Corrosion Potential Curves Research Articles

Corrosion resistance behavior of nitrogen ion-implanted in tantalum

This paper investigates the effect of nitrogen ion implantation on surface structure as well as resistance against tantalum corrosion. In this experiment, nitrogen ions which had energy of 30 keV and were in doses of 1 × 1017 to 9 × 1017 ions/cm2 were used. The X-ray diffraction analysis was applied for both the metallic analysis and the study of new structures having been created through the nitrogen ion implantation. Atomic force microscopy was also used to check the roughness variations prior to and also after the implantation phase. Moreover, the corrosion analysis apparatus was applied in order to compare resistance against tantalum corrosion in advance to and after the ion implantation. The results indicate that nitrogen ion implantation has a significant impact on increasing resistance against tantalum corrosion. After the corrosion test, the surface morphology of samples was analyzed by scanning electron microscopy. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. The purpose of this article is to obtain the perfect condition of the formation of tantalum corrosion resistance. The corrosion potential curves and roughness values obviously indicate that corrosion potential variations caused by the different doses of nitrogen ion bombardment are proportional to surface roughness in an inverse manner. The EDX analysis demonstrates the existence of the elemental composition of nitrogen ion implantation in the samples.

Theoretical Considerations in the Measurements of Polarization and Corrosion Potential Curves

Abstract The polarization curve is defined as the current density potential relationship for a given electrode immersed in a given electrolyte. Based on this definition, the use of hemi-spherical or of cylindrical iso-potential test electrodes is proposed for its accurate determination. For these test electrodes, combined with counter electrodes of equal symmetry, drop of the potential in the electrolyte is shown to be: I1 ρr1 (1–r1/rc) for hemi-spherical and l1ρr1 1n (rc/r1) for cylindrical symmetry, where l1 = current density on the test electrode (amp/cm2), ρ = resistivity of the electrolyte (ohm x cm), and Y1,rc = radii of the test and counter electrode (cm), respectively. By adding to either of these values, the potential drop between test electrode and electrolyte and by subtracting the potential drop between counter electrode and electrolyte, the total potential drop between these electrodes is obtained. The product I1ρr1 is found to be the parameter of deciding importance for an exact determination of the potential field which surrounds electrodes and of the potential of test electrodes. For test electrodes of conventional shape, the average potential drop in the electrolyte is estimated and a similar parameter defined. For sets of hemi-spherical or cylindrical test electrodes arranged in circular order with the reference electrode in the center, the potential field is expressed by an equation which provides a sound basis for the use of such multi-test electrode arrangements. Finally, the effect on the course of polarization curves of redox reagents such as originally contained in the electrolyte or produced by corrosion, is reviewed. From the relations derived, some conclusions are drawn and incorporated in the design of various types of experimental equipment for the determination of polarization and corrosion potential curves in laboratory and field studies, including the study of crevice corrosion.