Showing 4 results for Corrosion
M. H. Fathi, Gh. Feizi, Sb. Moosavi, Gh. Gahanshahi, M. Salehi, A. Saatchi and V. Mortazavi,
Volume 20, Issue 1 (7-2001)
Abstract
Hydroxyapatite coatings have been used on metallic substrates in a variety of applications, including modifying the surface of human implants, bone osseointegration and biological fixation. In this paper, the effects of various kinds of metallic substrate on clinical and pathological results of in vivo tests are presented. Four kinds of endodontic implants i.e, stainless steel, cobalt base alloy, plasma sprayed hydroxyapatite coated stainless steel, plasma sprayed hydroxyapatite coated cobalt base alloy were prapared and implanted in mandibular canine of
cats. After a healing period of 4 months, investigation by SEM and histopathological interpretation and evaluation showed significant differences in tissue response and osseointegration between coated and non-coated metallic implants. It was concluded that the results were affected by the kind of metallic substrate .
Keywords: Hydroxyapatite coating, Dental endodontic implant, Osseointegration, Corrosion, Stainless steel,
Cobalt base alloy
A. Nasr-Esfahany and M.heydarzadeh Sohi,
Volume 23, Issue 2 (1-2005)
Abstract
Zinc-Nickel electrodeposits have been widely adopted for surface treatment of automobile steel sheet for high corrosion resistance. In this work the effect of pulse parameters on the Zn-Ni alloy electrodeposits was investigated. The hardness, thickness, corrosion resistance and composition of deposits thus produced were investigated. The surface topography of the deposits was also observed in SEM and results are reported. It has been shown that the thickness of the pulse electrodeposits
was almost even. The hardness in the pulse electrodeposits increased by increasing the on-time period and by decreasing the current density. It was also noticed that increasing the on-time period increases the nickel content of the deposit. Pulse electrodposits had fine structure and the structure become finer by reducung the on-time period and pulse frequency. The corrosion dehaviors of the deposits were then investigated. The results showed that the corrosion resistance of the DC electrodeposits improves in their nickel content increases. Pulse electodeposits show the same behavior, but deposits with about 13% nickel show maximum corrosion resistance.
T. Shahrabi Farahani, V. Baigi and S. A. Lajevardi,
Volume 27, Issue 1 (7-2008)
Abstract
Prediction of SCC risk of austenitic stainless steels in aqueous chloride solution and estimation of the time to failure as a result of SCC form important and complicated topics for study. Despite the many studies reported in the literature, a formulation or a reliable method for the prediction of time to failure as a result of SCC is yet to be developed. This paper is an
effort to investigate the capability of artificial neural network in estimatiing the time to failure for SCC of 304 stainless steel in aqueous chloride solution and to provide a sensitivity analysis thereof. The input parameters considered are temperature, chloride ion concentration, and applied stress. The time to failure is defined as the output parameter and the key criterion to evaluate the effective parameters. The statistical performance of the neural network is expressed as the average of three learning and testing results. The SCC database is divided into two sections designated as the learning set and the testing set. The output results show that artificial neural network can predict the time to failure for about 74% of the variance of SCC experimental data. Furthermore, the sensitivity analysis also exhibits the effects of input parameters on SCC of 304 stainless steel in aqueous chloride solutions.
Y. Mollapour, E. Poursaeidi, H. Shayani-Jam, O. Pedram,
Volume 40, Issue 1 (9-2021)
Abstract
Corrosive factors along with mechanical loads on the gas turbine compressor blades, cause phenomena such as pitting corrosion, stress corrosion cracking and corrosion fatigue. Due to erosion of particles in the presence of a corrosive environment, pitting happens on the blade surfaces, which is a source of subsequent cracks. Therefore, it is necessary to get knowledge of its mechanism in order to prevent the phenomena as much as possible. The main purpose of this paper is to investigate the growth of pitting corrosion in CUSTOM 450 stainless steel and to obtain strain values in the growing pits at the maximum bending region. In this regard, a two-point bending specimen was made and subjected to a potentio-static test under the potential of 350 mVSCE in the 3.5 wt% sodium chloride solution. Then the propagated pits were numerically examined. By the digital image correlation method, the local strain was calculated in the pits and a relation was presented to obtain the maximum strain time. Therefore, growth direction of pitting corrosion could be estimated by having maximum strain region. Finally, by simulating the pitting corrosion process of a stress-free sample under the potential of 350 mVSCE in 3.5 wt% sodium chloride solution in COMSOL Multiphysics software, variations in the concentration of ions, electric potential, and corrosion current density were shown in the existing pit. The potential was decreased by moving in-depth and the maximum current density was found at the depth of 18 μm. Thus, without the need of advanced laboratory facilities for surface scanning and analysis, useful information from surface corrosion conditions could be obtained
