High nickel alloys

Stainless steel alloys show exceUent corrosion resistance to HCl gas up to a temperature of 400°C. However, these are normally not recommended for process equipment owing to stress corrosion cracking during periods of cooling and shut down. The corrosion rate of Monel is similar to that of mild steel. Pure (99.6%) nickel and high nickel alloys such as Inconel 600 can be used for operation at temperatures up to 525°C where the corrosion rate is reported to be about 0.08 cm/yr (see Nickel and nickel alloys). 

C. K. Redmond and co-workers. High Nickel Alloys Workers Study Update. Fiaal Report to the Nickel Producers Environmental Research Association, Durham, N.C., Nov. 1993. 

Equipment Materials and Abrasion Resistance. Stainless steel, especially Type 316, is the constmction material of choice and can resist a variety of corrosive conditions and temperatures. Carbon steels are occasionally used. Rusting may, however, cause time-consuming maintenance and can damage mating locating surfaces, which increases the vibration and noise level. Titanium, HasteUoy, or high nickel alloys are used in special instances, at a considerable increase in capital cost. 

The submitters employed a nickel autoclave and noted that product from Step D may contain a small amount of hydrogen chloride or chlorinated material than can adversely affect a stainless steel pressure vessel. Hastelloy C is a high-nickel alloy. 

A high-nickel alloy is used for increased strength at elevated temperature, and a chromium content in excess of 20% is desired for corrosion resistance. An optimum composition to satisfy the interaction of stress, temperature, and corrosion has not been developed. The rate of corrosion is directly related to alloy composition, stress level, and environment. The corrosive atmosphere contains chloride salts, vanadium, sulfides, and particulate matter. Other combustion products, such as NO, CO, CO2, also contribute to the corrosion mechanism. The atmosphere changes with the type of fuel used. Fuels, such as natural gas, diesel 2, naphtha, butane, propane, methane, and fossil fuels, will produce different combustion products that affect the corrosion mechanism in different ways. 

Use fully killed or fine grain steel, controlled rolling temperatures high Mn/C ratios eliminate sharp corners in design, remove defects from steel heat treat steel. For cryogenic operations use high nickel alloy steels or austenitic stainless steels, depending on temperature. 

D02 G.E. Duvall, D.E. Davenport, and J.J. Kelly, Metallurgical Effects of Explosion-Induced Shock Waves, in Research Seminar on High Nickel Alloys for High Temperatures, Iron-Nickel Alloys, Stainless Steels (The International Nickel Co., New York, 1960). 

Metals usually used are stainless steel, nickel, monel, inconel, high nickel alloys, and special designs for unique services. 

Sulfur oxides produce sulphurous/sulfuric acid. Because oxygen and halides are often also present, high-nickel alloys are required. 

A more detailed treatment of sensitisation of austenitic stainless steels, of intergranular corrosion of austenitic stainless steels without sensitisation, and of sensitisation and intergranular corrosion of ferritic stainless steels and high-nickel alloys, is given by Cowan and Tedmon . 

Metals and alloys vary in their ability to resist crevice corrosion, and this applies particularly to those that rely on passivity for their resistance to corrosion. Titanium and high-nickel alloys such as the Inconels and Hastel-loys are amongst the most resistant, but even these will be attacked under highly aggressive environmental conditions. 

Pakhomova, N. A. and Levin, I. A., Effect of Grain Size on the Inter-crystalline Corrosion of Stainless Steel Type 18-8 , Zashch. Metal, 9, 676 (1973) C.A., 80, 86207j Brown, M. H. and Kirchner, R. W., Corrosion of High Alloy Weldments 1. Sensitisation of Wrought High Nickel Alloys , Corrosion, 29, 470 (1973)... 

Copper-palladium-nickel-manganese brazes give very low erosion of the parent metals to be brazed, and are therefore used to join thin sections of stainless steels and high-nickel alloys. 

The question of the compatibility of metals and alloys with carbon and carbonaceous gases has assumed considerable importance in connection with the development of the gas-cooled nuclear reactor in which graphite is used as a moderator and a constituent of the fuel element, and carbon dioxide as the coolant. Tests of up to 1 000 h on a series of metals and nickel-containing alloys under pressure contact with graphite at 1 010°C" showed that only copper was more resistant than nickel to diffusion of carbon and that the high-nickel alloys were superior to those of lower nickel content. The more complex nickel-chromium alloys containing titanium, niobium and aluminium were better than the basic nickel-chromium materials. 

In the gas-cooled reactor, reaction.between the coolant and the moderator results in formation of a proportion of carbon monoxide in the atmosphere. This gas can be carburising to nickel-base alloys but the results of tests in which CO2 was allowed to react with graphite in the furnace indicate that the attack on high-nickel alloys is slight, even at moderately high temperatures and is still mainly due to simple oxidation. 

For aggressive conditions it may be advantageous to use one of the many high-nickel alloys available. The high cost of such alloys may be economically beneficial although some of the alloys are subject to stress-corrosion cracking, but in a more restricted range of environments than the lower nickel alloys that they would replace. 

In general, stainless steels are used for corrosion resistance when oxidising conditions exist. Special types, or other high nickel alloys, should be specified if reducing conditions are likely to occur. The properties, corrosion resistance, and uses of the various grades of stainless steel are discussed fully by Peckner and Bernstein (1977). A comprehensive discussion of the corrosion resistance of stainless steels is given in Sedriks (1979). 

Redmond CK. 1984. Site-specific cancer mortality among workers involved in the production of high nickel alloys In Sunderman FW Jr, Aitio A, Berlin A, eds. Nickel in the human environment. lARC scientific publication no. 53. Lyon, France International Agency for Research on Cancer 73-86. 

Stabilization of nickel(II) and copper(II) by complexing with EDTA4-or NTA3- similarly increases the vulnerability of these normally corrosion-resistant metals to corrosion by aerated waters. For this reason, EDTA4-or NTA3- solutions should not be used in copper or high nickel alloy equipment. 

Nickel confers excellent resistance to alkaline attack and to stress-cracking corrosion and is also quite resistant to nonoxidizing acids. It is widely used to the extent of a few percent in stainless steels (300 series, see Section 16.8), and in several high nickel alloys, including the following proprietary metals ... 

Weeton, J. W., Mechanisms of Failure of High Nickel-Alloy Turbojet Combustion... 

Wrought Nickel and High-Nickel Alloys. Some of the major nickel alloys, along with wrought nickel, are described in Table 1. 

Staff A Quick Reference Guide to Nickel and High-Nickel Alloys, Advanced Materials and Processes, 54 (October 1991). 

The submitters used a 1-L autoclave lined with Hastelloy C-4. Hastelloy C materials are high nickel alloys. A highly resistant alloy is employed to avoid possible side reactions. 

Copper alloys (brass, bronze, etc.) for very shock-sensitive perchlorate salts Aluminum (dissolves at room temperature) High nickel alloys (dissolves), others Cotton Wood... 

INCO Corrosion Engineering Bulletin CEB-1. Resistance of Nickel and High Nickel alloys to Corrosion by Sulfuric Acid." New York, NY International Nickel Company, 1983. 

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