T HE passivation effect of polyaniline (PANI) was utilized to enhance the protection efficiency of styrene-acrylate waterborne coatings against corrosion of carbon steel (CS). Styrene-acrylate emulsion (SACE) based on poly (styrene-co-butyl acrylate) was synthesized via a semi-batch emulsion polymerization while the PANI emulsion (PANE) was prepared by chemical oxidative polymerization of aniline in the micelles of sodium dodecyl benzene sulfonate. The coating formulations (Fs) were prepared by adding PANE to SACE at different weight solid ratios. The viscosity, density, solid content, particle size distribution, the shape of the particles, and stability of the blended emulsions were studied. The properties of the coatedfilms were evaluated such as hardness, impact resistance, flexibility, adhesion to the steel, glass transition temperature (Tg), and surface morphology. The effect of PANE in enhancing the protection efficiency of SACE film against corrosion of CS was estimated by visual corrosion test, weight loss measurements, and electrochemical Tafel polarization. The results showed an increase in the Tg from 23 o C for pure SACE film up to 36 o C for the film containing the maximum PANI content. SACE film loaded with 0.75% and 1% PANI exhibited the least corrosion current density of 0.07 and 0.11 µA/cm 2 , respectively. The formation of a passive layer on the coated-CS was recorded by the shift of corrosion potential for steel to the anodic direction.

Kaolinite/polyaniline nanocomposites (KPAns) were prepared by in situ chemical oxidative polymerization. The nanocomposites were synthesized with four different aniline to kaolinite weight percentage; 5, 10, 15, and 20% to produce KPAn5, KPAn10, KPAn15, and KPAn20, respectively. The structural, morphological and thermal properties of the nanocomposites were characterized using Fourier transform infrared, X‐ray diffraction, scanning electron microscope (SEM)–energy dispersive X‐ray analyzer, transmission electron microscope, and Thermogravimetric analysis. The results revealed a very slight increase in the d‐spacing of kaolinite XRD peaks. SEM images showed hexagonal platy sheets of kaolinite crystals that are indistinguishable in KPAn nanocomposites images, especially on using a high amount of polyaniline (PANI). The increase in the percentage of carbon and nitrogen elements in EDAX data proved the adsorption of PANI on the surface of kaolinite platelets. To investigate the anticorrosive performance of the synthesized nanocomposites, kaolinite and KPAn nanocomposites were loaded in various amounts (1, 5, and 9%) in a blend of chlorinated rubber/medium oil alkyd resin (CR/MA) to prepare different formulations that were applied and evaluated as protective coats on steel substrates. Visual corrosion test revealed that 5% KPAn‐loaded CR/MA coats exhibited the best protection against corrosion amongst other formulations as indicated by their lowest degree of rusting and blistering. Potentiodynamic polarization measurements confirmed the highest protection of 5% KPAn10‐loaded CR/MA coat as indicated by the quantitative corrosion rates obtained from Tafel extrapolation. POLYM. COMPOS., 40:2777–2789, 2019. © 2018 Society of Plastics Engineers

The stress corrosion cracking (SCC) behavior of α-Al bronze alloy (Cu 7 Al) was investigated in 3.5% NaCl solution in the absence and in the presence of different concentrations of Na 2 S under open circuit potentials using the constant slow strain rate technique. Also, the addition of different concentrations of cysteine (cys), and alanine (ala) to the test solution, as corrosion inhibitors, was studied. Increasing the sulfide ions concentration in polluted salt water resulted in a reduction in the maximum stress (σ max) and an increase in the susceptibility of α-Al bronze towards SCC. The addition of ala and cys to the test electrolyte increased the time to failure by changing the mode of failure from brittle transgranular cracking to ductile failure. Electrochemical tests were performed to assist the interpretation of the SCC data. Electrochemical impedance spectroscopy (EIS) was used to investigate the mechanism of corrosion inhibition. The results support film rupture and anodic dissolution at slip steps as the operating mechanism of the SCC process. Therefore, cys and ala can be considered as potential environmentally-friendly corrosion inhibitors for the SCC of α-Al bronze in 3.5% NaCl solution containing sulfide ions.

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