Rubber lining corrosive chemicals

The principal benefits of rubber lining are its excellent resistance to corrosive and abrasive chemicals and materials, e.g., acids, alkalies, salt water, slurries, sand, shot blast media, crushed ores etc. In addition to this, rubber linings provide other benefits including noise and vibration reduction, electrical and thermal insulation and product protection. 

Design and fabrication of tanks, vessels, piping and other equipment which are required to be protected with rubber lining against corrosion need special consideration in chemical plant construction. Certain features are to be incorporated in the design, and precautionary methods should be taken while fabricating the mild steel equipment to be suitable for rubber lining application. These are discussed below. 

The solids are thrown outwards against the wall of the vessel and then move away from the gas inlet and are collected in the conical base of the equipment. This separation process is very effective unless the gas contains a large proportion of solid particles less than 10 p in diameter and is equally effective when used with dust or mist-laden gases. The cyclone separators are obviously rubber lined to withstand wear at the velocity of gas and corrosion and are the most commonly used general purpose separator in the chemical process industry. 

The chemical reaction of rubber lining with the corrosive chemicals and acids is much deteriorating to it, resulting in progressive damage of the lining, unless the reaction is not allowed to continue... 

Rubber sheets are the most important materials for the construction and fabrication of much chemical plant equipment such as storage tanks, reactor vessels, pipelines, seals, hoses and rubber lined mild steel equipment of different sizes and shapes, inflatables, etc., and almost all equipment subjected to different corrosive environments. The rubber sheets can be either plain or fabrics coated with rubber. The fabrics used for coating are nylon, rayon, cotton or various other synthetics. Rubberized fabric cords are also used as reinforcing members in various products. 

If the environment slowly attacks either the substrate or the membrane, the interposition of a brick lining between the contained liquid and the substrate or membrane will reduce to a tiny trickle the amount of chemical that reaches the membrane or substrate. Corrosion products, if any, are trapped behind the brick and cannot be washed away to uncover further material to be corroded, so that the corrosion slows down and may eventually stop. Example In a dished bottom, cylindrical steel tank containing a mixture of acid and oil, the steel was lined originally with sheet natural rubber. The rubber lining swells as the oil enters it, but the brickwork holds it in place until the rubber has swollen into all the pores of the brickwork and blocked them preventing any more of the contained liquid from passing behind the brick. 

Typically, the entire contents of a calcium hypochlorite container are emptied into a mixing tank where they are readily and completely dissolved in water. The resulting corrosive solution is stored in and fed from a stock solution vessel constructed of corrosion-resistant materials such as plastic, ceramic, glass, or rubber-lined steel. Solutions of 1% or 2% available chlorine can be delivered by a diaphragm-type, chemical feed pump or metering pump. 

The outstanding property of rubber in general is resilience, or low modulus of elasticity. The flexibility and physical properties of rubber account for its application in general engineering and automobile industries whereas its chemical, wear and abrasion resistance as a sacrificial material, plus its insulating properties are utilised in many corrosion and erosion applications in process industries. Rubber lined mild steel, pipes and tankages have been standard materials of construction for hydrochloric acid service for many years. 

Rubber Lining for Corrosion Protection in the Chemical Industry... 

Rubber lining is one of the best known and proven methods employed to protect chemical process equipment against the corrosive and abrasive attacks of the fluids. One of the most important characteristics of both natural rubber and synthetic rubber is the remarkable resistance to corrosive chemicals, fumes, acids, alkalies and other salt solutions. Without protection, corrosion would be so extensive that most products of modern technology could not exist. The variations and large percentages of corrosive impurities have little influence on the rubber lining up to temperatures as high as 100 °C to 120 °C. 

The anti-abrasive or anti-corrosive rubber linings are applied to the metal surface by adopting different kinds of bonding systems such as ebonite bonding, chemical adhesive bonding or self-vulcanising cement bonding. 

It is quite useful to have some basic understanding of the chemical reactions of polymers with acids and other corrosive chemicals while designing a lining compound. An exhaustive study although inevitable in the context of rubber lining can only be made as a separate topic which is not within the scope of this book. However some typical reactions of polymers with some important chemicals are described next. 

The Indian Standard for lining of vessels and equipment for chemical processes, IS 4682-1 [22], mentions that the use of linings with rubber for protection against corrosion has been the normal industrial practice for more than half a century. The lined vessels and tanks are quite suitable for use either under vacuum condition or high pressure conditions. The appropriate thicknesses for rubber linings are recommended in this standard for various corrosive and abrasive conditions as follows ... 

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