Titanium corrosion resistant alloys

Use Hardener for platinum and palladinum in jewelry, electrical contact alloys, catalyst, medical instruments, corrosion-resistant alloys, electrodeposited coatings, nitrogen-fixing agent (experimental), solar cells (experimental) the oxide is used to coat titanium anodes in electrolytic production of chloride the dioxide serves as an oxidizer in photolysis of hydrogen sulfide. 

Corrosion-resistant alloys are used where corrosive conditions are severe enough to prohibit the corrosion prone carbon steels and where protective coatings provide insufficient protection or are economically not good enough. The total cost for these alloys used in corrosion control applications is 8.3 billion with 7.9 billion for stainless steels, 0.28 billion for nickel-based alloys, and 0.15 billion for titanium alloys. 

Filiform corrosion is observed under thin organic coatings (typically 0.1 mm) on aluminum and steel exposed to a humid atmosphere. It has been observed in aircraft structures, beverage cans, flanges, gaskets, and weld zones [111—113]. Corrosion-resistant alloys of stainless steel, copper, and titanium are not susceptible to fihform corrosion. Metals with thin organic coatings are in contact with water from the humid atmosphere. 

Description and corrosion resistance. Alloy K-500 is a nickel-copper alloy, precipitation hardenable through additions of aluminum and titanium. Alloy K-500... 

Nickel—Copper. In the soHd state, nickel and copper form a continuous soHd solution. The nickel-rich, nickel—copper alloys are characterized by a good compromise of strength and ductihty and are resistant to corrosion and stress corrosion ia many environments, ia particular water and seawater, nonoxidizing acids, neutral and alkaline salts, and alkaUes. These alloys are weldable and are characterized by elevated and high temperature mechanical properties for certain appHcations. The copper content ia these alloys also easure improved thermal coaductivity for heat exchange. MONEL alloy 400 is a typical nickel-rich, nickel—copper alloy ia which the nickel content is ca 66 wt %. MONEL alloy K-500 is essentially alloy 400 with small additions of aluminum and titanium. Aging of alloy K-500 results in very fine y -precipitates and increased strength (see also Copper alloys). 

Titanium alloy systems have been extensively studied. A single company evaluated over 3000 compositions in eight years (Rem-Cm sponsored work at BatteUe Memorial Institute). AHoy development has been aimed at elevated-temperature aerospace appHcations, strength for stmctural appHcations, biocompatibiHty, and corrosion resistance. The original effort has been in aerospace appHcations to replace nickel- and cobalt-base alloys in the 250—600°C range. The useful strength and corrosion-resistance temperature limit is ca 550°C. 

In energy extraction, titanium alloys are being used in deep-water hydrocarbon and geothermal weUs for risers. Corrosion resistance, high strength, low modulus (flexible), and low density can result in risers one-fourth the weight and three times the flexibiHty of steel. 

Stainless Steel There are more than 70 standard types of stainless steel and many special alloys. These steels are produced in the wrought form (AISI types) and as cast alloys [Alloy Casting Institute (ACI) types]. Gener y, all are iron-based, with 12 to 30 percent chromium, 0 to 22 percent nickel, and minor amounts of carbon, niobium (columbium), copper, molybdenum, selenium, tantalum, and titanium. These alloys are veiy popular in the process industries. They are heat- and corrosion-resistant, noncontaminating, and easily fabricated into complex shapes. 

For resistance against fatigue, Nimonic 75 has been used with Nimonic 80 and Nimonic 90. Nimonic 75 is an 80-20 nickel-chromium alloy stiffened with a small amount of titanium carbide. Nimonic 75 has excellent oxidation and corrosion resistance at elevated temperatures, a reasonable creep strength, and good fatigue resistance. In addition, it is easy to press, draw, and mold. As firing temperatures have increased in the newer gas turbine models, HA-188, a Cr, Ni-based alloy, has recently been employed in the latter section of some combustion liners for improved creep rupture strength. 

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