Optimization of potassium zinc phosphate anticorrosion pigment by Taguchi experimental design

The synthesis condition of potassium zinc phosphate pigment was optimized with respect to corrosion inhibition in extract solution and dispersion stability in an epoxy resin by application of Taguchi experimental design. Processing parameters, including calcinations time, quiescent time, mixing rate and KOH/ZnCl₂ mole ratio are selected as the influential parameters. Corrosion inhibition of the pigments in the extract solutions and dispersion stability in the epoxy resin were evaluated by electrochemical impedance spectroscopy (EIS) and turbidity measurement, respectively. The pigment synthesized under optimal condition was characterized by XRD, which showed formation of KZnPO₄ and KZn₂PO₄(HPO₄). Corrosion protection of the epoxy coating containing synthesized pigment at optimal condition was evaluated by salt spray and compared to the unpigmented epoxy coating. Salt spray results showed higher corrosion protection of the epoxy coating in the presence of potassium zinc phosphate, which could be attributed to lower diffusivity of the pigmented coating to Cl⁻ or formation of phosphate layer confirmed by SEM–EDX.     

石墨烯改性涂层防护性能研究

为减少团聚，提高石墨烯在涂层中的分散性，研究采用纳米分散技术预先制备了石墨烯分散液，再将其分散至环氧树脂中获得石墨烯改性复合涂层。通过对石墨烯含量为 0、0.3%、0.6%的复合涂层进行盐水浸泡、盐雾、阴极剥离实验及电化学性能测试，证明石墨烯的加入显著增强了涂层的防护性能。石墨烯复合涂层在 3.5%盐水中浸泡 1 008 h后，涂层低频阻抗仍大于 106 Ω·cm²比未添加石墨烯的涂层提高了 3个数量级，且盐雾实验 6 000 h后涂层表面仍保持完好；含 0.6%石墨烯，的涂层耐蚀行为劣于石墨烯含量为 0.3%的涂层。     

A new approach to using submicron emeraldine-base polyaniline in corrosion-resistant epoxy coatings

The present work reports on a new approach to the preparation of special corrosion-resistant epoxy coatings. The aminic hardener of these coatings contained emeraldine-base polyaniline (EB-PANi). The aminic hardener was prepared by dispersion of EB-PANi in 3-(aminomethyl)-3,5,5-trimethylcyclohexan-1-amine employing sonication, centrifuging and submicron filtering methods. The state of dispersion and dissolution of these coating materials, during different stages of preparation, were characterized by optical microscopy and scanning electron microscopy. The corrosion resistances of resulting coatings were measured by electrochemical impedance spectroscopy (EIS) and salt spray methods. As little as 0.5% EB in initial mixture of EB-hardener compositions led to relatively better corrosion protection of resulting coating compared with neat resin coating. Presence of initial 2.5% of EB in the hardener and its processing through our approach resulted in the formulation of an epoxy coating with superior corrosion protection properties.     

Synergic enhancement of the anticorrosion properties of an epoxy coating by compositing with both graphene and halloysite nanotubes

The aim of this research was to improve the corrosion resistance of metal surfaces with polymer coatings. Both graphene and halloysite nanotubes (HNTs) were introduced together into the epoxy resin coating for the enhanced barrier protection of the metallic surface. The anticorrosion behaviors of different coatings were comparatively evaluated by the potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS) tests. The potentiodynamic polarization curves showed that the coating containing 0.5 wt % HNTs and 0.8 wt % graphene (H05G08EP) together had the most positive corrosion potential and the minimum corrosion current density. The EIS results revealed that graphene endowed the composite coatings with excellent electrochemical performance for anticorrosive purposes. The NSS tests indicated that H05G08EP endured the longest NSS time. These results suggest that H05G08EP had the best corrosion resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47562.     

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.     

Preparation and investigation of anticorrosion properties of the water-based epoxy-clay nanocoating modified by Na+-MMT and Cloisite 30B

In this study the effect of using nanoclay particles in two different matrices on anticorrosive performance improvement of a novel water-based epoxy coating was investigated. For this purpose, Na⁺-montmorillonite (Na⁺-MMT) and organo-montmorillonite (Cloisite 30B) were introduced into water-based hardener (RIPI-W.B.H.) and epoxy resin matrices, separately. Nanoclays were added to polymeric matrices using direct mixing under an ultrasonic homogenizer. The coatings were analyzed to ensure the intercalation and distribution of layered silicates by means of X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses. The structure of products is studied by infrared (IR) spectrometer. The corrosion protection performances of the coatings were investigated using salt spray test and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. The results showed that using Cloisite 30B in water-based hardener had the best performance and its application in anticorrosion water-based zinc rich epoxy coating approved of it.     

