h. eivaz mohammadloo

In this study, synthesize of the non-isocyanate-based polyhydroxy urethane from linseed oil and the effect of increasing the carbonation conversion percentage on the resulted polyurethane coating properties were studied. For this purpose, double bonds of the linseed oil were converted to the epoxy rings at the first step, and then these epoxy rings were turned into the carbonate rings with carbonation reaction with different percentages (45%, 75% and 100%), which will break these rings and form urethane bond by reacting with amine hardeners. The Fourier-transform infrared spectroscopy (FTIR) was used to characterize the samples )In the epoxidation step, the 1689 cm-1 peak, which corresponds to the carbonate double bonds in linseed oil, became smaller, and the 823 cm-1 peak, which corresponds to the epoxy rings, formed, and then in the second stage, 823 cm-1 become smaller and the formation of the peak of 1800 cm-1 represent the carbonate ring formed instead of epoxy rings). Differential scanning calorimetry (DSC) was used to assesses the curing conditions. After that, the optimal curing temperature and time were determined (suitable time for curing is 2 hours for preheating at 100°C and then 2 hours to complete the cure process at 180°C), and finally, the physical, mechanical and anti-corrosion properties of samples were compared through Pull-off, Crosscut, hardness, impact, bending and Electrochemical Impedance Spectroscopy (EIS) tests. The results of the characterization tests confirmed the epoxidation of linseed oil and carbonation of the epoxidized linseed oil. Also, coating properties showed improvement of adhesion and hardness and reduction of flexibility by increasing the carbonation conversion and increasing of the anti-corrosion properties first and then decreasing it by increasing the percentage of carbonation. After 2 weeks immersion in corrosive electrolyte, sample with 75% of carbonation revealed anti-corrosion resistance equal to 5.38×106 ohm.cm2 while solvent-base polyurethane indicated 1.03×107 ohm.cm2 . Finally, polyurethane resine synthesized from 75% carbonated linseed oil represents the optimum properties for coating application.

Solvent and water-based polyester resins are used in many different applications; one of them is the automotive paints' primary layers. In this research, a water-reducible polyester resin curable with melamine was synthesized (PS1). This resin was cured for 30 minutes with a temperature of 120 ̊C. The final product is a water-reducible resin, which was synthesized, neutralized and diluted with water, and consequently, a milky white water-based dispersion was obtained. The indicating peaks of the Fourier Transform Infrared (FTIR) test alongside the results of the Differential Scanning Calorimetry (DSC) test were proof to confirm the control over the polyester resin synthesis. To evaluate the anti-corrosion and adhesion properties, the synthesized resin in a full-coating system was compared with a commercial resin. The pull-off test was used to check the adhesion strengths. PS1 (polyester resin) coating system revealed an adhesion strength value of 2.05 MPa compared to 2.51 MPa for RW100. Digital images taken from the samples' surface in the salt spray test showed that after one month in a corrosive environment, synthesized resin has better anti-corrosion resistance than commercial sample. Electrochemical Impedance Spectroscopy (EIS) test indicated that after 15 weeks of immersion in the 3.5% sodium chloride electrolyte solution, the synthesized resin system indicated an impedance resistance at low frequency of 4.05 ×109 ohm.cm2, which is more than the Daotan VTW 1225 (2.75 ×106 ohm.cm2).

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.

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.

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.