High-temperature corrosion alloying elements

The development of CVD films for high-temperature corrosion protection of ferrous alloy has focused on methods with and without addition of oxygen-active elements. CVD processes, which employ vapor-transport and heat treatment of a stabilized alloy substrate to... 

The objective of surface modification by CVD is to develop additional corrosion protection for high-temperature alloys (e.g., Fe-25Cr-0.3Y) beyond that achieved by reactive-element additions which will be effective for a long period. Because CVD is a high temperature process, the following topics must be discussed before we can develop successful high-temperature corrosion-proteetion coatings. ... 

The nickel-based alloys show a wider range of application than any other class of alloys. These alloys are used as corrosion-resistant alloys, heating elements, controlled expansion alloys, creep-resistant alloys in turbines and jet engines, and high-temperature, corrosion-resistant alloys. 

D. Naumenko, W.J. Quadakkers, V. Guttmann, et al.. Critical role of minor elemental constituents on the life time oxidation behaviour of FeCrAl-RE alloys, in Lifetime Modelling of High Temperature Corrosion Processes, EFC Monograph No. 34, The Institute of Materials, London (2001). 

Y. Kawahara, High Temperature Corrosion Mechanisms and Effect of Alloying Elements for Materials nsed in Waste Incineration Environment, Corros. Sci. 2002, 44, p 223... 

Nonferrous alloys account for only about 2 wt % of the total chromium used ia the United States. Nonetheless, some of these appHcations are unique and constitute a vital role for chromium. Eor example, ia high temperature materials, chromium ia amounts of 15—30 wt % confers corrosion and oxidation resistance on the nickel-base and cobalt-base superaHoys used ia jet engines the familiar electrical resistance heating elements are made of Ni-Cr alloy and a variety of Ee-Ni and Ni-based alloys used ia a diverse array of appHcations, especially for nuclear reactors, depend on chromium for oxidation and corrosion resistance. Evaporated, amorphous, thin-film resistors based on Ni-Cr with A1 additions have the advantageous property of a near-2ero temperature coefficient of resistance (58). 

The addition of cathodically active elements to pure lead was the main objective of investigations to improve its corrosion resistance to H2SO4 [42,44]. Best known is copper-lead with 0.04 to 0.08% Cu. By adding combinations of alloying elements, it was possible to produce lead alloys that not only had much better corrosion resistance, but also had greater high-temperature strength. Lead alloy with 0.1% Sn, 0.1% Cu and 0.1% Pd is an example [45]. 

The corrosion behaviour of amorphous alloys has received particular attention since the extraordinarily high corrosion resistance of amorphous iron-chromium-metalloid alloys was reported. The majority of amorphous ferrous alloys contain large amounts of metalloids. The corrosion rate of amorphous iron-metalloid alloys decreases with the addition of most second metallic elements such as titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, copper, ruthenium, rhodium, palladium, iridium and platinum . The addition of chromium is particularly effective. For instance amorphous Fe-8Cr-13P-7C alloy passivates spontaneously even in 2 N HCl at ambient temperature ". (The number denoting the concentration of an alloy element in the amorphous alloy formulae is the atomic percent unless otherwise stated.)... 

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