A new corrosion protection coating with polyaniline-TiO2 composite for steel

Organic coating strategies for corrosion protection with inherently conducting polymers have become important because of restriction on the use of heavy metals and chromates in coatings due to their environmental problems. This work presents the synthesis of polyaniline-TiO₂ composites (PTC) and the corrosion protection behaviour of PTC containing coating on steel. PTC was prepared by chemical oxidation of aniline and TiO₂ by ammonium persulfate in phosphoric acid medium. The PTC was characterized by FTIR, XRD and SEM techniques. Suitable coating with PTC was formed on steel using acrylic resin. Using electrochemical impedance spectroscopy, the PTC containing coating's behaviour in 3% NaCl immersion test and salt spray test has been found out. Results indicate that the coating containing PTC is able to maintain the potential of steel in passive region due to its redox property. The resistance of the coating containing PTC was more than 10⁷ Ω cm² in 3% NaCl solution after 60 days and 10⁹ Ω cm² in the salt spray test of 35 days. But the resistance of the TiO₂ containing coating was found to be less than 10⁴ Ω cm² in both the cases. The high performance of PTC containing coating is attributed to the passivation of steel by polyaniline.     

Investigation of corrosion protection properties of an epoxy nanocomposite loaded with polysiloxane surface modified nanosilica particles on the steel substrate

In this study, it has been aimed to investigate the corrosion protection properties of an epoxy/polyamide coating loaded with different concentrations (ranged from 3 to 6% (w/w)) of the polysiloxane surface modified silica nanoparticles (nano-SiO₂). The nanocomposites were applied on the steel substrates. Field emission scanning electron microscope (FE-SEM) and UV–vis techniques were utilized in order to investigate the nanoparticles dispersion in the coating matrix. The effects of addition of nanoparticles on the corrosion resistance of the coating were studied by an electrochemical impedance spectroscopy (EIS) and salt spray test. The coating surface degradation was studied by optical microscope and Fourier transform infrared radiation (FT-IR) spectroscopy. Results obtained from UV–vis and FE-SEM analyses revealed proper and uniform distribution of surface modified nanoparticles in the epoxy coating matrix. It was shown that the coating corrosion protection properties were significantly enhanced in the presence of 5 wt% silica nanoparticles. Less degradation occurred on the surface of the coatings loaded with 5 wt% nanoparticles.     

Epoxy powder coatings containing polyaniline for enhanced corrosion protection

Incorporation of polyaniline (PANI) in epoxy type powder coating formulations has not been attempted earlier. Using specific grade of PANI with low doping, it can be incorporated in epoxy powder coating formulations by twin screw extrusion process. The powder formulations were deposited on steel substrates by electrostatic spray coating at −60 kV and baked at 140 °C for 20 min. These were extensively tested for corrosion resistance by exposure to hot saline conditions followed by electrochemical impedance spectroscopy and also salt spray testing. PANI incorporated coatings showed no deterioration even after 1400 h of hot (65 °C) saline treatment. The coatings intentionally scratched also exhibited self healing property and there was no rust formation even after prolonged exposure to hot saline conditions. These results could be explained on the basis of additional crosslinking due to PANI, as confirmed by DSC results, which gave rise to improved barrier property and self healing was associated with the scavenging of ions by PANI which prevented corrosion of the underlying substrate.     

Polyaniline for corrosion prevention of mild steel coupled with copper

Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5-10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1-40 days and subsequently remained constant above 10⁹ Ω cm², whereas that for pure ER coating fell below 10⁶ Ω cm² after only 30 or 40 days. Immersion tests on coated steel-copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 μm EB/ER coating protected steel-copper couple for at least 2000 h.     

