Corrosion protection performance of ceria‐copolymer bilayer coating on low nickel stainless steel in 0.5 M H2SO4 medium

In this paper, we have reported the anti‐corrosion performance of ceria / poly (indole‐co‐pyrrole) (Ce/(poly(In‐co‐Py)) bilayer coating on low nickel stainless steel (LN SS). Electrochemical polymerization of (poly (In‐co‐Py)) was achieved on ceria‐coated LN SS (CeO₂/LN SS) in acetonitrile medium containing LiClO₄ (ACN‐LiClO₄) by cyclic voltammetric technique. The coatings were characterized by analytical techniques like Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive analysis of X‐ray, respectively. The mechanical behavior of the coatings was studied using peel test, hardness and wear resistance tests. The corrosion defensive performance of this bilayer coating on LN SS was investigated using electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy in 0.5 M H₂SO₄. These results show that the bilayer coating on LN SS lowered the permeability of corrosive ions present in the acidic medium and thus acts as a barrier against the attack of corrosive environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Electro-less plating nickel-phosphorus of low carbon steel using various pretreatments and an external magnetic field

Electro-less plating nickel-phosphorus (EPNP) subject to various pretreatments and an external magnetic field, are prepared onto low carbon steel (LCS). The surface hardness (SH), fatigue life (FL) and corrosion behavior (CB) of Ni-P coated are respectively obtained using a nano-indenter and a high strain low cycle fatigue life (HSLCFL) and polarization test. The experimental outcome reveals that LCS substrates that are pretreated using the proposed acid mixture (25% H₂SO₄ + 5% HCl) roughening and activation allow good Ni-P films to be deposited. In terms of EPNP, as the P content decreases, the SH and FL increase. Specimens that a coated in a Ni–P film using an external magnetic field have better mechanical performance than those that are not produced in an external magnetic field. As the external magnetic field intensity is increased, the film thickness, SH and FL increase, the concentration of P decreases and thin grains are formed on the film surface. The specimens without using an external magnetic field that are coated with a Ni–P film exhibit better resistance to corrosion than the uncoated sample of LCS. However, the Ni–P film that is coated using an external magnetic field has higher SH, so it exhibits increased resistance to corrosion.     

Characterization of cerium-based conversion coatings for corrosion protection of AISI-1010 commercial carbon steel

The role of hydrogen peroxide in the formation of cerium conversion coatings by immersing AISI 1010 commercial carbon steel substrates into solutions containing various concentrations of CeCl₃ (0.1, 1, and 10 g L⁻¹) has been investigated as an alternative method for their protection against corrosion. The deposits prepared from the solutions with H₂O₂ consist of yellow thin and non-uniform coatings with agglomerates of small CeO₂ and Ce₂O₃ crystallites whose sizes increased over the metallic surface as the cerium concentration was increased. Cerium pre-treatments in the presence of H₂O₂ displayed layers that were rougher than those synthesized without H₂O₂. A comparison with the chromate conversion pre-treatment is also simultaneously carried out with the discussion of the possible reactions involved in the different stages of process. The coating obtained from the solution containing 0.1 g in 1,000 mL produced better corrosion resistance on the substrate than that observed for its counterparts due to the fact that the surface was more uniformly covered by the conversion coating. The addition of H₂O₂ to the cerate baths improves visible roughness, corrosion resistance of the conversion coatings and bond strength because hydrogen peroxide acts as an oxygen source during the formation of the coatings.     

Chemical and electrochemical characterization of hybrid PVD + ALD hard coatings on tool steel

In the last 30 years, thin hard coatings were intensively investigated due to their high-performance characteristics: high wear resistance, low friction coefficient and good thermal stability. Performances were furthermore improved using multilayer configurations, although often limited by feasibility or cost considerations. One of the main problems to overcome was the low corrosion protection that these coatings assure to the tool steel substrates on which they are applied. To assure high performances and corrosion protection it is possible to employ a completely new approach, suitable either as a pre-treatment of the substrate or as top coating, by using materials of different nature in the form of nano-layers.Monolayer and multilayer coatings obtained by PVD (Physical Vapor Deposition, using reactive arc evaporation) and by PVD + ALD (Atomic Layer Deposition) were studied and compared. Both in-depth composition and corrosion resistance properties were investigated using SEM–EDXS, GDOES (Glow Discharge Optical Emission Spectrometry) and polarization curves in a 0.2 M NaCl solution. The coatings studied were a TiAlN/TiN bi-layer and a TiCN monolayer obtained by PVD and an Al₂O₃ nano-layer obtained by ALD.     

