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Wednesday, March 19, 2008 - 9:55 AM
Convention Center, Second Level, 210 (Ernest N. Morial Convention Center)
08580
Environmental and Metallurgical Variables Affecting Crevice Corrosion Susceptibility of Alloy 22 - A Review
Alloy 22 is a Ni base alloy with a Chromium content of aproximately 22%. It belongs to the Ni-Cr-Mo-W alloys family. Numerous studies show that it is highly resistant both to uniform corrosion and to localized corrosion. The objective of this work is to study the influence of phosphate ions on the corrosion behavior of Alloy 22 in severe environmental conditions, such as high temperatures and high chloride concentrations in which this alloy suffers crevice corrosion.
Potentiodynamic polarization curves were run in pure 1M NaCl aqueous solutions and with different concentrations of phosphate ions at near neutral pH and90ºC . Full passivity and transpassivity regions were observed in these curves. The film formed at the transpassive potential region was observed at the Scanning Electron Microscope (SEM) and its composition was analyzed using Energy Dispersive X-ray Spectroscopy (EDS). Semi-quantitative measurements and elementary X-ray mapping were performed on the transpassive film.
By comparing the results of the phosphate containing solutions with those corresponding to pure chloride solutions it was concluded that the presence of phosphate ions in the solution produced changes both in the polarization curves and in the composition of the film formed at the end of these tests.
Potentiodynamic polarization curves were run in pure 1M NaCl aqueous solutions and with different concentrations of phosphate ions at near neutral pH and
By comparing the results of the phosphate containing solutions with those corresponding to pure chloride solutions it was concluded that the presence of phosphate ions in the solution produced changes both in the polarization curves and in the composition of the film formed at the end of these tests.
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