The research focuses mostly on the use of teos gptms

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the research focuses mostly on the use of TEOS, GPTMS, TMOS, and ZrTPO and includes, in some cases, the performance of coating materials with embedded corrosion inhibitor species and the deposi- tion of multilayers produced by several deposition- curing cycles. The intensive use of TEOS is explained by the reasons stated in the previous section, with a lower price than MTMS or ZrTPO, boosting the search for effective OIH coatings using this specific precursor. The use of GPTMS reported in 72% of the publi- cations found for these substrates may be explained by the fact that this precursor is a combination of two different components, in particular, glycidoxy (organic) and silicon alkoxy (inorganic) groups. It can thereby form, at the same time, an organic network through the polymerization of glycidoxy groups and an inorganic network through the hydrolysis and subsequent con- densation reactions of alkoxy groups. 134 Moreover, it can be used as a binder in organic–inorganic silica- based systems increasing the density and improving adhesion to the substrates. 125 It should also be men- tioned that this precursor has an epoxy terminal group that exists as a component of commercially available epoxy glues that have an intensive industrial and domestic use for a large variety of purposes and application. The most recent publications (since 2007) also showed that the innovations for coatings on these substrates are moving toward self-healing coatings doped with nanocontainers able to release entrapped corrosion inhibitors. 193 195 The majority of the OIH coatings studied showed promising performance in protecting the aluminum-based alloys against corro- sion. Some of the OIH coatings studied have reached a remarkable degree of development and the next step will undoubtedly be large-scale industrial production and marketing. OIH coatings for corrosion protection of copper-based alloys Copper and copper-based alloys are versatile materi- als. This group of alloys has a wide application in sculptures, kitchen utensils, heat exchange tubes, tube sheeting, valves, and piping in seawater and fresh water systems. 65 Copper shows excellent corrosion resistance and scaling, high mechanical strength, high tempera- ture resistance, and lifetime resistance to UV degra- dation. However, in wet environments its corrosion processes are accelerated. OIH sol–gel coatings have also been investigated for the protection of copper and the few studies found are summarized in Table 5 . Figure 12 shows that only 3% of the considered papers report tests using OIH class II based on siloxanes (i.e., at least one of the precursors used is based on siloxanes) and Table 5 shows that the most used precursor was GPTMS. The reduced number of publications could be explained by several reasons. The native copper oxide Others 12% GPTMS and TEOS 17% GPTMS and TMOS 15% TEOS and others 17% GPTMS and MTMS 5% GPTMS and others 10% GPTMS, TEOS and others 10% GPTMS, TEOS and ZrTPO 2% GPTMS and ZrTPO 13% Fig. 12: Precursors used for the production of OIH (class II) gel coatings based on siloxanes (i.e., at least one of the
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  • Fall '19
  • 1984, oIh, OIH coatings

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