Sandra R. Moraes

Electrosynthesized polyaniline for the corrosion protection of aluminum alloy 2024-T3

Adherent polyaniline films on aluminum alloy 2024-T3 have been prepared by electrodeposition from aniline containing oxalic acid solution. The most appropriate method to prepare protective films was a successive galvanostatic deposition of 500 seconds. With this type of film, the open circuit potential of the coating shifted around 0.065V vs. SCE compared to the uncoated alloy. The polyaniline coatings can be considered as candidates to protect copper-rich (3 - 5%) aluminum alloys by avoiding the galvanic couple between re-deposited copper on the surface and the bulk alloy. The performance of the polyaniline films was verified by immersion tests up to 2.5 months. It was good with formation of some aluminum oxides due to electrolyte permeation so, in order to optimize the performance a coating formulation would content an isolation topcoat.

Influence of the Synthesis Parameters on the Polyluminol Properties

Polyluminol was synthesized from sulfuric acid aqueous solution (1 to 5 mol–L−1) containing luminol (0.5 to 10 mmol–L−1) on platinum electrode by cyclic voltammetry. A systematic investigation was performed on the synthesis parameters, resulting in optimized conditions to obtain polyluminol, which are: (i) 2 mol–L−1 H2SO4 aqueous solution; ii) containing 7.5 mmol–L−1 of luminol; (iii) using thirty potential cycles; (iv) at 100 mVs−1. Preparation parameters and electrosynthesis solutions play important roles in eletropolymerization of polyluminol. In general way, all polyluminol films were electroactives in H2SO4 solution independent of synthesis conditions.

PAni as Prospective Replacement of Chromium Conversion Coating in the Protection of Steels and Aluminum Alloys

Corrosion inhibition properties of chemical and electrochemically synthesized polyaniline(PAni), poly-o-methoxianiline(POMA)and their copolymers, in form of coatings of stainless steel AISI 304 and aluminum alloy 6061-T6 are studied in 3%and 0.1 M NaCl solutions, respectively. Polarization curves showed that the protection of steels by PAni is of anodic nature by setting the redox potential in the passive potential of the substrate. However, the protection of aluminum alloys after separation of both the corrosion and pitting potential is also anodic.

Aspects of the Chemical Synthesis of PAni-DBSA and its Properties

An investigation of the synthesis parameters (i.e., temperature and acid concentrations) in the chemical preparation of PAni-DBSA, was performed. The synthesis temperature was varied from 0° to 40°C, producing a strong effect on both the oxidation states during chain propagation stage and properties of polymers. DBSA molecules are incorporated in the PAni chain. The synthesis temperature has a strong influence on the properties of PAni-DBSA. PAni with a needle-like structure and compact morphology was obtained. The conductivity of polymers is dependent on the benzenoid/quinoid ratio in the polymer chain.

PAni-CMC: Preparation, Characterization and Application to Corrosion Protection

ABSTRACT By using cyclic voltammetry composites of polyaniline and carboxymethylcellulose were synthesized on AISI 304 from a 1 MH3PO4 aqueous solution containing 0.2M aniline and CMC varying from 0.1 to 1% wt. The characterization was performed by different techniques and it was possible to observe that increasing the CMC content, a more packed structure is promoted, compared to the granular structure of PAni films. The evaluation of the composites to protect the substrate against corrosion showed that in doped and undoped states the composites present effective corrosion protection of AISI-304 and that the composition of the films changes after corrosion tests.

Influence of Reaction Conditions on Synthesis of PAni/MnO2 Composites

An investigation of the parameters as aniline:MnO2 and temperature on synthesis of polyaniline/MnO2 composites was performed. The composites were chemically prepared in H2SO4 media using different aniline: MnO2 ratios at 0°C. After the ratio optimization, the syntheses were performed at 20°C. The polyaniline/MnO2 composites were characterized by scanning electron microscopy (SEM), ultraviolet-visible, near infrared and infrared spectroscopic techniques. Composites obtained with a uniform, homogeneous and thicker coating of polyaniline films under oxide was considered as the best condition for synthesis.

Preparation and characterization of polyaniline powder synthesized on microstructured aluminium

Aluminium surfaces were microstructured in 0.1 M HNO3 by potentiodynamic anodic activation to potentials generating pitting. This surface was then used as an electrode to prepare polyaniline powder. The number of pits is responsible for the amount of powder produced. Emeraldine salt powder was successfully prepared from 0.4 M aniline in 0.5 M H2SO4 solution. Other acid solutions for deposition are not convenient because powders are electrochemically inactive (e.g., in 1 M HNO3) or the electrode is covered by a film (e.g., in 0.5 M H2C2O4).

Polyaniline Synthesized in Phosphate Buffered Media Applied to Corrosion Protection

Successful attempts to prepare compact and excellent adherent films of polyaniline (PAni) from phosphate buffered solutions on stainless steel are reported. Chemically synthesized PAni applied by coating from NMP-solution is compared to the electrochemically deposited one prepared by cyclic voltammetry. A systematic study of the corrosion inhibiting action of PAni in 3% NaCl solution shows a beneficial effect on protection in its doped state where the redox process controls the surface reaction. In undoped form PAni acts as a simple barrier film.