Electrochemical storage properties of polyaniline-, poly(N-methylaniline)-, and poly(N-ethylaniline)-coated pencil graphite electrodes

Three types of conducting polymers, polyaniline (PANI), poly(N-methylaniline) (PNMA), poly(N-ethylaniline) (PNEA) were electrochemically deposited on pencil graphite electrode (PGE) surfaces characterized as electrode active materials for supercapacitor applications. The obtained films were electrochemically characterized using different electrochemical methods. Redox parameters, electro-active characteristics, and electrostability of the polymer films were investigated via cyclic voltammetry (CV). Doping types of the polymer films were determined by the Mott-Schottky method. Electrochemical capacitance properties of the polymer film coating PGE (PGE/PANI, PGE/PNMA, and PGE/PNEA) were investigated by the CV and potentiostatic electrochemical impedance spectroscopy (EIS) methods in a 0.1 M H₂SO₄ aqueous solution. Thus, capacitance values of the electrodes were calculated. Results show that PGE/PANI, PGE/PNMA, and PGE/PNEA exhibit maximum specific capacitances of 131.78 F g^?1 (≈ 436.50 mF cm^?2), 38.00 F g^?1 (≈ 130.70 mF cm^?2), and 16.50 F g^?1 (≈ 57.83 mF cm^?2), respectively. Moreover, charge-discharge capacities of the electrodes are reported and the specific power (SP) and specific energy (SE) values of the electrodes as supercapacitor materials were calculated using repeating chronopotentiometry.     

Essential oil of Salvia aucheri mesatlantica as a green inhibitor for the corrosion of steel in 0.5 M H2SO4

Essential oil of aerial parts of Salvia aucheri Boiss. var. mesatlantica was obtained by hydrodistillation and analyzed by GC and GC/MS. The oil was predominated by camphor (49.59%). The inhibitory effect of this essential oil was estimated on the corrosion of steel in 0.5 M H₂SO₄ using electrochemical polarization and weight loss measurements. The corrosion rate of steel is decreased in the presence of natural oil. The inhibition efficiency was found to increase with oil content to attain 86.12% at 2 g/L. Polarization curves revealed that the oil of S. aucheri mesatlantica acts as mixed type inhibitor with a strong predominance of anodic character. The temperature effect on the corrosion behavior of steel in 0.5 M H₂SO₄ without and with the inhibitor at 2 g/L was studied in the temperature range from 303 to 343 K, the associated activation energy have been determined. The adsorption of oil on the steel surface was found to obey Langmuir’s adsorption isotherm.     

Corrosion properties of nickel coatings obtained from aqueous and nonaqueous electrolytes

Nickel was deposited on a copper substrate from aqueous and nonaqueous ethanol electrolytes. X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and chronovoltametry, scanning electron microscopy, and atomic force microscopy were used to study the effect of the solvent on the surface and corrosion properties of the Ni coatings formed. Unifom and relatively smooth Ni films were obtained as measured with microscopy techniques. The formation of a passive film in acidic, alkaline, and neutral chloride-containing media was confirmed with X-ray photoelectron spectroscopy. The water-based nickel-plating electrolyte makes it possible to deposit coatings with higher corrosion resistance as compared with coatings deposited from ethanol electrolyte in NaOH and NaCl media. The proposed mechanism of corrosion in a 0.5 M H₂SO₄ solution involves cycles of active-passive surface behavior due to its passivation by corrosion products.     

Ormocer (ZrO2-PMMA) Films for Stainless Steel Corrosion Protection

The chemical protection of 316 L stainless steel coated with ORMOCER coatings of polymethylmethacrylate (PMMA) and ZrO₂ has been verified. The coatings were dip-coated on the substrates from sols prepared by mixing zirconium propoxide (ZrOC₃H₇)₄, isopropanol (C₃H₇OH), glacial acetic acid (CH₃COOH), polymethylmethacrylate and water under application of ultrasounds. The films were heat treated between 40 and 300°C in air up to 20 h. Their morphology was studied by electron scanning microscopy (SEM). Their anticorrosion behavior was analysed in 0.5M-H₂SO₄ solutions through potentiodynamic polarization curves at room temperature.The influence of the sol preparation, coating composition as well as of the duration and temperature of heat treatments on the corrosion parameters is reported. The films act as geometric blocking layers against the corrosive media and increase the lifetime of the substrate up to a factor 30.     

