Metal Finishing Guide Book


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Table VIII. Chemical Resistance of Structural Plastics Medium Aluminum salts Cadmium salts Chromic acid, to 10% Copper salts Gold cyanide Hydrochloric acid Hydrofluoric acid Iron salts Magnesium salts Nickel salts Nitric acid, to 20% Perchloric acid Phosphoric acid Sodium chloride Sodium cyanide Sodium hydroxide, to 30% Sodium salts Sulfuric acid, to 50% Trichloroethylene Trisodium phosphate Zinc salts Polyvinyl Chloride Polyethylene Polypropylene R R R R R R R R R R R R R R R R R R NR R R R R R R R R R R R R R C R R R R R R NR R R R R R R R R R R R R R C R R R R R R NR R R C, conditional; R, recommended; NR, not recommended. All of these plastics have been successfully used as self-supporting tanks and "drop-in" tank liners for process and storage applications. The thermoplastics (PVC, PP, and PE) are being used for mechanical bonding to concrete for similar applications. Polyvinyl chloride is one of the oldest proven plastics for fabricating highly chemical-resistant structures. (See Table VIII for the chemical resistance of structural plastics.) Type I PVC is one of the best plastics available for resistance to a multitude of strong oxidizing environments up to its thermal limitation of approximately 150OF (66OC). Type I PVC has outstanding structural integrity attributable to its high tensile, compressive, and flexural properties. It is one of the easiest plastics from which to construct tanks, tank liners, dipping baskets, and other storage and process equipment. PVC is easily thermoformed, cut, drilled, tapped, machined, and welded, consequently, making it an excellent, versatile, and cost-effective material from which to fabricate corrosion-resistant equipment. Polypropylene has arrived. Its popularity is attributable to its excellent chemical resistance and surpasses PVC because of its superior physical and thermal resistance. It is available as flame and nonflame retardant homopolymer and copolymer sheet stock. Polypropylene utilizes fabricating techniques similar to those used for PVC. Small tanks for pickling and plating, large tanks for continuous strip pickling lines, and pickling line covers have been fabricated of polypropylene. These and similar fabrications are enjoying an enviable record of success in challenging chemical and physical applications. Linear polyethylene fabrications have performed well in the small-parts metal766

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