a. a. sarabi

Usually, in all applications where an organic coating is applied on the surface, physical and chemical surface preparations need to enhance adhesion and anti-corrosion resistance of the system. Control of surface roughness and chemistry of modified metal by conversion coatings are effective factors in the adhesion properties of organic coatings. In this project, the behavior of anti-corrosion resistance and adhesion of epoxy coatings in the presence and absence of anti-corrosion glass flakes pigments on the surface of steel prepared by applying the zirconium conversion coating and sandblast method were examined. Conversion coating was formed on the surface in the optimum condition of practical parameters. In the next step, the effect of the type of surface preparation on the anti-corrosion resistance and morphology behavior of the coating was investigated using electrochemical tests and atomic force microscope images. It was found that the samples prepared with conversion coating indicated the best anti-corrosion resistance and adhesion strength as a result of the change in the roughness and changing the surface chemistry. Finally, epoxy/glass flake coating with 10% of glass flake was applied on the prepared surface through conversion coating and it was found that adding glass flakes increase the anti-corrosion resistance of the coating and these results confirmed by the salt spray test.

Conversion Coatings are one of the effective ways for improving adhesion of organic coatings to metallic substrates and consequently increasing anti-corrosion performance of a fully coated system. In the current research, multi-cationic conversion coating formed from sources such as hexafluorotitanic acid, sodium molybdate, phytic acid and nickel sulphate was studied and investigated. Results obtained from electrochemical impedance spectroscopy and polarization revealed that conversion coating which formed in the presence of sodium molybdate has not appropriate polarization resistance and the reason for this weak performance investigated by field emission scanning electron microscope. Obtained results showed that in the presence of sodium molybdate, there were abundant micro-cracks on the surface of the coating. After optimizing the multicationic conversion coating, an epoxy coating applied on the surface of bare steel and conversion coated one. The results obtained from adhesion and salt-spray tests indicated that the multi-cationic conversion coating causes improvement in adhesion strength of epoxy coating to steel substrate and finally increased the anti-corrosion performance of the system.

In this research, the anti-corrosion resistance of titanium/zirconium based conversion coating on Al-2024 substrate was investigated. Ti/Zr solution practical parameters such as acids concentrations(1, 5, 10 g/lit) solution pH (3, 4, 5), and immersion time (1, 3, 5 min) were optimized Obtained result from DC (Direct polarization) and EIS (Electrochemical Impedance Spectroscopy) revealed that Ti/Zr conversion coating with the acid concentration of 1 g/lit for both H2ZrF6 and H2TiF6 solution pH equal to 4 and immersion time of 3min had the highest anti-corrosion performance. Corrosion current density and low frequency impedance values for untreated substrate are 48.1 μA/cm2 and 1439 ohm.cm2 respectively. These values for optimized Ti/ Zr conversion coating are 6.1 μA/cm2 and 4206 ohm.cm2. Also, field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM) images indicated the presence of fine and compact particles on the surface of Ti/Zr treated substrate

Phosphate conversion coating is one of the conversion coatings that have high applications indifferent industries due to the good corrosion resistance. In this study, anti-corrosion resistance of the zinc phosphate conversion coatings on cold rolled steel (CRS) with different immersion times (1, 5 and 25 min), different solution temperatures (37-57 ° C) and different pH values (1.7, 2.7, 3.7, 4.7 and 5.7) was studied, using direct current (DC) polarization and electrochemical impedance spectroscopy (EIS). Electrochemical results revealed that the best anti-corrosion resistance from zinc phosphate conversion coating was obtained in 47 °C, immersion time of 25 minutes and pH =2.7. In this point the polarization resistance (Rp) value is 225 times higher than the bare sample polarization resistance (Rp: 0.39 kΩ.cm2). Also the morphology of coated sample in optimum condition by using a field emission scanning electron microscope (FE-SEM) was evaluated. The granular structure and uniform distribution of crystals on the sample surface is a reason to confirm the obtained results from electrochemical tests for optimized sample.

Epoxy–clay nanocomposites were prepared by applying high- intensity ultrasound during the synthesis of clay – epoxy nanocomposites by two kinds of amineous curing agent, cycloaliphatic and amidoamine. Exfoliation and intercalation of nanoclay have a significant effect in improvement of physical and chemical epoxy coatings properties. The choice and condition of curing agent controls the contribution of nanoclay of these coatings.In this article, X-ray diffraction (XRD), Optical microscopy and Scanning Elecron Spectroscopy(SEM) analyses were carried out. The results of XRD showed that the distances between the silicate layer were increased from 18.02 A° to 38.5 and 41.6 A°, in two coating systems. The results of Scanning Elecron Spectroscopy(SEM) showed the nanoclay particles in the polyamidoamine coating are composed of 3% of nano with flake structure that increase the direction of the ions in the time of getting the metal surface. The result of optical microscopy also shows the appropriateness of the ultrasound method in preparing nanocomposits. By using the results of Electrochemical Impedance(EIS)and Salt spray, the corrosion resistance of nanocomposites were obtained. From electrochemical impedance spectroscopy, it was observed that nanocomposite coating epoxy-polyamidoamine, with the formulation consisting of 3% nanoclay had the excellent corrosion resistance in comparison to pure epoxy coating.

