Study of Adsorption/Desorption Effect of 2-Mercaptobenzothiazole as Sweet Corrosion Inhibitor on API-5L X60 Steel

Protection of Metals and Physical Chemistry of Surfaces - In this study, the inhibitive performance of 2-mercaptobenzothiazole (2MBT) and 2-aminobenzothiazole (2ABT) were investigated on API-5L X60...     

Evaluating protection performance of zinc rich epoxy paints modified with polyaniline and polyaniline-clay nanocomposite

Cloisite 30B nano clay was delaminated in the presence of aniline monomers using supercritical CO₂ (ScCO₂) process. Rapid mixing polymerization of aniline monomers was done in supercritical CO₂ to produce exfoliated polyaniline clay (PAniC) nanocomposites with high barrier properties. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and XRD analysis have been used to characterize morphology and structure of the synthesized products. The synthesized products were added to a commercial zinc rich epoxy primer to improve its initial barrier properties. Barrier properties of unmodified and modified primers were then studied by determining water vapour transmission (WVT) rate of their free films, free corrosion potential (E_corr) and electrochemical impedance spectroscopy (EIS) measurements of carbon steel coated panels. Results showed that samples modified with PAniC nanocomposites had better barrier properties compared to PAni modified and original primers. The coating resistance of PAniC modified primer was at least one order of magnitude higher than other primers at the begining of immersion. After one year of immersion, the coating resistance of original, PAni modified and PAniC modified primers were found to be 267, 1610 and 5540 ohm, respectively.     

Corrosion inhibition of steel in sodium chloride solution by undoped polyaniline epoxy blend coating

In this study an undoped polyaniline (PAni) was synthesized by chemical oxidative polymerization with ammonium persulfate as an oxidizing reagent. The synthesized PAni was used as a corrosion inhibitive pigment in an epoxy matrix. The corrosion protection performance of steel coated panels in 3.5% sodium chloride solution was evaluated via determination of open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). It was found that after 300 days of immersing the resistance of coating was about 4 × 10⁵ Ω cm². The OCP was shifted to the noble region due to the passivation effect of PAni pigment. Besides, the phase angle (theta) at 10 kHz was stable around 87 ± 1° during immersion period. Results revealed that PAni pigmented paint showed acceptable protection against the corrosion of carbon steel in 3.5% sodium chloride solution.     

Evaluation of a high resistance paint coating with EIS measurements: Effect of high AC perturbations

Electrochemical impedance spectroscopy (EIS) was used to evaluate a high resistance paint coating immersed in 10% sodium chloride solution. Although this method was valuable in evaluating this type of coating there were many fluctuations in measured data at low AC perturbations. In this work the role of high AC perturbation to fit EIS data of high resistance coating with equivalent electrical circuit (EEC) was studied. EIS measurements showed that these fluctuations could be reduced by high AC perturbation. The impedance plots showed best fitting at 400 mV AC perturbation at the initial time of immersion and at 100 mV AC perturbation after 90 days of immersion. The coating resistance and coating capacitance were extracted from the Bode and Nyquist plots during the period of 90 days of immersion.     

Electrochemical evaluations of zinc-rich epoxy primers modified with polyaniline and exfoliated polyaniline graphite nanocomposite

ABSTRACT

Polyaniline (Pani) and exfoliated polyaniline graphite (EPaniG) nanocomposites were used to modify the protective properties of an epoxy zinc-rich primer (ZRP). The corrosion resistance properties of primers were evaluated in 3.5% sodium chloride solution for a period of 120 days via electrochemical noise (EN) and electrochemical impedance spectroscopy (EIS). EN data were analysed via Wavelet and Hilbert spectra analysis to evaluate the protection mechanism of different ZRP coatings during immersion. Coating resistance and charge transfer resistance of the primers were evaluated by EIS measurements. Results showed good compatibility between |Z|_0.01Hz from EIS measurements and mean noise resistance which results from EN data and these evaluations allowed the examination of coating performances during immersion. Free corrosion potential (E_corr) measurements and salt spray test revealed that both the cathodic protection and barrier properties of the ZRP primer were improved after addition of EPaniG nanocomposite to the ZRP sample.     

