16593 17 tủ tài liệu bách khoa
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16593 17 tủ tài liệu bách khoa
_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoar Resources DivisionCincinnati, OhioCorrosion is one of the most important problems in the drinking waler industry-. It can affect public health, public acceptance of a water supply, and the cost of providing safe water. Deterioration of materials resulting from corrosion can necessitate huge yearly 16593 17 tủ tài liệu bách khoa expenditures of resources for repairs, replacement, and system. Many times the problem is not given the attention it needs until expensive changes or16593 17 tủ tài liệu bách khoa
repairs are required.Corrosion tends to increase the concentrations of certain metals in tap water. Two potentially toxic metals (lead and cadmium) a_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoate, or both. Low levels of tin and antimony can be caused by the corrosion of lead-free solders (Henera, Ferguson, and Benjamin, 1982: Subramanian.Connor, and Mcranger. 1991:Subramanian. Sastri, and Connor. 1994). Nickel has sometimes been mentioned as a potential contaminant from the plating of dec 16593 17 tủ tài liệu bách khoaorative plumbing fixtures. The promulgation of the Lead and Copper Rule by the U.S. Environmental Protection Agency (USEPA) in 1991 has created an emp16593 17 tủ tài liệu bách khoa
hasis on corrosion control in distribution systems, as well as domestic, public, and institutional plumbing systems (Federal Register, I991a,b, 1994a)_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoa Chapter 18). These organisms can reproduce and cause problems such as had tastes, odors, slimes, and additional corrosion Several researchers have recently promoted corrosion control within the distribution system as an effective way to maintain water quality and adequate disinfection (Rompré et al 16593 17 tủ tài liệu bách khoa.. 1996; Schreppel. Frederickson, and Gciss. 1997; Camper. 1997; Kiene. Lu. and Levy. 1996; Norton et al.. 1995; Olson. 1996).17.10CHAPTER SEVENTEENw.16593 17 tủ tài liệu bách khoa
*-<-ShdOite*fp«*eftc I*J-Wonjna pr.< surface -—Topoindc lar*F eCO, Siđenee reO, Maeo Oxide c Graph*ReducedFeCOj sterileFeố RyrmoBtoFe,(POt)r • 8HjO Va_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoađocrocnaCasiMDfl PC*FIGURE 172 Schematic of scale on a cast-iron distribution pipe, showing complex layered structure. < Staffer; internal (.or nưũm of Water Distribution Systems. 2nd cd . American Waler Wot ks Association Research I oundation, Denver.co. IW6.)adherability, and permeability IO oxida 16593 17 tủ tài liệu bách khoants can vary depending upon such factors as trace impurities, presence of certain organics, temperature of deposition, length of time of formation, an16593 17 tủ tài liệu bách khoa
d so forth.Scales that form on pipes may have deleterious effects in addition to the beneficial effect of protecting the metal from rapid corrosion or_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoasible, because as bulk of scale increases, the capacity of the main to carry water is reduced. The formation of uneven deposits such as tubercles increases the roughness of the pipe surface, reducing the ability of the mains to carry water, and may provide shelters for the growth of microorganisms.T 16593 17 tủ tài liệu bách khoao properly interpret field and laboratory' data from corrosion control studies, it is important to understand that there may be significantly differen16593 17 tủ tài liệu bách khoa
t reactions occurring between the water constituents and the surfaces of “new” pi|)es compared with ’’old" pipes. Conceptually, this is illustrated in_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoapment of a passivating film. Once the film is sufficient!V developed [Figure 173(0)]. the oxidants in the water no longer can directly contact the metal of the pipe material itself.Therefore, the oxidation step will not occur, and metal release will become a function of the physical adherence or the 16593 17 tủ tài liệu bách khoa solubility of the surface deposit, unless water conditions become anoxic and the metal(s) in the surface deposit become electrochemically reduced Thu16593 17 tủ tài liệu bách khoa
s, corrosion inhibitor chemicals that stifle reactions occurring al cathodic surface sites may appear much better in tests using new metal surfaces th_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water 16593 17 tủ tài liệu bách khoaent, the solubility and surface sorption chemistry of the existingI 111- avan Fa»-a ♦ tV I r-s 1-1 1tva >« ■-> 44«• 4 117100CHAPTER SEVENTEENCorrosion of Water Distribution Systems, pp 317—116. Denver. CO: AWWA Research Foun-dation/DVGW Forschungsstellc. 1985.De if eyes. K. s. "Carbonate equilibria: 16593 17 tủ tài liệu bách khoa A graphic and algebraic approach.’' LimnoL Oceanogr., 10,1965:412-426.de Mora, s. J., and R. M. Harrison,“l-cad in tap water Contamination and chemis16593 17 tủ tài liệu bách khoa
try.’' Chem. Hritain. 10. 1984:901-90«'de Mora. s. J.. R. M. Harrison, and s. J. Wilson.'‘Hie effect of water treatment on the speciation and concentr_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and Water_______CHAPTER 17______INTERNAL CORROSION AND DEPOSITION CONTROL1Michael R. Schock, ChemistU.S. Environmental Protection Agency Water Supply and WaterGọi ngay
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