Xiaoshuang Yin

Amino acids modified konjac glucomannan as green corrosion inhibitors for mild steel in HCl solution

Konjac glucomannan (KGM) was modified with amino acids to synthesize polysaccharide esters (KGMA and KGMH) which were evaluated as corrosion inhibitor for mild steel in 0.5M HCl solution by weight loss tests, Tafel curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The synthetic polymers were found to have the lower water absorbency and the higher water solubility than KGM. Gravimetric measurements showed the maximum efficiencies of KGMA and KGMH for decreasing the corrosion rate of metal at 2000ppm are up to 89.9% and 92.4%, respectively. Polarization curves indicated polysaccharide esters could retard both hydrogen evolution reaction and metal dissolution reaction and that the inhibitory effect was concentration dependent. Besides, EIS studies demonstrated the corrosion resistance of mild steel in hydrochloric acid was enhanced by polymer additives. The observations on mild steel surface by SEM suggested the metallic substrate obtained good protection against corrosion in inhibitor-containing HCl solution. The adsorptive behavior of polymer molecules including physisorption and chemisorption obeyed Langmuir isotherm and UV-vis spectra revealed the formation of inhibitor-ion complex. The better performance of KGMH on corrosion inhibition was attributed to the easier transfer of π-electron or n-electron, which was confirmed by quantum chemical calculations.

3,5‐Bis(2‐thienyl)‐4‐amino‐1,2,4‐triazole as a corrosion inhibitor for copper in acidic media

Purpose – The aim of this paper is to investigate inhibition of copper corrosion by 3,5‐bis(2‐thienyl)‐4‐amino‐1,2,4‐triazole (2‐TAT) in 1 M HCl and 0.5 M H2SO4.Design/methodology/approach – Potentiodynamic polarization curves and electrochemical impedance measurements were carried out on copper in 1 M HCl and 0.5 M H2SO4 containing various concentrations of 2‐TAT, and the effects of temperature were also investigated.Findings – As an efficient inhibitor, 2‐TAT behaves better in 1 M HCl than in 0.5 M H2SO4. 2‐TAT can be classified as cathodic‐type corrosion inhibitor in 1 M HCl and acts as relatively mixed type in 0.5 M H2SO4. Activation energies in the presence and absence of 2‐TAT were obtained by measuring the temperature independence of corrosion current. Adsorption of the inhibitor on the copper surface was found to obey the Langmuir adsorption isotherm.Practical implications – This inhibitor could have application in industries where hydrochloric acid solutions are used to remove scale and salts fro...

Inhibitory effect of konjac glucomanan on pitting corrosion of AA5052 aluminium alloy in NaCl solution

A natural carbohydrate polymer, konjac glucomanan, has been extracted from commercial product and studied as a green corrosion inhibitor for AA5052 aluminium alloy in 3.5 wt% NaCl solution by high-performance gel permeation chromatography (GPC), thermo gravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectra, electrochemical measurement and surface characterization techniques. The results of GPC measurements suggest the weight-average molecular weight and the number-average molecular weight of KGM with 98.2% purity are 1.61 × 105 g/mol and 1.54 × 105 g/mol, respectively. Potentiodynamic polarization curves show konjac glucomanan behaves as a mixed-type inhibitor with dominant anodic effect and that its maximum efficiency at 200 ppm is 94%. Electrochemical impedance spectroscopy (EIS) studies reveal the resistance of oxide film is approximately two orders of magnitude greater than the resistance of adsorbed inhibitor layer and that they both increase with KGM concentration. Moreover, in-situ electrochemical noise (EN) detection demonstrates that the growth and propagation stages of the pitting corrosion germinating on metal surface are blocked by polysaccharide additive, which is confirmed by the surface analysis of aluminium alloy using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Raman spectroscopy. At last, it is found that the addition of KGM makes it harder for water droplet containing NaCl to wet the metallic substrate.

Narrow-disperse Highly Cross-linked ＂Living＂ Polymer Microspheres by Two-stage Precipitation Polymerization

Narrow-disperse, surface-functionalized “living” polymer microspheres with uniformly cross-linked structures were prepared by two-stage precipitation copolymerization of styrene and divinylbenzene. The two-stage precipitation polymerization is composed of an initial conventional precipitation polymerization for the nucleation followed by a reverse atom transfer radical polymerization (reverse ATRP) for the controlled polymerization process. The polymerization parameters (including reaction time for the first stage, AIBN amount and monomer loading) have been studied to show significant influences on the morphologies. Moreover, narrower size distribution and an ATRP initiator-functional surface of resulting particles can be obtained by applying reverse ATRP to conventional precipitation polymerization in the second stage. Furthermore, the “livingness” of the resulting polymer microspheres was testified by their surface modification of poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) brushes via surface-initiated ATRP (SI-ATRP).