Copper—water system

Part I The Water and Copper Water Systems", Atomic Energy of Canada Ltd., Report AECL-4136 (1972). 

FIGURE 7.1 Pourbaix diagram of copper-water system (from Ref. 1). 

FIGURE 21.11 Potential-pH equilibrium for the copper-water system at 25 °C. [Considering the solid substances Cu, CU2O, and CuO Cu(OH)2 is not considered.] (from Ref. 23). 

The Pourbaix diagram for the copper/water system is shown in Fig. 2.15. The more positive standard electrode potential of copper (+337 mV (SHE)) as compared to iron (-440 mV (SHE)) is evident. This greater nobility results in copper being thermodynamically stable in water that is, line 14 (-6) representing aCu2+ = 10-6 lies above line a. 

A Pourbaix diagram for copper/water system is shown in Fig. 2.22. Copper (E° = 0.337 V) is more noble than iron ( p = —0.444V), however, it is more stable in water (SHE) than iron. Copper is not passive in acid electrolytes. The oxide of copper, Cu+ and Cu " " are only... 

Figure 2.22 Pourbaix diagram for the copper-water system at 25° C...

Wood preservatives ate appHed either from an oil system, such as creosote, petroleum solutions of pentachlorophenol, or copper naphthanate, or a water system. Oil treatments ate relatively inert with wood material, and thus, have Htde effect on mechanical properties. However, most oil treatments require simultaneous thermal treatments, which ate specifically limited in treating standards to preclude strength losses (24). 

Silt, sand, concrete chips, shells, and so on, foul many cooling water systems. These siliceous materials produce indirect attack by establishing oxygen concentration cells. Attack is usually general on steel, cast iron, and most copper alloys. Localized attack is almost always confined to strongly passivating metals such as stainless steels and aluminum alloys. 

Essentially all industrial metals are susceptible to SCC in some specific environment. Of the metals commonly used in cooling water systems, copper-based alloys and stainless steels are most frequently affected. Common specific corrodents causing SCC in these and other heat exchanger metals are listed in Table 9.1. 

Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L. 

The first partial chiral resolution reported in CCC dates from 1982 [120]. The separation of the two enantiomers of norephedrine was partially achieved, in almost 4 days, using (/ ,/ )-di-5-nonyltartrate as a chiral selector in the organic stationary phase. In 1984, the complete resolution of d,l-isoleucine was described, with N-dodecyl-L-proline as a selector in a two-phase buffered n-butanol/water system containing a copper (II) salt, in approximately 2 days [121]. A few partial resolutions of amino acids and dmg enantiomers with proteic selectors were also published [122, 123]. 

The metals most commonly used for water systems are iron and steel. These metals often have some sort of applied protective coating galvanised steel, for example, relies on a thin layer of zinc, which is anodic to the steel except at high temperatures. Many systems, however, contain a wide variety of other metals and the effect of various water constituents on these must be considered. The more usual are copper, brasses, bronzes, lead, aluminium, stainless steel and solder. 

Fig. 4.10 Potential-pH equilibrium for the system copper-water at 25°C (courtesy M. J. N. Pourbaix of Centre Beige d Etude de la Corrosion, after Delhez, R., Depommier, C. and van Muylder, J., Report RT 1(X), July (1962))...

The effect of pH on the corrosion of zinc has already been mentioned (p. 4.170). In the range of pH values from 5 -5 to 12, zinc is quite stable, and since most natural waters come within this range little difficulty is encountered in respect of pH. The pH does, however, affect the scale-forming properties of hard water (see Section 2.3 for a discussion of the Langelier index). If the pH is below the value at which the water is in equilibrium with calcium carbonate, the calcium carbonate will tend to dissolve rather than form a scale. The same effect is produced in the presence of considerable amounts of carbon dioxide, which also favours the dissolution of calcium carbonate. In addition, it is important to note that small amounts of metallic impurities (particularly copper) in the water can cause quite severe corrosion, and as little as 0-05 p.p.m. of copper in a domestic water system can be a source of considerable trouble with galvanised tanks and pipes. 

Platinised-titanium installations have now been in use for 30 years for jetties, ships and submarines and for internal protection, particularly of cooling-water systems . For the protection of heat exchangers an extruded anode of approximately 6 mm in diameter (copper-cored titanium-platinum) has shown a reduction in current requirement (together with improved longitudinal current spread) over cantilever anodes of some 30% . This continuous or coaxial anode is usually fitted around the water box periphery a few centimetres away from the tubeplate. 

Reagents. Dinuclear copper(ll) complex 4 was prepared as described earlier (20). Nanopure water was obtained from an EASYpure 11 water system by Bamstead (18.2 MD/cm). HPLC grade acetonitrile (99.93%) was purchased from... 

Figure 5.2 Potential (volts) - pH diagrams for metal (M)-water system (for metal (M) ion activity of 10-3 mol kg-1 at 25 °C (A) M = Zn, (B) M = copper, (C) M = gold. S stands for solubilization.

It is important to recognize some of the limitations of the Pourbaix diagrams. One factor which has an important bearing on the thermodynamics of metal ions in aqueous solutions is the presence of complex ions. For example, in ammoniacal solutions, nickel, cobalt, and copper are present as complex ions which are characterized by their different stabilities from hydrated ions. Thus, the potential-pH diagrams for simple metal-water systems are not directly applicable in these cases. The Pourbaix diagrams relate to 25 °C but, as is known, it is often necessary to implement operation at elevated temperatures to improve reaction rates, and at elevated temperatures used in practice the thermodynamic equilibria calculated at 25 °C are no longer valid. 

According to EPA s National Compliance Report for calendar year 1996 (EPA 1998g), the vast majority of people in the nation received water from systems that had no reported violations of the maximum contaminant level and treatment technique requirements or significant monitoring and reporting requirements. Lead has a maximum permissible level of 15 pg/L delivered to any user of a public water system. Lead and copper are regulated in a treatment technique that requires systems to take tap water samples at sites with lead pipes or copper pipes that have lead solder and/or are served by lead service lines. The water system is required to take treatment steps if the action level (15 pg/L for lead) is exceeded in more than 10% of tap water samples. For calendar year 1996, nearly 6 million people in the United States were served by community water systems that reported maximum contaminant level and treatment technique violations of the Lead and Copper Rule (EPA 1998g). 

This comprehensive survey of the title topic is in three parts, the first dealing with the theoretical background and laboratory studies, with 29 references. The second part, with 21 references deals with case histories and experimental studies of industrial vapour explosions. These involved the systems molten titanium-water, molten copper-water, molten aluminium-water, smelt-water, water-various cryogenic liquids, molten salt-water and molten uranium dioxide-liquid sodium. In the third part (with a further 26 references) is discussion of the various theories which abound, and the general conclusion that superheated liquids most likely play a major role in all these phenomena [1]. A further related publication covers BLEVEs and pressure let-down explosions [2],... 

B92004 Lead and Copper Monitoring Guidance for Water Systems Serving 101 to 500 Persons... 

F00009 Lead and Copper Rule Minor Revisions Fact Sheet for Public Water Systems That Serve More Than 50,000 Persons 816F00010 Lead and Copper Rule Minor Revisions Fact Sheet for Large System Owners and Operators [Draft]... 

R96001 Microscopic Particulate Analysis (MPA) for Filtration Plant Optimization 812B92007 Monitoring Requirements for Lead and Copper Rules Water Systems Serving 10,001 to 50,000 Persons... 

---