Incorporation of silica network and modified graphene oxide into epoxy resin for improving thermal and anticorrosion properties

In this study, the silica network and functionalized graphene oxide (GO) were incorporated into the epoxy coating systems, which was aimed to improve the thermal property and corrosion resistance of epoxy coatings. First, tetraethyl orthosilicate (TEOS) oligomers and epoxy hybrid was fabricated through sol–gel method. Then the (3-aminopropyl) triethoxysilane (APTES) modified graphene oxide (FGO) was added into the epoxy hybrid composite to obtain anticorrosion coatings. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectrum, and X-ray photoelectron spectrum were conducted to evaluate the structural information of GO and APTES modified GO nanosheets. The results indicated that the APTES successfully grafted onto the surface of GO sheets. Besides, TGA curves, electrochemical measurements and salt spray test were also carried out to characterize the thermal performance and corrosion resistance of GO based epoxy coatings. The TGA results revealed that the thermal performance of epoxy coating containing silica network and FGO nanofiller (ES/FGO) was significantly strengthened compared to pure epoxy. The initial degradation temperature of epoxy coating was increased from 300 to 343.7°C after incorporation of silica component and FGO. The EIS measurements demonstrated that the impedance modulus of ES/FGO was significantly higher than neat epoxy, which indicated that the corrosion resistance of epoxy was substantially strengthened after introduction of silica component and FGO. The corrosion rate and inhibition efficiency of epoxy composite coatings were also shifted from 1.237 × 10⁻⁷ mm/year and 76.6% (for neat epoxy) to 1.870 × 10⁻⁹ mm/year and 99.6% (for ES/FGO), respectively. The salt spray test also revealed that the silica and FGO can improve the corrosion resistance of epoxy coating. Additionally, the dispersion of GO sheets was also enhanced after the modification of APTES siloxane.     

Effect of zinc oxide in combating corrosion in zinc-rich primer

During the production of zinc pigments, some zinc may get oxidized and remains as impurity. In the present study, the effect of spherical ZnO on corrosion protection properties was evaluated along with lamellar zinc. ZnO was added in various weight fractions in epoxy primer coating at 60% PVC. The coated panels were evaluated among others for their conductance, packing density and morphology. The corrosion resistance was measured using salt spray test for 3000 h of exposure. Open circuit potential (i.e. corrosion potential) was measured in 3.5 wt.% NaCl salt solution. The best corrosion protection was obtained with 15 wt.% of ZnO.     

新型活化环氧富锌涂层的耐腐蚀性研究

富锌涂料在防腐蚀领域具有广泛应用，然而其长效防护性能却受到锌粉活性影响。本文以冷涂锌涂层、传统环氧富锌涂层作为对照，研究了新型具有电化学活性的环氧富锌涂层在盐雾加速腐蚀试验后的耐腐蚀性。宏观形貌分析表明：盐雾加速腐蚀 1 800 h后，活化环氧富锌涂层表面并未出现锈点；采用扫描电子显微镜、维体式显微镜观察试验后涂层的表面形貌和涂层结构，发现活化环氧富锌涂层微观表面更加平滑，锌粉并未出现大面积的氧化，涂层内部大小锌粉颗粒均匀排列；通过电化学方法研究涂层的耐蚀机理与防护性，发现活化富锌涂层具有更持久的低防护电位。以上研究结果表明，较冷涂锌及传统环氧富锌涂层而言，新型活化环氧富锌涂层具有优异的长期防护性能，是值得关注和研究的一种新型技术。     

Formulation and study of corrosion prevention behavior of epoxy cerium nitrate–montmorillonite nanocomposite coated carbon steel

Nanocomposite coatings which were applied on carbon steel panels based on epoxy cerium nitrate–montmorillonite (MMT) were synthesized and formulated. Nanoparticles were incorporated into epoxy resin by mechanical and sonication processes. The state of dispersion, dissolution, and incorporation were characterized by optical microscopy, sedimentation tests, X-ray diffraction, and transmission electron microscopy. To investigate anticorrosive properties of nanocomposite coatings, electrochemical impedance spectroscopy and salt spray tests were employed. The experimental results showed that epoxy cerium nitrate–MMT nanocomposite coatings were superior to the neat epoxy in corrosion protection effects. In addition, it was observed that the corrosion protection of nanocomposite coatings was improved as the clay loading was increased up to 4–2 wt% cerium nitrate.     

Eco‐friendly,acrylic resin‐modified potassium silicate as water‐based vehicle for anticorrosive zinc‐rich primers

Potassium silicate binder of zinc‐rich coating was modified by adding water‐based acrylic resin. Several series of coatings containing 5, 10, and 15 wt % of acrylic and acrylic/styrene binders were added to potassium silicate. The coatings were applied on steel and the corrosion resistance of coatings was evaluated by conventional methods such as electrochemical impedance spectroscopy, corrosion potential, salt spray, and scanning electron microscopy. The results indicated that the modification of silicate binder with acrylic and acrylic/styrene led to shortening the curing time, improved corrosion protection, better dispersion of zinc particles, and enhanced salt spray resistance of resultant coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40370.     

