Showing 3 results for Pitting
Moayed M.h.,
Volume 2, Issue 3 (9-2005)
Abstract
In this research pitting Corrosion of a sensitized 316 stainless steel was investigated employing potentiodynamic, potentiostatic techniques. Sensitization process was carried out on as-received alloy by submitting the specimen in electric furnace set at 650°Cfor five hours and then the specimen was quenched 25°C water. Potentiodynamic polarization of as received and sensitized specimens in 1M H2SO4 solution at room temperature and 70°C clearly revealed that the sensitization process has caused a magnificent change on electrochemical behavior of the specimen by changing critical current density for passivation, passivation potential and passive current density. Optical microscopy examination of the specimen surface after oxalic acid electrochemical etching also showed the deterioration of grain boundary of sensitized specimen due to chromium carbide precipitation in compared to as-received one. Several anodic potentiodynamic polarization on rode shaped working electrodes prepared from as-received and sensitized specimen in 3.5% NaCl test solution proved an average ~220 mV drop in pitting potential due to sensitization. Anodic potentiostatic polarization at 400 and 200 mV above corrosion potential also demonstrate the deterioration of pitting resistance of alloy as a result of sensitization. Scanning electron microscopy examination of anodically polarized of sensitized specimen at 700mVprior and after oxalic acid etching revealed large stable pits with lacy cover and also openpits with deep crevice for etched specimens.
H. Fattahi, M. H. Shariat,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: In chloride salt solutions, titanium alloys exhibit reasonably high pitting potentials as
high as +10 V (vs. Ag/AgCl) at room temperatures. On the other hand, anodic pitting potentials
are significantly lower in bromide solutions. In this study, pitting corrosion of commercially pure
titanium in aqueous NaBr solution of 0.1 M concentration at room temperature was studied and
the effect of an external magnetic field oriented both parallel and perpendicular to electrode
surface was investigated. Cyclic potentiodynamic and potentiostatic polarization tests were
carried out. Anodic breakdown potential of +1.45 V (vs. Ag/AgCl) obtained in the absence of
magnetic field, decreasing to +1.11 V in the presence of a 0.05 T parallel magnetic field. The
perpendicular magnetic field actually did not affect the breakdown potential. Applying of an
external magnetic field, independent of its orientation, shifted the repassivation potential
approximately 150 mV in the positive direction. SEM microscopy observations of sample surfaces
indicated that applying of magnetic field results in some variations in the pit shapes and their
sizes.
B.y.r. Surnam, B.s. Audit, A. Soopee,
Volume 14, Issue 3 (9-2017)
Abstract
In this study the use titanium and tungsten as alternatives to the noble metals in the jewellery industry was investigated. The degradation of titanium and tungsten were compared to that of gold, used as reference. Alternate immersion tests were performed in 3.5% sodium chloride and artificial perspiration. The metals’ abrasion resistance with respect to textile fabrics was determined.
In general, there is around 30% difference in pit density for titanium and tungsten as compared to that of gold. Pit depth and pit diameter showed a similar trend. From the abrasive test performed, it was observed that titanium and tungsten had insignificant changes in the surface reflectivity with time. Hence, it was deduced that titanium and tungsten products would have longer maintenance intervals than that of gold. New tools and techniques, however, would be required by jewellers to work with titanium and tungsten.
