Long-term Anti-corrosion Performance Research Articles

Anticorrosion study of phytic acid ligand binding with exceptional self-sealing functionality

Self-sealing functionality has attracted significant interest over the past few decades because it can generously extend the alloy corrosion protection ability. Faced with this trend of anti-corrosion, we fabricated a smart composite ceramic coating on magnesium-lithium (Mg–Li) alloys. Meanwhile, the composite coating was fabricated by incorporating a coupling agent (phytic acid) between the micro-arc oxidation (MAO) film and stannate coating to improve the coverage of the conversion coating. The corrosion behavior in simulated seawater was examined by electrochemical impedance spectroscopy. Surface structure and composition were characterized by scanning electron microscopy (SEM). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Results revealed that the composite coating displayed an excellent enhancement in corrosion resistance and outstanding long-term anticorrosion performance due to the self-sealing feature. Moreover, self-sealing performance of stannate conversion coating was described by the theory of dissolution-reprecipitation, which is the process of an old phase dissolving and new phase generating, and the new phase is deposited on the surface of the sample. These results suggested that the advantages of the prepared composite coating have a great value in the practical application.

In-situ growth of layered double hydroxides nanosheet arrays on graphite fiber as highly dispersed nanofillers for polymer coating with excellent anticorrosion performances

Abstract The design and fabrication of uniform and compact nanocomposite coating with excellent anticorrosion performances are critical in reducing the metal consumption. Herein, we describe a facile and ingenious strategy to obtain a polymer coating that consists of well-dispersed nanosheet fillers via preparing highly ordered layered double hydroxides (LDHs) nanosheet arrays on oxidized graphite fiber (OGF) (as support body and dispersion phase). We found that the incorporation of 0.5 wt.% OGF-LDHs into the polyvinyl butyral (PVB) matrix caused excellent long-term anti-corrosion performance of mild steel in 3.5 wt.% NaCl solution. The uniformly staggered OGF-LDHs acted as a three-dimensional shielding against the corrosive media. The present study, together with a facile and highly efficient method of excellent anticorrosion nanocomposite coating fabrication paved an important step towards real-world applications of anticorrosive coatings using polymer/LDHs composites.

Corrosion resistance of composite coating used for fastener protection

Purpose The purpose of this paper is to examine the performance of a fastener composite coating system, sherardized (SD) coating/zinc-aluminum (ZA) coating whether it has good performance in marine environment. Design/methodology/approach In this paper, SD coating was fabricated on fastener surface by solid-diffusion method. ZA coating was fabricated by thermal sintering method. Corrosion behaviours of the composite coating were investigated with potentiodynamic polarization curves, open circuit potential and electrochemical impedance spectroscopy methods. Findings Neutral salt spray (NSS) and deep sea exposure tests revealed that the composite coating had excellent corrosion resistance. Polarization curve tests showed that corrosion current density of the sample with composite coating was significantly decreased, indicating an effective corrosion protection of the composite coating. OCP measurement of the sample in NaCl solution demonstrated that the composite coating had the best cathodic protection effect. The good corrosion resistance of the composite coating was obtained by the synergy of SD and ZA coating. Practical implications SD/ZA coating can be used in marine environment to prolong the life of carbon steel fastener. Social implications SD/ZA composite coating can reduce the risk and accident caused by failed fastener, avoid huge economic losses. Originality/value A new kind of composite coating was explored to protect the carbon steel fastener in marine environment. And the composite coating has the long-term anti-corrosion performance both in simulated and marine environment test.

Superanticorrosive Graphene Nanosheets through π Deposition of Boron Nitride Nanodots

Graphene has been demonstrated as an excellent protection material because of its complete impermeability. Unfortunately, graphene fails to prevent metals corrosion for the long term because its essential conductivity promotes the electrochemical reaction between the graphene and the metals. In this work we encapsulated commercial graphene nanosheets (GNSs) with boron nitride nanodots (BNNDs). Interestingly, introduction of BNNDs also allowed the fabrication of aqueous compatible BNND@GNSs complex dispersions with an expected high concentration of 5 mg/mL and stability over 1 month under environmental conditions. The long-term anticorrosion performance of BNND@GNSs-reinforced epoxy coatings (BNND@GNSs/EP) are comparably evaluated by aging in 3.5% NaCl(aq). Our work reveals that the BNNDs anchored on BNND@GNSs act as a spacer separating GNSs and metals to prevent BNND@GNSs from connecting with the metals, which suppresses the galvanic corrosion and achieves superanticorrosion. Electrochemical results revea...

