Corrosion Protection Properties Research Articles

Synthesis, characterization and protective functioning of surface decorated Zn-Al layered double hydroxide with SiO2 nano-particles

In this paper, ZnAl layered double hydroxide particles surface were decorated with SiO2 nanoparticles to investigate the influence of SiO2 nanoparticles presence on molybdate anion loading and release behavior as a corrosion inhibitor. For this purpose, we have synthesis a carbonate-based layered double hydroxide (LDH). Nano SiO2 particles were used to decorate the surface of carbonate-based LDH nano-plates. Molybdate was then intercalated into LDH interlayer space through an ion exchange process. Characterization of the synthesized nano-plates was done by XRD, FTIR, FE-SEM, and ICP tests. The decorated nano-plates were employed in silane coating to investigate and compare their corrosion protective properties using EIS and polarization tests. The results illustrated that the protective functioning enhanced after SiO2 decoration. Moreover, molybdate loaded in SiO2 decorated LDH had a better protective functioning, and provided more extended protection due to its higher loading, and controlled release of molybdate anions.

A crosslinkable graphene oxide in waterborne polyurethane anticorrosive coatings: Experiments and simulation

A crosslinkable graphene oxide (GO) was synthesized and employed as reinforcement in waterborne polyurethane (WPU) composite coatings for improving corrosion protection properties. Polycarbodiimide (PCD), a crosslinking agent of WPU, was chosen to modify GO. Three different conformations of functionalized graphene will be generated: grape cluster conformation, network conformation and tail conformation, varying mainly with the PCD/GO ratio. Experiments and molecular dynamics simulation were carried out to study the correlations between the PCD/GO ratio, the conformations of functionalized graphene, as well as the dispersion state of graphene layers. The functionalized graphene with tail conformation was crosslinkable with WPU molecules along the interfaces. Electrochemical impedance spectroscopy showed that the WPU coatings with 0.2 wt% crosslinkable graphene remained at a maximum impedance modulus of 109 Ω cm2 after 120 days immersion without any decrease. The superior anticorrosive properties benefited from the barrier properties of well-dispersed graphene layers, the crosslinking structure along the functionalized graphene/WPU interfaces, as well as the improved water resistance of the coatings.

Preparation and anticorrosion resistance of a self‐curing epoxy nanocomposite coating based on mesoporous silica nanoparticles loaded with perfluorooctyl triethoxysilane

AbstractOrganic coatings are prone to failure due to diffusion of the corrosion media toward the metal surface through the microcracks caused by internal and environmental stresses especially in immersion environment. In order to extend the service lifetime of organic coatings, we developed a self‐curing epoxy resin/perfluorooctyl triethoxysilane (POTS)‐loaded mesoporous silica nanoparticles (MSNs) nanocomposite (SEP/POTS‐MSNs) coating, by embedding the POTS‐loaded MSNs (POTS‐MSNs) into an SEP resin. Fourier transform infrared, X‐ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analyses were conducted to confirm the successful loading of POTS in the MSNs. Thermogravimetric analysis was used to characterize the loading amount of POTS. The corrosion protection properties of the SEP, SEP/MSNs, and SEP/POTS‐MSNs coatings were evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization tests. The results indicate that the SEP/POTS‐MSNs coating with only 30 μm thickness showed corrosion resistance with Z f = 0.01 Hz of 4.7 × 108 Ω/cm2 and icorr of 0.026 nA/cm2 after 58 hr of immersion in boiling water, which were both two orders of magnitude higher than those of the SEP coating. The SEP/POTS‐MSNs coating combines the advantages of the SEP coating and the POTS‐MSNs. We anticipate that the SEP/POTS‐MSNs coating has promising potential for use in immersion environments.