In this research, the europium Eu-activated SrZn2Si2O7 phosphors were successfully prepared by sol-gel method in reductive and oxidative atmospheres. Thermogravimetric-differential thermal analysis (TG-DTA), X ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and photoluminescence (PL) spectra were used to characterize the resulting products. Obtained phosphor in reductive atmosphere is efficiently excited in the wavelength range of 350-390 nm which matches to a near UV (NUV) emitting InGaN chip and emits strong band blue light peaking at 481 nm with color coordination x=0.176, y=0.193 due to 4f65d1(2D)$4f7(8S7/2) transition of Eu2+ ions. Also, synthesized phosphor in oxidative atmosphere emits at approximately 480 and 600 nm that attributed to f-d transitions of Eu2+ and f-f electronic transitions of Eu3+, respectively. Finally, the crystallite size of the products was estimated about 30 nm by using Scherrer’s equation that this measurement was consistent with TEM observations.

effect of practical parameters such as solution pH، temperature and dipping time on coating morphology and anticorrosion resistance of coating was evaluated. Anti-corrosion resistance of so-called nanoceramic conversion coating on cold rolled steel (CRS) substrates in different solution pH، temperatures and immersion’s time، utilizing DC Polarization was studied. The conversion coating which was formed at dipping temperature of 20 °C، pH=5 and immersion’s time of 60 seconds had the best anti-corrosion resistance. The morphology of the conversion coating surface formed at different pH was investigated using Atomic Force Microscopy (AFM). Images obtained from the microscope indicate that the conversion coating which formed in pH=5 was more consistent and had finer aggregates in comparison with pH=4. 25 coating. Field Emission Scanning Electron Microscopy (FE-SEM) of conversion coating formed in 20 and 40 °C indicated that surface of conversion coating with higher temperature had micro cracks and was not uniform، also nodules on the scale of tens of nm (40–60 nm) in size، was observed on the surface. J. Color Sci. Tech. 6 (2012)، 9-18© Institute for Color Science and Technology.

Corrosion inhibition effect of cationic surfactant DTAB (dodecyl three methyl ammonium bromide) on low carbon steel in 1M HCl was studied using weight loss method. Inhibition efficiency increased with the increase of surfactant concentration. The adsorption of the surfactant on the steel surface forms a barrier layer on the surface and it was the main reason of its inhibition effect. Effect of three long chain alcohols C7OH (1-heptanol), C12OH (1-dodecanol), C15OH (1-pentanol) on inhibition efficiency of DTAB was studied considering chain length compatibility. Also synergistic effect between surfactant and chloride ions in 1M HCl was investigated with the presence of different concentration of NaCl. The inhibition efficiency increased with the increase of NaCl concentration and reached the maximum value near 0.1 M. This composite inhibitor system containing cationic surfactant and chloride ions was efficient and low-cast for steel corrosion inhibition in HCl medium. J. Color Sci. Tech. 2(2009), 257-263.© Institute for Colorants, Paint and Coatings.

Electrically conductive coatings are mainly required for static charge dissipation and electromagnetic/radio frequency interference (EMI/RFI) shielding. Electrically conductive coatings are prepared by the incorporation of the metallic pigments/graphite or carbon black onto the binder. In the present investigation, a study on the correlation between electrical, percolation threshold, filler volume concentration and some other physical and mechanical properties for graphite filled epoxy coating was carried out through an examination of the filler concentration dependence of the volume resistivity and othermechanical properties. The impact strength of epoxy resin filled with graphite was also investigated. A decrease in impact strength with an increase in filler content was observed. It is found that there are two critical threshold, in plot of electrical resistivity v.s. filler volume concentration. The adhesion of the filled resin to substrate was also determined by pull-off test. A decrease in the adhesion to substrate with an increase in filler content was observed in Then to find out the correlation between filler concentration and viscoelastic behavior of the system tensile test carried out. Then for expand a theory that can explain the transfer between insulator-semiconductor and semiconductor-conductor behavior of graphite filled system images was gived by SEM and optical microscopy and also oil absorption (for determine CPVC) test carried out. All data show that formation of internal network by graphite particles and particle by particle contact of them is the reason of formation a conductive network in epoxy system. J. Color Sci. Tech. 2(2008), 129-140.© Institute for Colorants, Paint and Coatings.