不同材料表面镍-磷-锌盐纳米复合化学镀层性质的比较

研究比较了D310硅钢片和A3钢片表面Ni-P-Zn3(PO4)2,Ni-P-ZnSnO3和Ni-P-ZnSiO3纳米复合化学镀层的外貌和性质。用扫描电子显微镜（SEM）观察外貌：称重法测定厚度,通过10％NaCl溶液,1％H2S气体加速腐蚀试验,10％,CuSO4溶液点滴试验,饱和KCl溶液循环伏安（CV）试验,抗粘性试验及抗高温氧化试验等多种手段测定其性能。结果表明：纳米复合化学镀层的性能优于镍－磷镀层和其它微米复合镀层。     

Corrosion resistance of phosphate coatings obtained by cathodic electrochemical treatment: Role of anode–graphite versus steel

The formation of phosphate coatings by cathodic electrochemical treatment using graphite and steel anodes and evaluation of their corrosion resistance is addressed in this paper. The type of anode used, graphite/steel, has an obvious influence on the composition of the coating, resulting in zinc–zinc phosphate composite coating with graphite anode and zinc–iron alloy–zinc phosphate–zinc–iron phosphate composite coating with steel anode. The corrosion resistance of the coating is found to be a function of the composition of the coating. The deposition of zinc/zinc–iron alloy along with the zinc phosphate/zinc and zinc–iron phosphate using graphite/steel anodes has caused a cathodic shift in the E_corr compared to uncoated mild steel substrates. The i_corr values of these coatings is very high. EIS studies reveal that zinc/zinc–iron alloy dissolution is the predominant reaction during the initial stages of immersion. Subsequently, the formation of zinc and iron corrosion products imparts resistance to the charge transfer process and increases the corrosion resistance with increase in immersion time. The corrosion products formed might consist of oxides and hydroxychlorides of zinc and iron. The study suggests that cathodic electrochemical treatment could be effectively utilized to impart the desirable characteristics of the coating by choosing appropriate anode materials, bath composition and operating conditions.     

无机材料对超薄型钢结构防火涂料性能的影响

介绍了晶须、石墨插层化合物、硅微粉、纳米二氧化硅、二氧化钛、硼酸锌等无机材料对超薄型钢结构防火涂料的防火性能、涂膜质量等理化性能的影响,指出以合适的无机新材料在适当的用量下对传统防火涂料进行必要的改性,是进一步提高超薄型钢结构防火涂料各项性能的有效方法。     

Effect of pore content and pH on the corrosion behavior of hydrophobic ceramic coatings

In this paper, superhydrophobic ceramic coatings were successfully prepared on stainless steel substrates (S304) by sol–gel method, and the effects of pore content and pH conditions on the corrosion resistance of hydrophobic ceramic coatings were studied. As the porosity increases, the contact angle of the coating increases. Among them, the contact angles of the coatings with 15% and 20% porosity in different pH solutions are all greater than 150°, achieving superhydrophobic surfaces. The contact angle results before and after corrosion show that the solution with a higher pH has a greater damage to the hydrophobicity of the coating. The corrosion resistance of the coatings was evaluated comparatively from polarization curves and electrochemical impedance spectroscopy. As the hydrophobicity improves, the corrosion resistance of the hydrophobic ceramic coating is enhanced. The impedance moduli at .01 Hz of the coating are 1.04 × 10³ times (pH 4), .13 × 10³ times (pH 7), and .74 × 10³ times (pH 10) of the bare steel, respectively. With the increase of pH, the corrosion resistance of hydrophobic ceramic coatings decreases, because OH⁻ in the corrosion solution is more easily adsorbed on the surface of the coating, thereby destroying the long hydrophobic chains.     