Modified salicylaldehyde@ZIF-8/graphene oxide for enhancing epoxy coating corrosion protection property on AA2024-T3

Salicylaldehyde@ZIF-8/graphene oxide (SZG) nanosheets were fabricated by anchoring salicylaldehyde@ZIF-8 nanoparticles on graphene oxide. SZG nanosheets were modified by amino silane 3-aminopropyltriethoxysilane (f-SZG) to improve the compatibility with epoxy coating. Sedimentation test showed the excellent dispersion stability of f-SZG in resin epoxy even after standing for 480 h. The cross-sectional microstructure of coatings implied the strong f-SZG/coating matrix interface by transforming the cleavage fracture to the ductile. Additionally, the stimuli-responsive release to H+ and Al3+ ions of f-SZG is maintained after the silanization. Compared with other samples, f-SZG0.5 epoxy coatings show the optimal long-term corrosion protection property with the lowest reduction rate of |Z|0.01Hz (13.6%) after 480 h immersion and the intact surface after 27d salt spray test due to the stronger interfaces of f-SZG/epoxy matrix and coating/substrate, the proper content (0.5 wt.%) and the enhanced cross-linked density of coating.

Mechanical and corrosion protection properties of polymer–clay nanocomposite coatings for mild steel in marine environment

Polymer–clay nanocomposites (PCNs) are potentially interesting as anti-corrosion surface pretreatment layers because of their outstanding barrier characteristics. Corrosion behavior of steel coated with epoxy–indole-modified clay nanocomposite films was studied. The electrochemical behavior of films containing polymer–clay nanocomposites was analyzed by potentiodynamic polarization techniques, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) measurements in 3.5% NaCl solution. Microstructural characterization and surface analysis of substrates and coatings were performed by FE-SEM/EDX techniques. Results from electrochemical measurements reveal good long-term corrosion protection of steel provided by polymer–indole-modified clay coating. This polymer–clay coating yields a highly ordered multilayered brick and mortar structure, where polymer provides a physical barrier for the diffusion of corrosive agents/corrosion products within the coating. The results of the study show that the incorporation of nanoclay has a significant effect on the mechanical behavior of composites. Mechanical properties of the coatings were found to be improved in the presence of modified nanoparticle. The adhesion strength was found to have increased (8.10 MPa) up to 2 wt.% and decreased in its value to 7.56 MPa for 3 wt.% of nanoclay reinforcement, which made the composite to become more brittle. The optimum loading of clay in the epoxy–fclay composites was attained at 2 wt.%, where the improvement in hardness and properties was seen.

Designing a zinc-encapsulated Feldspar as a unique rock-forming tectosilicate nanocontainer in the epoxy coating; improving the robust barrier and self-healing anti-corrosion properties

For the first time, Feldspar (F) nanocontainer, which is a group of rock-forming tectosilicate minerals with the chemical composition of KAlSi3O8-NaAlSi3O8-CaAl2Si2O8, was used for the construction of an epoxy composite coating with superior barrier and self-healing anti-corrosion performance. Feldspar (F) based nanocontainer with robust corrosion inhibitive activity was fabricated through the encapsulation of zinc cations as a cathodic inhibitor. It was understood from the electrochemical measurements that in the saline solution including F/Zn extract the metal corrosion was significantly retarded (by protection efficiency of 73%) due to the inhibitor release activity of the F/Zn container and protective film generation on the metal surface. The inductively coupled plasma (ICP) analysis results confirmed the Zn2+ cations (5.33 mg/L) release in the chloride solution from the F/Zn container. EIS test results evidenced the significant effect of the F/Zn in the epoxy ester composite coating barrier and self-healing anti-corrosion functions in the intact and scratched forms. In the presence of F/Zn an improvement in the charge transfer resistance (about 83%) of the scratched coating was observed, indicating the active self-healing inhibition effect of the F/Zn nanocarrier. By incorporation of the F/Zn particles into the epoxy ester coating the E′ (at 30 °C), glass transition temperature (Tg), stress, strain and energy at break were significantly enhanced. These results proved that not only the corrosion protection properties but also the mechanical properties of the epoxy ester coating were excellently improved in the presence of F/Zn nanocarrier.

