Showing 5 results for Corrosion Resistance
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.
A. Azimi Dastgerdi, F. Ashrafizadeh, M. R. Toroghinejad, F. Shahriari , H. Zahraei,
Volume 30, Issue 2 (12-2011)
Abstract
In this paper, bare spot defects in hot-dip galvanized sheets were studied in terms of the microstructure and their influence on the corrosion and mechanical properties. Surface characteristics and microstructural features were examined by scanning electron microscopy equipped with energy dispersive spectroscopy microanalysis system. The results showed that the major cause of the bare spots was the lack of wetability of the sheet surface due to contamination, improper heat treatment or chemical composition. Corrosion resistance was evaluated by standard salt spray test. Mechanical properties were examined by tensile testing. The time to red rust was much shorter on the bare spots as compared to other regions, but it appeared that bare spot defects had no significant effect on the mechanical properties of the galvanized steel sheets.
B. Bakhit, A. Akbari,
Volume 31, Issue 2 (12-2012)
Abstract
Composite and nanocomposite Ni-Co/SiC coatings were synthesized by electro-codeposition of micro and nano-sized SiC particles with average diameter of 10m and 20nm using horizontal electrodes. Surface morphology, chemical composition, phase composition, hardness and corrosion resistance of the deposited coatings were studied using SEM observations and EDX, XRD, microhardness and polarization measurements as a function of the electrodeposition current density. The results indicated that the nanocomposite coatings exhibit higher hardness and corrosion resistance compared with the composite coatings containing micro-sized SiC particles despite their lower percentage of the SiC content. The maximum hardness values of 615HV and 490HV were obtained for nanocomposite and composite coatings deposited at current density of 3A/dm2. The observed properties were discussed based on the structural details.
S. Khorsand, K. Raeissi, F. Ashrafizadeh,
Volume 34, Issue 4 (3-2016)
Abstract
Super-hydrophobic nickel and nickel-cobalt alloy coatings with micro-nano structure were successfully electrodeposited on copper substrates with one and two steps electrodeposition. Surface morphology, wettability and corrosion
resistance were characterized by scanning electron microscopy, water contact angle measurements, electrochemical impedanc spectroscopy (EIS) and potentiodynamic polarization curves. The results showed that the wettability of the micro-nano Ni and Ni-Co films varied from super-hydrophilicity to super-hydrophobicity by exposure of the surface to air at room temperature. The corrosion results revealed the positive effect of hydrophobicity on corrosion resistance of Ni coating (~10 times) and Ni-Co coating (~100 times) in comparison with their fresh coatings. The results showed that super-hydrophobic nickel coating had higher corrosion resistance than super-hydrophobic nickel-cobalt coating.
M. Alizadeh, A. Cheshmpish,
Volume 37, Issue 2 (9-2018)
Abstract
In this research, Ni-Mo-Al2O3 composite coatings were electro-deposited on the mild carbon steel in a citrate bath containing micro- sized Al2O3 particles. Afterward, the effect of the particle concentration in the electrolyte bath (ranging from 0 g/L to 30 g/L) on the microstructure, microhardness, and corrosion performance was evaluated. To investigate the microstructural changes and the surface morphology of the coatings, as well as the particle distribution in the deposits, optical and scanning electron microscopy coupled with the energy dispersive X-ray spectroscopy was utilized. The corrosion behavior of the prepared coatings was investigated in a 3.5 wt. % NaCl solution. The results showed that the presence of the Al2O3 particles in the Ni-Mo coatings changed the microstructure and also, increased the microhardness and corrosion resistance of them. It was also found that the desirable structure of the protruding crystallite morphology with no detectable pores could be achieved at the medium concentrations of reinforcement (e.g. 20 g/L). Further the optimum concentration of the particles in the electrolyte bath to attain the composite coating with the desirable microstructure and consequently, the desirable corrosion resistance was found to be 20 g/L.