Designing of corrosion resistant epoxy coatings embedded with polypyrrole/SiO2 composite

Polypyrrole/SiO₂ composite was synthesized by chemical oxidative polymerization of pyrrole using FeCl₃. The synthesized polymer composite was loaded in epoxy resin to develop coatings for mild steel substrates using powder coating technique. SEM and TEM images reveal homogenous dispersion of SiO₂ particles in polypyrrole matrix. TGA analysis confirms good thermal stability of the polymer composite. Tafel polarization and electrochemical impedance spectroscopy (EIS) results exhibit remarkably high corrosion protection efficiency of epoxy coatings with polymer composite in 3.5% NaCl solution. Corrosion studies of coatings with an artificial defect reveal the passivation of defect by the polymer composite present in the epoxy coatings. Salt spray test results revealed superior corrosion resistance offered by the polymer composite.     

Formation and characteristics of Al−Zn hydrotalcite coatings on galvanized steel

In this study, a process for depositing hydrotalcite (HT) coatings on galvanized steel was developed and the resulting coatings were characterized. Results showed that coatings formed spontaneously on galvanized surfaces upon exposure to ambient temperature alkaline aluminate solutions. Anodic polarization and electrochemical impedance spectroscopy experiments showed clear evidence of surface passivation. Scanning electron microscopy showed the formation of a continuous and conformal surface film comprised on a compact mass of crystallites. X-ray diffraction confirmed that the coating contained an Al−Zn hydrotalcite compound. Coating formation was enhanced by oxidizer and ammonium salt additions. Coatings formed by using best practices were deposited in less than 10 minutes and demonstrated good surface coverage and good organic coating adhesion. HT coatings formed by using best practices showed excellent organic coating adhesion compared to zinc phosphate control coatings. In salt spray testing, the presence of a hydrotalcite conversion coating under an epoxy neat resin was found to delay the onset of red rusting compared to control samples that were epoxy coated, but not conversion coated.     

Effect of the incorporation of montmorillonite-layered double hydroxide nanoclays on the corrosion protection of epoxy coatings

A series of layered double hydroxide (LDH)/montmorillonite (MMT) nanocomposite coating, LDH nanocomposite coating, and MMT nanocomposite coating were successfully prepared. The nanocomposite materials were characterized by X-ray diffraction and scanning electron microscopy (SEM). To understand the effect of MMT and LDH on the corrosion inhibition performance of epoxy resin coatings immersed in 3.5 wt% saline solution at 90°C, electrochemical impedance spectroscopy and an autoclave test were performed on epoxy resin; epoxy resin blended with LDH, MMT, and LDH + MMT (LM) coatings painted on Q345 steel. The metal/coating interfaces were observed by SEM and energy-dispersive spectroscopy. Results showed that addition of LDH and MMT improved the protection properties of the epoxy resin coatings. The corrosion protection of the LM nanocomposite coating was superior to that of the other coatings. This finding can be attributed to the ionic selectivity and barrier effect of MMT and LDH nanoclay platelets dispersed within the composite coatings.     

用杜仲胶/碳纳米管改性环氧树脂制备导电防腐涂料及其性能

以杜仲胶(EUG)和环氧树脂(E-51)为涂层基质、碳纳米管为导电填料制备了导电防腐涂料,考察了 EUG用量对复合涂层导电性和耐腐蚀性的影响.采用差示扫描量热仪和动态热机械分析仪研究了复合涂层的热性能,用四探针测试仪研究了导电性能,分别通过电化学阻抗谱及盐雾测试和附着力测试研究了耐腐蚀性和附着力.结果表明,当EUG用量...     

An investigation of the effects of polymer binder compositional variables on the corrosion control of aluminum alloys using magnesium-rich primers

It has recently been shown that magnesium (Mg) particles possessing a thin oxide surface layer can be used to produce primers that provide corrosion protection to aluminum (Al) alloys through a galvanic coupling mechanism. In addition to the Mg particles, polymer binder properties also affect corrosion protection. As a result, the effects of compositional variables associated with a two-component epoxy binder system on the ability of Mg-rich primers to protect an aerospace Al alloy were determined. The variables investigated were epoxy resin molecular mass, curing agent functionality, epoxy/NH ratio, and Mg content. All of the variables investigated had a significant effect on coating system performance and an optimized coating composition was identified that showed very good corrosion protection for at least 3,000 h of ASTM B117 salt spray exposure.