Optimization of electrochemical polymerization parameters of polypyrrole on Mg–Al alloy (AZ91D) electrodes and corrosion performance

Preparation and Corrosion Performance of PPy/Silane Film on AZ31 Magnesium Alloy via One-Step Cyclic Voltammetry

PPy/silane composite film on a magnesium alloy surface was prepared by one-step cycle voltammetry. The mixed solution of methanol and water was used as the hydrolysis solvent of a γ-(2,3-glycidoxypropyl) trimethoxysilane coupling agent (KH-560). The surface morphology of the PPy/silane film, the electro-polymerization progress of KH-560 and PPy, the influence of the silane coupling agent and the corrosion behavior of the coated AZ31 Mg alloy were all investigated. The results indicated that the PPy/silane film on AZ31 Mg alloy via one-step cyclic voltammetry could provide better corrosion protection for an Mg alloy when the volume fraction of KH-560 in the hydrolysis solution was 15% and the time span of hydrolysis was 24 h with the 5.935 × 10⁻¹⁰ A cm⁻² corrosion current density.

Synthesis of Polypyrrole/V2O5 Composite Film on the Surface of Magnesium Using a Mild Vapor Phase Polymerization (VPP) Method for Corrosion Resistance

The vapor phase polymerization (VPP) method is a conventional strategy for synthesizing conducting polymers (CPs) on the surfaces of various materials. However, the current VPP method performed on a metal surface usually requires harsh reaction conditions, such as high temperature and low vacuum. In this paper, a polypyrrole (PPy) and vanadium pentoxide (V2O5) composite film was synthesized on the surface of Mg using a mild VPP method. Here, V2O5 was used as an oxidant, and it was found that the oxidation of pyrrole (Py) vapor on the surface of V2O5, which had been previously coated on the surface of Mg, could be performed at room temperature under normal atmospheric pressure. The formation of the PPy/V2O5 composite was verified by Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray (EDX) spectroscopy. A thermogravimetric analyzer (TGA) was used to study the thermal stability of the composite. Subsequent corrosion tests showed that the PPy/V2O5 composite film could slow down the corrosion of Mg in 3.5 wt% NaCl. It is expected that the mild VPP method may find great potential in the fields of synthesis of CPs and the corrosion protection of reactive metals.

Analyses of New Electrochemical Techniques to Study the Behavior of Some Corrosion Mitigating Polymers on N80 Tubing Steel

Two synthesized polymers were studied as potential corrosion inhibitors for N80 Steel in a sweet corrosive environment. Poly-2-(methacryloyloxy)ethyltrimethyl ammonium chloride (PDMC), or P1, and poly-2-(methacryloyloxy)ethyltrimethyl ammonium chloride-co-N-vinyl-2-pyrrolidone P(DMC-co-NVP), or P2, were investigated using electrochemical impedance spectroscopy, polarization technique, scanning electrochemical microscopy (SECM), scanning Kelvin probe (SKP), and scanning vibrating electrode technique (SVET). The surface was examined using contact angle, scanning electron microscopy, and atomic force microscopy methods. Analyses of electrochemical and polarization techniques revealed a PDMC polymer with a better inhibition efficiency. The SECM, SKP, and SVET methods showed the insulating ability of the polymers that formed a protective coating on the metal surface.

Corrosion protection of AZ31 alloy and constrained bacterial adhesion mediated by a polymeric coating obtained from a phytocompound

The prevention of microbial biofilm formation on a biomaterial surface is crucial in avoiding implants failures and the development of antibiotic resistant bacteria. It was reported that biodegradable Mg alloys may show antimicrobial effects due to the alkalinization of the corroding area. However, this issue is controversial and deserves a detailed study, since the processes occurring at the [biodegradable metal/biological medium] interface are complex and varied. Results showed that bacterial adhesion on AZ31 was lower than that of the titanium control and revealed that was dependent on surface composition, depicting some preferential sites for bacterial attachment (C-, P-, O-containing corrosion products) and others that are particularly avoided (active corrosion sites). As a key challenge, a strategy able to improve the performance of Mg alloys by both, reducing the formation of corrosion products and inhibiting bacterial adhesion was subsequently developed. A polymeric layer (polyTOH) was obtained by electropolymerization of thymol (TOH), a phytophenolic compound. The polyTOH can operate as a multifunctional film that improves the surface characteristics of the AZ31 Mg alloy by enhancing corrosion resistance (ions release was reduced to almost the half during the first days) and create an anti-adherent surface (bacterial attachment was 30-fold lower on polyTOH-AZ31 than on non-coated Mg alloy and 200-fold lower than Ti control and was constrained to specific regions). This anti-adherent property implies an additional advantage: enhancement of the efficacy of antibiotic treatments.

Enhancement of corrosion resistance of polypyrrole using metal oxide nanoparticles: Potentiodynamic and electrochemical impedance spectroscopy study

We introduce a simple and facile strategy for dispersing of nanoparticles within a p-type conducting polymer matrix by in situ electropolymerization using oxalic acid as the supporting electrolyte. Coatings prepared from polypyrrole-nano-metal oxide particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polypyrrole (Ppy) in aggressive environments. The anti-corrosion behavior of polypyrrole films in different states and the presence of TiO₂, Mn₂O₃ and ZnO nanoparticles synthesized by electropolymerization on Al electrodes have been investigated in corrosive solutions using potentiodynamic polarization and electrochemical impedance spectroscopy. The electrochemical response of the coated electrodes in polymer and nanocomposite state was compared with bare electrodes. The use of TiO₂ nanoparticles has proved to be a great improvement in the performances of polypyrrole films for corrosion protection of Al samples. The polypyrrole synthesized in the presence of TiO₂ nanoparticles coated electrodes offered a noticeable enhancement of protection against corrosion processes. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nanosize TiO₂, redox properties of polypyrrole as well as very large surface area available for the liberation of dopant due to nano-size additive.

Corrosion Performance of Polypyrrole Coated Type 304 Stainless Steel for Bipolar Plates of Proton Exchange Membrane Fuel Cell

Polypyrrole coating doped with dodecylsulfate anions was electrodeposited by cyclic voltammetry and constant current technique on type 304 stainless steel used for bipolar plates of a proton-exchange membrane fuel cell from a basic solution of 0.2M pyrrole monomer solution containing dodecylsulfate sodium as supporting electrolyte. The morphology and corrosion performance of Ppy coated samples were investigated. Microscopic observations showed that the polypyrrole synthesized by constant current technique present a more dense constitution. Electrochemical measurements in 0.1M HCl solution showed that the polypyrrole synthesized by constant current technique provided better protection for the stainless steel.