipelines and critical infrastructure is a pervasive issue that can lead to catastrophic failures and substantial economic losses. Therefore, predicting, locating and continuously monitoring corrosion is critical to maintaining functionality and structural integrity. Environmental factors like humidity can significantly influence corrosion rates, and traditional monitoring methods often rely on costly periodic visual inspections or localized sensors that lack continuous, real-time data, especially over extended distances and wide areas. These conventional techniques fail to detect early signs of deterioration or changes in environmental conditions, limiting the effectiveness of maintenance strategies. This underscores the need for advanced sensing technologies that provide real-time, comprehensive, distributed, high-resolution measurements to enhance safety and reliability.

The invention is distributed multi-parameter sensors that simultaneously monitor corrosion and humidity using either OFS or wireless SAW sensors. The OFS system operates on backscattered light intensity changes and strain measurements, enabling the detection of corrosion and humidity along the length of a single optical fiber. In this implementation, an optical fiber is coated with a corrosion-proxy metal film (such as iron, nickel or X65 carbon steel) to detect corrosion through changes in light intensity along the fiber while a humidity response induces a strain on optical fiber through polymer jacket expansion under varying humidity—both detected by an Optical Frequency Domain Reflectometry (OFDR) system.

The OFDR interrogator analyzes the backscattered light intensity and strain profile, providing precise location information of any ‘corrosive event’ to be identified. Significantly, multiple sensors can be spliced into a single optical fiber creating a distributed sensor network when placed along a pipeline or other metallic structure.

NETL’s passive wireless multi-element SAW sensor array can be used for simultaneous corrosion and humidity monitoring to allow for predictive indication of corrosivity and quantification of corrosion rate in structures such as oil and gas infrastructure. The reflective delay line SAW sensor arrays consist of at least three sensor elements that can be powered simultaneously with a single radio frequency (RF) signal, either wirelessly or with a wired connection, for detection and monitoring of humidity and corrosion onset. The sensor devices may use a variant of SAW modes including Rayleigh, Pseudo SAW, Shear Horizontal and Love modes, and can be fabricated on a piezoelectric substrate such as LiNbO3, LiTaO3 and Quartz by depositing comb-like metallic interdigital electrodes (IDTs). Materials for the IDTs are selected based on a specific proposed application and may include aluminum, gold or platinum metals and their alloys. These devices are then functionalized with humidity and corrosion-sensitive materials to enable them for humidity and corrosion detection and quantification.

Both of NETL’s systems are functional in harsh conditions, such as turbines and nuclear reactors, as well as across significant distances and areas, characteristic of pipelines and bridges.