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ABSTRACT The corrosion potential fluctuation, or electrochemical noise (EN) of UNS 10276 Alloy (C-276 alloy) working electrode (WE) was measured in an oxidizing hydrochloric acid (1.04x10-3mol dm -3 HC1 + 100ppm H202) at high temperatures up to 380°C. The potential of the WE was sampled every 0.5s with respect to a Ti electrode immersed in the ambient temperature region. The change in the fluctuation form and its intensity with the solution temperature was examined. To investigate the relationship between the fluctuation form and the corrosion phenomenon taken place on the WE, the temperature dependence of the polarization resistances (Rp) and the cross-sectional views was examined. The random potential fluctuations were measured at the temperatures of 210 and 240°C, and the RD-type (rapid drop followed by slow recovery) fluctuations were observed at temperatures between 270 to 330°C. The RpS and the cross-sectional views proved the WE had been subjected intense general corrosion at the former temperatures but localized corrosion at the later temperatures. No distinct fluctuations were measured at the temperatures below 210°C and above 330°C, and in these conditions, no corrosion traces were observed on the cross-sectional views. INTRODUCTION Supercritical and high-subcritical water oxidation (SCWO) have been received great attention as a promising process for destroying hazardous organic-waste. This process, however, must be carried out in highly corrosive solution, and also at elevated temperatures, so that even precious metals as well as nickel-base alloys are not immune from the corrosion damages at some stages in the process. Therefore, the precise corrosion control must be required to avoid happening the serious corrosion damages to the plant materials. To conduct the control precisely, the severity of process environment for corrosion development should be monitored on-site. The corrosion potential fluctuation of a working electrode has a possibility for providing information about the present electrode condition directly, because the potential fluctuations come from the change in the localized current with pre-pitting events (2-4~ or the fluctuations of redox reaction and others with general corrosion (5,6~. Furthermore, the object to be measured in the potential fluctuation measurement is only the fluctuation components, so that the long-term stability of its potential, and the potential reproducibility with respect to the normal hydrogen electrode (NHE) are not required for the reference electrode for the potential fluctuation measurement. This means any passive metals display partial stability can be available for the reference electrode for the measurement. Therefore, it is considered the potential fluctuation measurement fits for on-site corrosion monitoring for the SCWO process. In the present experiments, the potential fluctuation of UNS10276 Alloy (C-276 alloy) was measured in an oxidizing hydrochloric acid at high-subcritical temperatures. This material is a prominent candidate for the plant material at the SCWO processes, and it is likely subjected serious corrosion damages at this temperature range (7). After measuring the potential fluctuation, the change in the polarization resistance (Rp) of the C-276 alloy electrode with the solution's temperature was measured, to evaluated the change in the general-corrosion tendency with that. Also the difference in the cross-sectional views of the electrode immersed at the various temperatures was examined by using a SEM. From relationships between the measured fluctuation forms and the general-corrosion tendency or the corrosion phenomena, we discussed the applicability of the potential fluctuation measurement as a corrosion
- Asia > Japan (0.28)
- North America > United States > Texas (0.28)
ABSTRACT Flammable and toxic hazards can now be eliminated in rubber lining applications where adhesives containing high-level solvents are applied in confined spaces. This paper outlines the development of a solvent-free rubber lining adhesion system that provides sufficient bond strength of rubber to metal without the hazards associated with traditional solvent based products. INTRODUCTION In response to mounting safety and environmental concerns a new adhesion system for rubber linings has been successfully developed that entirely eliminates solvent emissions thus allowing application of tank linings to be carried out in a non-flammable and non-toxic atmosphere. Since their introduction in the early 1930's all rubber linings have relied upon adhesion systems that include high levels of solvent in their makeup. Primers, intermediate, tack cements and curing agents all contained varying amounts of these toxic and flammable components. Because of their risks every new system that was introduced sought not only to improve adhesion and simplify the application but also reduce the amount of solvent emission. This paper concentrates on the quest to develop a system that provides sufficient bond strength without the use of solvent in its formula. On July 15, 2002 a word search of all previous NACE publications and Cambridge Scientific Abstracts (1~ failed to uncover details of any successful work on solvent-free adhesive for rubber linings. Some work on water-based systems has been carried out in the past. These systems were found to produce low adhesion values under exhaust steam cure conditions at zero pressure due to lack of temperature to activate the bond line (1). Higher bond strengths were achieved after curing the rubber to metal under steam pressure, but steam pressure cure only is not always possible or practical within the rubber curing process. Therefore, there is an absolute need within the rubber tank lining industry for a solvent-free adhesion system that provides sufficient adhesion values after an exhaust steam cure as well as with the steam pressure cure. The author was personally compelled to begin to find a way to reduce these flammable and toxic hazards in July 13, 1971. This date is significant because at the author's former company an explosion tragically killed a co-worker while he was applying a solvent based metal primer inside a tank car to be rubber lined (2). Since this accident occurred OSHA's Labor Statistics indicate about five fatalities occur every year in the USA due to accidents involving solvents (3). NIOSH also states "Millions of workers are exposed to solvents on a daily basis. Health hazards associated with solvent exposure include toxicity to the nervous system, reproductive, liver and kidney damage, respiratory impairment, cancer, and dermatitis" (4). The needless loss of lives and disease really becomes not only a personal and national issue but also a global one. The saving of one life and the many health afflictions makes this development project very worthwhile. This paper will present the final product results without disclosing the patented (5) technology of and specific proprietary ingredients or their quantities. The search for suitable ingredients for a solvent- free adhesion system that would meet tank lining production, application, curing and performance requirements resulted in the discovery of the following system. TWO COAT RUBBER TO METAL ADHESIVES AB -A two component, one coat primer, easily mixed (1/1) and applied, solvent-flee, room temperature and accelerated curing, elastomeric epoxy/amine complex. C- A second intermediate coat of water-based adhesive necessary to provide tack to the tackles