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A common circuit for a zero-resistance ammeter (Reprinted with permission from ref. [73]. Copyright 2008 Elsevier).
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![Figure 3. Ultrasonic testing principle. Reprinted from ref. [31].](profile/Eifion-Jewell/publication/354762636/figure/fig3/AS:1070935352299522@1632342293927/Ultrasonic-testing-principle-Reprinted-from-ref-31_Q320.jpg)
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 performan...
Citations
... Hence, with the evolution of the space industry, several nondestructive evaluation techniques have been developed to monitor the health state of the materials during ground testing and in service [9][10][11][12][13][14]. However, although many technologies might be used for in situ evaluation/ remote/real-time monitoring [15], the sensors and the support apparatus must match the space compatibility [16] and embedding requirements [17]. Another issue is in regard to the need to perform multiparameter measurements to evaluate the overall state of a material or for simple cross-sensitivity compensation of some sensors to a determined parameter (as in the case of temperature for strain gauges). ...
Tilted fiber Bragg grating (TFBG) sensors were demonstrated to simultaneously measure the material thermomechanical and refractometric state in which they are embedded. In this work, for the first time, TFBGs are investigated for three-parameter monitoring of space-qualified NuSil® CV16-2500 silicone operating during high-vacuum ultraviolet (UV) exposure. The first part of the work is focused on the ultraviolet effect on the TFBG spectrum when the sensor is 1) directly exposed to the radiation, 2) covered by a thin cover glass, and with a Kapton layer on top. Successively, the silicone is used as an adhesive in a sandwich structure in which the TFBGs are embedded and exposed under high vacuum to various UV/vacuum UV intensity radiations and durations. The sensors’ spectra were acquired and demodulated to detect the silicone strain–temperature–refractive index variations and correlate the silicone refractometric changes with the equivalent exposure solar hours. The second part of the paper is on silicone degradation state evaluation using the same sensor but during a direct exposure of the adhesive to the radiation. This allowed the UV effects on the silicone to be enhanced but needed a method to compensate for the damaging effect of UV radiation on the TFBG spectrum.
... There are several different mechanisms by which OCS can degrade, which require different atmospheric conditions to be present. The most important environmental factors affecting the coating durability are light, solvents, temperature, humidity, mechanical abrasion, and biological contaminants [5]. Light, specifically that in the UV range present in sunlight, can cause photooxidation and bond scission, which can increase the permeability and brittleness of the coating and reduce adhesion [6,7]. ...
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.
... 140 Savill and Jewell discussed the use for in situ monitoring for improved estimation of field lifespans for precoated steel substrates. 141 One significant area of research is the application of probabilistic methods, such as Bayesian modeling, to address the uncertainty in the degradation of coatings for the many reasons discussed within this review. This approach is particularly useful due to the probabilistic nature of coating degradation and failure in use. ...
There has been a dedicated effort by multiple groups to determine which performance attributes of coatings, such as adhesion, electrochemical properties, and appearance will give an indication of overall performance of a coating. Complicating lifetime performance predictions of coatings are the many variables that consistently change in differing industrial markets – substrates, pretreatments, coating chemistries, and coating layers to name a few; with coatings failing in different manners. While the focus of this paper is the lifetime prediction of corrosion performance in atmospheric corrosion scenarios, it should be noted that there are other failure modes (Table 1), beyond corrosion, which may be considered ‘end of life’ by users. These include appearance changes such as UV degradation resulting in color, gloss loss, coating erosion and loss or changes in adhesion strength. While these failure modes are out of scope for this paper, it must be realized that the chemical changes occurring during UV exposure may significantly impact the coating performance in the area corrosion. To be of value, lifetime prediction must accurately determine the coating lifetime when under real-world conditions, noting that accelerated testing protocols used in lifetime prediction studies need to be interpreted with caution, as many do not accurately replicate the modes of failure that occur during real-world use. Complicating this is the fact that coatings are studied in the laboratory under ideal conditions, with well-prepared substrates, and properly applied and cured coatings at controlled dry coating thicknesses. Coating lifetimes in the field are often not determined by this “Best Case Scenario.” Instead, coatings tend to fail in use due to substrate preparation issues, application defects, incomplete cure, damage during use, along with a variety of other unknown unknowns.
... Real time monitoring could allow more accurate estimates of building cladding lifespan, as well as required maintenance schedules, providing the customer with active performance data [3]. A significant amount of emerging research in this field shows the appetite for this technology [4]. ...
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.
... All these methods have their own advantages, however, each of them also has its particular limitations. For example, a smooth or polished surface is required for ultrasonic and eddy current techniques; the electrical resistance (ER) sensor technique is more suitable for measuring uniform corrosion than localized corrosion; the infrared thermography technique has disadvantages such as a time-consuming process and the need for relatively expensive microwave equipment [8]; and the embedding of optical fibers runs the risk of decreased coating protectiveness through decreased adhesion or increased defect formation [30]. More importantly, these aforementioned methods are incapable of characterizing and monitoring the early degradation of organic coatings or being applied in field monitoring. ...
This study proposes coating impedance detector 3.0 (CID 3.0), an improved version of our previously developed CID 2.0. The new circuit design in CID 3.0 has lower power consumption because it has fewer components, and it affords better accuracy through the modification of the analog part of CID 2.0 and the use of oversampling. This approach successfully afforded CID 3.0 with higher measurement stability for evaluating a high-performance coating with impedance values exceeding
$10^{9}~\Omega $
. Furthermore, CID 3.0 could detect impedance decreases associated with coating delamination when the coating suffers an attack.
Perfluorodecyltrichlorosilane (PFDS)-modified PDMS-ZnO hydrophobic coating and 2-ethylhexanoic acid (EHA)/PFDS-modified amphiphilic coating were fabricated. The effect of EHA on the barrier properties and corrosion protection effectiveness of PFDS-modified hydrophobic PDMS-ZnO coating was investigated using electrochemical impedance spectroscopy (EIS) and molecular dynamics simulation techniques. The EIS results showed the amphiphilic coating exhibited higher barrier and corrosion protection properties than the hydrophobic coating. The observed EIS results were confirmed by results of the water contact angle measurement, SEM, AFM, EDS and FTIR. The molecular dynamics (MD) simulation results revealed the nature of interaction between the amphiphilic coating and the corrodent, as well as the interaction between hydrophobic coating and the corrodent. The results clearly indicate that amphiphilic coating was most favourable for hydrophilic interaction, whereas the hydrophobic coating was well-disposed to hydrophobic interaction. These agree with the experimental results.
