The effect of Artemisia annua L. extract on microbiologically influenced corrosion of A36 steel caused by Pseudomonas aeruginosa.

The protective effect of A. annua against microbiologically influenced corrosion (MIC) of A36 steel caused by P. aeruginosa (PA) in a simulated marine environment was investigated using electrochemical, spectroscopic, and surface techniques. PA was found to accelerate the local dissolution of A36 which led to the formation of a porous α-FeOOH and γ-FeOOH surface layer. 2D and 3D profiles of treated coupons, obtained by optical profilometer, revealed the formation of crevices in the presence of PA. On the contrary, adding A. annua to the biotic medium led to the formation of a thinner, more uniform surface without significant damage. Electrochemical data showed that the addition of A. annua prevented the MIC of A36 steel with an inhibition efficiency of 60%. The protective effect was attributed to the formation of a more compact Fe3O4 surface layer, as well as the adsorption of phenolics, such as caffeic acid and its derivatives on the A36 steel surfaces, as detected by FTIR and SEM-EDS analysis. ICP-OES confirmed that Fe and Cr species more readily diffuse from A36 steel surfaces incubated in biotic media (Fe; 1516.35 ± 7.94 µg L-1 cm-2, Cr; 11.77 ± 0.40 µg L-1 cm-2) compared to the inhibited media (Fe; 35.01 ± 0.28 µg L-1 cm-2, Cr; 1.58 ± 0.01 µg L-1 cm-2).

Green Inhibition of Corrosion of Aluminium Alloy 5083 by Artemisia annua L. Extract in Artificial Seawater.

Plant extracts are increasingly being examined in the corrosion inhibition of metal and alloys in various environments due to their potent antioxidant properties. The use of Artemisia annua L. aqueous extract (AAE) as an aluminium alloy 5083 (ALA) corrosion inhibitor in artificial seawater (ASW) was investigated using electrochemical tests and spectroscopy tools, while the active biocompounds found in AAE were analyzed using high-performance liquid chromatography (HPLC). Electrochemical results showed that AAE acts as an anodic inhibitor through the physisorption (ΔG ≈ -16.33 kJ mol-1) of extract molecules on the ALA surface, thus reducing the active sites for the dissolution of the alloy in ASW. Fourier-transform infrared spectra confirmed that phenolic acids found in AAE formed the surface layer that protects ALA against the corrosive marine environment, while HPLC analysis confirmed that the main phytoconstituents of AAE were chlorogenic acid and caffeic acid. The inhibition action of phenolic acids and their derivatives found in the AAE was based on the physisorption of caffeic acid on the ALA surface, which improved physicochemical properties of the barrier film and/or conversion of Al3+ to elemental aluminium by phenolic acids as reducens, which slowed down the diffusion rate of Al3+ to or from the ALA surfaces. The protective effect of the surface layer formed in the presence of AAE against ASW was also confirmed by inductively coupled plasma-optical emission spectrometry (ICP-OES) whereby the measured concentration of Al ions after 1 h of immersion of ALA in the pure ASW was 15.30 µg L-1 cm-2, while after the addition of 1 g L-1 AAE, the concentration was 3.09 µg L-1 cm-2.

Influence of alloying elements on the corrosion stability of CoCrMo implant alloy in Hank's solution.

The behavior of a CoCrMo alloy and its components was studied in simulated physiological solution (Hank's solution) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The passivation of all samples occurred spontaneously at the open circuit potential. The composition of the oxide films as a function of the solution components and the applied potential is discussed. The electrochemical properties of the spontaneously passivated electrodes at the open circuit potential were studied by EIS. The polarization resistance (R(p)) and the electrode capacitance (C(dl)) were determined. The higher R(p) of the alloy than of the chromium pointed to the stabilizing effect of the other alloy components. The concentration of the metallic ions in a simulated physiological solution, measured by inductively coupled plasma-mass spectrometry, was in accordance with the values of both the R(p) determined from EIS data and current densities measured with CV.