The effect of chlorides on the corrosion behaviour of weathered reinforcing bars

The present contribution is intended to provide an in depth approximation to the role plaid by the thick passive layers formed over years in atmospheric exposure in the electrochemical response of steel embedded in concrete. This information is expected to be of general interest for the interpretation of electrochemical data as the corrosion potential and the polarization resistance, commonly employed for assessing steel corrosion in this system. Results for blank samples and samples containing chlorides are discussed based on findings from electrochemical impedance spectroscopy. Temperature was considered in the study as a parameter for acting on both the chemistry of the pore electrolyte and the specific volume of the oxides layer. By this approach, we were able to identify the contribution of the oxides layer to the impedance spectra in the 10 kHz-1 Hz frequency range. Kinetic information for corrosion rate can be obtained in the low frequency region of the impedance spectrum. The polarization resistance, the DC resistance value, has to be corrected for the impedance at about 1 Hz. The oxides layer supports the oxygen cathodic reaction, but also the anodic and cathodic processes corresponding to the re-oxidation and reduction of the layer itself. Compared to layers formed in the absence of chlorides, the presence of chlorides in the concrete mix leads to the formation of a more oxidised oxide layer, with decreased redox activity and more prone to cracking under thermal cycling. Thus, the presence of chlorides decreases the corrosion protective property of the oxide layer.

Mechanical and corrosion properties in 3.5% NaCl solution of cold sprayed Al-based coatings

The recent development of the cold spray method has made it possible to deposit dense coating with good adhesion and with almost no change in the microstructure, which is promising in repairing damaged Al-based aircraft skin. In this work, the in-situ shot-peening-assisted low-pressure cold spray method was used to deposit Al-based dense coatings with good mechanical and corrosion protection properties on AA 2024-T3 alloy. The detailed microstructure, coating adhesion, and corrosion protection performance were systematically investigated. A dense microstructure with low porosity (<1.7%), high cohesive strength (>45 MPa) is achieved for the coatings. By comparison, Al 5083 coating exhibited the optimum mechanical properties. The Al and Al 5083 coatings reveal similar pitting resistance and repassivation ability. During long-term immersion test (>480 h) the corrosion resistance of Al 5083 coating surpassed that of CP Al coating. In conclusion, Al 5083 coating has a good combination of mechanical and anti-corrosion properties.

Corrosion Resistance of MAO Coatings on Al-Si Alloys

The paper presents the results of an experimental study of the influence of micro-arc oxidation (MAO) on the parameters and the corrosion resistance of MAO-treated surfaces on a high-silicon aluminum alloy, M244 (Si ~ 25 %). The article describes the study methodology, comprising forming a coating on the surface of laboratory samples by means of MAO at different process modes and the study of their parameters, properties, and corrosion resistance. The experiments were conducted in accordance with the 23 full factorial experiment design theory. The MAO process was carried out using a silicate-alkaline electrolyte. MAO factors were as follows: the concentration of the electrolyte components (potassium hydroxide – KOH and liquid glass – Na2SiO3) and electrical parameters of the process, determined by the capacitor capacitance of the processing unit. The samples were tested to define thickness, porosity and micro-hardness of the MAO layer. Being corroded in a corrosive solution for 144 hours, their corrosion resistance was estimated by a mass corrosion rate. The data obtained made it possible to form mathematical models, based on the dependence of corrosion resistance, thickness, porosity and micro-hardness on the process factors. A verification of the obtained models was carried out to determine adequacy and their analysis. Conclusions on the extent of the MAO effect on the corrosion resistance of the samples were drawn. MAO modes were stated to have a significant impact on the corrosion resistance of the samples. MAO should be carried out using low electrolyte concentrations and a low-capacity processing unit for improved corrosion-protective properties of the coating on the M244 (Mahle) aluminum alloy. It is necessary to increase the concentration of the electrolyte components and the processing unit capacity, to obtain a thicker coating with low micro-hardness and porosity.

