Pumpkin (Cucurbita maxima) seed-derived nitrogen, phosphorus, and sulfur carbon quantum dot as an inhibitor of corrosion for mild steel in HCl solution

In this work, an endogenous self-doping N,P,S-CQDs was synthesized by the acid hydrolysis of pumpkin seeds (Cucurbita maxima) and its performance as a corrosion inhibitor was evaluated. Mild steel (MS) is one of the most used materials in the industry; however, it has low corrosion resistance in acidic environments. Pumpkin is cultivated worldwide, and this compositional characteristic makes pumpkin seeds a great alternative as a raw material to produce CQDs. The results show that endogenous self-doping CQD was successfully obtained with a size distribution smaller than 10 nm. The N,P,S-CQDs presented 91.3% at 60 ppm and 94.6% at 10 ppm as maximum inhibition efficiency after 2 and 24 h immersion, respectively. Activation energy studies, XPS analysis, and isotherm studies show that the inhibition mechanism occurs through physical interaction. These results show an excellent alternative for using pumpkin seeds (Cucurbita maxima), an agroindustry waste, as a corrosion inhibitor

Study of the characteristics and properties of the SiO2/TiO2/Nb2O5 material obtained by the sol–gel process

Abstract The SiO2/TiO2/Nb2O5 material was set by the sol–gel method and was characterized by several techniques through thermogravimetric, spectroscopic, and textural analyzes. For the two synthesized materials, the specific surface area was 350.0 and 494.0 m2 g−1 (SiTiNb-A and SiTiNb-B, respectively). An enhance of the crystalline order with the temperature increase of the thermal treatment was observed. Through X-ray Photoelectron Spectroscopy analysis, the binding energy values for the Ti 2p and Nb 3d levels showed the insertion of Ti and Nb atoms in the silica matrix. The Electron Dispersive Spectroscopy analyses also confirmed the high dispersion of the metals presented on the materials surface. The Thermogravimetric Analysis showed weight loss for the of 37.6% (SiTiNb-A) and 29.7% (SiTiNb-B). The presence of the crystalline phases TiO2-anatase and monoclinic-Nb2O5 in the materials was confirmed through the data obtained by association of powder X-ray Diffraction and FT-Raman. Values obtained from optical band-gap aimed the dependence of the oxides concentration and the calcination temperature. Finally, the pyridine adsorption studies have indicated the presence of Lewis and Brønsted acid sites

Ziziphus joazeiro Stem Bark Extract as a Green Corrosion Inhibitor for Mild Steel in Acid Medium

The aqueous extract of Joazeiro stem bark (EJSB) and its high molecular weight fraction (HMWF) were examined as potential corrosion inhibitors of mild steel in 1 mol L−1 hydrochloric acid media, using weight-loss measurements, potentiodynamic polarization curves and an electrochemical impedance spectroscopy (EIS).Varying the concentration of the inhibitors from 100 to 800 mg L−1, the results show an increase in anticorrosive efficiency from 85.4 to 89.8 and 89.8 to 93.0% for EJSB and its HMWF, respectively, using the data of the gravimetric essay, and from 84.5 to 94.5 and 89.9 to 94.7% for EJSB and its HMWF, respectively, from the impedance data. The composition of the crude extract was chemically characterized by liquid chromatography-high resolution mass spectrometry. Additionally, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used, respectively, to morphologically and chemically characterize the surface. Considering that the saponin molecules, the main constituent from juá, are responsible for its inhibitory action, quantum chemical calculations showed that the C67, C69 and O144 atoms likely have an important role in the process of electron-donation of saponin to metal, due to the higher values of ƒk+ and %HOMO observed on these atoms