Metals admiralty

Antimony may be added to copper-base alloys such as naval brass. Admiralty Metal, and leaded Muntz metal in amounts of 0.02—0.10% to prevent dezincification. Additions of antimony to ductile iron in an amount of 50 ppm, preferably with some cerium, can make the graphite fliUy nodular to the center of thick castings and when added to gray cast iron in the amount of 0.05%, antimony acts as a powerflil carbide stabilizer with an improvement in both the wear resistance and thermal cycling properties (26) (see Carbides). 

Alloys. Tin is widely used as both a major and minor ingredient of alloy metals. These applications are summarized in Tables 1, 2, and 3. Phosphor bronzes (Table 3) actually contain very little phosphorus, ranging from 0.03 to 0.50%, and hence the alloys are poorly designated. Tin bronzes is the better term. High-silicon bronzes contain about 2.8% tin low-silicon bronzes about 2.0% tin. Gun metals are tin bronze casting alloys with a 5 10% zinc content. Some wrought copper-base alloys contain tin (1) Inhibited Admiralty metal, 1% fin (2) manganese bronze, 1% tin (3) naval brass, 0.75% tin, (4) leaded naval brass, 0.75% tin. See also Copper. 

It will also be possible by relatively minor piping changes to convert the forward-feed evaporator to backward feed, which might be more favorable if the calcium sulfate scale problem can be solved. Except for tubes, pump shaft sleeves, impellers, etc., the plant will be built exclusively of steel and cast iron. Tube materials will be evaluated by tubing different evaporator effects and heat exchangers with steel, admiralty metal, aluminum brass, and 90/10 cupronickel. The copper alloy tubes will be used exclusively in the final condenser and in the few heat exchangers that are in contact with nondeaerated sea water. 

Dezincification of a-brass can be minimized by adding 1% Sn, as in admiralty brass (71 Cu-28Zn-lSn, and further inhibited by adding less than 0.1% of arsenic),55 antimony, or phosphorus. Where dezincification is a problem, red brass, commercial bronze, inhibited admiralty metal, and inhibited brass can be successfully used. 

See admiralty metal aluminum brass red brass yellow brass Muntz metal. 

J.A. Beavers and E.N. Pugh, The Propagation of Transgranular Stress-Corrosion Cracks in Admiralty Metal,Metall. Trans., Vol 11A, 1980, p 809-820... 

The tubes were 0.902 in. ID and 1.000 in. OD, made of admiralty metal, for which /c = 63 Btu/ft-h- F. From these data calculate (a) the steam-film coefficient (based on steam-side area), (6) the water-film coefficient when the water velocity is I ft/s (based on water-side area), (c) value of for the scale in the fouled tube, assuming the clean tube was free of deposit. 

Larger water rates with a small t are normally prefmed also for direct cooling with river or sea water. Provided that the flow rate is kept within a relatively narrow range, carbon steel can still be used for sea water piping whereas the coolers themselves often require expensive alloys which are not always easy to handle, for instance admiralty metal or copper/nickel alloys. 

Yellow brass, 30% Zn—Cu, is used for a variety of applications where easy machining and casting are desirable. The alloy gradually dezincifies in seawater and in soft fresh waters. This tendency is retarded by addition of 1% Sn, the corresponding alloy being called admiralty metal or admiralty brass. Addition of small amounts of arsenic, antimony, or phosphorus stUl further retards the rate of dezincification the resulting alloy, called inhibited admiralty metal, is used in seawater or fresh-water condensers. 

For fresh waters, copper, Muntz metal, and admiralty metal (inhibited) are frequently used. For brackish or seawater, admiralty metal, one of the cupro-nickel alloys (10-30% Ni,bal. Cu) and aluminum brass (22% Zn,76% Cu,2% Al,0.04% As) are used. For polluted waters, cupro-nickel alloys are preferred over aluminum brass because the latter is subject to pitting attack. Aluminum brass may also pit readily in unpolluted, but stagnant, seawater. 

Aluminum brass resists high-velocity waters (impingement attack) better than does admiralty metal. Cupro-nickel alloys are especially resistant to high-velocity seawater when they contain small amounts of iron and sometimes manganese as well. For the 10% Ni cupro-nickel alloy, the optimum iron content is about 1.0-1.75%, with 0.75% Mn maximum for the analogous 30% Ni composition, the amount of alloyed iron is usually less (e.g., 0.40-0.70% Fe accompanied by 1.0% Mn maximum) [46]. It is found that supplementary protective films are formed on condenser tube surfaces when iron is contained in water as a result of corrosion products upstream or when added intentionally as ferrous salts. Accordingly, the beneficial effect of iron alloyed with copper-nickel alloys is considered to result from similar availability of iron in the formation of protective films. 

