Wei He,Ru Yan,Xiang Gao,Yan Wang,Xinxiao Sun,Houyi Ma
Most Zr conversion coatings are prepared on Al alloys , with Al 3+ from the substrate contributing significantly to the film growth process. Thus, the effect of Al 3+ on the electrochemical characteristics, surface microstructure and film-formation mechanism of Zr-based conversion coatings on old- rolled steel (CRS) substrates was investigated by growing the coatings with and without Al 3+ as an additive. Electrochemical tests indicated that the anticorrosion performance of the Zr-Al coatings prepared in the presence of Al 3+ was greatly superior to that of Zr conversion coatings obtained in the absence of Al 3+ . Field-emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis indicated that adding of Al 3+ in the conversion bath changed the surface microstructure of the Zr coating, greatly promoted the deposition of Zr and F on the CRS substrate and increased the film thickness and density. Both coatings were embedded into the etched CRS substrates. The presence of Al 3+ additive induced the formation of different coating components . The Zr coating mainly consisted of ZrO 2 and some FeF x , whereas the Zr-Al coatings comprised of ZrO 2 , ZrO x F y , Al 2 O 3 , AlF x and some FeF x . The present study results confirm the key role of Al 3+ as an additive in the film formation and growth process of Zr coatings and its effect on enhancing the anticorrosion performance of CRS substrates in NaCl solutions.
PAM formed by self-organization can be considered as nanocontainers of phytic acid (PA) molecules and used for the corrosion protection of metal materials. Herein, self-strengthening PAM-Zn conversion films were successfully constructed on CRS substrate by a simple dipping method. The highest protection efficiency of PAM-Zn films was 81.0 % and was further increased beyond 90 % after immersion in NaCl solution. The immersion treatment in NaCl solution not only promoted the formation of more P O 4 3 − and PAM-Zn complex, but also changed the surface microstructure and increased the film thickness and compactness, thereby leading to the great enhancement of anti-corrosion performance.
Amorphous phytic acid nanoparticles were prepared via a condensation reaction of phytic acid with aminopropyltriethoxysilane. X-ray photoelectron spectroscopy and fourier transform infrared characterizations demonstrated that there were abundant phosphate groups on the surface of as-prepared phytic acid nanoparticles. The advanced composite phytic acid nanoparticles doped silane sol-gel coating was fabricated on the cold-rolled steel substrates using sol-gel technique and introducing phytic acid nanoparticles into the coating. The results of electrochemical tests showed that the doping of phytic acid nanoparticles greatly improved the anti-corrosion and durable performances of the silane coatings. The simple strategy which utilized the “active” nanoparticles to improve the corrosion mitigation and durable performances of coating is expected to find wide application in the anti-corrosion coating industry.
Dandan Lv,Hongfei Shao,Xiang Gao,Ke Lu,Haifeng Lu,Houyi Ma
Super-hydrophobic surfaces are usually prepared by manipulating the surface roughness and surface chemistry of various materials. Herein, we report two facile, environmentally friendly and inexpensive methods for the fabrication of super-hydrophobic (SH) coatings on cold rolled steel (CRS) and iron substrates using electrodeposition and etching to control surface roughness in combination with the self-assembly technique. By modifying the rough surfaces with stearic acid (SA) and hydrolysed octyltriethoxysilane (OTES), the water contact angles (WCA) of the super-hydrophobic ZnO coatings reaches up to 160° and the WCA of the super-hydrophobic coatings on etched iron is 155°. The mechanisms for the formation of the super-hydrophobic coatings fabricated by SA and OTES self-assembled thin films on rough steel and iron substrates are investigated by means of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results show that the SH coatings effectively protect the substrate metals from corrosion in 3.5% NaCl solution and increase the inhibition efficiency to approximately 93% and 86%, for the super-hydrophobic ZnO coating and super-hydrophobic silica coating on etched iron, respectively.
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