Deposition of zinc–zinc phosphate composite coatings on steel by cathodic electrochemical treatment

The present work aims at the development of an energy-efficient and eco-friendly approach for the deposition of zinc phosphate coatings on steel. The study describes the possibility of preparing zinc–zinc phosphate composite coatings by cathodic electrochemical treatment using dilute phosphoric acid as an electrolyte and zinc as an anode. The methodology enables the preparation of coatings with different proportions of zinc and zinc phosphate by suitably varying the applied current density, pH, and treatment time. Adhesion of the coating on mild steel and adhesion of paint film on the phosphate coating were found to be good. The surface morphology of the coatings exhibited platelet-type features and small white crystals (agglomerated at some places) which represented zinc and zinc phosphate, respectively. An increase in current density (from 20 to 50 mA/cm²) increased the size of the zinc crystals, and coatings prepared at 40 and 50 mA/cm² resembled that of electrodeposited zinc. Since the proportions of zinc and zinc phosphate could be varied with applied current density, pH, and treatment time, it would be possible to use this methodology to prepare coatings that would offer different degrees of corrosion protection.     

Performance of zinc phosphate coatings obtained by cathodic electrochemical treatment in accelerated corrosion tests

The formation of zinc phosphate coating by cathodic electrochemical treatment and evaluation of its corrosion resistance is addressed. The corrosion behaviour of cathodically phosphated mild steel substrate in 3.5% sodium chloride solution exhibits the stability of these coatings, which lasts for a week's time with no red rust formation. Salt spray test convincingly proves the white rust formation in the scribed region on the painted substrates and in most part of the surface on unpainted surface. The protective ability of the zinc corrosion product formed on the surface of the coated steel is evidenced by the decrease in the loss in weight due to corrosion of the uncoated mild steel, when it is galvanically coupled with cathodically phosphated mild steel. Potentiodynamic polarization curves reveal that E_corr shifts towards higher cathodic values (in the range of −1000 to −1100 mV versus SCE) compared to that of uncoated mild steel and conventionally phosphated mild steel substrates. The i_corr value is also very high for these coatings. EIS studies reveal that zinc dissolution is the predominant reaction during the initial stages of immersion. Subsequently, the non-metallic nature of the coating is progressively increased due to the formation of zinc corrosion products, which in turn enables an increase in corrosion resistance with increase in immersion time. The zinc corrosion products formed may consist of zinc oxide and zinc hydroxychloride.     

Studying the corrosion protection properties of an epoxy coating containing different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments

Epoxy/polyamide coatings were loaded with different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments. Moreover, a coating containing zinc phosphate (ZP) was prepared as a reference sample. The coatings were applied on St-37 steel substrates and then were exposed to 3.5 wt% NaCl solution up to 35 days. The corrosion inhibition properties of the pigments extracts were studied on bare steel samples by a potentiodynamic polarization technique after 24 h immersion. The morphological properties and corrosion resistance of the coatings were investigated by scanning electron microscope (SEM), optical microscope, electrochemical impedance spectroscopy (EIS) and salt spray tests.     

Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride

Silicon nitride was firstly used as anticorrosive pigment in organic coatings. An effective strategy by combining inorganic fillers and organosilanes was used to enhance the dispersibility of silicon nitride in epoxy resin. The formed nanocomposites were applied to protect Q235 carbon steel from corrosion. The anticorrosive performance of modified silicon nitride with silane (KH-570) was investigated by electrochemical impedance spectroscopy (EIS), water absorption and pull-off adhesion methods. With the increase of immersion time, the corrosion resistance as well as adhesion strength of epoxy resin coating and unmodified silicon nitride coating decreased significantly. However, for the modified silicon nitride coating, the corrosion resistance and adhesion strength still maintained 5.7×10¹⁰ Ω cm² and 7.6 MPa after 2400-h and 1200-h immersion, respectively. The excellent corrosion resistance performance could be attributed to the chemical interactions between KH-570 functional groups and silicon nitride powders, which mainly came from the easy formation of Si-O-Si bonds. Furthermore, the modified silicon nitride coating formed a strong barrier to corrosive electrolyte due to the hydrophobic of modified silicon nitride powder and increased bonds.     

