Oxidation corrosion data

Oxidation-corrosion data included in this paper were generated in Phases I and II of the program. 

Corrosion data have been generated for metals in the quench systems and refractories in the gasifier. However, specific oxidation-corrosion data in this paper will be limited to metals exposed in the high-temperature gas phase locations of the HYGAS and CONOCO COAL plants. Again, the results reported will emphasize trends indicated by the pilot plant exposures. 

High-temperature gas phase oxidation-corrosion data have been obtained for two exposures in the CONOCO COAL plant and one exposure in the HYGAS plant. Table VI summarizes the operating environments and in-plant times for these exposures. Since the pilot plants operate at variable temperatures, pressures, and gas compositions, weighted average values are given for the plant exposures. 

Linearly extrapolated oxidation-corrosion data for the 1150 hr first exposure in the HYGAS gasifier offgas are plotted in Fig. 7. In this location at 580°F (average) carbon steel, AISI 410, AISI 304, IN-800, and titanium exhibited very limited corrosion. Alloy IN-600 and Monel 400 had corrosion rates of 42 and 124 mpy, respectively. 

Oxidation-corrosion data obtained from the pilot plants generally compare well with laboratory data in ranking of high-temperature alloys. Pilot plant results, however, indicate more severe corrosion than laboratory oxidation-corrosion data. This should be expected because of cyclic operation of pilot plants and additional variables comprising the pilot plant environments. The contribution of erosion and erosion-corrosion by coal ash, char, and sulfur sorbents to the corrosion process in the pilot plants has not been defined. 

Laboratory oxidation-corrosion data indicate that extrapolation of short-term oxidation-corrosion data to yearly rates is difficult. These extrapolations are necessary to provide a basis for comparing oxidation-corrosion data obtained from variable CGA exposure times. Extrapolated data, particularly at high H2S concentrations in the CGA atmosphere, should be employed with caution. Long-term kinetics of the oxidation-corrosion process can result in transitions in corrosion behavior to high rates not predictable by short exposures. Similar behavior, breakaway oxidation, occurs in air primarily at temperatures above 2000 F. 

It is evident from the foregoing that considerable effort has gone into improving the high temperature properties and microstructure of the alloys. However, if 7-T1AI alloys are to find service as high temperature components within the gas turbine, then data on the oxidation and corrosion data of the alloy is required. 

This paper therefore concentrates on a study of the hot salt corrosion of 7-TiAl over the temperature range 500-700°C. Limited oxidation data at 700°C is also presented by way of comparison with the hot salt corrosion data, and published high temperature oxidation data. 

Toxicology ACGIH TLV/TWA 10 ppm LD50 (oral, rat) 156 mg/kg, (subcut., mouse) 1150 mg/kg, (skin, rabbit) 277 mg/kg poison by ing., skin contact, IP mod. toxic by subcut. severe human skin irritant can cause dermatitis corrosive human mutagenic data experimental teratogen, reproductive effects TSCA listed Precaution Flamm. liq. dangerous fire hazard exposed to heat, flame, or oxidizers corrosive to copper and copper alloys, aluminum, zinc, and... 

Thornton, E. W. Activity transport mechanisms in water cooled reactors. Report IAEA TECDOC-667 Coolant Technology of Water Cooled Reactors, Vol. 3 Activity Transport Mechanisms in Water Cooled Reactors., Vienna, 1992, p. 9—51 Walker, S. M., Thornton, E. W. Reanalysis of oxide solubility data. Proc. 5. BNES Conf Water Chemistry of Nuclear Reactor Systems, Bournemouth, UK, 1989, Vol. 1, p. 89—95 Walton, G. N., Hesford, E. The migration of activated corrosion products in high-pressure water loops. Proc. Conf Corrosion of Reactor Materials, Salzburg 1962, Vol. 2, p. 547-556... 

Most corrosion testing in support of SCWR development has been performed at constant pressure, such that the SCW density changes as the temperature changes. While experimentally simple and directly applicable to the SCWR (which will operate at constant pressure) it complicates data interpretation because the solubility, S, of a metal oxide corrosion film depends on the SCW density, p ... 

Analysis of variance is the usual technique for analysing the results of designed experiments (see, Nicholls and Hancock, 1983, for examples of analysis of variance applied to oxidation and corrosion data). However, where interest is focussed on many different aspects of the data, then there may not be sufficient degrees of freedom left to enable an ANOVA. Regression is an alternative approach but this also requires sufficient degrees of freedom. 

Nicholls, J.R. and P. Hancock (1983) The analysis of oxidation and hot corrosion data a statistical approach . High Temperature Corrosion, NACE-6, 198-210. 

Caro s acid is highly corrosive and a powerfiil oxidant. Its acidic properties are similar to those of sulfuric acid of equivalent strength. A strong irritant, it is toxic and should always be handled accordingly. No specific toxicological data are available. 

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