Tin additions significantly increase the corrosion resistance of some brasses, especially dezincification. Uninhibited Admiralty metal is a variation of Cartridge brass (alloy C26000), which is produced by the addition of 1 % tin to... 

The addition of arsenic, antimony, or phosphorus (typically 0.05 %) to Admiralty metal. Naval brass or aluminum brass produces high resistance to dezincification and SCC. 

There were also unique corrosion problems associated with foam cleaning by using air as the gas phase. When air was used, a cyclical type corrosion process could occur. In the presence of an iron oxide deposit and an acidic foam, the ferric ion would spend on base metal to become reduced to the ferrous ion. Exposure to the oxidant air, present as the gaseous phase of foam, regenerated the ferrous ion to the ferric ion and the corrosion process was repeated. If recycle of the foam cleaning was attempted, the corrosion could become quite severe. The same type of cyclical process could occur in the presence of cupric copper. Cupric copper would reduce on admiralty metal and form the cuprous ion. In the presence of air, the cuprous would be regenerated into the cupric ion for a repetition of the corrosion process. Equations (4)-(7) show the corrosive processes. 

The cooler consists of a rectangular vertical sheU, 0.75 m wide, fitted with 400 Admiralty Metal tubes, 19.05 mm OD, 1.65 mm wall thickness, 3.75 m long, on equilateral-triangular centers 38 mm apart. The tubes are arranged in horizontal rows of 20 tubes throu which the oil flows in parallel, in stacks 10 tubes tall, as in Fig. 7.21 h. Cooling water will be recycled at the rate 10 kg/s. The design air rate is to be 2.3 kg dry air/s, entering at 30 C dry-bulb temperature, standard atmospheric pressure, humidity 0.01 kg H O/kg dry air. 

The term sour water denotes various types of process water containing H2S,NH3HCN, and small amounts of phenols, mercaptanes, chlorides, and fluorides. High concentrations of ammonia can saturate process water with ammonium bisulfide (NH HS) and canses serious corrosion of carbon steel components. Ammonium bisulfide will also rapidly attack admiralty metal (C44300) tubes. Only titanium Grade 2 (R50400) tubes have sufficient resistance to be used in this case. 

Ammonia has caused two types of SCC in refineries and petrochemical plants. The first is cracking of carbon steel in anhydrous ammonia service, and the second type is cracking of copper alloys, such as admiralty metal (C 44300). In copper alloys, SCC can occur with ammonia-base neutralizers that are added to control corrosion. 

Cracking of admiralty metal (C 44300) heat-exchanger tubes has been a recurring problem in a number of refining units and petrochemical process units. For example, ammonia is often used to neutralize acidic constituents, such as hydrogen chloride or sulfur dioxide, in overhead systems of crude distillation or alkylation units, respectively. Stripped sour water containing residual ammonia is used as desalter water at some crude distillation units. This practice causes ammonia contamination of the overhead system even if no ammonia is added intentionally. 

Dezincification can be minimized by reducing the aggressiveness of the environment (i.e. oxygen removal) or by cathodic protection, but in most cases these methods are not economical. UsnaUy a less susceptible alloy is used. For example, red brass (15% Zn) is almost immune. Better brass is made by addition of 1% tin to a 70-30 brass (Admiralty metal). Further improvement is obtained by adding small amounts of arsenic, antimony or phosphorus as inhibitors. ... 

P. Condensers may require Monel-metal shells or lining, but admiralty metal is usually satisfactory for tubes. 

Admiralty metal or other copper-base alloys. 21.7 68.8 82.4 1.2... 

Ammonia is unsuitable as a neutralizer if copper-base alloys are used, because if used in excess it may destroy the metal faster than acid corrosion. The other neutralizers appear to produce protective films so that corrosion halts after an initial action. If scale-forming water is used, admiralty-metal tubes must be cleaned frequently, because corrosion occurs mainly beneath breaks or porous spots in the scale. The zinc in the brass is dissolved and is replaced by spongy copper. ... 

Carbon-steel tubes and cast-iron shells are least expensive, but high-sulfur crude oils may justify the use of 5 per cent chromium or even 18-8-chrome nickel tubes" particularly in cracking service. Refer to Chap. 9, pages 276 to 284. For the acid corrosion produced by salt brine, admiralty metal or occasionally cupronickel tubes are justified. Ammonia is often used as a neutralizer for acid corrosion, and it attacks admiralty metal so rapidly that admiralty metal cannot be used for such a situation. The mechanical properties of this alloy are also impaired by temperatures above 500°F, although under favorable conditions it can be used up to tube-wall temperatures of 600 F. Recommendations are as follows ... 

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