Corrosion control measures

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. 

Effective corrosion control programs are essential in reducing unit downtimes. To be effective, the program must address not only specific corrosion problems, but anticipate and prevent them as well. Consequently, effective pretreatment in addition to other corrosion control measures is important. 

It is evident from the data presented on the economics of corrosion that corrosion costs amount to about 2-4% of GNP, and about 25% of the costs are avoidable by adopting corrosion control measures. The measures taken to combat corrosion in UK, USA, Australia, China and Canada have been discussed.18 The following is a short summary of the activities in various parts of the world to combat corrosion. 

In such cases, the third parties in question have little or no control over the use of suitable corrosion control measures. Thus, in such cases where the savings from corrosion prevention measures accrue to different persons or bodies from those who would have to bear the costs of the corrosion prevention measures, then the government alone can tax such beneficiaries for the overall benefit of the community. 

Because of the high cost of failure and inability to rehabilitate facilities in deep water, offshore production in deep water requires the use of high alloy steels and more exotic corrosion control measures. A similar need for advanced corrosion control measures is encountered when dealing with high-pressure and high-temperature offshore oil and gas fields where conventional corrosion mitigation is not applicable. Typical costs for various expenses for one large oilfield area are listed in Table 4.41. 

Corrosion costs in Canada (14,15) are about 3,475 billion out of which 235 million are avoidable by adopting corrosion control measures. So far, there has been no initiative in implementing corrosion control measures to reduce the corrosion costs. This aspect is in the realm of activity of a federal government or a national research laboratory that deals with materials science. The following recommendations have been made to counter the effects of wear and corrosion in Canada establish a national secretariat whose functions are to ... 

In most cases, the process of corrosion is inevitable however, in practice its control is possible and practicable. Corrosion control measures include the use of cathodic protection and coatings, severally and jointly. The conjoint use of coatings and cathodic protection is an aninently powerful tool in corrosion protection, for while coatings will offer a first line of protection, the cathodic protection current will protect the substrate at imperfections and/or holidays in the coatings. Thus the cathodic current required for protection will be infinitesimally low. 

Installation and maintenance of corrosion control measures Onduding. swales, silt fencing, and seeding). 

Practice For Calculation of Corrosion Rates and Related Information from Electrochemical Measurements Calculating of Economic Appraisals of Corrosion Control Measures... 

Prevention and minimization of corrosion is achieved by a combination of design (steady and vibratory stresses, heat flux, and flow), feedwater and boiler water treatment (control of pH tmd corrosion potential, and control of impurity concentration), and operation (control of impurity ingress and stress and temperature conditions) (Fig. 3). These corrosion control measures are discussed in Refs 4—6 and 9-19. 

For electrical safety reasons, the telecommunication cable plant has to be grounded and bonded. This means that some bare metallic components of the plant have to be directly exposed to corrosive environments. Some of these alloys are not particularly corrosion resistant, and at some locations they require corrosion-control measures. An example of such a condition is where the galvanized-steel support hardware is part of the ground in a flooded manhole. 

In enhanced recovery, materials selection and corrosion control measures may significantly differ from those used during the primary production phase. Thus, additional corrosion testing may be required during the selection of corrosion control measures. For example, in some water and steam floods, the produced fluids may change during the well or facility life from sweet to sour because of increased... 

Corrosion control measures for immersion-type applications include ... 

The various corrosion-control measures hsted previously cannot ah be used in buried exposures. From a practical point of view there is not much that can be done to modify the environment to make it less corrosive, and material selection options are often hmited by engineering requirements. Although clean, uniform, well-draining backhU materials wiU reduce corrosion activity, chemicals present in the soil will tend to leach into the backfill due to movement of water through the soil. 

However, IRB still have the power to surprise us Lee et al. reported that a mixed culture (biofilm) containing IRB (Shewanella oneidensis ) and SRB (Desul-fovibrio desuljuricans) that had been formed on mild steel could provide a shortterm (four days) protection to the steel [116]. As the authors put it, [t]he fact that an iron-reducing bacterium can inhibit corrosion when a corrosion-enhancing bacterium is present warrants future study with respect to its potential applicability to the design of biological corrosion-control measures . Such reports can lead us into another aspect of IRB a corrosion-inhibiting bacteria This matter is discussed in Section 5.2, Corrosion deceleration effect of biofilms of Chapter 5 and will not repeated here. 

Corrosion control measures should be implemented during the design stage of petroleum and chemical plants and include ... 

Specification of corrosion-control measures and selection of optimal materials... 

The cost and degree of efficiency of the embodied corrosion-control measures can be predetermined and their system varied to suit. The unexpected is more expensive than the planned and predicted. For this reason preventive control should be the prime consideration of every designer. On the other hand, curative control of the designed utility must not be altogether forgotten and all newly designed products must be made ready for its probable deployment at any appropriate time. 

Instructs on cost limits for implementation of corrosion-control measures. In the latter stages provides budgetary control to prevent corrosion control from running wild and to prevent uimec-essary and excessive precautions. 

Represents management and design office on corrosion and failure committees for interpretation of apphed corrosion-control measures and proposes revisions. 

Trains and supphes efficient advisory staff, approved contractors, and site inspectors to secure effective corrosion-control measures (materials and work) when arranged. 

It attempts only to indicate the system of parallel evaluation of corrosivity of different petroleum environments, the effect of process parameters, estimation of corrosion rates, determination of corrosion allowances for a given life, and a few guidelines in selection of materials in conjunction with corrosion control measures and economic principals. 

Such test methods can be used to compare the many variables in material composition, manufacturing, and field performance. The tests also can be used to compare different types of material, or the same material grade from various manufacturers using different manufacturing process, and to evaluate different corrosion control measures. However, the objective set of variables for the test dictates the selection of test methods. Therefore, a careful study of both process and material (physical. 

Several different techniques exist for economic appraisal of different materials and alternative corrosion control measures. Among these are the concepts of ... 

Therefore, for economic evaluation, reference is made to the NACE Standard Method RP-02-72, Direct Calculation of Economic Appraisal of Corrosion Control Measures, in which the excellent presentation of the subject matter makes it superfluous to enlarge on the factors to be considered in economic evalnation. 

For an overall simplified and standard approach to the economic appraisal calculations, reference is made to NACE, RP-02-72 (direct calculation of economic appraisals of corrosion-control measure, based on the method of discounted cash flow analysis.)... 

Permanent structures designed for a service life of more than five years should be protected from deterioration with the best coating system available. Other corrosion-control measures should also be considered. The cost limit in each case is individual and should not be arbitrarily dictated. 

Although corrosion problems cannot be completely remedied, it is estimated that corrosion-related costs can be reduced by more than 30% with development and use of better corrosion control technologies. Corrosion control measures include corrosion inhibitors, cathodic protection, and coatings (Priyantha et al., 2003). Corrosion of metals occurs when they come in electrical contact with a corrosive environment. Therefore metallic corrosion can be prevented by either changing the metal or altering the environment or by separating the metal from the environment as shown in Fig. 7.7 (Narayan, 1983). 

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