SUBJECTS brass

In unalloyed steel containers formamide discolors slowly during shipment and storage. Both copper and brass are also subject to corrosion, particularly in the presence of water. Lead is less readily attacked. Aluminum and stainless steel are resistant to attack by formamide and should be used for shipping and storage containers where the color of the product is important or when metallic impurities must be minimized. Formamide attacks natural mbber but not neoprene. As a result of the solvent action of formamide, most protective paints and finishes are unsatisfactory when in contact with formamide. Therefore, formamide is best shipped in containers made of stainless steel or in dmms made of, or coated with, polyethylene. Formamide supphed by BASF is packed in Lupolen dmms (230 kg) or Lupolen canisters (60 kg) both in continental Europe and overseas. 

Brasses with up to 15 percent Zn are ductile but difficult to machine. Machinability improves with increasing zinc up to 36 percent Zn. Brasses with less than 20 percent Zn have corrosion resistance eqmvalent to that of copper but with better tensile strengths. Brasses with 20 to 40 percent Zn have lower corrosion resistance and are subject to dezincincation and stress-corrosion cracking, especially when ammonia is present. 

Liquids may break down if exposed to air, water, salt, or other impurities, especially if they are in constant motion or subjected to heat. Some metals, such as zinc, lead, brass, and copper, have undesirable chemical reactions with certain liquids. 

Dezincification is readily apparent, since the yellow colour of the brass is replaced by the characteristic red of copper, which may take the form of small plugs or of layers that in some cases can extend over the whole of the surface (Fig. 1.60). In plug-type dezincification a mechanically weak, porous residue of copper is produced, which may remain in situ or become removed by the pressure of water, leading to a perforation. In the layer type the transformation of the alloy into a mechanically weak layer of copper results in loss of strength, and failure may occur by splitting when the metal is subjected to water pressure or to external stress. 

This example of aluminium illustrates the importance of the protective him, and hlms that are hard, dense and adherent will provide better protection than those that are loosely adherent or that are brittle and therefore crack and spall when the metal is subjected to stress. The ability of the metal to reform a protective him is highly important and metals like titanium and tantalum that are readily passivated are more resistant to erosion-corrosion than copper, brass, lead and some of the stainless steels. There is some evidence that the hardness of a metal is a signihcant factor in resistance to erosion-corrosion, but since alloying to increase hardness will also affect the chemical properties of the alloy it is difficult to separate these two factors. Thus althou copper is highly susceptible to impingement attack its resistance increases with increase in zinc content, with a corresponding increase in hardness. However, the increase in resistance to attack is due to the formation of a more protective him rather than to an increase in hardness. 

This type of corrosion is liable to occur in any part of a boiler where silt, muds, scales, precipitants, or foulants exist and is by no means limited to ferrous metals. Stainless steels, brasses, and cupronickels are all subject to under-deposit corrosion and deep pitting. 

The ammonia production is less than in hydrazine, but there may be a perceived of copper and brass corrosion. In fact, any corrosion risk is small, provided that DEHA-treated boiler plants are subjected to the same requirements as hydrazine-treated units, namely, ensuring that all in-leakage of oxygen in the condensate system is fully eliminated. If this objective is achieved, the oxidation of cuprous oxide to cupric oxide tends not occur to any significant degree, and the susceptibility for copper corrosion in the presence of ammonia is equally low. 

In principle, one can carry out a four-dimensional optimization in which the four parameters are varied subject to constraints (< 1 and P4 < 1 ), to minimize the deposition time with the non-uniformity bounded e.g., MN < 3. However, objective function evaluations involve solutions of the Navier-Stokes and species balance equations and are computationally expensive. Instead, Brass and Lee carry out successive unidirectional optimizations, which show the key trends and lead to excellent designs. A summary of the observed trends is shown in Table 10.4-1. Both the deposition rate and the non-uniformity are monotonic functions of the geometric parameters within the bounds considered, with the exception that the non-uniformity goes through a minimum at optimal values of P3 and P4. 

Alloy deposition is almost as old an art and/or science as is the electrodeposition of individual metals. (Brass deposition, for instance, was invented circa 1840 ) In the last analysis, as can well be expected, alloy deposition is subject to the same scientific principles as individual metal plating. Indeed, progress in either of the two has almost always depended on similar advances in electrodeposition science and/or technology. 

The invention of percussion compositions for igniting powders is usually attributed to Forsyth [5]. In 1805 he employed pellets composed of a mixture of potassium chlorate and combustible materials, coated with wax to render them safer to handle, but even so they were still dangerous since the mixture was sensitive to friction. The first ignition caps were invented in the early nineteenth century. In these caps the ignitable composition was enclosed in a casing of brass or copper. This invention cannot be traced with any certainty to any individual. The literature on the subject names several chemists including Bellot and Egg in 1815 [5]. 

RDX, Compns A B, PETN, Pentolite, Tetry-tol, Haleite andEdnatol) in contact with strips of Cu, brass or mild steel plated with Cu, at atmospheric temp or at 50°, had very little effect on metals, provided all the components were dry. Some tarnishing and corrosion of metal took place with some expls. More detailed info on this subject may be found in Addnl Ref E] E) O.E. Sheffield, PATR 1783 (1950), "Effects of Materials on the Properties of Explosives (Action of many expls, proplnts and pyrotechnic compns on various substances, including Cu, its alloys brass bronze and Cu-plated steel was investigated and tabulated. Results of investigations shown in this very extensive report are essentially the same as mentioned in Addnl Ref D) F) S. Kinoshita T. Sakamaki, Japan P 2498 (1953) CA 48, 6700 (1954) [Electric detonator compns, such as ... 

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