Effect of surface modified WO3 nanoparticle on the epoxy coatings for the adhesive and anticorrosion properties of mild steel

The effect of introducing WO₃ (tungsten oxide) nanoparticle in the epoxy coating was analyzed by electrochemical impedance spectroscopy and scanning electrochemical microscopy (SECM) methods in 3.5% NaCl. The (3-glycidyloxypropyl)trimethoxysilane was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of WO₃ nanoparticle in the epoxy coating enhances the charge transfer resistance (R_ct) as well as the film resistance (R_f). The observation of iron dissolution and oxygen consumption was done by applying the appropriate SECM tip potential in the WO₃-modified nanocomposite coated steel. The epoxy and epoxy–WO₃ nanocomposite-coated samples were used to study the adhesion and anticorrosion properties. The analysis by SEM/EDX displayed that the enriched W was detected in the nanocomposite coating of steel. The presence of the nano level corrosion product containing W was confirmed by focused ion beam-transmission electron microscope analysis. The high corrosion protection properties of the epoxy-based nanocomposite coating was due to the complex nanoscale layer formed and chemical interactions of epoxy resin with surface-modified nanoparticle in nanocomposites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48323.     

Behaviour of intact and scratched phosphate coatings on zinc, zinc–nickel and mild steel in dilute sodium phosphate solution

Impedance measurements were performed at room temperature in a 0.005 M Na₂HPO₄ solution on steel and on electrodeposited Zn and Zn–12%Ni before and after phosphating. It was found that potential and impedance parameters (R _ct and C _d) for phosphated materials attained nearly steady values within about 20 min, indicating that this solution did not cause meaningful changes in phosphate coatings and that it could therefore be used for the quality evaluation of these coatings. On scratches in phosphate coatings on Zn or Zn–12%Ni phosphate deposits rapidly formed, probably owing to enhanced dissolution of the locally exposed substrates at the nobler potentials of the coated materials. This demonstrates that damaged coatings can easily recover on Zn substrates in a non-aggressive phosphate solution. It is suggested that the formation of phosphate deposits on bare metal amidst phosphate coatings should be taken into account in the porosity determination by chemical or electrochemical methods.     

封闭处理对建筑结构钢锌系磷酸盐转化膜性能的影响

以建筑结构钢作基体制备锌系磷酸盐转化膜,并采用不同类型封闭液对磷酸盐转化膜进行封闭处理,研究了封闭处理对磷酸盐转化膜的微观形貌、表面成分、厚度和耐蚀性能的影响。结果表明：封闭处理对磷酸盐转化膜的宏观形貌和厚度没有显著性影响,但是微观形貌、表面成分和耐蚀性能存在差异。未封闭及封闭处理后磷酸盐转化膜的表面成分都以锌、氧和磷元素为主,封闭处理后磷酸盐转化膜表面趋于平整、致密性改善、耐蚀性能明显提高,主要归因于不同类型封闭液都起到填补晶粒间缝隙的作用,阻止腐蚀介质向磷酸盐转化膜内部渗透。采用硅酸钠和硝酸铈配成的封闭液封闭处理后的磷酸盐转化膜表面更加平整致密,其溶液电阻和电荷转移电阻均最大,分别达到58.2、4.02×10³ Ω·cm ²,且具有最大的相位角和最宽的频率范围。该磷酸盐转化膜的耐蚀性能更好,腐蚀耐久性也较理想,具有应用潜力,有望用作建筑结构钢表面防护层。     