The study of self-assembled films of triazole on iron electrodes using electrochemical methods,XPS, SEM and molecular simulation

3-Alkyl-4-amino-5-mercapto-1,2,4-triazole (AAMT) has been evaluated as corrosion inhibition for iron in 0.1 M H₂SO₄ when the films of AAMT were self-assembled on the surface of iron. The films of AAMT inhibitor were characterized by electrochemical impedance spectroscopy, electrochemical polarization curves Results revealed that AAMT performed excellently as a corrosion inhibitor for iron in H₂SO₄ solution. Surface analysis was carried out using X-ray photoelectron spectroscopy and scanning electron microscope. The mechanism of adsorption was discussed using molecular simulation.     

Poly(2,5-dimethoxyaniline) film coating for corrosion protection of iron

A poly(2,5-dimethoxyaniline) (PDMA) film was coated on the iron surface by the electropolymerization of 2,5-dimethoxyaniline in neutral buffer solution (pH?6.86). The PDMA film strongly adhered to the surface because of the polar methoxy groups of the PDMA molecules. The fact that no electrochemical response of the PDMA film-coated iron electrode to dissolved Fe²⁺ exhibited that the PDMA film was less permeable to dissolved species, acting as a diffusion barrier against agents causing corrosion such as H₂O and O₂. The PDMA film coating greatly lowered the anodic current peak ascribed to the anodic dissolution of iron and the corrosion current in strongly acidic medium, 0.5?M H₂SO₄ aqueous solution (1?M?????mol?dm^??) as well as neutral medium (pH?6.86). The high anti-corrosion ability was due to a hybrid effect of the PDMA film not only as the diffusion barrier, but also as an in situ oxidant in spite of the slight redox activity of PDMA. In addition, the PDMA film is much more durable and adhesive than polyaniline film against over-oxidation.     

Preparation and characterization of anticorrosion Ormosil sol–gel coatings for aluminum alloy

Organically modified silicate (Ormosil) coatings have been synthesized through the sol–gel method for corrosion protection of aluminum alloy. Silica-based unmodified coatings were also designed to investigate the effect of tetraethoxysilane (TEOS) content on the properties of the coatings. The surface morphology of the coatings was characterized by scanning electron microscopy. The corrosion resistance was evaluated by immersion test, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. In addition, the surface potential differences of the coated samples were determined by scanning Kelvin probe. The results showed that a better corrosion resistance of unmodified coating was prepared by controlling the TEOS/EtOH/H₂O molar ratio of 0.109/1/1.52. Ormosil coatings provided excellent barrier properties and corrosion resistance in comparison with the unmodified sol–gel coatings. The Ormosil coating modified with triethoxyoctylsilane exhibited corrosion resistance properties superior to the other Ormosil coatings after exposure to 3.5 wt% NaCl solution for 10 days.     

Conducting poly(o-anisidine)-coated steel electrodes for supercapacitors

Conducting poly(o-anisidine) coatings were obtained on low carbon steel in aqueous oxalic acid solution by using the galvanostatic technique. The coatings were characterised by potential-time relations, UV-VIS absorption spectroscopy, scanning electron microscopy, and X-ray diffraction measurements. The electrochemical performance of coated steel electrodes was evaluated on the basis of galvanostatic charge-discharge performance and electrochemical impedance spectroscopy in 0.5 M H₂SO₄. Maximum charging current was found in the case of the coating obtained at a current density of 8 mA cm^?2 for 600 s duration at the supply voltage of 0.5 V. The estimated capacitance of the coated steel electrode for charging is 42.67 mF and 7.2 mF for discharging. It was also found that there was an increase in capacitance as a function of supply voltage and the maximum value was obtained at 0.5 V. The study reveals the possibility of using conducting poly(o-anisidine)-coated low carbon steel from oxalic acid medium as supercapacitor electrode materials.     

Spirulina platensis – A novel green inhibitor for acid corrosion of mild steel

The inhibition of the corrosion of mild steel in 1 M HCl and 1 M H₂SO₄ by Spirulina platensis has been studied at different temperatures viz., 303 K, 313 K and 323 K by weight loss method, potentiodynamic polarization method, electrochemical impedance spectroscopy measurements and SEM analysis. The inhibition efficiency increased with increasing concentration of the inhibitor in both HCl and H₂SO₄ media. The results of weight loss studies correlated well with those of impedance and polarization studies. From the results of weight loss studies at various temperatures, the mode of adsorption is confirmed to be physisorption. Further the adsorption has been found to follow Temkin isotherm. From this isotherm, the free energy of adsorption (ΔG) and entropy (ΔS) are calculated. The study reveals the corrosion inhibition potential of S. platensis in both the acid media, thus bringing to light another facet of this microalga as it has so far been used only to produce antioxidant principles, finding extensive use in medicine especially as neutraceutical.     

