Copper in sea-water

Bianchi and Longhi (53) Potential -pH diagram (25°C) for copper in sea water activity coefficient corrections included. 

M. C. Yebra and A. Moreno-Cid, Optimisation of a field flow preconcentration system by experimental design for the determination of copper in sea water by flow-injection-atomic absorption spectrometry, Spectrochim. Acta, Part B, 57(1), 2002, 85-93. 

Adsorptive stripping voltammetry (ASV) is another specialised technique where the SMDE electrode is used for reducible species and carbon paste electrodes for oxidisable ones. This allows enrichment (by factors of 100-1000) of ions at the working electrode before stripping them off for measurement this improves the detection limits. This technique is rapid, sensitive (10 "M), economical and simple for trace analysis. The basic instrumentation for stripping analysis is apotentiostat (with voltammetric analyser), electrode and recorder. While voltammetry is generally very useful for compounds that do not have a chromophore or fluorophore, stripping analysis is the best analytical tool for direct, simultaneous determination of metals of environmental concern, e.g. lead, cadmium, zinc and copper in sea water. 

Batley, G.E. and Florence, T.M., 1976a. Determination of the chemical forms of dissolved cadmium, lead and copper, in sea water. Mar. Chem., 4 347—363. 

Yuan et al.[lS] used an on-line dual column preconcentration system with FAAS detection to determine copper in sea water. The quinolin-8-ol copper complex was sorbed on columns packed with Cig sorbent and eluted by methanol... 

Bianchi, G., and Longhi, P, Copper in Sea-Water, Potential-pH Diagrams, Corrosion Science, 13 853-864 (1973). 

Many shell-and-tube condensers use copper alloy tubes, such as admiralty brasses (those containing small concentrations of arsenic, phosphorus, or antimony are called inhibited grades), aluminum brasses, and cupronickel austenitic stainless steel and titanium are also often used. Utility surface condensers have used and continue to use these alloys routinely. Titanium is gaining wider acceptance for use in sea water and severe service environments but often is rejected based on perceived economic disadvantages. 

This form of attack, especially as affecting copper alloys in sea water, has been widely studied since the pioneer work of Bengough and May . Impingement attack of sea water pipe and heat exchanger systems is considered in Sections 1.6 and 4.2. In such engineering systems the water flow is invariably turbulent and the thickness of the laminar boundary layer is an important factor in controlling localised corrosion. 

Contact of brass, bronze, copper or the more resistant stainless steels with the 13% Cr steels in sea-water can lead to accelerated corrosion of the latter. Galvanic contact effects on metals coupled to the austenitic types are only slight with brass, bronze and copper, but with cadmium, zinc, aluminium and magnesium alloys, insulation or protective measures are necessary to avoid serious attack on the non-ferrous material. Mild steel and the 13% chromium types are also liable to accelerated attack from contact with the chromium-nickel grades. The austenitic materials do not themselves suffer anodic attack in sea-water from contact with any of the usual materials of construction. 

The copper-bearing aluminium alloys are more noble than most other aluminium alloys and can accelerate attack on these, notably in sea-water. Mercury and all the precious metals are harmful to aluminium. 

There are several distinctive types of corrosion that copper and copper alloys may suffer, particularly in sea-water, but also on occasion in fresh waters. The more important of these are discussed briefly below. 

The rate of corrosion and damage caused to the more negative metal will depend upon the relative sizes of the anodic (corroding metal) and cathodic areas. A small anode and a large cathode will result in intensive corrosion of the anodic area. On the other hand, if the anode is large compared with the cathode, the corrosion of the anodic area will be more general and less likely to result in rapid failure. For example, a steel rivet in a copper plate will be rapidly attacked in sea-water, whereas a copper rivet in a steel plate may lead only to slightly accelerated corrosion of the steel in the area adjacent to the rivet. Prediction of the rate of corrosion of the less noble metal... 

Wooden racks used in sea-water tests are likely to be subject to severe damage by marine borers. The wood used, therefore, must be treated with an effective preservative, for example creosote applied under pressure, if the test is to extend for several years. Organic copper compound preservatives may suffice for shorter tests, for example 2 or 3 years. Since the leaching of such preservatives may have some effects on corrosion, metal racks fitted with porcelain or plastics insulators have an advantage over wooden racks. 

