Not ensure fully uniform coatings particularly when

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not ensure fully uniform coatings, particularly when dip-coating systems for the deposition of low viscosity OIH gel precursors are used. Representative SEM images and EDS analysis data obtained for the HDGS samples coated with two matrices of the OIHs synthe- sized and deposited on the substrate by dip-coating method as described elsewhere 215 are shown in Figs. 14 and 15 . It can be observed that the distribution of the OIH coatings is not uniform. As shown by EDS analysis, the gray areas correspond to the OIH coating (assigned by high peaks of C, Si, and O) and the lighter areas are representative of the substrate (HDGS). In the absence of the OIH coating, the peak assigned to zinc is particularly intense. It is also highlighted that it is difficult to achieve a uniform distribution even with a triple-dip step process as shown in Fig. 15 a. Neverthe- less, these obstacles can be overcome by the use of intermediate deposition and curing steps. However, the increase in the number of steps involved in coating methods make these procedures extremely complex and time consuming. As such, a compromise between the improvement of the final material properties and the associated costs should be made. Another important limitation considered by the consumer industry is the difficulty in assessing the behavior of the coating against corrosion after being exposed to the environment. In certain cases, such as underground pipelines and storage tanks, visual obser- vation is impossible without exceptional efforts and Fig. 14: SEM images of HDGS samples coated with the same OIH matrix by dip step method (a) one layer and (b) two layers J. Coat. Technol. Res.
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costs. In such situations, research should be carried out by pre-evaluating the performance and lifetime of the protective coatings, on lab or at a pilot scale, to plan the adequate maintenance/replacement interventions or by the development of appropriate sensors and monitoring methods based on self-sustainable and remote control devices. Arkles 258 in 2001 published a paper about the commercial applications of the synthesized OIH gel materials and, according to him, these show viability in the market either owing to uncommon properties that allow new end-use applications or significantly better cost/performance relation when compared with the available materials. Until now, the traditional CCCs confer the best corrosion protection known at controlled costs making this area even more challenging leading to continuous research for contemporary OIH materials that fulfill the same properties and performances exhibited by CCCs coatings. It is noteworthy that no report has yet been found, either in industrial or academic research, of OIH sol– gel coatings with the same production costs and of equal or superior corrosion performance to traditional conversion layers used processes (chromating and phosphating). As far as authors are aware, no system- atic theoretical and experimental approach on how to evaluate the viability, efficiency, and stability of OIH
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  • Fall '19
  • 1984, oIh, OIH coatings

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