Metal dusting corrosion

The ACGIH adopted TLV/TWA for 1992—1993 for fluorides as F is TWA 2.5 mg/m, and for cobalt as Co metal dust TWA 0.05 mg/m. Dust masks should be used while handling both the cobalt fluorides and all other cobalt compounds. CoF is shipped as an oxidizer and a corrosive material. 

Koszman, I., Antifoulant Additive for Steam-Cracking Process, U.S. Patent 3,531,394, Sept. 29, 1970. Hochman, R. F, Fundamentals of the Metal Dusting Reaction, Proceedings, Fourth International Congress on Metallic Corrosion, NACF (1971). 

Metal dusting usually occurs in high carbon activity environments combined with a low oxygen partial pressure where carburisation and graphi-tisation occur. Usually pits develop which contain a mixture of carbon, carbides, oxide and metal (Fig. 7.52). Hochmann" proposed that dusting occurs as the result of metastable carbide formation in the high carbon activity gas mixture which subsequently breaks down into metal plus free carbon. The dependence of the corrosion resistance of these nickel alloys on the protective oxide him has been described accelerated or internal oxidation occurs only under conditions that either prevent the formation, or lead to the disruption, of this him. In many petrochemical applications the pO is too low to permit chromia formation (ethylene furnaces for example) so that additions of silicon" or aluminium are commonly made to alloys to improve carburisation resistance (Fig. 7.53). 

Figure 1. Metal dusting corrosion characteristics of Fe (adapted from ref. 15).

The general features described above for the metal dusting corrosion of Inconel 600 can also be extended to the other Ni based alloys except that the corrosion intensity decreases with increase of Cr content. The rate of corrosion is also a strong function of temperature. The maximum local metal dusting rate is plotted as a function of temperature in Fig.5. It is interesting to note that a maximum in... 

H. J. Grabke, Thermodynamics, Mechanisms and Kinetics of Metal Dusting, Materials and Corrosion, 49 303-308 (1998). 

E. Pippel, J. Woltersdorf and R. Schneider, Micromechanisms of Metal Dusting on Fe-base and Ni-base Alloys, Materials and Corrosion, 49 309-316 (1998). 

C. M. Chun and T. A. Ramanarayanan, Metal Dusting Corrosion of Low-chromium Steels,... 

J. Zhang and D. J. Young, Kinetics and Mechanisms of Nickel Metal Dusting 1. Kinetics and Morphology, Corrosion Science, 49 1496-1512(2007). 

T. A. Ramanarayanan and C. M. Chun, Chapter 6 Metal Dusting Corrosion of Metals and Alloys, New Development in High Temperature Corrosion and Protection of Materials, Ed. W. Gao and Z. Li, Woodhead Publishing Ltd., Cambridge, UK p.80-116 (2008). 

Y. Nishiyama, N. Otsuka and T. Kudo, Metal Dusting Behavior of Cr-Ni Steel and Ni-base Alloys in a Simulated Syngas Mixture, Corrosion Science, 48 2064-2083 (2006). 

K.. E. Bagnoli, G. P. Anderson, C. M. Chun and T. A. Ramanarayanan, High Performance Coated Material with Improved Metal Dusting Corrosion Resistance , U.S. Patent Application Publication US2006/0257675 A1 (2006). 

Physical Form. Metal dusts, pyro powders, welding fumes When exposed to air, an aluminum surface becomes oxidized to form a thin coating of aluminum oxide, which protects against ordinary corrosion. Powder and flake aluminum are flammable and can form explosive mixtures in air, especially when treated to reduce surface oxidation (pyro powders). 

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