Corrosion protection coating containing polyaniline glass flake composite for steel

Corrosion protection of steel by glass flake (GF) containing coatings is widely used in marine atmosphere. Even though, the coatings containing glass flake are highly corrosion resistant, their performance is decreased due to the presence of pinholes and coating defects. It is well established that polyaniline containing coating is able to protect the pinhole defects in the coatings due to passivating ability of polyaniline. Hence a study has been made on the corrosion protection ability of steel using polyaniline-glass flake composite containing coating with 10% loading of glass flake in epoxy binder. The polyaniline glass flake composite (PGFC) was synthesized by chemical oxidation of aniline by ammonium persulphate in presence of glass flake. The corrosion protection ability of GF and PGFC containing coating on steel was found out by salt spray test and EIS test in 3% NaCl. In both the tests, the resistance value of the PGFC containing coating has remained at 10⁸-10⁹ Ω cm² where as for the GF containing coating, the resistance values decreased to 10⁵ Ω cm². The enhanced corrosion protection ability of the PGFC containing coating is due to the passivation ability of the polyaniline present in the coating.     

Formulation and performance evaluation of hydroxyl terminated hyperbranched polyesters based poly (ester–urethane–urea) coatings on mild steel

A low molecular weight, anticorrosive hyperbranched poly (ester–urethane–urea) [HB-P(EUU)] coatings were formulated using 2nd generation hydroxyl terminated hyperbranched polyesters (OH–HBPEs), isophorone di-isocyanate (IPDI) as a cross linking agent and dibutyltin dilaurate (DBTDL) as a catalyst with certain additives. First, NCO terminated prepolymers (HBPEUs) were formulated by reacting OH–HBPEs with IPDI at NCO:OH ratio of 1.1:1 for 4 h at 70–80 °C, then HBPEUs were mixed with DBTDL and various additives and finally coated on pretreated cold rolled mild steel (MS) substrates by dip coating method. Before applying on MS substrates, viscosity and volume solid of coatings were measured. The molecular structure of HBPEUs was characterized by ATR-FTIR and ¹H NMR analysis. Surface morphology of coated panels was characterized by atomic force microscopy (AFM) and found that coating components were homogeneously distributed and surface was smooth and crack free. Performance of coated substrates was evaluated by various tests such as cross hatch and pull off adhesion, abrasion resistance, scratch resistance, impact resistance, flexibility, and pencil hardness. UV stability of coated substrates was evaluated by UV-whether-o-meter and corrosion resistance property was evaluated by salt spray, humidity, polarization and electrochemical impedance (EIS) test. Results were also compared with polyurethane coating based on linear polyester. HB-P(EUU) coatings showed excellent enhancement in mechanical, durability as well as corrosion resistance properties than their linear counterpart.     

Corrosion stability of polyester coatings on steel pretreated with different iron–phosphate coatings

The influence of steel surface pretreatment with different types of iron–phosphate coatings on the corrosion stability and adhesion characteristics of polyester coatings on steel was investigated. The phosphate coating was chemically deposited either from the simple novel plating bath, or with the addition of NaNO₂, as an accelerator in the plating bath. The morphology of phosphate coatings was investigated using atomic force microscopy (AFM). The corrosion stability of polyester coatings on steel pretreated by iron–phosphate coatings was investigated by electrochemical impedance spectroscopy (EIS) in 3% NaCl solution, while “dry” and “wet” adhesion were measured by a direct pull-off standardized procedure. It was shown that greater values of pore resistance, R_p, and smaller values of coating capacitance of polyester coating, C_c, on steel pretreated with iron–phosphate coating were obtained, as compared to polyester coating on steel phosphated with accelerator, and on the bare steel. The surface roughness of phosphate coating deposited on steel from the bath without accelerator is favorable in forming stronger bonds with polyester coating. Namely, the dry and wet adhesion measurements are in accordance with EIS measurements in 3% NaCl solution, i.e. lower adhesion values were obtained for polyester coating on steel phosphated with accelerator and on the bare steel, while the iron–phosphate pretreatment from the novel bath enhanced the adhesion of polyester coating on steel.     