碳钢表面超疏水锌涂层的制备及防腐性能

采用电化学沉积法,通过改变电流密度和沉积时间,在碳钢基体上生成锌(Zn)镀层的分层结构,再经十四酸改性,制备出具有微纳米结构的超疏水Zn涂层.通过场发射扫描电子显微镜(FESEM)、激光共聚焦显微镜(CLSM)、X射线光电子能谱仪(XPS)和接触角测量仪表征了超疏水Zn涂层的表面形貌、粗糙度、化学组成和润湿性能.结果发现,当电流密度为0.18 A/cm2,沉积时间为9 min时,制备的改性Zn涂层对水呈现出160°的接触角和1.3°的滚动角,具有优异的超疏水性和自清洁性.在砂纸磨损、刀片划擦、胶带剥离等外力破坏的过程中,该改性Zn涂层表现出较强的机械稳定性和耐用性.此外,超疏水Zn涂层在3.5％NaCl溶液中的腐蚀电流密度约为Zn镀层的1/4以及裸钢的1/45,并对pH=2～12的酸碱溶液有一定的耐受性,可为碳钢提供优异的腐蚀保护.     

Protective properties of epoxy-based organic coatings on mild steel

The protective properties of epoxy-based organic coatings on mild steel substrates have been studied using the electrochemical impedance spectroscopy (EIS) technique. The effects of coating composition, film thickness and curing temperature on the lifetime of the epoxy coating were investigated. The results obtained indicate that the film composition dramatically affects the rate of corrosion of the metallic substrate. Coatings with low and high content of curing agent exhibit early failure when exposed to an air-saturated 0.5 M aqueous solution of NaCl. Extended lifetimes were observed for samples with a content of the curing agent equal to 8.5% by weight. An increase in lifetime was also observed on increasing the film thickness and the curing temperature. The failure mechanism seems to occur in two steps: the first step is related to water uptake in the film while the second step is related to Cl⁻ ion diffusion through the coating. The results have been interpreted in terms of a model in which the dielectric properties (capacitance and resistance) of the coating depend strongly on the coating composition and are affected by both the water and salt uptake into the film.     

磷化聚苯胺用量对复合涂层防腐蚀性能的影响

以植酸(PhA)为掺杂剂通过化学氧化法合成了一种磷化聚苯胺(P-PANI),并将其混入硅树脂(SiR)中,刷涂在镁锂(Mg-Li)合金表面制备了P-PANI/SiR复合防腐蚀涂层。采用FTIR、UV-Vis-NIR和XPS表征了P-PANI的结构;研究了P-PANI含量对复合涂层疏水性、附着力及防腐蚀性能的影响。结果表明：当P-PANI占SiR的质量分数为2.0%时,得到的复合涂层表现出较好的疏水性和防腐蚀性能。其水接触角为125.4°,复合涂层的干、湿附着力均为0级,腐蚀电流密度为5.15×10-10 A/cm2,电化学阻抗值达到108 Ω•cm2。     

Improved mechanical and anticorrosion properties of metal oxide-loaded hybrid sol–gel coatings for mild steel in a saline medium

Abstract

A hybrid organic–inorganic sol–gel coating was successfully prepared and subsequently functionalized individually with five different metal oxide additives. The effect of the incorporated oxides on the corrosion protection performance and scratch-resistance properties of the hybrid base coating on mild steel substrates was investigated using electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) as well as mechanical testing. The steel-coated specimens were immersed in 3.5?wt.% NaCl corrosive medium for two weeks and the results reveal an excellent corrosion protection performance by all coating formulations with a significant high corrosion-resistance property for the sample loaded with molybdenum oxide. Scanning electron microscopy (SEM) images proved the absence of corrosion signs, defects, micro cracks, or delamination on the surface of the coated samples. Compared with the pure hybrid coating, all the metal oxide-embedded coatings (except for the sample loaded with yttrium(III) oxide) show comparable aqueous contact angle values as well as enhanced hardness and adherence properties. No noticeable dependence was observed for the surface roughness parameters as a function of the type of incorporated metal oxide within the sol–gel matrix. Overall, the results of this study demonstrate that metal oxides can be advantageous to the desired properties of hybrid sol–gel coatings applied to steel surfaces.     

