Convegni ATI - Accesso riservato soci CTI

Data: 04-2009

Autore: Giandomenico Vita- Praxair Surface Technologies s.r.l.. Division Smaltiriva

Collana: BT - 44 - Apr 09 - Processi di combustione: Tecnologie innovative per la compatibilità ambientale

Note:
Coating systems made with high performance materials are a convenient way to modify and enhance surface properties. Whenever protection against acidic corrosion is sought, according to the working conditions (gas composition and concentration, temperature, pressure), both nickel alloys or special polymers can be used. Particularly, the use of coating systems based with Fluoropolymers have been proved widely suitable and successful in handling moist gas streams with high SOx content close to the dew point. Fluoropolymers are special plastic materials having the following outstanding properties: 1. Exceptional heat resistance, in comparison with normal plastics and organic materials (up to 250 °C); 2. Chemical inertness to virtually any corrosive media, so that they can withstand operating conditions between pH 0 and 14 and also both oxidizing and reducing conditions; Their use in a coating system, with thicknesses included between 300 and 1200 micron, according to the performance requirements, allows therefore the possibility to protect the operation equipments (vessels, ducts, pipes, fans, etc) with a perfectly seamless lining, insulating the whole metallic surface from the exposure to the corrosive media. After a review of the basic properties of fluoropolymers and coatings made with these polymers, real cases of application into industrial desox plants are herewith presented. It is also stressed that, beside the basic choice to work with coating systems containing fluoropolymers, some other technical features are equally important for the complete success in fighting permeation and potential corrosion threats in a SOx environment. Among those ones, it is worth mentioning: 1. The importance of a design and construction fit for the correct application of a fluoropolymer coating systems 2. The importance of a correct surface preparation and primerization, to better enhance the permeation barrier properties and a perfect bonding between the fluoropolymer lining and the metal surface; 3. The importance to provide, both to engineering contractors as well to operators, a complete service during transportation of coated parts, their installation and finally during real operating life. This service includes also the possibility for local small repairs on scratches or mechanical damages.