Corrosion of Piping

For cross country lines containing oil or gas, the corrosive constituents such as water, carbon dioxide, and hydrogen sulfide are usually reduced to a very low level before the fluid enters the line. The lost efficiency required to pump the unwanted constituents and the extra wall thickness required for corrosion allowance usually cannot be economically justified. Even with cleanup systems, some water will get into pipelines. In oil lines, oil soluble corrosion inhibitors usually prevent attack by water settling in low spots, etc. Gas lines are usually dehydrated to 60% of saturation to avoid corrosion from condensing water containing dissolved carbon dioxide. Molecular sieves that reduce water to 5 ppm have proved necessary in lines containing 100% carbon dioxide. 

The limiting velocity to avoid erosion-corrosion according to API RP 14E is  

C - empirical constant usually taken as 100 for continuous service, although some 

When velocities exceed 20 ft/s (6.1 m/s), bubbles or dispersed flow conditions result SS s are used with these conditions. The martensitic SS s have performed well, but austenitic SS s (e.g., type 304L [UNS S30403] SS) are required for complete immunity to metal loss unless oxygen is completely absent. 

Both austenitic and super SS s have excellent resistance to erosion-corrosion in velocities up to 85 ft/s (26 m/s). Usually, copper base alloys are not considered because of poor resistance to hydrogen sulfide/10 poor resistance to erosion, and low strength. Prevention of corrosion by coatings is usually impractical in production equipment because of limited life, as described previously, and because the coating can be blown off by sudden depressurization when the operating pressure is above -650 psi (4,480 kPa). 

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Phosphorus is also important in the production of steels, phosphor bronze, and many other products. Trisodium phosphate is important as a cleaning agent, as a water softener, and for preventing boiler scale and corrosion of pipes and boiler tubes. 

In 1929, an international commission, the Commission Mixte Internationale pour les experiences relatives a la protection des lignes de telecommunication et des canalisations souterraines (C.M.I.), was enlarged and its scope extended for the purpose of making experimental studies concerning the corrosion of pipes and cables. The C.M.I. membership was composed of international technical experts from learned bodies, research laboratories and manufacturers of electrical equipment, and representatives of authori-... 

Highly viscous petroleum oil containing 30% to 80% water can be transported through pipes more efficiently when a 1 1 mixture of washing liquid and antifreeze (i.e., ethylene glycol with borax) is added to the oil in amounts of 0.002% to 0.2% by weight. In addition to increased efficiency of transport, reduced corrosion of pipes can be achieved [893]. 

Aluminum Pipe) A Heavy Wall Alclad Aluminum "Spool Piece" Will Avoid Galvanic Corrosion of Pipe... 

In contrast to the situation of a decade ago [3.1). a substantial literature has now accumulated on copper removal by activated carbons. This is not only because of metal recovery from acid mine wastes [176] and acidic corrosion of pipes [33] but also because of increasing industrial contamination of water streams [177-182]. In particular.many wastewaters contain complexing ions such as ethylenedi-aminetetraacetate (EDTA) and the removal of EDTA-chelated copper (and other) ions has been a special focus of attention [45,173,183-186]. 

Corrosion of pipes in boilers by oxygen can be alleviated through the use of sodium sulfite. Sodium sulfite removes oxygen firom boiler feedwater by the following reaction ... 

Chemicals are also deliberately added to water. In the treatment of wastewater, and more particularly in the treatment of drinking water, a variety of chemicals are added for purposes of disinfecting, clarifying, and preventing corrosion of pipes. Moreover, as water is distributed to consumers, the surfaces it contacts have the potential of contaminating the water. These surfaces may be the water mains and pipes in a municipal distribution system, or they may be the surface of a plastic bottle in which the water is purchased in a supermarket. 

Maximize Fmi, which is related to a ratio of FI, F4 and Dt. FI feed is high in sulfur that will form acid gas, which causes serious corrosion of pipes and extremely hazardous to people when inhaled. By optimizing this formula the unconverted oil of F4 and Dt will reduce the acidity in some way and make it feasible for the reaction to take place at the same time. 

Lead and copper ions in water pose health risks and contribnte to the corrosion of pipes and fittings, as does water that is at a high or low pH. Lead solder was banned from pipes in 1986, but much old plumbing still contains a mixture of 50 percent lead and 50 percent tin solder in joints. In plumbing systems having pipes and fittings of two different metals, corrosion may lead to the failnre of joints. 

Visual examination and the metal ion content of the water samples shows internal corrosion of pipe in various locations in the hot water distribution system that compromises the quality of hot water. The internal pipe corrosion is because of the following factors or a combination of the factors. 

Water cooling Corrosion of pipes Probably not completely Very small Fastest Higher rate of production. Not very good economy in long run. 

Active metal targets in electrolyte headers can intercept leakage currents and prevent corrosion of piping and equipment. Leakage can also be prevented at its source by installing current breakers that actually disrupt the continuous stream of liquid (Fig. 8.10). 

Hack, H. P., Galvanic Corrosion of Piping and Fitting Alloys in Sulfide-Modified Seawater, DTNSRDC/SME-79-31, May, 1979. 

Factors affecting the corrosion of pipe include soil resistivity, moisture content of the soil, pH, permeability of soil to moisture and air, soluble ion content of the soil, oxygen content, and the presence of corrosion-activating bacteria. 

Chloride 250mg/L Salty taste corrosion of pipes... 

Electricity is an ignition source ttiat can cause fires and explosions if equipment is installed or wired inadequately or if a static discharge occurs. Table 2-2 showed that electrical systems are the leading cause of fires. Improperly installed electrical systems may also cause accidental electrocution. Stray ciurents may result in corrosion of piping and equipment. 

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