Beryllium corrosion resistant alloys

Beryllium Beryllium was first detected in 1798 in the gemstones beryl and emerald (BesA SigOis) and was subsequently prepared in pure form in 1828 by the reduction of BeCl2 with potassium. It is obtained today from large commercial deposits of beryl in Brazil and southern Africa. Though beryllium compounds are extremely toxic, particularly when inhaled as dust, the metal is nevertheless useful in forming alloys. Addition of a few percent beryllium to copper or nickel results in hard, corrosion-resistant alloys that are used in airplane engines and precision instruments. 

Many of the alloys of copper are more resistant to corrosion than is copper itself, owing to the incorporation either of relatively corrosion-resistant metals such as nickel or tin, or of metals such as aluminium or beryllium that would be expected to assist in the formation of protective oxide films. Several of the copper alloys are liable to undergo a selective type of corrosion in certain circumstances, the most notable example being the dezincification of brasses. Some alloys again are liable to suffer stress corrosion by the combined effects of internal or applied stresses and the corrosive effects of certain specific environments. The most widely known example of this is the season cracking of brasses. In general brasses are the least corrosion-resistant of the commonly used copper-base alloys. 

Aluminum and silicon bronzes are very popular in the process industries because they combine good strength with corrosion resistance. Copper-beryllium alloys offer the greatest strength and excellent corrosion resistance in seawater and are resistant to stress-corrosion cracking in hydrogen sulfide. 

The most important part of the gauge is the Bourdon tube. Bourdon tubes are made of many materials beryllium copper, phosphor bronze, and various alloys of steel and stainless steel [7]. Beryllium copper is typically used for high pressure applications. Most gauges in air, light oil, or water applications use phosphor bronze. Stainless steel alloys usually add cost to the gauge if specific corrosion resistance is not required. 

Some copper-rich alloys containing no tin are also called bronzes. Aluminum bronzes, for example, with up to 10% aluminum, are strong, resistant to corrosion and wear, and can be worked cold or hot silicon bronzes, with 1-5% silicon, have high corrosion-resistance beryllium bronzes, with about 2% beryllium, are very hard and strong. 

Magnesium corrosion resistance is typically considered to be good in dry air to about 400°C and to about 350°C in moist air. Magnesium with small alloy additions of zirconium or beryllium has been used in gas cooled nuclear reactors in England and France where operating temjjeratures exceed 350°C. These alloys are reported to have adequate corrosion resistance in wet CO2 and wet air at temperatures to 500°C [4,45]. 

For any corrosion reaction to proceed, copper ions and electrons must migrate through the CU2O film. Reducing the ionic or electronic conductivity of this film by doping the alloy with divalent or trivalent cations further improves corrosion resistance. In practice, alloying additions of aluminum, zinc, tin, iron, beryllium, and nickel are used to dope the corrosion product films, which lead to significant corrosion rate reduction. 

Operation of a nuclear power plant. Heat generation takes place in the reactor core of a nuclear plant (Figure 23.14). The core contains the fuel rods, which consist of fuel enclosed in tubes of a corrosion-resistant zirconinm alloy. The fuel is uranium(lV) oxide (UO2) that has been enriched from 0.7% the natural abundance of this fissionable isotope, to the 3% to 4% reqnired to snstain a chain reaction in a practical volume. (Enrichment of nuclear fuel is the most important application of Graham s law, see Section 5.5.) Sandwiched between the fuel rods are movable control rods made of cadmium or boron (or, in nnclear snbmarines, hafninm), substances that absorb neutrons very efficiently. When the control rods are lowered between the fuel rods, the chain reaction slows because fewer neutrons are available to bombard uranium atoms when they are raised, the chain reaction speeds up. Neutrons that leave the fuel-rod assembly collide with a reflector, usually made of a beryllium alloy, which absorbs very few neutrons. Reflecting the neutrons back to the fuel rods speeds the chain reaction. 

IV. 12% Cr 400 series steels, pH corrosion-resistant steels, 18% Cr 400 series steels, chromium, brass, bronze, copper, beryllium copper, aluminum, bronze alloys, 300 series stainless steels. Monel, Inconel, nickel alloys, titanium alloys... 

In dilute uranyl sulfate solutions the addition of sulfate salts also reduces the corrosion of stainless steel, but at temperatures of 250°C and higher the solutions are chemically unstable and complex hydrolytic precipitates form. At lower uranyl sulfate concentrations (0.04 to 0.17 m) the solutions demonstrating the greatest stability are those containing beryllium sulfate, and of the three sulfates most investigated, the least stable of the solutions were those with lithium sulfate. Sulfuric acid can be included in such solutions to prevent precipitation, but in so doing some of the effectiveness of the sulfate salt is lost. Howe cr, addition of both lithium. sulfate and sulfuric acid to dilute uranyl sulfate solutions has been found to result in improved corrosion resistance of zirconium alloys on in-pile exposure [35]. 

In many cases, the chemical composition of the surface of an alloy differs from that of the bulk composition. For example, the surface of a silver-2% beryllium alloy is enriched in beryllium during solidification. This beryllium then forms a coherent oxide, providing the alloy with corrosion resistance. 

Beryllium is obtained by electrolytic reduction of molten beryllium chloride. The element s low density makes it useful for the construction of missiles and satellites. Beryllium is also used as windows for x-ray tubes because Be atoms have so few electrons, thin sheets of the metal are transparent to x-rays and allow the rays to escape. Beryllium is added in small amounts to copper the small Be atoms pin the Cu atoms together in an interstitial alloy that is more rigid than pure copper but still conducts electricity well. These hard, electrically conducting alloys are formed into nonsparking tools for use in oil refineries and grain elevators, where there is a risk of explosion. Beryllium-copper alloys are also used in the electronics industry to form tiny nonmagnetic parts and contacts that resist deformation and corrosion. 

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