Brass zinc content

Charging Smoke particulates, oil mist Low-zinc-content red brass use of... 

Pouring Zinc oxide fume, lead oxide fume cover high-zinc-content brass use of good combustion controls, local exhaust system, and baghouse or... 

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. 

However, whilst the effects of change in alloy composition upon stress-corrosion cracking susceptibility in the present context may be partly due to their effect upon stacking-fault energy, this does not constitute a complete explanation, since alloying may have significant effects upon electrochemical parameters. The effect of the zinc content of brasses upon their filming characteristics has already been mentioned, while in more recent... 

Form of corrosion of brasses whereby the zinc is selectively leached out of the brass. Prevented by either reducing the zinc content to below 15% or by the addition of trace amounts of inhibiting elements, such as arsenic (As). 

Let us first consider, as an example, the copper-zinc system of alloys.1 The ordinary yellow brass of commerce is restricted in composition to the first (copper-rich) phase of the system. This phase, which has the face-centered cubic structure characteristic of copper, is followed successively, as the zinc content is increased, by the /3-phase (body-centered cubic),... 

Figure 6.5 Zinc content of European brass jettons with more than 20% Zn, ca. AD 1400-1850.

Figure 6.8 Summary of the maximum zinc content of European brass scientific instruments (ca. AD 1400-1800), classified by country of origin. (Redrawn from Pollard, 1983b, and Mortimer, 1989 Figure 1 by permission of Elsevier Science and the author.)...

Figure 6.9 Zinc content of English monumental brasses, ca. AD 1250-1700. (Redrawn from Cameron, 1974 Figure 3, by permission of the Royal Archaeological Institute).

Copper-zinc alloys with a higher zinc content (brass) cannot be ground or formed into flake pigments on account of their brittleness. Controlled oxidation of natural bronze powders converts them into fired bronze powders. These shades (e.g., English green, lemon, ducat gold, fire red) are produced as a result of interference effects that depend on the thickness of the oxide coating. 

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. 

Tarnishing is enhanced if the electrochemical potential is increased either by oxidizing species other than oxygen in the solution or by an externally applied potential the rate is decreased if the potential is decreased. The rate of formation and final thickness of the tarnish increases with an increase in the zinc content of the brass, an increase in the complex-ion concentration in the solution and an increase in temperature. The effect of the zinc concentration in the alloy has been attributed to the selective depletion of zinc at the surface, creating a surface with enhanced reactivity for the formation of Cu20. The selective depletion of zinc is readily related to the greater electrochemical activity of zinc relative to copper, but is confined to a few atom layers at the surface because of the slow rate of solid-state diffusion at practical service temperatures (Ref 146). The effect of the zinc content of the brass also has been attributed to the reaction (Ref 142, 147) ... 

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