High-temperature (> 200° C) corrosion of metals and alloys in atmospheres containing Cl2 and/or HCl, which are widely encountered in many industrial environments, is reviewed Topics include high-temperature corrosion mechanism and kinetics, thermodynamic considerations, and effects of gaseous components in the atmosphere (oxygen, air, water vapour, sulphur dioxide, and nitrogen) on the corrosion

High-temperature chlorine corrosion of metals and alloys

Estimation of and barriers to waste heat recovery from harsh environments in industrial processes

Corrosion and carburization behavior of Al-rich surface layer on Ni-base alloy in supercritical-carbon dioxide environment

Thermodynamic calculations are an important tool for prediction of chemical reactions. In many cases the results help to understand and describe the experimental observations. In others, especially if reaction kinetics play a major role, their predictive value can be rather limited and the projected results have to be treated with care. One such case are high temperature chlorine corrosion conditions.



For example, thermodynamically a similar corrosion behavior of nickel and molybdenum is predicted in chlorine-containing atmospheres at low oxygen partial pressures. In contrast to their calculated similarity, experimental results showed much higher resistance of molybdenum against the chlorinating attack. Above 800 °C nickel is rapidly consumed, whereas molybdenum remains almost inert.



This paper reviews the literature on the corrosion mechanisms and kinetics of nickel and molybdenum in chlorine-containing environments as well as in mixed oxygen-chlorine-containing atmospheres. Based on the literature review, differences in their reaction kinetics are discussed, taking into account the deviation from an ideal thermodynamic correlation between the partial pressure and the reaction kinetics via the often used Hertz-Langmuir equation. Finally it is shown that the findings concerning the special characteristics of molybdenum and nickel and the conclusions drawn from experimental observations on high temperature chlorine corrosion can also be transferred to other metals.

Refractory metals and nickel in high temperature chlorine-containing environments - thermodynamic prediction of volatile corrosion products and surface reaction mechanisms: a review

Difficulties of alloy selection for high-temperature halogen service are described with reference to product morphologies, vaporization and the manner by which alloy degradation may occur. Selected results from work with alloy 600 (Ni-16 Cr-8Fe) and Havnes® Alloy 230 (Ni-22 Cr-14W-2Mo-0.3Al-0.02 La) are used to contrast various modes of attack. Oxidizing chlorine-containing gases often give rise to heavy volatilization and intergranular attack at 900°C (1650°F) whilst HF/steam mixtures result in more uniform internal oxidation at 750°C (1380°F).

High Temperature Alloy Corrosion by Halogens

A new wrought nickel-base alloy, designated CABOT®* alloy No. 214, has been developed for applications in the heating industry. The alloy, composed principally of nickel, chromium, aluminum, iron, and yttrium, combines the outstanding oxidation and environmental resistance of the Ni-Al base coating systems with the workability of more conventional chromia-protected alloy systems to yield a superior product for extended service applications up to and above 2200°F (1200°C). The enhanced oxidation resistance of the alloy is the result of the tenacious Al2O3 film which forms on the surface of the alloy at high temperatures. In addition to describing the oxidation, carburization, and chlorination resistance of the alloy, the metallurgical traits of microstructure and mechanical properties are reviewed.

A New, Wrought, Heat-Resistant Ni-Cr-Al-Fe-Y Alloy

The utilization of heat recuperators in high-temperature industrial processing facilities to recover the waste heat from flue gas streams and use it to preheat incoming combustion air can result in significant energy savings. Little information concerning the performance characteristics of most commercial alloys in various corrosive flue gas environments is available to guide materials selection for heat recuperators. This paper discusses four principal flue gas environments, i.e. oxidizing, sulfidizing, carburizing, and chlorine-contaminated environments, that are frequently encountered in high-temperature industrial processing systems. A ranking of relative alloy performance in these hostile environments for a variety of commercial alloys is presented in order to help the design engineer select the most appropriate alloys for construction of recuperators. Other materials properties that are of importance in the materials selection, including short-time tensile properties, creep rupture properties, and thermal stability, are also discussed.

Recuperator Alloys for High-Temperature Waste Heat Recovery

Disclosed is a sulfidation-resistant alloy. The alloy preferably may contain about 27% each cobalt and chromium, 8% iron, 2.7% silicon and the balance nickel plus normal impurities found in alloys of this class. The alloy is eminently suitable for applications in high temperature, hostile environments generated by many industrial processes, such as refinery, chemical processing and power generations.

George Y Lai

Papers

A New, Wrought, Heat-Resistant Ni-Cr-Al-Fe-Y Alloy

Recuperator Alloys for High-Temperature Waste Heat Recovery

Sulfidation-resistant Co-Cr-Ni alloy with critical contents of silicon and cobalt

Sulfidation-resistant superalloy

Alliage resistant a la sulfuration