金属陶瓷涂层耐蚀性能研究

采用溶胶－凝胶浸渍提拉法在不锈钢、纯铜及铝合金基体上制备具有保护性的ＳｉＯ２、ＺｒＯ２、ＴｉＯ２、Ａｌ２Ｏ３及ＳｉＯ２－ＴｉＯ２陶瓷涂层,利用阳极极化曲线的、循环动电位极曲线、点蚀电位的测量以及三氯化铁和５％硫酸介质中的腐蚀试验研究了所得陶瓷涂层的耐蚀性。结果表明,这些陶瓷涂层能大幅芳提高金属基体在各种腐蚀介的耐蚀性。     

Study on electrochemical behavior of Nano‐ZnO modified alkyd‐based waterborne coatings

A nano‐composite coating was formed using nano‐ZnO as pigment in different concentrations, to a specially developed alkyd‐based waterborne coating. The nano‐ZnO modified composite coatings were applied on mild steel substrate by dipping. The dispersion of nano‐ZnO particles in coating system was investigated by scanning electron microscopic and atomic force microscopic techniques. The effect of the addition of these nano‐pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy. Coating modified with higher concentration of nano‐ZnO particles showed comparatively better performance as was evident from the pore resistance (R_po) and coating capacitance (C_c) values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano‐particle modified coatings as compared with the neat coating, confirming the positive effect of nano‐particle addition in coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phenol electropolymerization on phosphated mild steel via zinc electrodeposition

Phenol electropolymerization to polyoxyphenylene coatings on phosphated steel and phosphated galvanized steel, normally impossible under the conditions allowing effective coating formation on either steel or zinc, is activated by cathodic deposition of zinc. A critical zinc amount has been found to be necessary to suppress electrochemical processes competitive with electropolymerization and induce coating formation with nearly 100% efficiency. SEM analysis showed that this critical amount of zinc corresponded to the formation of a low number of zinc nuclei emerging at the surface of the phosphate layer, on which, however, polyoxyphenylene was formed as a continuous coating. A.c. impedance tests showed that initial barrier properties are worse for coatings grown on zinc-plated phosphated samples than for those grown on steel from the same solutions. However, the long term corrosion resistance is much better in the former case, the improvement being largely associated with zinc cathodic protection     

Hydrophobic benzoxazine-cured epoxy coatings for corrosion protection

A hydrophobic benzoxazine-cured epoxy coating (EPB) was prepared by a dip coating and thermal curing method using benzoxazine monomer (B-TMOS) as curing agent. Fourier transform infrared (FTIR) analyses confirmed the presence of thermal curing reactions and hydrogen-bonding interactions in the epoxy/polybenzoxazine system. The hydrophobicity of epoxy coatings induced by the incorporation of B-TMOS was enhanced significantly, and the water contact angles of resultant EPB coatings were higher than 98°. The corrosion protection ability of epoxy coatings was investigated by open-circuit potentials, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results showed that the charge transfer resistance (R_ct) of EPB coatings was increased by about three orders of magnitude compared with bare mild steel, and the protection efficiency values of all EPB samples were more than 98%. This increased corrosion protection property could be attributed to the high hydrophobic performance of EPB coatings.     

Formulation and performance evaluation of hydroxyl terminated hyperbranched polyesters based poly (ester–urethane–urea) coatings on mild steel

A low molecular weight, anticorrosive hyperbranched poly (ester–urethane–urea) [HB-P(EUU)] coatings were formulated using 2nd generation hydroxyl terminated hyperbranched polyesters (OH–HBPEs), isophorone di-isocyanate (IPDI) as a cross linking agent and dibutyltin dilaurate (DBTDL) as a catalyst with certain additives. First, NCO terminated prepolymers (HBPEUs) were formulated by reacting OH–HBPEs with IPDI at NCO:OH ratio of 1.1:1 for 4 h at 70–80 °C, then HBPEUs were mixed with DBTDL and various additives and finally coated on pretreated cold rolled mild steel (MS) substrates by dip coating method. Before applying on MS substrates, viscosity and volume solid of coatings were measured. The molecular structure of HBPEUs was characterized by ATR-FTIR and ¹H NMR analysis. Surface morphology of coated panels was characterized by atomic force microscopy (AFM) and found that coating components were homogeneously distributed and surface was smooth and crack free. Performance of coated substrates was evaluated by various tests such as cross hatch and pull off adhesion, abrasion resistance, scratch resistance, impact resistance, flexibility, and pencil hardness. UV stability of coated substrates was evaluated by UV-whether-o-meter and corrosion resistance property was evaluated by salt spray, humidity, polarization and electrochemical impedance (EIS) test. Results were also compared with polyurethane coating based on linear polyester. HB-P(EUU) coatings showed excellent enhancement in mechanical, durability as well as corrosion resistance properties than their linear counterpart.     

