Showing 5 results for Corrosion.
M.r. Garsivaz Jazi, M.a. Golozar , K. Raeissi,
Volume 33, Issue 3 (3-2015)
Abstract
In this study, the chemical composition, thickness and tribocorrosion behavior of oxide films prepared on Ti-6Al-4V alloy by anodising treatment in H2SO4/H3PO4 electrolyte at the potentials higher than the dielectric breakdown voltage were evaluated. The thickness measurement of the oxide layers showed a linear increase of thickness by increasing the anodizing voltage. The EDS analysis of oxide films demonstrated precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. Tribocorrosion results indicated that the tribocorrosion behavior of samples was significantly improved by anodising
process. Furthermore, the tribocorrosin performance of thesamples anodised at higher voltages was enhanced. SEM and EDS of worn surfaces indicated that the oxide layer on the samples anodised at lower voltages was totally removed, but for the samples anodised at higher voltages, the oxide layer was only locally removed within the wear track. Moreover, measurement of wear volume of the treated samples exhibited lower values on the samples anodised at higher voltages.
F. Soleimani, R. Emadi,
Volume 38, Issue 3 (12-2019)
Abstract
In this study, polycaprolactone/chitosan/1% baghdadite composite coating was applied on anodized AZ91 alloy to improve the corrosion rate of AZ91 alloy in simulated body fluid (SBF) solution for long immersion times, control its degradability and enhance its bioactivity. By applying the composite coating and after seven days of immersion in a phosphate buffer solution, the corrosion rate decreased from 0.21 mg/h.cm2 (for AZ91 sample) to 0.1 mg/h.cm2 (for anodized AZ91 sample). Formation of apatite layer on the surface of specimens is considered a criterion for bioactivity. In order to evaluate the ability of specimens to get covered by an apatite, the SBF test was used. Application of the composite coating yielded the highest ability for apatite formation, controlled release of ions, and the lowest corrosion rate in the SBF so that it could be considered a good choice for bone implants.
S. Arjmand, M. Tavoosi,
Volume 39, Issue 3 (12-2020)
Abstract
The present work aims to modify surface properties of pure Ti by development of Ti-Al-N intermetallic composite coatings. In this regard, tungsten inert gas (TIG) cladding process was carried out using Al 1100 as filler rod with Ar and Ar+N2 as shielding gases. Phase and structure of the samples were investigated by X-ray diffraction (XRD) technique, optical microscopy (OM) and scanning electron microscopy (SEM). Hardness values and corrosion behavior of the obtained coatings were also compared using Vickers microhardness tester and potentiostat, respectively. The results showed that composite structure containing Al3Ti, Ti3Al2N2 and Ti3Al intermetallic compounds could be formed on the surface of pure Ti. Amounts of brittle phases and welding defects at the titanium-coating interface were least by welding under pure Ar shielding. Despite the increasing amount of structural defects such as porosity and non-uniformity under Ar+N2 shielding, the prepared coatings had higher hardness (more than 100 HV) and corrosion resistance (more than twice) compared with those obtained under Ar shielding.
M. Salehi, M. Eskandari, M. Yeganeh,
Volume 40, Issue 2 (9-2021)
Abstract
In this study, microstructural changes in the thermomechanical processing and its effect on the corrosion behavior of 321 austenitic stainless steel were investigated. EDS analysis and optical microscopy were used to identify precipitates and microstructure, respectively. To evaluate the corrosion properties, potentiodynamic polarization test and electrochemical impedance spectroscopy were performed. First, the as-received sample was subjected to cold rolling with a 90% thickness reduction at liquid nitrogen temperature, and then annealing was performed at temperatures of 750, 850, and 1050 °C for 10 min. The results showed that severe cold rolling slightly improved the corrosion properties and in annealed samples, the corrosion resistance increased with more uniform microstructure, more reversion of martensite phase to austenite, and reduction of grain size. Annealed samples at 850 °C and 1050 °C with polarization resistance values of 8.200 kΩ.cm2 and 3.800 kΩ.cm2 depicted the highest and lowest corrosion resistance compared to other samples, respectively.
M. H. Rezvani, M. Yeganeh, S. M. Lari Baghal,
Volume 41, Issue 1 (8-2022)
Abstract
In this study, the addition of organic methionine inhibitor (as an eco-friendly inhibitor) to 0.1 M sulfuric acid media on corrosion resistance of 316L austenitic stainless steel (fabricated by rolling method and three-dimensional (3D) printing method) was investigated. Open-circuit potential electrochemical test and impedance, and structural tests such as optical and electron microscopy and x-ray photoelectron spectroscopy were conducted. The results showed that the corrosion resistance in the presence of inhibitor was higher than the sample without inhibitor and the inhibitory efficiency of methionine was increased up to 64% and the resistance to surface transfer between metal oxide and electrolyte was improved up to 2.77 times. The addition of methionine reduced the surface roughness and accumulation of the surface cavities. The chemical and physical adsorption mechanism of the inhibitor (negatively charged side adsorption of the methionine molecule with positively charged anodic regions of the metal surface) occurred at all points on the surface of the sample with the inhibitor. Also, the amount of oxygen in the cavities was reduced and the distribution of sulfur was uniform. The thickness of the passivator oxide layers was calculated more than the sample without inhibition due to the addition of inhibitor.