Excellent protection of mild steel in sodium chloride solution for a substantial period of time using a hybrid nanocoating of poly vinyl alcohol and Titania

The production of eco-friendly hybrid sol–gel coatings for long term protection of metallic substrates from aggressive environments was one of the emerging areas, competing with conventional chromate and phosphate coatings. Herein, a nanocomposite has been synthesized from TiO₂ and PVA through a novel sol-gel route and the structure and morphology of the same was characterized using X-ray diffraction, FTIR, UV–Vis spectroscopy, FESEM with EDAX, and AFM studies. The flower-like structured composite offers excellent corrosion protection properties in NaCl solution of sea water salinity. Impedance and polarization studies were carried out to monitor the anticorrosion performance of the materials coating. This coating on mild steel offers 98% inhibition efficiency in NaCl. The influence of loading PVA on TiO₂ and its effect on corrosion efficiency have also been investigated. It is found that an optimum weight of 20 wt% PVA is required in the composite for beneficial corrosion resistance. 92% inhibition efficiency is registered by the coated MS in NaCl solution after 40 days of exposure and is quite encouraging compared to many of the recent reports. The Ti–O–Ti, and Fe-Ti-O linkage along with compactness and adherence of the material together contribute to better blocking of steel corrosion.     

Inhibition of cold rolled steel corrosion in sulphuric acid solution by 2-mercapto-1-methylimidazole: Time and temperature effects treatments

2-Mercapto-1-methylimidazole (MMI) has been evaluated as a corrosion inhibitor for cold rolled steel in aerated 2 M H₂SO₄ by gravimetric method. The effect of MMI on the corrosion rate was determined at various immersions time and concentrations. The effect of the temperature on the corrosion behaviour with addition of different concentrations of MMI was studied in the temperature range 30–60 °C. The MMI acts as an effective corrosion inhibitor for cold rolled in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of MMI on the metal surface which protects the metal against corrosion. The protection efficiency increased with increase in inhibitor concentration at various immersions time and decreased with increase in temperature. Adsorption of MMI on the cold rolled steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined.     

Development of multifunctional polydimethylsiloxane (PDMS)‐epoxy‐zinc oxide nanocomposite coatings for marine applications

Multifunctional epoxy‐polydimethylsiloxane nanocomposite coatings with antifouling and anticorrosion characteristics have been developed via in situ polymerization method at different loading (1, 3, and 6.5 wt.%) of ZnO nanoparticles to cater marine applications. A detailed comparative analysis has been carried out between epoxy‐polydimethylsiloxane control (EPC) and ZnO‐reinforced coatings to determine the influence of ZnO loading on various properties. The incorporation of ZnO in EPC led to increase in root mean square (RMS) roughness to 126.75 nm and improved hydrophobicity showing maximum contact angle of 123.5° with low surface energy of 19.75 mN/m of nanocomposite coating as compared with control coating. The differential scanning calorimetry (DSC) result indicated improved glass transition temperature of nanocomposite coatings with highest T_g obtained at 83.69°C in case of 1 wt.% loading of ZnO. The increase in hydrophobicity of the system was accompanied by upgraded anticorrosion performance exhibiting 98.8% corrosion inhibition efficiency (CIE) as compared with control coating and lower corrosion rate of 0.12 × 10^?3 mm/year. The Taber abrasion resistance and pull‐off adhesion strength results indicated an increment of 34.7% and 150.7%, respectively, in case of nanocomposite coating as compared with the control coating. The hardness of nanocomposite coatings was also improved, and maximum hardness was found to be 65.75 MPa for nanocomposite coating with 1 wt.% of ZnO. Our study showed that the nanocomposite coating was efficient in inhibiting accumulation of marine bacteria and preventing biofouling for more than 8 months. The developed environment‐friendly and efficient nanocomposite material has a promising future as a high‐performance anticorrosive and antifouling coating for marine applications.     

