SCIENCE AND ENGINEERING CORROSION
Year:2017 | Volume:6 | Issue:12 (22)|Papers Count:7

Due to the formation of porous oxide on the steel surface it can't directly use by PEO procedure. Therefore, in this research, hot diPping process (at 750°C and 5 min) was used to deposit Al coating on steel substrate. Plasma electrolytic oxidation (PEO) was aPplied on the obtained aluminized coating to measure its resistance to corrosion attack. SEM was used to evaluate the microstructure of PEO coatings deposited on aluminized steel by different aPplied Voltages. XRD was also used to analyze the phases on PEO coatings generated by aPplied different Voltages.Corrosion behavior of the coatings was also investigated using polarization tests in 3.5% NaCl solution. Results in indicated that the coated samples prepared at 400 Volts developed a coatings with porosity of about 4.86% and a thickness of 30 mm had a corrosion current density of 2.88 ×10-8 A/cm2 which in comparison to that of coated samples produced at Voltages of 350 and 450 Volts with corrosion current densities of 1.04×10-7 A/cm2 and 2.18×10-7 A/cm2 respectively showed an improvement of 1.98 to 2.5 times in corrosion resistance.

Using fluoride mouth washes is recommended to protect the teeth during orthodontic treatment. Therefore it is important to investigate the effect of fluoride ion on the pitting corrosion of orthodontic archwires. The aim of this study is to investigate the effect of fluoride ion on the corrosion behaviour of NiTi and NiTiNb orthodontic archwires in chloride solution by means of potentiodynamic and potentiostatic polarysation techniques.Results revealed that NiTi orthodontic wire is susceptible to pitting corrosion in chloride solution. Fluoride ion was found to have an inhibition effect and its addition increases the pitting potential for NiTi wire. The pitting potential increases also by increment in the F-/Cl- concentration ratio. NiTiNb orthodontic archwire shows passivity behaviour in sole fluoride solutions; however, its pitting corrosion was observed in solution containing both chloride and fluoride ions.

The cladding of plain carbon steel with stainless steel is desired in industry because increase of corrosion resistance and reduction of economic costs. The cladding using tungsten electrode arc welding and shielding gas is in more attention due to unique features such as high quality and good adhesion to the base metal. In this study ER309L austenitic stainless steel was used as the primary layer and E316L as the final layer, on the SA516- Gr70 steel as well as the effect of heat input at four heat level (574.5 j/mm, 609, 673, 743.5) was investigated. The ferrite was measured by a ferrite meter and Cr-Ni equivalent chart. From these results the amount of ferrite was higher at minimum heat input with respect to other heat inputs. The corrosion resistance of the samples was evaluated. According to the results, it was observed that increasing the heat input reduced the corrosion resistance and the highest corrosion resistance was observed at minimum heat input (574.5 j /mm).

The study employed sequential DC plasma electrolytic oxidation on morphology and behavior of coatings on CP titanium. The coatings formed in two steps first in silicate, next in calcium phosphate. The influence of second step coating in silicate and calcium phosphate electrolytes on morphology, phase structure and corrosion behavior were studied using SEM followed by EDS, XRD and polarization. Due to low thickness coating in silicate electrolyte and increasing applied Voltage, coatings formed in calcium phosphate have a low size porosity compare to coating formed in silicate electrolyte and in turn revealing an improvement in corrosion resistance. Unlike coatings formed first in calcium phosphate then in silicate electrolyte, the size of porosity increased and corrosion resistance has been decreased.

Plasma electrolytic oxidation is a relatively recent coating technique that is used to enhance the corrosion resistance of metals such as titanium, aluminum, magnesium and zirconium. In this paper, the effects of adding sodium hydroxide to phosphate electrolyte on the microstructure and corrosion resistance of the plasma electrolytic oxidation coating of pure titanium have been evaluated. To analysis the corrosion behavior, samples were subjected to the Ringer's solution and potentiodynamic polarization and electrochemical impedance spectroscopic analysis were performed. The microstructural, phase and chemical analysis of the coating were carried out using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive X-ray spectroscopy (EDX) respectively. The results of the corrosion test showed that the addition of sodium hydroxide to the coating electrolyte enhances the corrosion resistance of the coating. Addition of sodium hydroxide to the electrolyte decreases the break down voltage of the dielectric and increases the absorption of the phosphorous.Moreover, SEM images revealed that the presence of sodium hydroxide modifies the structure of the coating, decreases the surface voids and enhances the growth of the coating.

In this article the results of the Duty Cycle on corrosion properties of Pulse Electrodeposited Ni-Cu-CeO2 nanocomposite coating are presented. The nanocomposite coating was obtained by the codeposition of CeO2 nanoparticles with Ni-Cu during the electroplating process. The coating thickness obtained on the St.37 low carbon steel was 26 mm. The surface morphology and composition of the coating was studied using SEM Field Emission (FESEM) with energy dispersive analyzer system (EDX). It was found that the Ni-Cu-CeO2 nanocomposite coating surface morphology is smooth. The electrochemical behavior of the coating was investigated by Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy methods. It was found that with the increase in Duty Cycle, The corrosion current increased and the potential became more negative. The results of energy dispersive analyzer system (EDX) showed that as the Duty Cycle increased the amount of nanoparticles in the coating is decreased.

Anticipating the protection performance of coatings, before using them in the field is a significantly factor. Quality control testing in accordance with the international standards is time-consuming, and the results are qualitative.In this research, a new strategy for determining vessel and tank internal coating performance has been developed, which is a fast assessment method with quantitative results. Some tests such as hot water soak, Immersion and electrochemical spectroscopy, impedance in high temperature conditions, and dry and wet adhesion have been selected as critical tests which were done on four different commercial Epoxy coating samples. The reaction of stoichiometric mixture of two components (Epoxy and hardener) and the effect of physical properties of polymer matrix on the coating resistance and corrosion control have been investigated by using FTIR measurement and thermo gravimetric analysis (TGA).The results of TGA and FTIR have shown that the selected coatings are different in terms of chemical structures and glass transition temperature (Tg). The results of mechanical and electrochemical tests have confirmed that the protective performance of these coatings is related to their chemical structures and Tg of polymer matrices. On the other hand, this new strategy makes it possible to quantitatively predict the protective performance of the coating, in a short time. The results of tests on the four epoxy coatings are demonstrated that although all of the coating samples are epoxy-based and suitable for using as recommended by the manufactures, their protective performance and resistance against electrolyte diffusions are considerably variant.