Abstract:Multifunctional nanocomposite coatings were synthesized by reinforcing a polymeric matrix with halloysite nanotubes (HNTs) loaded with corrosion inhibitor (NaNO3) and urea formaldehyde microcapsules (UFMCs) encapsulated with a self-healing agent (linseed oil (LO)). The developed polymeric nanocomposite coatings were applied on the polished mild steel substrate using the doctor’s blade technique. The structural (FTIR, XPS) and thermogravimetric (TGA) analyses reveal the loading of HNTs with NaNO3 and encapsulat… Show more
“…Most of the data found in the literature indicate that the OIH sol-gel materials show an enormous potential in the field of coatings for corrosion mitigation. Several multifunctional OIH coatings have been reported in the last few years showing promising results, with functions adapted according to each metallic substrate and environment [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77].…”
The corrosion process is a major source of metallic material degradation, particularly in aggressive environments, such as marine ones. Corrosion progression affects the service life of a given metallic structure, which may end in structural failure, leakage, product loss and environmental pollution linked to large financial costs. According to NACE, the annual cost of corrosion worldwide was estimated, in 2016, to be around 3%-4% of the world's gross domestic product. Therefore, the use of methodologies for corrosion mitigation are extremely important. The approaches used can be passive or active. A passive approach is preventive and may be achieved by emplacing a barrier layer, such as a coating that hinders the contact of the metallic substrate with the aggressive environment. An active approach is generally employed when the corrosion is set in. That seeks to reduce the corrosion rate when the protective barrier is already damaged and the aggressive species (i.e., corrosive agents) are in contact with the metallic substrate. In this case, this is more a remediation methodology than a preventive action, such as the use of coatings. The sol-gel synthesis process, over the past few decades, gained remarkable importance in diverse areas of application. Sol-gel allows the combination of inorganic and organic materials in a single-phase and has led to the development of organic-inorganic hybrid (OIH) coatings for several applications, including for corrosion mitigation. This manuscript succinctly reviews the fundamentals of sol-gel concepts and the parameters that influence the processing techniques. The state-of-the-art of the OIH sol-gel coatings reported in the last few years for corrosion protection, are also assessed. Lastly, a brief perspective on the limitations, standing challenges and future perspectives of the field are critically discussed.Polymers 2020, 12, 689 The development of OIH sol-gel coatings, based on siloxanes, for corrosion mitigation, has been widely studied in the last few years [2,31,[36][37][38]. Numerous studies have been conducted since the early 1990s [39,40]. The studies performed showed that siloxanes were effective in mitigating the corrosion processes of different metallic substrates. This development was mainly due to the need for alternative environmentally friend materials and processes to replace the traditional chromium-based pre-treatments. Hexavalent chromium (Cr (VI)) is carcinogenic and shows high environmental toxicity and its use has been forbidden since 2006. However, Cr(VI) based pre-treatments improve the coating adherence to the substrate and are effective corrosion inhibitors [41][42][43] which make its replacement challenging. The use of the sol-gel method to produce OIH coatings for corrosion mitigation suits the main requirements of what should be an environmentally friendly process (i.e., excludes washing stages; it is a waste-free method) and allows one to obtain coatings with high purity and specific pore volumes and surface areas. Since it is a mild synthesis...
“…Most of the data found in the literature indicate that the OIH sol-gel materials show an enormous potential in the field of coatings for corrosion mitigation. Several multifunctional OIH coatings have been reported in the last few years showing promising results, with functions adapted according to each metallic substrate and environment [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77].…”
The corrosion process is a major source of metallic material degradation, particularly in aggressive environments, such as marine ones. Corrosion progression affects the service life of a given metallic structure, which may end in structural failure, leakage, product loss and environmental pollution linked to large financial costs. According to NACE, the annual cost of corrosion worldwide was estimated, in 2016, to be around 3%-4% of the world's gross domestic product. Therefore, the use of methodologies for corrosion mitigation are extremely important. The approaches used can be passive or active. A passive approach is preventive and may be achieved by emplacing a barrier layer, such as a coating that hinders the contact of the metallic substrate with the aggressive environment. An active approach is generally employed when the corrosion is set in. That seeks to reduce the corrosion rate when the protective barrier is already damaged and the aggressive species (i.e., corrosive agents) are in contact with the metallic substrate. In this case, this is more a remediation methodology than a preventive action, such as the use of coatings. The sol-gel synthesis process, over the past few decades, gained remarkable importance in diverse areas of application. Sol-gel allows the combination of inorganic and organic materials in a single-phase and has led to the development of organic-inorganic hybrid (OIH) coatings for several applications, including for corrosion mitigation. This manuscript succinctly reviews the fundamentals of sol-gel concepts and the parameters that influence the processing techniques. The state-of-the-art of the OIH sol-gel coatings reported in the last few years for corrosion protection, are also assessed. Lastly, a brief perspective on the limitations, standing challenges and future perspectives of the field are critically discussed.Polymers 2020, 12, 689 The development of OIH sol-gel coatings, based on siloxanes, for corrosion mitigation, has been widely studied in the last few years [2,31,[36][37][38]. Numerous studies have been conducted since the early 1990s [39,40]. The studies performed showed that siloxanes were effective in mitigating the corrosion processes of different metallic substrates. This development was mainly due to the need for alternative environmentally friend materials and processes to replace the traditional chromium-based pre-treatments. Hexavalent chromium (Cr (VI)) is carcinogenic and shows high environmental toxicity and its use has been forbidden since 2006. However, Cr(VI) based pre-treatments improve the coating adherence to the substrate and are effective corrosion inhibitors [41][42][43] which make its replacement challenging. The use of the sol-gel method to produce OIH coatings for corrosion mitigation suits the main requirements of what should be an environmentally friendly process (i.e., excludes washing stages; it is a waste-free method) and allows one to obtain coatings with high purity and specific pore volumes and surface areas. Since it is a mild synthesis...
“…FTIR, and XPS used for structural analysis, and thermogravimetric (TGA) analyses demonstrate synergy of HNT/NaNO 3 with UFMCs encapsulation of linseed oil. Figure 4 is a schemetic representation of the concept of PNC coating [62] . Figure 5 represents FESEM analysis of samples.…”
Section: Anti-corrosion Coatingsmentioning
confidence: 99%
“… Fig. 4 Schematic elucidation of the multifunctional nanocomposite coating concept [62] Fig. 5 FESEM analysis of: (a) HNTs (b) HNTs with inclusion of NaNO3, (c) urea formaldehyde microcapsules/linseed oil (UFMC/LO), and (e.g) PNC coatings; and EDX analysis of: (d) HNTs, (f) HNTs with NaNO3 inclusion, and (h) PNC coatings [62] .…”
Section: Anti-corrosion Coatingsmentioning
confidence: 99%
“…The corrosion inhibition demonstrated by the developed PNC smart coatings may be attributed to effective release of inhibiting entity and self-mending agent while responding to external stimulation. Therefore, PNC coatings treated with multi-functional entity is a potential steel corrosion inhibitor for the oil and gas industry [62] .…”
Section: Anti-corrosion Coatingsmentioning
confidence: 99%
“…In line with this procedure, the coatings were exposed to controlled damages. To study the SH performances of developed PNC coatings, SEM images of the deteriorated PNC coatings were derived at varying durations, as elucidated in Figure 22 [62] .…”
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