Role of free volume in molecular mobility and performance of glassy polymers for corrosion-protective coatings

ABSTRACTGlassy polymer coatings on metal substrates rely on their mechanical, physical, and transport properties for corrosion protection. These properties are influenced by free volume between polymer chains that plays a critical role in coating performance. Free volume permits local segmental mobility that affects mechanical properties, such as yield and adhesion, and also permits diffusion of small molecules (water, ions, and oxygen) through the coating to the substrate. Fractional free volume is calculated from the specific volume and Bondi group contribution theory for the occupied volume. Free volume distribution (free volume element size and number) is measured by positron annihilation lifetime spectroscopy (PALS) using the ortho-positronium (oPs) probe, which detects free volume elements in glassy polymer coatings. The oPs probe is sensitive to phenomena that affect both the mechanical and barrier properties of coatings including physical ageing, water sorption, and plasticisation, making PALS a suitable allied testing method for corrosion-protective coatings.

Effect of structure of electrodeposited nickel-phosphorous coatings on their physico-mechanical and corrosion-protective properties

Effect of structure of electrodeposited nickel-phosphorous coatings on their physico-mechanical and corrosion-protective properties

Investigation of corrosion protection properties of TiO2-CdO nanocomposite coating prepared by sol-gel method on copper

the Sol–gel nanocomposite coatings have been investigated for copper metal as a potential replacement for the hazardous and banned hexavalent chromate conversion coatings. TiO2–CdO nanocomposite thin films were deposited on copper using the sol–gel method. The sol-gel coatings were prepared using a sol obtained by the hydrolysis and condensation of tetra-o-butyl titanate. They were doped with cadmium oxide inhibitor to provide active corrosion protection. The synthesized coatings were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The anticorrosion performances of TiO2-CdO nanocomposite coatings were investigated in 3.5% NaCl solution by the potentiodynamic polarization technique Tafle and electrochemical impedance spectroscopy (EIS). The potential corrosion increases from -210 mV versus Ag/AgCl (3M) for uncoated copper to -202 mV versus Ag/AgCl (3M) for TiO2-CdO nanocomposite-coated copper electrodes. The results of this study clearly ascertain that the TiO2-CdO nanocomposite has outstanding potential to protect the copper against corrosion in a chloride environment..

Corrosion protection of AZ91D magnesium alloy by a duplex coating

A duplex coating was formed under potentiostatic conditions on magnesium alloy AZ91D in order to improve its corrosion resistance in a simulated physiological environment. The first layer was formed by anodization at low potentials in molybdate solution. The outer layer was a PPy film electrosynthesized in sodium salicylate solution. The conditions of the formation were determined to obtain a layer with globular morphology. The bilayer was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion protection properties of the coatings were examined in Ringer solution by monitoring the open circuit potential (OCP), polarization techniques, and electrochemical impedance spectroscopy (EIS). The obtained results showed that the bilayer improves the corrosion resistance of the substrate. Moreover, the duplex coating presented better anticorrosive properties than a single PPy film. Afterwards, the bilayer was modified by cementation of silver ions from a solution containing AgNO3. The modified electrode exhibited good antibacterial properties.

Corrosion Resistance and Cathodic Disbondment of Epoxy Coating Applied on Zinc Phosphate Conversion Coating Containing Different Amounts of Cobalt Ions

In this study, the influence of phosphate surface pretreatment containing a cobalt ion additive on the anti-corrosion features of epoxy coating was investigated. Phosphate conversion coating (PCC) specimens were prepared. Then the epoxy coating was electrostatically sprayed on the phosphated substrate. The surface morphology and the composition of a zinc phosphate conversion coating with a cobalt ion additive were studied by scanning electron microscopy and X-ray diffraction, respectively. Also, the corrosion protection properties of specimens were studied by the polarization potentiodynamic test in 3.5% NaCl solution. Protective performance of double-layer coatings was studied using electrochemical impedance spectroscopy during 30 days in the mentioned solution. In addition, the impact of phosphate chemical treatment on increasing the adhesion strength of the powder coating was studied using the pull-off adhesion test and cathodic disbodnment test in the same solution. As a result, it was found that the corrosion resistance of PCC containing a cobalt additive enhanced significantly and that the PCC containing 3 g/L Co is less porous than other coatings. Also, the protection properties, adhesion strength, and cathodic disbondment resistance of the double-layer coatings with phosphate pretreatment containing 3 g/L Co increased significantly.

