Materials Performance

SEP 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

Issue link: https://mp.epubxp.com/i/1019429

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36 SEPTEMBER 2018 W W W.MATERIALSPERFORMANCE.COM COATINGS & LININGS ESSENTIALS Continued f rom page 35 temperatures up to 1,100 °F (593 °C). e poly siloxane hybrid chemistry still con- tained a densely cross-linked organic poly- meric structure. In cyclic ambient-hot- ambient service on small-diameter piping or convoluted small shapes, this first- generation polysiloxane coating tended to crack and disbond from the substrate due to internal stresses caused by the inherent two-component, highly cross-linked hybrid chemistry. In the intervening two decades, this poly siloxane has continued in ambient temperature service, but is rarely used on high-heat equipment. During the last 15 years, inorganic copolymer (IC) and inert multipolymeric matrix (IMM) coatings have been widely used for CUI mitigation. Reynolds and Bock explain that these coatings, which cure at temperatures between 300 to 360 °F (~150 to 180 °C), fall into the category of second- generation polysiloxanes. For these coating chemistries, the surface temperature limits are normally in the region of 1,200 °F (649 °C). e higher level of temperature toler- ance is mainly due to the elimination of organic counterparts, the high concentra- tion of inorganic siloxane-based polymers, and higher flexibility. e introduction of the second-genera- tion polysiloxane coatings was a step for- ward for providing protection to substrates under insulation; however, there are issues with the coatings' usage in the field, such as a soft film before they are heated to curing temperatures. e necessary heating step not only affects the mechanical properties of the coating but also corrosion, UV, and chemical resistance, as well as adhesion— all of which are required to ensure maxi- mum CUI protection. Multiple failures have been identified in the field, either before service temperatures reach >300 °F or dur- ing use below curing temperatures. Now, a third-generation polysiloxane for CUI mitigation is available. Launched in 2015, this coating is a single-component, fully ambient-temperature cure, inorganic polysiloxane. Developed and tested under multiple laboratory and field test protocols, the third-generation polysiloxane elimi- nates the field issues experienced with the second-generation polysiloxane coatings, including decreased film hardness, anticor- rosion properties, and weathering resis- tance prior to post-application curing. For example, Reynolds and Bock explain, removing the heating requirement to obtain properties for CUI protection, which is nec- essary for the second-generation coatings, facilitates full protection in ambient appli- cation temperatures as low as 50 °F (10 °C) and specification temperatures that range from –320 to 1,200 °F (–196 to 650 °C). Additionally, they comment, a new liq- uid-applied thermal insulation coating (TIC) was commercialized in early 2017. TICs have been used for more than 10 years in a range of different applications includ- ing thermal insulation and personnel pro- tection. e low thermal conductivity (λ) properties of the coatings reduce the hot or cold surface temperatures of processing

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