Influence of polyaniline and ceria nanoparticle additives on corrosion protection of a UV-cure coating on carbon steel

Influence of a few percents additives of polyaniline doped with phosphoric acid (PAni-PA) and ceria nanoparticle on corrosion protection of a new ultraviolet (UV)-cure polyester acrylate coating have been studied for coil coating on carbon steel by electrochemical measurements during exposure to a NaCl solution. The results demonstrate that the presence of ceria nanoparticles improves the barrier property and stability of the coating. Adding the PAni-PA results in active corrosion protection for carbon steel due to passivation of the steel, and the combination of both additives greatly enhances the protection property over that of the coating matrix alone.     

Influence of pH on corrosion behavior of carbon steel in simulated cooling water containing scale and corrosion inhibitors

In this paper, the influence of pH on the corrosion behavior of AISI 1020 carbon steel in simulated cooling water was investigated by using electrochemical and surface analysis methods. The results of polarization showed that the corrosion resistance of carbon steel increased with an increase in pH of the simulated water, and the corrosion control process changed from cathodic polarization to anode polarization control. The scale and corrosion inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) had a certain anodic corrosion inhibition effect on carbon steel, whereas Zn²⁺ acted as a cathodic inhibitor for carbon steel in simulated water with pH 7–9. In simulated water containing both PBTCA and Zn²⁺, a good synergistic corrosion inhibition was found between PBTCA and Zn²⁺, and their corrosion inhibition effect on carbon steel was the best at pH 8. This was attributed to the formation of Zn(OH)₂ precipitate film in the cathode region and the formation of Zn–PBTCA complex film in the anode region at this pH.     

The effects of a CeO2 coating on the corrosion parameters of type 304 stainless steel

Coatings of CeO₂ derived from inorganic sol-gel dispersions were applied to type 304 bright annealed stainless steel (British Standard 1449 type 304S31) coupons and subjected to heat treatments at 450 and 550 °C. The coatings, 0.5 μm thick, were transparent, adherent, and stable. The aqueous corrosion properties of the coated coupons in 1 molar NaCl were then studied by potentiodynamic polarization measurements and electrochemical impedance spectroscopy. The derived corrosion parameters were then compared with similarly heat-treated, uncoated 304SS coupons. The results indicate that the application of a CeO₂ coating, heat treated at 550 °C, improves the corrosion rate as compared to an uncoated heat-treated coupon. The polarization curve for the 450 °C heat-treated, coated coupon showed passive behavior compared to transpassive for the uncoated specimen. The impedance spectrum data for the uncoated, as-received coupon could be modeled using a resistor in series with a parallel capacitor resistor combination “Randles” equivalent circuit. A coated coupon, heat treated at 550 °C, could be modeled using a more complex equivalent circuit involving a constant phase element, due to the CeO₂ coating. Modeling of the impedance characteristics for the oxidized coupons required the addition of a second series element consisting of a parallel resistor capacitor combination to give a Chi square statistic fit of X² < 5 X 10^-4.     

Effect of pulse cathodic protection on corrosion mitigation and electrochemical conditions under a simulated coating disbondment on pipeline steel

Coating disbondments on pipeline steels are regions with high resistivity where conventional cathodic protection (CP) could not fully protect. Therefore, in an attempt to mitigate this challenge, this study investigates the effect of pulse CP on corrosion mitigation and electrochemical conditions under a simulated coating disbondment on X-52 pipeline steel. In this regard, conventional and pulse CP of ?870 mV_SCE were applied to the open mouth of a simulated coating disbondment. For pulse CP, frequencies of 1, 5, and 10 kHz were used. Results showed while the conventional CP was not able to fully protect the 20 cm simulated coating disbondment, for the pulse CP with increase in frequency from 1 to 5 kHz, and from 5 to 10 kHz, improve in CP potential protection under the simulated coating disbondment was achieved. This was accompanied by considerably lower corrosion and a more uniform pH distribution under the simulated coating disbondment.     