Effect of machine hammer peening on the surface integrity of a ZnAl-based corrosion protective coating

Thermally sprayed protective coatings are applied onto many mechanically stressed components such as support structures, shafts, turbine blades or heat exchangers. In addition to the static or cyclic load, a superimposition with corrosion processes occurs in many cases. Thermal sprayed ZnAl coatings are known for their performant corrosion protection properties. Within this context, the potential of ZnAl-based layer systems was analyzed regarding corrosion fatigue behavior. Therefore, a timeand cost-efficient testing strategy based on a corrosion-superimposed load increase procedure was used to estimate the effects of a corrosive attack during cyclic loading. The investigated coating systems were thermally sprayed and partially post-processed with a Machine Hammer Peening (MHP) operation. This treatment was identified as an appropriate technique for compressing and smoothing coated surfaces. The inter-relationships between the parametrization of the MHP process, the resulting surface integrity, and the estimated corrosion fatigue properties were analyzed. The investigations indicate a positive effect of MHP post-processing operations on the surface properties of the ZnAl-based coating system.

Evaluation of Mechanical Properties and Corrosion Protection Performance of Surface Modified Nano-alumina Encapsulated Epoxy Coated Mild Steel

The incorporation of imidazole-modified nano-alumina on the corrosion protection properties of epoxy coating on mild steel was studied by electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) in 3.5% NaCl solution. The dispersability of the alumina nanoparticles was greatly improved by the surface modification using imidazole in the epoxy matrix. The imidazole-modified nanoparticle was analyzed by Fourier transform infrared spectroscopy. Both EIS and SECM studies confirmed that the corrosion resistance is higher for the alumina–epoxy nanocomposite coated steel than that of the pure epoxy-coated steel. It is evidenced that alumina–epoxy nanocomposite coated mild steel has higher charge transfer resistance values, 156,344 Ω cm2, compared to pure epoxy coated mild steel, 79,546 Ω cm2, at 40 days of immersion. The modified nanoparticles enhanced the adhesive properties of the coatings. Possible chemical interactions between epoxy matrix and surface-modified alumina nanoparticles in nanocomposites cause high protection properties and ionic resistances. FE-SEM/EDX analysis showed the presence of Fe, Al, and O in the corrosion products. Hardness and tensile strength measurements showed that the improved mechanical properties were noticed for alumina–epoxy nanocomposite coated mild steel.

Non-covalently functionalized boron nitride by graphene oxide for anticorrosive reinforcement of water-borne epoxy coating

Hexagonal boron nitride (h-BN) has great promise for metal corrosion due to its good impermeability to gas and liquid. However, it is difficult for h-BN to disperse in water-borne epoxy (WBE) matrix owing to its nature hydrophobicity. In this work, h-BN was non-covalently modified by graphene oxide (GO) to enhance the compatibility of h-BN for WBE. And the GO/h-BN composite was characterized by transmittance electron microscopy (TEM), Raman spectroscopy, UV–vis absorbance spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion protection and barrier performance of GO/h-BN/WBE were evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test, which indicated that the composite coating with 0.3 wt. % GO/h-BN (1:1 w/w) additive exhibited excellent barrier and corrosion protection properties owing to the synergistic impermeable performance of h-BN and GO.

