Corrosion control applications

The best known polymeric materials are natural rubber and synthetic rubber. These materials have low modulus of elasticity. The flexibility of these materials enables their application in tubing, belting and automotive tires as encountered in everyday usage. Resistance to chemicals, abrasive attack and insulating property can be advantageous in corrosion control applications. 

The polymeric materials are used in (i) barrier applications (ii) self-supporting structures (tanks, piping, valves and pumps) (ii) column internals, seals, gaskets, adhesives and caulkings. An overview of polymeric materials used in corrosion control applications is given in Figure 4.8. 

Corrosion-resistant alloys are used where corrosive conditions are severe enough to prohibit the corrosion prone carbon steels and where protective coatings provide insufficient protection or are economically not good enough. The total cost for these alloys used in corrosion control applications is 8.3 billion with 7.9 billion for stainless steels, 0.28 billion for nickel-based alloys, and 0.15 billion for titanium alloys. 

In 1998,21,600 metric tons of titanium sponge was produced. The total consumption was 39,100 metric tons at a cost of 391 million. The cost of 150 million has been reported for titanium and titanium alloys for corrosion control applications. 

Positive information recorded in an index form, and accurately updated, can illustrate the whole development and progress of corrosion-control application in the design of a particular project or part and may become a source of valuable information for corrosion-control design analysis, specifications, working drawings, schedules, standards and procedures. 

Resistance to initiation of corrosion Economic permanency of corrosion control Application of protective coatings Final appearance Consistency of operation Reduction of vibration. 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

Cathodic Protection This electrochemical method of corrosion control has found wide application in the protection of carbon steel underground structures such as pipe lines and tanks from external soil corrosion. It is also widely used in water systems to protect ship hulls, offshore structures, and water-storage tanks. 

The primaiy purpose of materials selection is to provide the optimum equipment for a process application in terms of materials of construction, design, and corrosion-control measures. Optimum here means that which comprises the best combination of cost, life, safety, and reliability. 

Molten vanadate ashes (melts) can exhibit both semiconducting and ionic conduction and experiments have shown that semiconducting melts are more coiTosive than those exhibiting ionic conduction. Application of this knowledge as a corrosion control technique is not yet feasible, and a more complete discussion will not be attempted in this article. 

An understanding of the basic principles of the science of metallic corrosion is clearly vital for corrosion control, and as knowledge of the subject advances the application of scientific principle rather than an empirical approach may be used for such purposes as the selection of corrosion inhibitors, formulation of corrosion-resisting alloys, etc. 

A recent NACE publication devoted entirely to the economic aspects of corrosion control contains several worked examples applicable to a number of industries. These examples serve to illustrate that anti-corrosion procedure and materials should be selected on economic grounds, and not solely on performance grounds. In presenting a proposal to management. 

The complexity of the systems to be protected and the variety of techniques available for cathodic protection are in direct contrast to the simplicity of the principles involved, and, at present the application of this method of corrosion control remains more of an art than a science. However, as shown by the potential-pH diagrams, the lowering of the potential of a metal into the region of immunity is one of the two fundamental methods of corrosion control. 

Loushin, L. L., First Application of Artificial Intelligence for Corrosion Control in the Petroleum Industry , Materials Performance, Tl, 6, 77-83, June (1988)... 

The continuous development of new materials has resulted in changing attitudes towards materials selection for corrosion control, and the range of materials now available can be gauged from the Materials Selector Review", which becomes considerably thicker each time it is updated. Plastics are replacing metals for a variety of applications and a recent application is the use of g.r.p. in place of metals for the construction of hulls of hovercrafts the corrosive action of the high velocity spray of sea-water is such that very few metals are capable of withstanding it and the use of g.r.p. represents the... 

Paints are one of the most important methods of corrosion control, but it is well known that many cases of failure result from inadequate surface preparation of the metal and careless application of the paint system procedures that are often carried out under adverse or unsuitable environmental conditions by labour that is relatively unskilled. A great deal of research and... 