The effect of cerium pre-treatment on the corrosion resistance of steel sheets

The steel samples have been coated with cerium layer by cathodic electrolytic deposition from the Ce(NO₃)₃·6H₂O solution in aqueous ethyleneglycol in the presence of hydrogen peroxide. The influence of the coating parameters (cathodic current density, pH, cerium concentration, hydrogen peroxide concentration, temperature, and treatment duration) on the surface properties; the optimum conditions of the formation of corrosion preventing coating have been elucidated. Hydrogen peroxide concentration and pH are the major factors influencing the deposition process. The corrosion resistance has been further enhanced after treatment with Na₃PO₄·12H₂O solution. The cerium-coated samples have been subsequently coated by cathodic electrostatic deposition from the colloidal solution of the paint. The coated materials have been subjected to mechanical testing (hardness, impact, cross cut, bending, and cupping tests), and their structure has been visualized by electron microscopy. The cerium coating has been found to improve the steel corrosion resistance by 15%.     

Synthesis and performance of electroless Ni–P–TiCN composite coatings on Al substrate

Electroless Ni–P and Ni–P–TiCN composite coatings have been deposited successfully on Al substrates. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) techniques were applied to study the surface morphology and the chemical composition of the deposited films. Moreover, X‐ray diffraction (XRD) proved that Ni–P and Ni–P–TiCN deposits have amorphous structures. The properties of Ni–P–TiCN/Al composite films such as hardness, corrosion resistance and electrocatalytic activity were examined and compared with that of Ni–P/Al film. The results of hardness measurements reveal that the presence of TiCN particles with Ni–P matrix improves its hardness. Additionally, the performance against corrosion was examined using Tafel lines and electrochemical impedance spectroscopy techniques in both of 0.6 M NaCl and a mixture of 0.5 M H₂SO₄ with 2 ppm HF solutions. The results indicate that the incorporation of high dispersed TiCN particles into Ni–P matrix led to a positive shift of the corrosion potential and an increase in the corrosion resistance for all aluminum substrates after their coating with Ni–P–TiCN. In addition, Ni–P–TiCN/Al electrodes showed a higher electrochemical catalytic activity and stability toward methanol oxidation in 0.5 M NaOH solution compared with that of Ni–P/Al. Copyright © 2014 John Wiley & Sons, Ltd.     

Superior corrosion protection and in vitro biocompatibility of Na-HAp/CS composite coating on PoPD-coated 316L SS

The synthesis and development of sodium (Na)-substituted hydroxyapatite (HAp)/chitosan (CS) composite using poly (O-phenylenediamine) (PoPD) coating on 316L SS substrate for improving bioactivity and corrosion protection was studied. The surface of Na-HAp/CS/PoPD bilayer coatings on 316L SS substrate was characterized by diverse analytical techniques. The open circuit potential (OCP) measurement, potentiodynamic polarization, and impedance test revealed that the bilayer coating provides excellent protection to the substrate against the corrosion in the simulated body fluid (SBF) solution. This interior layer of the coating acts as a barrier against the release of metal ions from the substrate, which was confirmed by inductively coupled plasma-atomic emission spectroscopy. Besides, the mechanical properties of the coatings were analyzed. From the obtained results, the bilayer coating exhibited greater mechanical strength than the individual coating. An in vitro bioactivity of the coatings was assessed by immersion in the SBF solution at 7–28 days. The apatite formation of bilayer coatings on 316L SS substrate is found to be more bioactive compared with the Na-HAp, PoPD, and Na-HAp/CS. The in vitro biocompatibility test showed no adverse effects, which was proved by the enhanced biocompatibility of the bilayer coating on 316L SS.     

Corrosion behavior of tantalum alloying on γ‐TiAl by double‐glow plasma surface metallurgy technique

The Ta coating with corrosion resistance is grown on the γ‐TiAl substrate by double‐glow plasma surface metallurgy technique, followed by the electrochemical test in 10 wt%, 20 wt% HCl and 10 wt%, 40 wt% H₂SO₄ solution. The data of nanohardness and elastic modulus are collected by the nanoindention test. The adhesion strength of Ta coating is investigated by means of the scratch test. The study of corrosion resistance is performed using potentiodynamic polarization and electrochemical impedance spectroscopy and measured by SEM and X‐ray diffraction. Results highlight that the Ta coating is tightly bonded to the γ‐TiAl substrate, consisting of the deposition layer and diffusion layer. Experimental data indicate that the Ta coating presents excellent corrosion resistance, which is confirmed by the high values of polarization resistance (R_p) and the low values of corrosion current density (i_corr). The surface nanohardness of the Ta coating is improved from 3.41 to 7.29 GPa, nearly twice of that of the substrate. The Ta₂O₅ formed on the coating is able to hold back the penetration of adverse ions inwardly, owing to its dense structure and adhesion effect. Copyright © 2017 John Wiley & Sons, Ltd.