Rubberizing

the application of a rubber or ebonite coating to metal objects for protection against corrosion and other harmful effects. The high resistance of rubbers and ebonites to the influence of corrosive mediums makes rubberizing one of the best methods of protecting chemical equipment. Thus, at ambient temperatures up to 65° C these materials resist the influence of hydrochloric acid and alkalis in any concentration and sulfuric and phosphoric acids in concentrations of 50 percent and 85 percent, respectively. Coverings of soft rubbers effectively protect equipment from the effects of diluted nitric acid (up to 5 percent), acetic acid (up to 15 percent), and aqueous solutions of ammonia. Soft rubbers also resist abrasion and withstand sharp temperature changes and varying mechanical loads. These qualities are absent from ebonite, which, however, has a higher resistance to chemicals. Hard rubbers (semiebonites) occupy an intermediate position.

The qualities of coverings depend on the nature of the rubber and on the composition of the rubber mixture. Carbon-chain rubbers (such as butadiene, butadiene-styrene, isoprene, chloroprene, and butyl-rubber) are considerably more resistant to solutions of acids and alkalis than heterocyclic rubbers (such as polysulfide rubbers and silicoorganic rubbers), which possess other valuable qualities. Thus, the polysulfide rubbers are more highly resistant to gasoline and mineral oils. In turn, a silicoorganic rubber covering can be used at temperatures up to 200°-250° C. The chemical stability of the same rubber material can be altered within certain limits depending on the vulcanization method employed.

Items may be rubberized by the following processes: (1) gluing (covering) with unvulcanized sheets of rubber or ebonite mixtures; applying the rubber mixtures in the form of a paste or solution with subsequent vulcanization; (2) the application of latexes that form a coating as a result of coagulation; (3) gas-flame and vortex spray-coating of powdered-rubber mixtures; and (4) application of vulcanized bushings or sheaths. The service life of coverings depends on the temperature and nature of the surrounding corrosive environment. Under favorable conditions a covering can continue to provide protection for up to seven years.