Experimental evaluation of high solid polyurethane coating in the presence of salt at high temperature

Ions' presence and high temperature affect the performance and service life of all types of coatings including pipeline coatings. Pipeline coatings are relatively thick and their evaluations are very time consuming. In this study, experiments on the thick coating samples (roughly 250 and 400 µm) of high solid polyurethane (HSPU) have been conducted to evaluate the effect of high temperature and presence of ions in the media, on the performance of coatings. The experiments were performed in two types of electrolytes, sodium chloride solution (3.5 wt% fraction) and distilled water, at two temperature levels of 25 and 75 °C, respectively. The coating performance was studied using electrochemical spectroscopy impedance (EIS) method. The results of experiments show that the presence of ions reduces the service life of the coating and higher temperature accelerates the degradation process further if oxygen is not limited.     

Synthesis and evaluating corrosion protection effects of emeraldine base PAni/clay nanocomposite as a barrier pigment in zinc-rich ethyl silicate primer

In the present work, polyaniline/clay nanocomposite (PAniCN) was synthesized by chemical oxidative polymerization of aniline monomers in the presence of Closite30B powders. XRD and SEM examinations were used to examine the intercalation and morphologies of PAniCN, respectively. Electrical conductivity test showed that the conductivity of final PAniCN was higher than pristine PAni by one order of magnitude. Synthesized nanocomposite was added to the zinc rich ethyl silicate primer to modify its barrier properties. The corrosion protection performances of modified and unmodified primers were evaluated using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution for a period of 120 days. It was found that the modified primer had higher barrier properties than original primer. After 120 days of immersion, resistance of modified and unmodified primers reaches 5.565 × 10³ Ω cm² and 6.056 × 10² Ω cm² respectively. The OCP of both primers were lower than −800 mV/SCE during the immersion. Besides, the OCP of modified primer was higher than the original primer due to the passivation and barrier effects of PAniCN. Results revealed that the performance of modified primer improved strongly.     

Sulfonation of base oils as corrosion inhibitor for temporary protection of steel in atmospheric environment

Base oil corrosion temporary protective coatings were synthesized. These coatings contain of inhibitor agent, antioxidant agent, and base oil as main bed. Inhibitor agents were prepared by sulfonation of Iran traditional mineral base oils. Iran traditional base oils were SAE10, SAE30 and SAE40. They are sulfonated at different temperatures with oleume as reactive agent. Sulfonation efficiency and production quality of this process are evaluated in different conditions. Neutralization of sulfonate groups were complied with calcium hydroxide to achieved hydrophilic salt groups of calcium sulfonate. Final products are used as inhibitor agents in base oils to prepare temporary protective coatings. They are applied to 1020 steel panels by dipping method.     

Highly protective performance of water-based epoxy coating loaded with self-doped nanopolyaniline synthesized under supercritical CO2 condition

In this study corrosion properties of water-based epoxy coating on carbon steel (CS) are improved by adding self-doped nano-polyaniline (SPAni) synthesized under supercritical carbon dioxide (ScCO₂) condition. The modified ScCO₂-synthesized SPAni using water-based polyamidoamine hardener results in formation of the water-based SPAni composite (Sc-WB). To obtain the water-based polyaniline epoxy coating (SP-WBE), the Sc-WB was mixed with epoxy resin in stoichiometric ratio. Applying SP-WBE on CS substrate resulted in high improvement in corrosion properties compared to the similar coating without SPAni. Formation of oxide layers and adhesion properties of SP-WBE at corrosive medium were evaluated using scanning electron microscope (SEM). The transmission electron microscope (TEM) was used to observe the distribution and particles size of nanopolyaniline in the final dried film. The anti-corrosion performance of water-based epoxy coating (blank sample) and SP-WBE coating on CS substrates were studied using salt spray standard test according to ASTM B-117, electrochemical impedance spectroscopy (EIS) and adhesion tests. EIS studies, after 1800 hrs of exposure to corrosive solutions, result in charge transfer resistance of 1.816E9 Ω and 8.64E7 Ω for SP-WBE and blank samples, respectively.     

Synthesis and evaluation of water-reducible acrylic–alkyd resins with high hydrolytic stability

Relatively poor hydrolytic stability is one of the major drawbacks of waterborne alkyd resins. Therefore, the shelf life of the paints containing these kinds of resins is usually short. In this research, the hydrolytic stability of water-reducible alkyd resins has been improved by employing polyacid acrylic copolymers in alkyd resins structure. In addition, the effect of other raw materials (such as neutralizing agent) and synthesis conditions on the resins properties was investigated. The results showed that the optimum synthesized water-reducible acrylic–alkyd resins had a high hydrolytic stability and their acid values increased only 23.5% after 4 months storage at ambient temperature. The synthesized resin was also used in an air-drying water-reducible lacquer formulation and its physical and mechanical properties were evaluated.