Yamamoto et al. [33] applied this technique to the determination of arsenic (III), arsenic (V), antimony (III), and antimony (V) in Hiroshima Bay Water. These workers used a HGA-A spectrometric method with hydrogen-nitrogen flame using sodium borohydride solution as a reductant. For the determination of arsenic (III) and antimony (III) most of the elements, other than silver (I), copper (II), tin (II), selenium (IV), and tellurium (IV), do not interfere in at least 30 000-fold excess with respect to arsenic (III) or antimony (III). This method was applied to the determination of these species in sea water and it was found that a sample size of only 100 ml is enough to determine them with a precision of 1.5-2.5%. Analytical results for surface sea water of Hiroshima Bay were 0.72 xg/l, 0.27 xg/l, and 0.22 xg/l, for arsenic (total), arsenic (III), and antimony (total), respectively, but antimony (III) was not detected. The effect of acidification on storage was also examined. 

Bruland, K. W., Franks, R. P., Knauer, G. A. and Martin, J. H. (1979). Sampling and analytical methods for the determination of copper, cadmium, zinc and nickel at the nanogram per liter level in sea water, Anal. Chim. Acta, 105, 233-245. 

Table 1 Comparison between the new, unified ASTM and ISO standard test methods for copper release rates of AF coating systems in sea water (to be implemented during 2005 Arias, personal communication). The description of the original procedures (ASTM D6442-99 and ISO/DIS 15181-1,2) can be found in Arias (1999) and Haslbeck and Holm (2005).

Composition 70% copper, 29% zinc, 1% tin, and 0.03% arsenic. It has good corrosion resistance, especially in sea water. Arsenic inhibits the loss of zinc from the alloy. It is used for tubing applications in condensers, preheaters, evaporators, and heat exchangers which contact salt water, oil, steam, and other liquids below 500°F (260°C). 

Contact Mines were generally spherical, with several lead, steel horns screwed into the mine case. Horns were of several types but the most common was a lead chemical horn, such as described above under Type JE Antiboat Land Mine. Some contact mines had a long copper wire antenna extending out of the top or bottom of the case. Should a steel ship touch the antenna while both were immersed in sea water, the mine would explode. Moored contact mines usually had some type of safety mechanism to render them inactive if they borke adrift, as well as devices to make sure the mines were safe while aboard the mine-laying ship, submarine, or plane (p 34) ... 

The history of the iodides dates from the time of J. L. Gay Lussac s discovery 1 of hydriodic acid in 1813. Iodides occur in sea-water, and in the waters of many natural springs and brines. Iodides also occur in varec in the nitre beds of South America and in many natural phosphates. In whatever form iodine occurs in these substances, it is usual to extract this element as iodine, and subsequently to convert this into the iodide—generally potassium iodide. Potassium iodide is used in analytical and photographical work, and medicinally for the treatment of scrofulous, rheumatic, and syphilitic diseases. Sodium iodide is used as a precipitant for gold and silver in the treatment of weak copper ores from Tharsis, etc. 

Some metals depend on formation of a protective film for corrosion resistance in sea water. A fresh supply of oxygen brought to the surface of the metal tends to promote the corrosion reaction in some cases, and in others it helps form desired protective films. If a critical velocity of flowing sea water is exceeded, the film may be eroded away. The velocity for useful corrosion resistance is low for copper, higher for aluminum, cupro-nickels, and aluminum bronzes, and highest for stainless steels, Hastelloy C, and titanium. 

Aluminum and Aluminum Alloys. Aluminum can be employed in sea water as a resistant material of construction. Experiments at Fort Bel voir, Virginia, and elsewhere, indicate that by proper corrosion-control practices, aluminum can be used for an entire plant which processes sea water. The sea water entering the plant should be free of all metallic ions, especially copper or nickel. It is essential, in such a plant, that no copper-base alloys be used at all and that galvanic couples to most other metals be avoided. 

Stainless steel generally withstands polluted sea water and polluted brackish water better than copper-base alloys. Substituting an austenitic stainless screen for silicon-bronze trash racks has resulted in greatly improved service at a west coast power plant. Normally stainless steel screens, because of the crevices involved (where the wires cross), are not recommended for use in sea water. This alteration of the usual corrosion mechanism, presumably related to the hydrogen sulfide content of polluted sea water, needs to be studied. 

Copper-Base Alloys. There is a wide range of copper-base alloys that have given good service in sea water. Admiralty brass, 70 Cu-29 Zn-1 Sn, plus an inhibitor such as arsenic, has found wide use as condenser tubes in marine-based plants using sea water for cooling. While it is not so resistant as the cupro-nickels, it often seems to be preferred because of the lower initial cost. 

A large number of copper-base and nickel-base alloys (such as cupro-nickels, Monel, and aluminum brass) have been used in sea-water service with success. Special materials such as Hastelloy C, Illium, and titanium are available for extremely corrosive situations. The evidence, so far, indicates titanium to be outstanding and to rank above other commercially available metals in corrosion resistance under conditions involving high temperature, velocity, and other adverse environmental conditions. 

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