Investigation on the anticorrosion,adhesion and mechanical performance of epoxy nanocomposite coatings containing epoxy-silane treated nano-MoO3 on mild steel

Abstract

The effect of introducing MoO₃ (Molybdenum oxide) nanoparticle in the epoxy coating was analyzed by EIS and SECM methods in natural seawater. The aminopropyl triethoxy silane (APTES) was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of MoO₃ nanoparticle in the epoxy coating enhances the charge transfer resistance (R_ct) as well as the film resistance (R_f). The observation of iron dissolution and oxygen consumption was carried out by applying the appropriate SECM tip potential in the MoO₃ modified nanocomposite coated steel. The epoxy and epoxy-MoO₃ nanocomposite-coated samples were used to study the mechanical, adhesion and anticorrosion properties. The analysis using SEM/EDX displayed that the enriched Mo was detected in the nanocomposite coated steel. The presence of the nano level corrosion product containing Mo was confirmed by FIB-TEM analysis. The high corrosion protection properties of the epoxy based nanocomposite coating was due to the complex nanoscale layer formed and chemical interactions of epoxy resin with surface-modified nanoparticle in nanocomposites.     

酸洗对中低温锌系磷化膜质量的影响

出于成本的考虑,酸洗在涂装行业中被广泛应用,但是经过酸洗的工件可使磷化程度降低,尤其对于致密性好的薄膜磷化.本文采用扫描电镜观察磷化膜的结晶形貌,讨论了不同的酸洗工艺对普锌磷化和低锌磷化膜质量的影响.实验表明,对于普锌磷化,酸洗后的钢板能磷化成膜,但膜的致密性变差;而低锌磷化则难以成膜.采用适当的表调工艺,可以改善其成膜性及磷化膜质量.     

Synthesis and characterisation of surface gradient thin conversion films on zinc coated steel

Surface gradient layers on hot-dip galvanised steel were synthesised in order to determine the barrier properties and corrosion resistance of thin amorphous conversion coatings as a function of layer thickness and processing time. For this purpose, a dip coating procedure was established that yields well-defined gradient layers. As a model system for conversion film formation on zinc coated steel, a zirconium based bath chemistry was used. The synthesised zirconium oxyhydroxide gradient films were characterised by localised electrochemical techniques, such as Scanning Kelvin Probe (SKP) and electrochemical impedance spectroscopy using an electrochemical capillary cell. Microscopic infrared reflection absorption spectroscopy (μ-FT-IRRAS) measurements and small-spot X-ray photo electron spectroscopy (XPS) were used as complementary surface analytical techniques. The applied analysing techniques provide a spatial resolution of 100-1600 μm. Thereby, a complete variation of thin film properties, such as thickness, barrier properties, corrosion resistance and chemical composition can be measured as function of the time of film growth on a sample with a length of a few centimetres. This approach allows a precise and accurate determination of structure-to-property relationships of thin conversion films. Moreover, it could be shown that a surface gradient film analysis significantly rationalises experimental time and increases the reliability of the experimental results.     

老化时间对桥连聚硅氧烷涂层防腐性能的影响

为提高涂层防腐蚀性能,以环氧丙氧丙基三甲氧基硅烷(GPTMS)和N-(3-三甲氧基硅基乙基)乙二胺(NTMDA)为原料经环氧-胺基开环反应得到含羟基有机桥联硅烷前驱体GN。然后,前驱体GN在乙酸催化下制得硅烷溶胶。最后,将硅烷溶胶以浸渍-提拉方式沉积在Q235钢片上,得到含羟基桥联聚倍半硅氧烷涂层。用极化曲线和电化学阻抗谱等技术对涂层的防腐蚀性能进行评价,重点探究了胶体老化时间对涂层防腐蚀性能的影响规律。结果表明：当胶体老化时间为4 h时,涂层在低频0.01 Hz处的电化学交流阻抗相较于空白钢片高出1.5个数量级,具有优异的防腐蚀性能。另外,涂层附着力级别为1级。     

锌及镀锌层稀土转化膜研究进展

锌及镀锌层表面稀土转化膜具有良好的耐蚀性能和无毒、无污染等优点,是最有希望替代铬酸盐处理的转化膜之一,具有良好的发展前景.本文综述了国内外关于锌及镀锌层上单一稀土转化膜的成膜工艺及其机理,并概述了国内外稀土复合膜的研究成果.     