Various phospono- and phosphinopolycarboxylic acids (PCAs) are available in the market. These polymers are similar to phosphonates and some actually are phosphonates. They tend to exhibit varying degrees of both deposit control and corrosion control properties. For BW applications, the acrylic acid/organic phosphate polymer (PCA type 16) is the only important phosphinopolycarboxylic and has a C-P-C bond (phosphonates have a C-P-O bond). 

Chemical treatment programs are designed to promote clean internal waterside surfaces, but continuous freedom from deposition and corrosion requires excellent operational control. Application of products, regular monitoring, and comparison of analytical results with recognized standards and interpretation of data are all important components of the program. 

Marine coatings Organic coatings for corrosion control Paint acrylic ester polymers, 7 388-389 adhesion, 7 90-92 advanced ceramic, 7 704-705 alkanolamines from olefin oxides and ammonia, 2 136 alkyd resins, 2.T67-168 amino acid resin applications, 2 635—637 anticorrosion, 25 134 anticorrosion metallic, 7 713-714... 

Phosphonates are surface-active chelants and are widely used in industry for scale and corrosion control, and in cleaning agents, dispersants, and other applications. The annual sales of phosphonates in the U S A amount to over two billion dollars per year [8]. Phosphonates inhibit calcium scale formation by interfering with the crystal structure of calcium salts, making the crystals softer so that they are more easily removed by washing - the threshold effect [9]. A key application is controlling scale particularly in hard-to-reach places such as laundry and dishwashing machines. 

Corrosion. Anticorrosion measures have become standard in pipeline design, construction, and maintenance in the oil and gas industries the principal measures are application of corrosion-preventive coatings and cathodic protection for exterior protection and chemical additives for interior protection. Pipe for pipelines may be bought with a variety of coatings, such as tar, fiber glass, felt and heavy paper, epoxy, polyethylene, etc, either pre-applied or coated and wrapped on the job with special machines as the pipe is lowered into the trench. An electric detector is used to determine if a coating gap (holiday) exists bare spots are coated before the pipe is laid (see Corrosion and corrosion control). 

Mcroorgamsms - piSINFECTANTSAND ANTISEPTICS] (Vol 8) - [ANALYTICALMETHODS - TRENDS] (Vol 2) - controlof [INDUSTRIAL ANTIMICROBIAL AGENTS] (Vol 14) -as corrosive agents [CORROSION AND CORROSION CONTROL] (Vol 7) -in cosmetics [COSMETICS] (Vol 7) -H2 production from [HYDROGEN] (Vol 13) -industrial enzymes from pNZYME APPLICATIONS - INDUSTRIAL] (Vol 9) -nonconventnonal food sources [FOODS, NONCONVENTIONAL] (Vol 11)... 

Corrosion can also be suppressed by Ihe controlled application of current to the metal as an anode. This is called anodic protection. Passivity is induced and preserved hy maintaining the potential nf the alloy at. or above, a critical potential in what is called the range of passivity in a potcntiostalic diagram. Such diagrams are based on the relationship between applied anodic current density and the corresponding potential in the environment of interest. 

Corrosion control of metal surfaces depends on the formation and maintenance of a protective corrosion inhibitor film on the exposed metal surface. This protective film may be established during normal application of a corrosion inhibitor program however, there will be some lag time before the film is completely built up. Metal surfaces that are exposed to the cooling water before the film is completed may become candidates for accelerated corrosion during the initial system operation. Normally, localized corrosion or pitting is common during these early stages of operation. 

From the standpoint of corrosion protection, a slight amount of mineral scale formation—if the thickness can be controlled—is desirable. This helps to explain why, in some cases, sea water is found to be less corrosive than a brine of sodium chloride with the same salinity. However, in applications where heat is being transferred across the metal wall, the presence of scale markedly affects the efficiency. In distillation units, a method of corrosion control based on intentional mineral-scale formation would thus lead to greater fuel consumption. 

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