Anticorrosive Behavior and Porosity of Tricationic Phosphate and Zirconium Conversion Coating on Galvanized Steel

This work evaluates the corrosion resistance of galvanized steel treated with tricationic phosphate and zirconium conversion coating after painting, by using electrochemical techniques, accelerated and field corrosion tests. A non-uniform and heterogeneous distribution of zirconium on the steel surface was observed due to preferential nucleation of the zirconium on the aluminum-rich sites on the surface of galvanized steel. The long-term anti-corrosion performance in a saline solution was better for the phosphate coating up to 120 days. The coating capacitance registered a higher increase for the zirconium coatings than the phosphate coatings up to 120 days of immersion. This result agrees with the higher porosity of zirconium coating in relation to the phosphate coating. After 3840 h of accelerated corrosion test, and after 1 year of accelerated field test, zirconium-treated samples showed an average scribe delamination length higher than the phosphate-treated samples.

Corrosion behavior of low pressure cold sprayed Zn-Ni composites coating

PurposeThis paper aims to examine the performance of low-pressure cold-sprayed zinc–nickel (Zn-Ni) composites coating, i.e. whether it has the same performance as Zn-Ni alloy coating.Design/methodology/approachIn this paper, Zn-Ni composites coatings containing four different nickel contents were prepared with commercial DYMET 413 low-pressure cold spraying system under the same parameters. Corrosion behaviors of four kinds of coatings were examined with potentiodynamic polarization curves and electrochemical impedance spectroscopy methods, combined with scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.FindingsCorrosion behavior of Zn-Ni composites coating is similar to Zn-Ni alloy coating. In the early stages of immersion, the anodic dissolution of zinc happens, which results in the formation of a zinc hydroxide layer. With the continuous infiltration of chloride ion, zinc hydroxide will get converted to zinc oxide, basic zinc chloride and basic zinc carbonate. The presence of nickel in coatings can prevent zinc hydroxide from converting into zinc oxide.Research limitations/implicationsFurther research should be done on improving the deposition efficiency, as the deposition efficiency of low-pressure cold spray is lower than 30 per cent.Practical implicationsLow-pressure cold spray coating can be used in cyclic dry/wet conditions to prolong the life of a steel structure.Social implicationsLow-pressure cold spray Zn-Ni coating is an environmentally friendly anticorrosion method which can be used as an alternative of hexavalent chromium passivation coating.Originality/valueZn-Ni composite coating can be deposited on steel directly by low-pressure cold spray by mechanically mixing the powders together. The composite coating also has the same long-term anticorrosion performance as Zn-Ni alloy coating.

Long-Term Anti-Corrosion Performance of a Conducting Polymer-Based Coating System for Steels

The long-term durability of a two-layer coating system was evaluated by two accelerated corrosion tests, i.e., the ASTM B117 Salt spray test and the ASTM D5894 Cyclic salt fog/UV exposure test, and a series of surface analyses. The coating system was developed for protecting structural steels from corrosion, including a functional primer made of intrinsically conducting polymer (ICP) and a protective topcoat. The standard pull-off test per ASTM D4541 was employed for characterizing the adhesion of the coating systems to substrate, aided by visual examination of the surface deterioration of the samples. The ICP-based systems demonstrated superior long-term anti-corrosion capacity when a polyurethane topcoat is used. The ICP-based primer made of a waterborne epoxy gave poorer anti-corrosion performance than the ICP-based primer made of regular non-waterborne epoxy, which can be attributed to the lower adhesion the waterborne epoxy demonstrated to the substrate surface. The zinc-rich control systems showed good anti-corrosion durability; however, they may produce excessive oxidative products of zinc to cause coating delamination. Based on the test results, the two-layer coating system consisting of an ICP-based primer and a polyurethane topcoat outperforms the conventional zinc-rich coating systems for corrosion protection of steels.