Phase morphology and surface properties of moisture cured polyurethane-urea (MCPU) coatings: Effect of catalysts

Effect of catalysts on curing behaviour, phase morphology and surface properties of a moisture cured polyurethane-urea (MCPU) coating has been studied. The prepolymer, prepared by capping hydroxy terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI), was cured with moisture using different urethane catalysts at 30 °C and relative humidity of 60%. Fourier transform infrared spectroscopy (FTIR) was used to monitor the curing process. Gel fraction studies through solubility method, show catalyst induced shortening of induction period for gelation and increase in gel fraction. Effect of catalysts on phase morphology of the MCPU was evaluated by X-ray diffraction, small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). The results show that the heat of fusion and interdomain distance of hard segments are influenced by the choice of catalysts. The effect on surface properties was evaluated by FTIR-ATR and contact angle goniometry. The type of H-bonding interaction was identified by deconvolution of the FTIR spectra. The results show that the surface polar group concentrations increase with increasing efficiency of the catalysts. Consequently there is a clear observation of catalyst induced surface energy changes of the MCPU.     

Mechanical properties of plasma sprayed nanostructured TiO2 coatings on mild steel

This paper discusses the effects of plasma spray parameters on the mechanical properties of nanostructured TiO₂ coatings deposited on mild steel substrates. The design of experiment method was applied to investigate the significant effects of each property and to optimize the operational spray parameters. Plasma power, powder feed rate, and stand-off distance were selected as independent variables. Agglomerated and sintered nano-TiO₂ powder was deposited on A-36 commercial mild steel. The microstructural and mechanical properties of the coatings such as porosity, microhardness, surface roughness, and wear rate were evaluated. Both plasma power and powder feed rate were found to be the main factors affecting all four responses. It was also noted that the stand-off distance was a significant factor mainly in influencing the surface roughness of the coatings. All in all, the optimized properties can be achieved by applying a plasma power of 30 KW (high level), a powder feed rate of 22 g/min (high level), and a stand-off distance of 80 mm (low level).     

Effect of surface morphology of calcium phosphate on osteoblast-like HOS cell responses

Calcium phosphate (CaP) films with different surface roughness are synthesized on a polystyrene surface as a possible candidate for improving the biocompatibility of solid surfaces. These CaP films are used to investigate the influences of the surface roughness and chemical composition on the HOS osteoblast-like cells adhesion, spreading, proliferation, and differentiation. A polystyrene culture plate is used as the control surface. The CaP substrates are designated as a smooth, moderate, and rough surface according to the surface roughness. For smooth and moderate surfaces, a relatively small difference in the surface roughness is observed but the difference in their chemical composition is more significant than the others. Cell adhesion, spreading, proliferation, and differentiation appear to be dependent on surface roughness. These cellular responses are more active on the smoother surfaces than on the rough surface but are more pronounced on the moderate surface. The cell responses are reduced when HOS cells are cultured on the rough surface. The number of cells released from the control surface by trypsinization is greater than the CaP surfaces after a short period of incubation (5 h). However the cells released from smooth and moderate CaP surfaces are equivalent to or greater than the control at the longer period of incubation (17 h). Spreading and proliferation are greater on the CaP surfaces than on the control. The alkaline phosphatase-specific activity is very low during 1 and 2 weeks of culturing but dramatically increases after 3 weeks on all surfaces. The enzyme activity on the control is greater than on the CaP surfaces. The moderate surface shows the greatest enzyme activity in all cases among the CaP surfaces. Although a direct relation between surface chemistry and cell responses has not been established, the surface composition may play a cooperative role in characterizing the cellular responses. According to these results, the moderate surface is the most favorable substrate in terms of surface roughness and chemical composition for cell adhesion, spreading, proliferation and differentiation among all the CaP surfaces.     