Synthesis and properties of high corrosion resistant Ni–cerium oxide nano‐composite coating

The effect of cerium ion on the formation, morphology, composition, and corrosion behavior of Ni–cerium oxide coatings was investigated by SEM, FESEM, XRD, EDS, XPS, EIS, and potentiodynamic polarization. The extremely highest corrosion resistant coating was obtained when the cerium ion concentration in the plating bath was 16 mM. It has been observed that the presence of cerium ion in the plating bath led to changes in the morphology of the coating from pyramid nodular structure to coaxial structure. By adding cerium ion to the plating bath, a considerable grain refinement in the nanometer region was observed.     

Investigation of electrodeposited cerium oxide based films on carbon steel and of the induced formation of carbonated green rusts

Cerium oxide based films on carbon steel were deposited using a cathodic electrodeposition approach and from relatively concentrated solutions. The effects of the relatively high cerium nitrate concentrations (0.1 and 0.25 M) and of applied current density (0.25 mA cm⁻² ? j ? 3 mA cm⁻²) on the composition and microstructure of the films were thoroughly investigated with the support of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman and Fourier transformed infrared (FTIR) spectroscopies. The results showed that the use of 0.25 M solutions brought about immediate formation of the films compared to the 0.1 M. As the applied current density was increased, the time elapsed for achieving a stabilisation of the potential decreased. Also, the CeO₂ crystallite size decreased with increasing applied current density. However, at high cathodic current densities, the crystallite size was similar regardless of the concentration, hence suggesting that the precipitation mechanisms became predominant. CeO₂ was the major species deposited on carbon steel. Ce(OH)₃ was also well distinguished in the deposits elaborated from 0.25 M solutions. Both concentrations led to the formation of a carbonated green rust in which some carbonates were probably replaced by nitrate anions. The mechanisms of formation of the green rust and its evolution with time are also elucidated in this work.     

The effect of tannins and pH on the corrosion of steel in wood extracts

Tannins and pH are often cited as factors that affect the corrosiveness of wood yet there are few data to confirm these statements. The purpose of this paper is to systematically investigate the effect of tannins and pH on corrosion of metals in wood. Four wood species known to vary in both their pH and extractives were chosen and extracted with water. The pH, tannin content, and corrosion rate of carbon steel were determined for each extract. To test if pH and tannin were the only factors influencing corrosion, “synthetic” extracts were made by adding tannins to distilled water and adjusting the pH. At a given pH, increasing the tannin content inhibited corrosion and at a given level of tannin content, lowering the pH increased corrosion. An isocorrosion map as a function of pH and tannins was developed by using simple kinetic models to extrapolate the data. The data may be useful in estimating the relative corrosiveness of new, nonmetallic wood preservatives based upon the chemistry of naturally durable wood species.     

Studies on waterline corrosion processes and corrosion product characteristics of carbon steel in 3.5 wt% NaCl solution

The waterline corrosion behaviors of carbon steel partially immersed in a 3.5 wt% NaCl solution were investigated using the wire beam electrode technique, and the effects of corrosion products on the processes of waterline corrosion were analyzed. The results demonstrated that the initial stage and development stage of waterline corrosion were mainly controlled by the concentration and diffusion of dissolved oxygen, respectively, and the deceleration stage of waterline corrosion was mainly affected by corrosion products. The main component of the yellow corrosion products was γ-FeOOH, and γ-FeOOH that exhibited a high reduction reactivity could be involved in the cathodic reaction. The black corrosion products were mainly composed of Fe₃O₄ with strong thermodynamic stability and the processes of dissolved oxygen diffusion and ion transports were obviously affected due to the continuous accumulation of Fe₃O₄ on the surface of the electrodes. Polarity reversals were observed on the single electrodes below the waterline, but the reasons for the phenomena were different from each other.     