无取向硅钢用磷酸盐涂层材料 制备及其防腐性能

系统研究了无取向硅钢用磷酸盐系涂层性能的影响因素。以氢氧化铝和磷酸为原料制备磷酸二氢铝,再添加适量的添加剂酒石酸铵、二氧化硅、环氧树脂,得到的涂液涂布于硅钢表面,并控制合适的烘干温度,通过耐盐雾实验考察各因素对涂液耐腐蚀性能的影响。实验结果表明,在磷酸与氢氧化铝物质的量比为3.4∶1、酒石酸铵用量为2%、二氧化硅用量为1%、环氧树脂用量为5%、烘干温度为300 ℃条件下,所得涂层材料的防（耐）腐蚀效果最佳。     

Evaluation of Ni‐Mo and Ni‐Mo‐P Electroplated Coatings on Stainless Steel for PEM Fuel Cells Bipolar Plates

Stainless steel bipolar plates (BPPs) are the preferred choice for proton exchange membrane fuel cells (PEMFCs); however, a surface coating is needed to minimize contact resistance and corrosion. In this paper, Ni–Mo and Ni–Mo–P coatings were electroplated on stainless steel BPPs and investigated by XRD, SEM/EDX, AFM and contact angle measurements. The performance of the BPPs was studied by corrosion and conduction tests and by measuring their interfacial contact resistances (ICRs) ex situ in a PEMFC set‐up at varying clamping pressure, applied current and temperature. The results revealed that the applied coatings significantly reduce the ICR and corrosion rate of stainless steel BPP. All the coatings presented stable performance and the coatings electroplated at 100 mA cm⁻² showed even lower ICR than graphite. The excellent properties of the coatings compared to native oxide film of the bare stainless steel are due to their higher contact angle, crystallinity and roughness, improving hydrophobicity and electrical conductivity. Hence, the electroplated coatings investigated in this study have promising properties for stainless steel BPPs and are potentially good alternatives for the graphite BPP in PEMFC.     

Corrosion protection by epoxy coating containing multi-walled carbon nanotubes

Epoxy coatings that contained multiwalled carbon nanotubes (MWCNTs) were prepared. Further, the effect of the MWCNTs on the hydrophobicity and water transport behavior, and hence, on corrosion resistance provided by the epoxy coating were examined using hygrothermal cyclic tests and electrochemical impedance spectroscopy (EIS). The water transport behavior of epoxy coatings with higher MWCNT content decreased to a larger extent for coatings with higher surface hydrophobicity. The corrosion protection of carbon steel coated with epoxy coating that contained MWCNTs correlated well with water transport behavior and hydrophobicity.     

Evaluation of the corrosion resistance of phosphate coatings obtained by anodic electrochemical treatment

The corrosion resistance of phosphate coating obtained by anodic electrochemical treatment at 4–6 mA/cm² is addressed in this paper. The corrosion performance of these coatings is also compared with the coatings obtained by chemical treatment. The regenerated phosphoric acid under the influence of anodic current causes a large variation in morphological features of the coatings. Immersion and salt spray tests indicate the ability of these coatings to act as a barrier film on mild steel. Polarization and electrochemical impedance spectroscopic (EIS) studies indicate that the corrosion resistance of phosphate coatings obtained by anodic treatment decreases with increase in current density employed for deposition. In spite of their higher coating weight, the corrosion resistance of phosphate coatings obtained by anodic treatment is inferior to those obtained by chemical treatment. The porosity or discontinuities created due to the dissolution of the coating under the influence of anodic current are considered responsible for the inferior corrosion resistance of these coatings. The study concludes that anodic treatment has only a limited scope for preparing phosphate coatings with improved corrosion resistance.