Corrosion control prevention measures

Corrosion. Anticorrosion measures have become standard ia pipeline desiga, coastmctioa, and maintenance ia the oil and gas iadustries the principal measures are appHcation of corrosion-preventive coatings and cathodic protection for exterior protection and chemical additives for iaterior protectioa. Pipe for pipelines may be bought with a variety of coatiags, such as tar, fiber glass, felt and heavy paper, epoxy, polyethylene, etc, either pre-apphed or coated and wrapped on the job with special machines as the pipe is lowered iato the treach. An electric detector is used to determine if a coatiag gap (hoHday) exists bare spots are coated before the pipe is laid (see Corrosion and corrosion control). 

The best way to combat corrosion is to maintain an effective corrosionmonitoring program to supplement good preventative measures. It is also very important to keep complete records of monitoring programs, control programs and failures that occur. The importance of well-qualified responsible personnel cannot be overemphasized as effective corrosion control depends on their efforts [201,204,205]. 

I-3.6.2 Electronic control, monitoring, and hydrogen gas measurement equipment shall be properly grounded and isolated from piping to help prevent overpressure/ accidental shutoff situations caused by equipment failure due to lightning strikes and electrical transients and to prevent safety hazards caused by fault currents. Electrical isolation equipment for corrosion control purposes should not be installed in buildings unless specifically designed to be used in combustible atmospheres. 

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. 

Corrosion and its control mean the corrosion process and the measures taken to control or keep in check the corrosion process. Sometimes it is also referred to as corrosion, prevention and protection. Although the terms prevention and protection appear to be synonymous, prevention means measures taken to control corrosion to a limited extent while protection means extensive or more comprehensive measures taken to control the corrosion process. In more general terms preventive measures are knowledge-based while protection involves both known and unknown factors, such as natural disasters. 

Preventative measures, often referred to as additional protection measures, are employed as shown in Figure 11.5. They operate by hindering aggressive species from reaching the reinforcement, or by controlling the corrosion process through inhibition of the anodic process or the corrosion current flow in the concrete. 

Galvanized-steel rebars can be used as a preventative measure to control corrosion in reinforced concrete structures exposed to carbonation or mild contamination with chlorides, such as chimneys, bridge substructures, tunnels and coastal buildings. 

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. 

Batteries and capacitors Corrosion prevention Measuring and controlling devices... 

The two remaining components of the electrochemical industry are corrosion prevention and controlling and measuring devices. In both of these components, our interest is only in those devices whose operation is based on electrochemical principles. Such items fall within our definition of the electrochemical industry. There were no published figures available for the shipments value of either of these two components in 1958 or 1963. As a result, estimates based on interviews and correspondence with members of the industry are given. 

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. 

The resistance of aluminum alloys to flow induced corrosion depends on the stability of the protective oxide films on the surface. Dissolution of these films leads to accelerated corrosion. The protective films of bayerite and boehmite could be eroded by shear forces resulting from flow beyond a critical velocity. Aluminum alloys of series 5xxx are not adversely affected by velocities up to 3 m/s in the absence of abrasives in water. The removal of a film adjacent to a film surface sets up local corrosion cell which accelerates the corrosion process. AUoys of 5xxx series (such as 5454) show a good resistance to corrosion at velocities up to 3ms at temperatures up to 140°C. The corrosion rate increases with increased velocities in the presence of abrasive particles, which need to be controlled. The water chemistry, water velocity and pH needs to be controlled to minimize the effect of flow on localized corrosion. Maintaining pH below 9 would not allow aluminum to dissolve as AlO. The preventive measures include the minimizing of turbulent flow or changing water chemistry. 

Anune units must be designed to overcome these special problems. This chapter reviews both the causes of corrosion problems and possible solutions. It describes the locations within amine units where the various agents cause corrosion, discusses the corrosion mechanisms in these places, and reviews the design practices and preventive measures required to mitigate corrosion. These measures include control of velocities and inqiingement, process con-... 

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. 

Co-operate with prodnction control on adjnstment of corrosion-prevention measures to suit both parties and amend working drawings and schednles accordingly. 

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). 

Fig. 9.6 Method of preventing corrosion by premature condensation of acidic vapours. pH measured continuously at point X automatically controls flow of sodium hydroxide...

Quite separately, the results of a properly controlled trial were published in a 1974 paper entitled Electrostatic Descaler Testing an Evaluation (Meckler, M., Heating/Piping/Air Conditioning, Reinhold Publishing Co.). This paper concluded that the test descaler was not effective in preventing scale deposition, and we were unable to detect any measurable reduction in corrosion potentials. ... 

As discussed under boiler feedwater treatment, boiler blowdown is required to prevent the build up of solids in the boiler that would otherwise cause fouling and corrosion in the boiler. Carry over of solids from the boiler to the steam system via tiny water droplets should also be avoided. Total dissolved solids (TDS) and silica (SiC>2), as measured by the conductivity of water, are both important to be controlled in the boiler3. Dissolved solids carried over from the boiler will be a problem to all components of the steam system. Silica is a particular problem because of its damaging effect on steam turbines, particularly the low-pressure section of steam turbines where some condensation can occur. Blowdown... 

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