超疏水Co-MoS2复合镀层的制备及其性能

采用一步电沉积法制备了具有优异耐磨耐蚀的超疏水Co-MoS₂复合镀层。利用扫描电镜、X射线衍射仪、激光共聚焦显微镜、接触角测试仪及电化学工作站等系统研究了电流密度和电沉积时间对复合镀层的微观形貌结构、润湿性、自清洁效果、耐磨和耐蚀性能的影响规律及机理。结果表明,当电流密度为20 A/dm²,电沉积时间为30 min时,Co-MoS₂复合镀层实现超疏水效果,接触角达到最大值约151.4°,具有良好的自清洁防污性能。在2.5 kPa压力下与800 目砂纸摩擦1200 mm后,镀层表面仍具有高于146°接触角的良好疏水性,表现出优异的耐磨性能。该超疏水复合镀层还具有较好的耐腐蚀性能。一步电沉积法简单、经济高效且环保制备了高性能超疏水复合镀层,可望实现超疏水材料的实际应用。     

Stress corrosion cracking initiation under the disbonded coating of pipeline steel in near-neutral pH environment

A novel test setup has been used in this study to simulate stress corrosion cracking initiation under a disbonded coating on an X-65 pipeline steel. In this setup, the synergistic effects of cyclic loading, cathodic protection and soil solution environment under disbonded coatings have been considered. When the X-65 pipeline steel was exposed to the test environment, there existed a wide range of corrosion products on the steel surface in the gradient of cathodic protection. Increasing the test time and the maximum stress increased the possibility of stress corrosion cracking initiation in regions with a high susceptibility to pitting corrosion.     

General corrosion of carbon steel in a synthetic concrete pore solution

In this study, we reviewed our recent work on the general corrosion of carbon steel (P355QL2) overpack material for the isolation of high-level nuclear waste in Belgium's supercontainer concept. By using electrochemical impedance spectroscopy and by optimizing the mixed potential model, which incorporates quantum mechanical tunneling of charge carriers across the barrier layer to describe the kinetics of the partial cathodic process, we evaluated all parameters in the model as a function of independent variables such as voltage, temperature, and pH. By delineating the partial anodic and cathodic processes, we found that the corrosion rate (CR) is independent of voltage over the voltage range from 0.2 to −1.0 V_SHE, which is predicted to be experienced in the repository. Furthermore, the CR is found to increase strongly with decreasing pH and increasing temperature.     

Influence of pitting and iron oxide formation during corrosion of carbon steel in unbuffered NaCl solutions

The corrosion evolution over time of a carbon steel rotating disk immersed in aerated NaCl solutions was analyzed using a superposition model. Using this approach, partial polarization curves for iron oxidation and oxygen reduction were synthesized from experimental current-potential data at different corrosion time in order to determine the kinetics parameters, corrosion potential and current density of the underlying anodic and cathodic subprocesses. The distinctive features of the polarization curves are well described in terms of the simplifying assumptions of the model. In particular, the time evolution of the corrosion current density was linked to the morphology of the corroding surface under different NaCl concentrations.     

Effects of cathodic electrodeposition parameters of cerium oxide film on the corrosion resistance of the 2024 Al alloy

Cerium oxide thin films obtained by cathodic electrodeposition on 2024 aluminium alloy have been studied. The coatings, obtained with electrochemical deposition, offer an effective corrosion protection and require a lower deposition time when compared to chemical conversion coatings. The coatings were obtained at room temperature by deposition from CeCl₃/H₂O₂ aqueous solutions and the influence of several parameters (CeCl₃ concentration, H₂O₂ concentration, deposition time, current intensity) on the corrosion resistance was studied. The composition, morphology and microstructure of the films have been characterized by SEM, XPS and AFM. The corrosion resistance was investigated through potentiodynamic tests in 3% NaCl solution.     

Electrochemical corrosion behavior of X80 pipeline steel in a near‐neutral pH solution

In this work, the electrochemical corrosion behavior of X80 pipeline steel was investigated in a near‐neutral pH solution using electrochemical impedance spectroscopy (EIC) and photo‐electrochemical (PEC) measurements as well as X‐ray photo‐electron spectroscopy (XPS) technique. The effects of hydrogen‐charging and stress were considered. The results show that the steel is in an active dissolution state, and a layer of corrosion product is formed and deposited on the electrode surface, which is subjected to further oxidation to form ferric oxide and hydroxide. Photo‐illumination enhances anodic dissolution of the steel when it is under anodic polarization due to destroying of the corrosion product film. When the steel is under cathodic polarization, the cathodic current density decreases upon laser illumination due to the photo‐oxidation of hydrogen atoms generated during cathodic reactions, which behaves as an anodic reaction to offset the cathodic current density. Hydrogen‐charging and stress decrease the corrosion resistance of the steel and enhance the dissolution rate of the steel.     

