Copper waters, corrosion

Calcium carbonate has normal pH and inverse temperature solubilities. Hence, such deposits readily form as pH and water temperature rise. Copper carbonate can form beneath deposit accumulations, producing a friable bluish-white corrosion product (Fig. 4.17). Beneath the carbonate, sparkling, ruby-red cuprous oxide crystals will often be found on copper alloys (Fig. 4.18). The cuprous oxide is friable, as these crystals are small and do not readily cling to one another or other surfaces (Fig. 4.19). If chloride concentrations are high, a white copper chloride corrosion product may be present beneath the cuprous oxide layer. However, experience shows that copper chloride accumulation is usually slight relative to other corrosion product masses in most natural waters. 

Obrecht, M. F., Sastor, W. E. and Keyes, J. M., Integrated Design of Field Test Panel Pilot Unit for Investigating Pitting Corrosion of Copper Water Tube by Potable Water Supplies , Proc. 4th Int. Congr. Met. Corr., 1969, 576 (1972)... 

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))...

Addition of about 0 04% arsenic will inhibit dezincification of a brasses in most circumstances and arsenical a brasses can be considered immune to dezincification for most practical purposes . There are conditions of exposure in which dezincification of these materials has been observed, e.g. when exposed outdoors well away from the sea , or when immersed in pure water at high temperature and pressure, but trouble of this type rarely arises in practice. In other conditions, e.g. in polluted sea-water, corrosion can occur with copper redeposition away from the site of initial attack, but this is not truly dezincification, which, by definition, requires the metallic copper to be produced in situ. The work of Lucey goes far in explaining the mechanism by which arsenic prevents dezincification in a brasses, but not in a-/3 brasses (see also Section 1.6). An interesting observation is that the presence of a small impurity content of magnesium will prevent arsenic in a brass from having its usual inhibiting effect . 

Tin will protect copper from corrosion by neutral water. Pure tin is anodic to copper, and protects discontinuities by sacrificial corrosion. Both intermetallic phases are strongly cathodic to copper, and corrosion is stimulated at gaps in wholly alloyed coatings. An adequate thickness of tin is needed for long service, e.g. 25-50 xm. Another diffusion problem occurs with tin-plated brass. Zinc passes very quickly to the tin surface, where under conditions of damp storage zinc corrosion products produce a film... 

Motojima, S., andKosaki, H., Resistivities Against Sea-Water Corrosion and Sea-Sand Abrasion of TiB2 Coated Copper Plates, J. Mater. Sci. Lett, 4(11) 1350-1352 (Nov., 1985)... 

Copper is softer and more ductile than steel and is utilized frequently in the manufacture of pipes and tubing. Copper has good corrosion resistance but will corrode in the presence of nitric acid and other mineral acids. Organic acids do not corrode copper as readily. Dry ammonia does not corrode copper, but the presence of water in ammonia and ammonium hydroxide will corrode copper. Copper resists corrosion in the presence of caustic solutions, but the addition of zinc will increase corrosion rates. Also carbonate, phosphate, and silicate salts of sodium will corrode copper. See FIGURE 9-1. 

Composition These copper alloys can contain from 10% to 30% nickel. They are excellent heat exchanger tubes because of their resistance to salt water corrosion at high temperatures. 

Alloys containing principally copper and tin are referred to as true bronzes. Tin increases hardness and wear resistance more than zinc. It also improves salt water corrosion resistance. Common uses of copper-tin bronze are described in TABLE 9-5. 

Copper and its alloys are extensively used in everyday life, typical uses being copper pipes for domestic water supply, and aesthetic applications such as artwork in the form of statues. The annual production of copper water tubing is approximately 500000 tonnes, equivalent to a length 1.25 billion metres. The attractive features of copper and its alloys are corrosion resistance, ease of fabrication and its potential for recycling. 

Flash point Water content Kinematic viscosit Distillation Copper strip corrosion Cetane index Density Color... 

The copper strip test methods are used to determine the corrosiveness to copper of diesel fuel and are a measure of the relative degree of corrosivity of diesel fuel. Most sulfur compounds in petroleum are removed during refining. However, some residual sulfur compounds can have a corroding action on various metals, and the effect is dependent on the types of sulfur compounds present. One method (ASTM D-130, IP 154) uses a polished copper strip immersed in a given quantity of sample and heated at a temperature for a time period characteristic of the material being tested. At the end of this period the copper strip is removed, washed, and compared with the copper strip corrosion standards (ASTM, 2000). This is a pass/fail test. In another method (ASTM D-849) a polished copper strip is immersed in 200 ml of specimen in a flask with a condenser and placed in boiling water for 30 min. At the end of this period, the copper strip is removed and compared with the ASTM copper strip corrosion standards. This is also a pass/fail test. 

The resistance of copper to corrosion renders copper particularly valuable for water tanks and pipes, cooking utensils, sheathing of ships, etc. It possesses many advantages over lead for the covering of domes and other outdoor structures. It was used in a temple frieze at A1 Ubaid (Plate 1), near the ancient city of Ur of the Chaldees, Abraham s reputed city, some 3000 to 4000 b.c., worked up from sheet copper, and has been used by numerous peoples for like purposes ever since. The dome of the Library of the British Museum, London, dating back to 1857, is the largest copper-covered dome in the world. St Paul s Cathedral is lead-covered Wren would have preferred copper, but his workmen appear to have been unequal to the task (p. 195). Copper possesses... 

In water, corrosion limits the use of aluminum to temperatures near 100°C, unless special precautions are taken. In air, corrosion limits its use to temperatures slightly over 300°C. Failure is caused by pitting of the otherwise protective Al(OH)3 film. The presence of chloride salts and of some other metals that form strong galvanic couples (for example, copper) can promote pitting. 

Fig. 1.10 Copper pitting corrosion in drinking water system (a) stereomicrography of perforated membrane and (b) scanning electron micrograph of perforated pit [28].

D.A. Lyde, M.N. Nadagouda, A comprehensive investigation of copper pitting corrosion in a drinking water distribution system, Corros. Sci. 52 (2010) 1927—1938. 

Uses Chelating agent, sequestrant for copper ions corrosion inhibitor for copper and copper alloys for use in antifreeze, cleaners, corrosion preventive coatings, detergents, functional fluids, hydraulic fluids, lubricants, metalworking fluids, polishes, pkg. materials, polymers, water circulating systems... 

Bai] Bailey, G.L., Copper-Nickel-Iron Alloys Resistant to Sea-Water Corrosion , J. Inst. Met., 79, 243-292 (1951) (Experimental, Magn. Prop., Meehan. Prop., Morphology, 22)... 

Copper exhibits a good corrosion resistance in air, as well as in hot and cold water, provided the flow velocity does not exceed a certain value (Chapter 10). The standard potential of copper is more noble than that of hydrogen. Therefore, in the absence of oxygen, copper resists corrosion even in acid environments. The potential-pH diagram of Figure 12.10 illustrates this behavior. 

C.2.2 4.9 g sodium cyanide (NaCN) Reagent water to make 1000 mL 1 to 3 min 20 to 25°C Removes copper sulfide corrosion products that may not be removed by hydrochloric acid treatment (C.2.1). 

Electrically separating one metal, which otherwise would be in direct contact with smother dissimilar metal, can prevent the adverse effects of bi-metallic corrosion. A typical example is the use of di-electric unions where copper water pipe is connected to the steel tank of a hot water heater. 

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