Development of Techniques and Non-Destructive Methods for in-Situ Performance Monitoring of Organically Coated Pre-Finished Cladding Used in the Construction Sector
Authors: Savill Tim , Jewell Eifion , Barker Peter 
Published: July 2022

Asset corrosion is a huge problem for the construction and other industries with an estimated cost of approximately GBP 300 billion in the EU in 2013 [1]. To mitigate this cost and protect metal substrates from corrosion, organic coatings are often used. In 2017 the EU produced 4 million metric tonnes of organically coated steel, a large quantity of which is used for the production of building cladding material [2]. Cladding material is widely used in construction of both commercial, industrial, and residential buildings due to its convenience, speed of construction as well as aesthetic and weather resistant properties. Architects and customers are increasingly using pre-finished coated steel panels to provide a sleek modern design.
In order to maintain the required aesthetic value offered by these panels, it is of crucial importance that the coatings provide appropriate protection from the harsh conditions faced by building facades. It is paramount that manufacturers of the cladding can provide reassurances of the long-term coating performance to provide confidence to the end customer.
Despite this, coating performance is only currently estimated by accelerated lab-based tests and some short-term outdoor exposure testing. These tests are carried out in conditions that produce results that are often not representative of real life, leading to earlier than expected failure of the product in some conditions. The ability to monitor the environments that the coatings are exposed to, as well as the actual real-time performance of the coating itself, would provide a far better avenue to determine the expected lifetime of the coated product as well as maintenance scheduling and failure prevention. Furthermore, it would reduce the requirement for human inspection and allow remedial maintenance before the damage becomes too significant to warrant replacement. The advantages of in-situ, real time monitoring has long been recognized by the oil and gas industry, however, at this point in time they are the only sector deploying significant corrosion and coating monitoring techniques.
However, as we move to a more connected world, with an increase in devices and IOT systems there is increased interest by the construction section in sensing. There has been significant research effort to develop corrosion sensing of concrete embedded rebar [3–5] and it is clear there is an appetite to grow the field of asset monitoring.
The research undertaken develops novel deployments of existing techniques as well as new techniques to detect both corrosion of metallic substrates and degradation and failure of the organic coatings. The overall aim is to produce a sensor system that can work autonomously over long periods. This presented difficulties in terms of, powering, communication, durability, deployment, and sensitivity. The ideas explored include capacitive based sensing, magnetic flux leakage, RFID EMI based corrosion sensing and radiofrequency based dielectric sensing.
The designed sensors show promise in detecting early stages of corrosion and coating failure as well as indicating the severity of such changes. The work presented will discuss the challenges faced and how they were/are being overcome as well as the current sensor development and results.

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