WC对定向结构Ni60涂层耐蚀性能的影响研究

为了研究WC含量对Ni60合金涂层耐腐蚀性能的影响规律及相关机制,向Ni60合金粉体中添加不同质量分数的WC,通过高频感应重熔和强制冷却技术,在45^#钢表面制备WC添加的Ni60/WC复合定向结构涂层,采用SEM、EDS、XRD、电化学性能测试和浸泡实验等检测手段分析研究了WC颗粒增强Ni60合金的定向结构复合涂层的耐腐蚀性能及其机制。结果表明：随着WC添加量的增加,极化电阻先增大后减小,WC添加量10%时达到最大值9710.8 Ω;腐蚀电流密度先减小后增大,WC添加量10%时最小为1.34×10_^-6 A/cm_²。WC添加量对涂层显微形貌、元素分布、物相均有影响,进而影响涂层耐蚀性能。     

Effect of silicate pretreatment, post-sealing and additives on corrosion resistance of phosphated galvanized steel

Sodium silicate （water glass） pretreatment before phosphating, silicate post-sealing after phosphating and adding silicate to a traditional phosphating solution were respectively carried out to obtain the improved phosphate coatings with high corrosion resistance and coverage on hot-dip galvanized（HDG） steel. The corrosion resistance, morphology and chemical composition of the coatings were investigated using neutral salt spray（NSS） tests, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. The results show that pretreatment HDG steel with silicate solutions, phosphate coatings with finer crystals and higher coverage are formed and the corrosion resistance is enhanced. Adding silicate to a traditional phosphating solution, the surface morphology of the coatings is nearly unchanged. The corrosion resistance of the coatings is mainly dependent on phosphating time. Phosphating for a longer time （such as 5 min）, the corrosion resistance, increasing with concentration of silicate, is improved significantly. Post-sealing the phosphated HDG steel with silicate solutions, the pores among the zinc phosphate crystals are sealed with the films containing Si, P, O and Zn and the continuous composite coatings are formed. The corrosion resistance of the composite coatings, related to the pH value, contents of hydrated gel of silica and Si2O^2- 5 and post-sealing time, is increased markedly. The improved coatings with optimal corrosion resistance are obtained for phosphating 5 min and post-sealing with 5 g/L silicate solution for 10 min.     

钢基电镀铝层阳极氧化处理后的组织结构和性能

用扫描电镜（SEM）和X射线衍射分析（XRD）测定了Q235钢上电镀铝层在硫酸溶液中不同时间阳极氧化处理后的组织结构和表面形貌，并对其硬度和耐蚀性能进行了测试。结果表明：电镀铝层经不同时间阳极氧化处理后，表面由非晶态Al2O3相和Al相组成，其上存在有纳米级的孔洞。随着氧化时间的延长，非晶态Al2O3相增多，Al相减少，氧化膜厚度增加，表面孔洞尺寸增大；氧化膜的硬度呈现先增加后降低，最后趋于稳定，且都显著高于电镀铝层的硬度。并且电镀铝层经阳极氧化处理后，在3．5％NaCl溶液中的电化学耐蚀性能大幅度增加，但随着阳极氧化处理时间的延长，电镀铝层的耐蚀性能降低。     

Assessment of graphene oxide/epoxy nanocomposite as corrosion resistance coating on carbon steel

Graphene and its derivatives are new materials with unique properties. In recent years, various studies about the nanocomposites based on graphene oxide (GO) have been carried out. However, the electrochemical properties of nanocomposite coatings based on GO materials have not been widely studied. In this study, GO/epoxy nanocomposite coatings were prepared by incorporation of different amounts of GO nanosheets into the epoxy matrix via mechanical agitation and sonication process. The dispersion of GO nanosheets in matrix was analysed by optical microscopy, transmission electron microscopy and Fourier transform infrared. The anticorrosive properties of these nanocomposite coatings were investigated by electrochemical impedance spectroscopy tests. Results showed that the corrosion protection of coatings was improved by addition of GO into the coatings material. Furthermore, the best corrosion resistance was achieved in 0·25 wt-%GO/epoxy nanocomposite coatings.