Diffusion of highly corrosive media (HCM) into protective polymer coating materialsстатья
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Дата последнего поиска статьи во внешних источниках: 17 февраля 2021 г.
Аннотация:An important element of modern design of chemical technological devices operating underexposure to highly corrosive media (HCM) are polymer protective anti-corrosion coatings.Basic protective mechanism for these coatings is a barrier mechanism. It is based on ensuring alow solubility of the corrosive medium in the polymer and on a low diffusion transfer of themost corrosive components through the coating. So, the study and control of mass transfer, inparticular studies of diffusion, constitute the most important task in the design of coatingsystems for highly corrosive media. A comparative analysis of the laws of sorption and diffusionof water and solutions of salts and acids by the most widely used classes of anti-corrosivepolymers, i.e., hydrophobic thermoplastics and moderately hydrophilic cross-linked thermoplastics, is made. Data on the concentration profiles of distribution of diffusing acids,regularities of the acids penetration depth and the values of sorption are analyzed. Models ofdiffusion of highly corrosive media into polymers with binding the medium on chemicallyreactive polymer groups are considered. It is shown that the binding model can be used todescribe the diffusion of acids solutions in a wide range of concentrations and temperatures. Amathematical model of the diffusion of chemically reactive corrosive media into multi-layercomposite polymer coatings is suggested and tested experimentally. It is shown that by using acombination of layers of different polymer materials, one can significantly reduce thepermeability of the polymer coating, which allows the penetration depth to be reduced tenfoldand time “before breakdown” to be extended hundred-fold or more. It is also important thatcombining layers of a hydrophobic material and a material capable of binding the medium inone coating allows one to simultaneously solve the problem of eliminating the penetration ofthe most corrosive volatile components at the initial stage of coating operation. The experienceof using coatings in various fields of industry is considered.