The effect of inhibitors on the corrosion behavior of AZ91D magnesium (Mg) alloy was investigated via a combination of experimental and computational approaches. A new inhibition mechanism was proposed that the nucleation of corrosion products affected by inhibitor. The Mg(OH) 2 embryos carry positive charges during the metal dissolution process because the pH is lower than the isoelectric point. The positively charged embryos suppress the crystal nucleation, indicating that the inhibitor with negative charges can adsorb on the embryos, resulting in the acceleration of the embryo growths. Consequently, a dense corrosion product film and superior inhibition efficiency were obtained.
In this study, pyrite was used as the research object, and the behavior and mechanism of a copper-ion-enhanced organic depressant in depressing pyrite flotation were studied. Microflotation experiments showed that, after the addition of CuSO4 and N,N-dimethyldithiocarbamate (N,N-DDS), the floating collection efficiency of pyrite declined from 82.37 to 21.03% at pH 8.5. Infrared spectroscopy studies indicated that the addition of CuSO4 caused a significant enhancement in the characteristic N,N-DDS peaks on the pyrite surface. X-ray photoelectron spectroscopy (XPS) revealed that, following the addition of CuSO4 and N,N-DDS, the relative atomic concentration of N 1s considerably enhanced on the surface of pyrite, with N 1s derived from N,N-DDS. Time-of-flight secondary ion mass spectrometry showed that, before and after the addition of CuSO4, the normalized peak values of CSN– on the pyrite superficial layer were 0.0116 and 0.0032, respectively. All of the above-mentioned results indicate that the Cu ion promotes the adsorption of N,N-DDS on pyrite and facilitates the formation of complex ((CH3)2NCSS)2Cu. The N and S atoms in −NCS and metal ions formed chemical bonds, which were the primary mechanism of the interaction between N,N-DDS and pyrite. This process reduces the floatability of pyrite and achieves the selective depression of pyrite.
The combination of LDHs nanocontainer and organic inhibitor demonstrates a great prospect in the field of corrosion protection. Whereas the traditional ion exchange method has a low efficiency owing to the small space and the firm force between the LDHs laminates. A high-efficiency approach of intercalating organic inhibitor into the LDHs is delivered in this work. The MgAl-LDHs loaded with 5-aminoindazole (AIA) were synthesized by separating the layered structures of hydrotalcites into single-layer nanosheets and then restructuring the exfoliated nanosheets with organic inhibitor. The as-synthesized LDHs-AIA − displayed a controlled release behavior and excellent anti-corrosion performance on the copper in 3.5 wt% NaCl solution, which were characterized by UV–vis spectra and electrochemical tests. Furthermore, a series of structure and morphology tests involving SEM, TEM , XRD , FTIR, XPS and TGA were also used for further analysis the LDHs. And the analysis of corrosion products and the anti-corrosion mechanism were carried out by SEM, XRD tests. The theoretical calculations concerning the adsorption of corrosion inhibitors on the copper surface were also investigated. It can be concluded that the inhibitor-loaded LDHs have the ability to adjustably release the corrosion inhibitor in corrosive medium, thereafter the corrosion inhibitor can adsorb onto the active sites of copper surface to prevent corrosion.
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