Effect of surface treatment of pigment particles with polypyrrole and polyaniline phosphate on their corrosion inhibiting properties in organic coatings

The effect of pigment particle surface treatment with conductive polymers on the corrosion inhibiting properties of organic paints was investigated. Mixed oxides possessing the spinel and perovskite structures were synthesised for the study. Natural graphite and pigments based on ferric oxide and silicate were studied. Coating materials based on a water-based epoxy resin were prepared for the investigation of the corrosion protection properties of the pigments, the surfaces of which had been provided with a conductive polymer layer. Laboratory corrosion tests were applied to the paint films. A commercial corrosion protection pigment, based on modified zinc phosphate, served as the corrosion protection efficiency standard. Polyaniline phosphate was found preferable to polypyrrole as the modifying agent of the pigment surface regarding the pigment's corrosion inhibiting efficiency. Surface treatment with the conductive polymers is also beneficial to the mechanical properties of the paint.     

Investigation of the mechanical,thermal, and anticorrosion properties of epoxy nanocomposite coatings: Effect of synthetic hardener and nanoporous graphene

In the present study, epoxy samples containing nanoporous graphene (NPG) were synthesized and analyzed in terms of mechanical, morphological, thermal, adhesion, and anticorrosion properties. To this end, the employed curing agents (hardeners) were synthesized and NPG content was varied from 0 to 1 wt %. By using a hardener with aliphatic side chains, the toughness of the nanocomposite was improved without a decrease in the modulus. Adding 1 wt % NPG increased the modulus of the nanocomposite by about 30%. The dynamic mechanical results showed an increment in the glass transition of the samples containing 1 wt % NPG. Field emission scanning electron microscopy images were used to observe the fracture surface of the nanocomposites. The thermogravimetric analysis analysis also confirmed that using synthetic hardener and NPG as the nanofiller enhanced the thermal resistance of the samples. The images of the protected metal panel surfaces and their coatings were used to study adhesion and anticorrosion properties. These results indicated that the hardener synthesized in this work along with NPG improved the mechanical, thermal, adhesion, and anticorrosion properties of the epoxy nanocomposites effectively. The specific characteristic of the synthetic hardener was its chemical structure including both aliphatic and cyclic polyamines as the side groups. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46201.     

助剂对常温固化FEVE氟碳涂料耐溶剂性能的影响

比较了不同助剂对常温固化型FEVE氟碳涂料涂膜耐溶剂性能的影响,并且分析了其主要原因.     

氧化剂对钢铁表面氟铁酸盐转化膜的影响

通过中性盐雾试验,研究了过氧化氢、钼酸钠、澳酸钾、碘酸钾和过硫酸铵等氧化剂对Q195冷轧钢表面所形成的氟铁酸盐转化膜耐蚀性的影响.结果表明,氧化剂为过硫酸按时,形成的转化膜效果最好,其质量浓度为7 g/L时,转化膜的耐盐雾时间可达到8h.过硫酸按的加入使氟铁酸盐转化膜的形成加快,形成的无定形结构亦使得膜层耐蚀性能更好.     

The effects to the structure and electrochemical behavior of zinc phosphate conversion coatings with ethanolamine on magnesium alloy AZ91D

This paper discussed a zinc phosphate conversion coating formed on magnesium alloy AZ91D from the phosphating bath with varying amounts of ethanolamine (MEA). The effects of MEA on the form, structure, phase composition and electrochemical behavior of the phosphate coatings were examined using an scanning electron microscopy (SEM), X-ray diffraction (XRD) potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Interpretations of the electrical elements of the equivalent circuit were obtained from the SEM structure of the coatings, assumed to be formed of two layers: an outer porous crystal layer and an inner flat amorphous layer. The result showed that adding MEA refined the microstructure of the crystal layer and that the phosphate coating, derived at the optimal content of 1.2 g/L, with the most uniform and compact outer crystal layer provided the best corrosion protection.