Deng Wang,Jiaxin Yang,Fei Xue,Jihui Wang,Wenbin Hu
Zinc coordinated 1-hydroxyethylidene-1,1-diphosphonic acid (Zn-HEDP) film was fabricated on steel surface by coordination self-assembly method. The surface morphology and chemical composition of Zn-HEDP film were investigated by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the structural and valence state of Zn-HEDP film was determined by Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of Zn-HEDP film in 3.5wt% NaCl solution was investigated by using potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques. The experimental results show that Zn-HEDP film is in a smooth surface with disturbed nanoparticles. The protection efficiency of Zn-HEDP film to steel in 3.5 wt% NaCl solution is firstly increased and then decreased with the increasing of zinc concentration, pH value and assembly time. The optimum preparation conditions for Zn-HEDP film are the zinc concentration of 10 mmol/L, pH value of 5.0 and assembly time of 30 min, under which the protection efficiency of film is reached to 95.79 %. The coordination between zinc ions and HEDP can effectively increase the binding energy with Q235 steel. Zinc ions can improve the compactness and thickness of Zn-HEDP films as bridging agents, which prevent Q235 steel from corrosive solution.
Yuwei Zuo,Yue Sun,Wenzhong Yang,Kegui Zhang,Yun Chen,Xiaoshuang Yin,Ying Liu
The performance and mechanism of typical scaling inhibitors, i.e., 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), in inhibiting calcium carbonate scaling were investigated. Results of the static experiment at 30 °C and 80 °C revealed that at the optimal concentration, the scaling inhibition efficiency of PBTCA was superior to that of HEDP. Additionally, X-ray powder diffraction evaluation demonstrated that in comparison with HEDP, PBTCA inhibited the growth of the (1 0 4) crystal plane of calcite more evidently. Scanning electron microscopy analysis indicated that the addition of scaling inhibitors induced the crystal transformation of CaCO 3 from calcite to aragonite. Molecular dynamics simulation also confirmed that the interaction of PBTCA with the (1 0 4) crystal surface of calcite is more apparent than that of HEDP. This observation was a consequence of the PBTCA being more negatively charged, as determined via a quantum chemical calculation. The calculation further indicated that the spatial distance of PBTCA to the (1 0 4) face of calcite was less due to stronger chelating ability and better suitability of the structure. As a result, in the tested temperature range, PBTCA exhibited the more effective inhibitory effect against calcium carbonate scaling.
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