No abstract

Coating degradation is a critical issue when steel surfaces are subject to weathering. This paper presents a chipless, passive antenna tag, which can be applied onto organically coated steel. Simulations indicated that changes associated with organic coating degradation, such as the formation of defects and electrolyte uptake, produced changes in the backscattered radar cross section tag response. This may be used to determine the condition of the organic coating. Simulating multiple aging effects simultaneously produced a linear reduction in tag resonant frequency, suggesting coating monitoring and lifetime estimation may be possible via this method. For coatings thinner than calculations would suggest to be optimum, it was found that the simulated response could be improved by the use of a thin substrate between the coated sample and the antenna without vastly affecting results. Experimental results showed that changes to the dielectric properties of the coating through both the uptake of water and chemical degradation were detected through changes in the resonant frequency.

A review is carried out in this paper into techniques that currently exist for, of have the potential to be used for, monitoring the performance of organic coating. Specific attention is paid to the applicability of each method to pre-finished steel used in the construction industry as these are rarely monitored in situ and their expected performance is often only estimated from lab-based accelerated corrosion testing. Monitoring could allow more accurate estimates of building cladding lifespan and required maintenance schedules; provide customers with active performance data; additionally, with a better understanding of performance, more appropriate coatings or coating weights could be selected for a construction project, offering economic benefits as part of smart building developments. An introduction to coatings, their use for corrosion protection, failure mechanisms, and relevant monitoring techniques is given before current assessment techniques are described in terms of their working principles. Examples of recent work are presented for the techniques that have been investigated for monitoring or directly relatable purposes. The review concludes that there are several good reasons why an optimum corrosion monitoring technology does not currently exist, however, promising research is emerging in the field of wireless and embedded sensor design which is providing optimistic results.

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. Koch GH, Varney J, Thompson N, Moghissi O, Gould M, et al. (2012) International measures of prevention, application, and economics of corrosion technologies study. NACE International, Houston. Eurofer. European Steel in Figures 2008-2017. 2018. James A, Bazarchi E, Chiniforush AA, Panjebashi Aghdam P, Hosseini MR, Akbarnezhad A, et al. Rebar corrosion detection, protection, and rehabilitation of reinforced concrete structures in coastal environments: A review. Constr Build Mater [Internet]. 2019;224:1026–39. Available from: https://www.sciencedirect.com/science/article/pii/S0950061819319208 Xie L, Zhu X, Liu Z, Liu X, Wang T, Xing J. A rebar corrosion sensor embedded in concrete based on surface acoustic wave. Measurement [Internet]. 2020;165:108118. Available from: https://www.sciencedirect.com/science/article/pii/S0263224120306564 Fan L, Shi X. Techniques of corrosion monitoring of steel rebar in reinforced concrete structures: A review. Struct Heal Monit [Internet]. 0(0):14759217211030912. Available from: https://doi.org/10.1177/14759217211030911

Organically coated architectural steel provides an economic, visually attractive, innovation friendly and robust building cladding. However, its performance, usually calculated using accelerated weathering and ‘artificial’ outdoor weathering testing, can be compromised within specific areas of the building envelope. The exact reasons for this are not fully understood. In an attempt to discern where and why performance varies, an investigation is carried out into some possible reasons for the performance discrepancy, and it is concluded that a combination of high humidity and the build-up of aggressive natural deposits contribute to high degradation rates in sheltered regions, such as building eaves, where microclimates are created. The build-up of deposits and their effect is presented as a key degradation accelerant during in-use service. A numerical simulation approach is developed to predict the natural washing, via rain impact and characteristics of the building analysed. This approach shows promise for determining areas unlikely to be naturally washed, and therefore subjected to a degradation accelerating, build-up of deposits. It is shown that such a simulation could be used to optimize the building design process to promote natural washing as well as provide an area-of-concern map in which exposed cut edge should be avoided and any manual inspection should be concentrated. It is also shown that nearby buildings can provide sheltering effects leading to decreased natural washing, increased deposit build-up and ultimately accelerated failure.