Purpose: The purpose of this research paper was to investigate the use of methanolic extract ofSalvia hispanica(S. hispanica) as a green corrosion inhibitor for bronze in a simulated acid rain solution.Design/methodology/approach: Extract ofS. hispanicawas used as a green corrosion inhibitor for bronze in simulated acid rain solution. Electrochemical techniques such as potentiodynamic polarization curves, electrochemical impedance spectroscopy and electrochemical noise were used. Parameters such as polarization, charge transfer and noise resistance (Rp, Rct and Rn, respectively) were calculated.Findings: Results showed that the extract acts as a good, anodic type of inhibitor. The inhibitor efficiency increased with increasing its concentration up to 400 ppm, decreasing beyond this concentration. Efficiency also increased with an increase in the immersion time. The inhibition was due to the adsorption of components found in theS. hispanicaextract following a Langmuir adsorption isotherm.Practical implications: S. hispanicaextract can be used as a corrosion inhibitor for bronze in acid rain solution.Originality/value: This study provides new information on the inhibition features ofS. hispanicaunder specific conditions. This eco-friendly inhibitor could find applications to protect bronze exposed to polluted urban atmospheres.

The effect of plasma nitriding and oxidation on the corrosion resistance of AISI 304 type stainless steel in LiBr/H₂O and CaCl₂-LiBr-LiNO₃-H₂O mixtures at 80 °C has been evaluated by using potentiodynamic polarization curves and electrochemical impedance spectroscopy techniques (EIS). Steel was plasma treated at 500 °C during 8 h under different atmospheres, nominally 20% N₂ + 80% H₂, 100% N₂ and 100% O₂. X-ray diffraction analysis (XRD) showed the presence of a CrN layer in nitrided specimens, whereas scanning electronic microscopy analysis revealed that specimen treated in the 20% N₂ + 80% H₂ atmosphere showed the thickest nitride layer. Specimens nitrided in the 20% N₂ + 80% H₂ atmosphere had the noblest open circuit potential value in both solutions, whereas potentiodynamic polarization curves indicated the formation of a passive layer. These specimens exhibited the lowest corrosion and passivation current density values. Corrosion process was under charge transfer control in both solutions regardless of the plasma treatment. The type of corrosion suffered by the steel under all treatments was the pitting type of corrosion. Pits density was the lowest for nitrides steels rather than that for untreated or pre-oxidized ones.

Conventional absorption and refrigeration systems use a LiBr/H₂O mixture, which causes corrosion problems to the metallic components. In order to avoid this and some other problems such as crystallization and vapor pressure, some additives such as CaCl₂ and/or LiNO₃ are added to the LiBr/H₂O mixture. In the present work, the corrosion behavior of 1018 carbon steel as well as of type 304 and 316L stainless steels was evaluated in LiBr/H₂O at 80 °C with the addition of CaCl₂, LiNO₃, and CaCl₂+LiNO₃. Potentiodynamic polarization curves and electrochemical impedance spectroscopy were used for this purpose. The results showed that the corrosion current density values of all tested steels decreased with the addition of CaCl₂ and/or LiNO₃, which induced the formation of a passive film on carbon steel. Both types of stainless steels showed a passive film in all tested conditions, but the passive current density was the lowest, whereas the passive zone was the widest, for 316L steel. The corrosion mechanism remained unaltered for both stainless steels but was changed with the addition of CaCl₂ and/or LiNO₃ for carbon steel.

A study of the corrosion behaviour of T91 steel in molten 60 wt% NaNO₃-40%KNO₃ has been carried out at 300, 400 and 500 °C during 1000 h. Employed techniques included potentiodynamic polarization tests, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. Experiments were complemented by detailed scanning electronic measurements and X-ray diffraction studies. Polarization curves revealed the existence of a passive layer formed onto the steel, composed mainly of Cr₂O₃, FeCr₂O₄, NaCrO₄ and K₂Fe₂O₄. Corrosion current density values increased, whereas the polarization resistance value decreased more than one order of magnitude as the testing temperature increased. EIS tests indicated a charge transfer controlled corrosion process, regardless of the testing temperature, and that the double electrochemical layer resistance decreased with the temperature.

The corrosion inhibition action of Phalaris canariensis extract on 316 L stainless steel in the H₂O-35 (wt%) LiCl mixture at different temperatures has been evaluated with the aid of weight loss, potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy tests. These studies were complemented by Fourier Transformed Infrared spectroscopy, FTIR, gas/mass chromatography analytical techniques and detailed scanning electronic microscopy studies. Results have indicated that Phalaris canariensis extract is an efficient inhibitor, with an efficiency that increases with its concentration, but it decreases as the temperature increases. Phalaris canariensis extract is physically adsorbed onto stainless steel according to a Temkin type of adsorption isotherm. Phalaris canariensis extract affected both anodic and cathodic electrochemical reactions with a stronger effect on the anodic ones, acting, thus, as a mixed type of inhibitor. Main compounds contained in the Phalaris canariensis extract were palmitic and oleic acids, responsible for its inhibitory properties.