Enhanced protective properties of hydrothermally synthesized Ni(OH)2-YSZ/reduced graphene oxide (rGO) nanocomposite coating

The hydrothermally synthesized Ni(OH)2-YSZ composite reinforced with reduced graphene oxide (rGO), was applied for corrosion protection of 316L stainless steel (SS) by electrophoretic deposition. The effect of rGO introduction on corrosion properties of Ni(OH)2-YSZ coating was investigated. The morphology and structures were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The corrosion properties of specimens were determined by Tafel polarization and electrochemical impedance spectroscopy (EIS) analysis in 3.5 wt% NaCl corrosive solution. The results showed that the corrosion protection properties were remarkably improved by the introduction of rGO into Ni(OH)2-YSZ composite film. The Ni(OH)2-YSZ/rGO coated SS showed a higher charge transfer resistance (1.85 × 105 Ω cm2) compared to Ni(OH)2-YSZ coated SS (6.12 × 104 Ω cm2) and bare 316L SS (4.55 × 104 Ω cm2). The addition of rGO to Ni(OH)2-YSZ composites efficaciously improved the dispersion of nanoparticles and also reduced their size. Consequently, the electrochemical enhancement caused by rGO introduction was attributed to the nano-sized particles, compaction, and uniformity of the coating, which efficiently prevented the steel substrate from corrosion attack.

Epoxy composite coating corrosion protection properties reinforcement through the addition of hydroxyl-terminated hyperbranched polyamide non-covalently assembled graphene oxide platforms

This paper presents the role of GO particle functionalization by different contents of hydroxyl-terminated hyper-branched polyamide on the epoxy coating corrosion protection properties. Raman spectroscopy, UV–visible analysis, and field emission scanning electron microscopy (FE-SEM) methods were applied to study the HB/GO interactions and morphology at different ratios. Then, by electrochemical impedance spectroscopy (EIS) and accelerated corrosion test (salt spray) the Epoxy-GO and Epoxy-HB/GO = 0.25, 0.5, 1.0 and 2.5 systems corrosion protection properties were investigated. Results obtained from Raman spectroscopy, UV–Visible analysis, and FE-SEM measurement proved that the GO sheets were successfully modified by HB molecules. SEM results evidenced that the GO particle dispersion quality in the epoxy matrix was significantly improved after modification by HB. Pull-off results revealed significant improvement in the epoxy film adhesion to the steel surface in the presence of HB/GO. Results disclosed that the epoxy composite coating reinforced with HB/GO = 0.5 and 1.0 showed the largest impedance (>1010 ohm cm2) and lowest delamination values. Generally, the modified GO sheets significantly improved the epoxy coating corrosion protection properties due to the role of HB in improving the dispersion state (proved by SEM results) and interfacial interactions between the GO and epoxy matrix.

Development of Novel Poly (ɛ-Caprolactone)/ Fluorine Substituted Hydroxyapatite Bilayer Coated 316L Ss for &lt;i&gt;In Vitro&lt;/i&gt; Corrosion Protection

A novel biocompatible fluorine substituted hydroxyapatite (F-HAp) / poly (ε-caprolactone) (PCL) bilayer coating on 316L SS with superior adhesion strength and admirable corrosion protection properties. PCL slurry was coated on 316L SS as a first layer using dip coating method followed by F-HAp coating as the second layer using electrodeposition method. The structural and functional group analysis of bilayer coatings were characterized by different analytical technique. Also, the mechanical properties of the bilayer coating showed higher adhesion strength than HAp and F-HAp coatings on 316L SS. The potentiodynamic polarization and electrochemical impedance spectroscopy results indicated that the admirable corrosion protection nature. The in vitro bioactivity test for coated 316L SS substrate was carried out by soaking it in the SBF solution, the induced apatite formation confirming the improved bioactivity of the specimen. Further, dissolution of metal ions was considerably reduced which was confirmed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The in vitro cell–material interaction of the bilayer coating was studied with human osteosarcoma MG63 cells for cell viability at 3, 7, 14 and 21 days of incubation and good biocompatibility was observed. The obtained results show that the F-HAp/PCL bilayer coating provides effective corrosion protection and enhanced bioactivity.