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In order to improve the corrosion resistance of the automotive AM60B-Mg alloy, a nano-SiO2/MAO composite coating was prepared on the surface of the alloy. The electrochemical properties were studied in an 80 °C corrosion environment using potentiodynamic polarization tests. Local Electrochemical Impedance Spectroscopy (LEIS) was used to study the corrosion mechanisms of coating defect zone. The microstructure and phase of the samples were observed by confocal laser microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Macroscopic electrochemical test results showed that the impedance of the nano-SiO2/MAO coating was much higher than that of the MAO coating, by about 433 times. Local electrochemical test results showed that the minimum impedance of the nano-SiO2/MAO coating was 1–2 orders of magnitude higher than the maximum impedance of the MAO coating. The defective SiO2/MAO coating still had high corrosion resistance compared to the defective MAO coating. A physical model of local corrosion mechanisms was proposed. [ABSTRACT FROM AUTHOR]

Waterborne coating has recently been paid much attention. However, it cannot be used widely due to its performance limitations. Under the specified conditions of the selected resin, selecting the function pigment is key to improving the anticorrosive properties of the coating. Zinc phosphate is an environmentally protective and efficient anticorrosion pigment. In this work, zinc phosphate was used in modifying waterborne acrylic coatings. Moreover, the disbonding resistance of the coating was studied. Results showed that adding zinc phosphate can effectively inhibit the anode process of metal corrosion and enhance the wet adhesion of the coating, and consequently prevent the horizontal diffusion of the corrosive medium into the coating/metal interface and slow down the disbonding of the coating. [ABSTRACT FROM AUTHOR]

Corrosion behavior of epoxy-coated rebar with different size of microdefects in uncarbonated/carbonated simulated pore solution (U/CSPS) of seawater concrete was investigated. Specimens in both solutions underwent two stages of corrosion, according to the electrochemical impedance spectroscopy (EIS) response. The initial stage was the extension of corrosion. The second stage was dominated by the diffusion process, due to the corrosion products blocking the defects and hindering the transportation of the reaction matter. Local electrochemical impedance spectroscopy (LEIS), scanning vibrating electrode technique (SVET) measurements and the observation of corrosion products indicated that 50 μm might be the threshold, because the corrosion of specimens with defects bigger than 50 μm in diameter was significantly more severe. Crevice corrosion was identified to occur in the experiments. The corrosion products of specimens in USPS and CSPS were mainly Fe3O4 and FeOOH, respectively. α-FeOOH and β-FeOOH exhibited an anion ion-selective property in the corrosion process, which induced crevice corrosion in CSPS. In particular, it is contended herein that Fe3O4 has the cation ion-selective property to protect the substrate in USPS. [ABSTRACT FROM AUTHOR]

The corrosion behavior of zinc-rich epoxy primers or paints (ZRPs) with different conducting polyaniline-grafted graphene (PANI/Gr) contents was investigated. Conductivity of the formed PANI/Gr nanosheets was significantly improved by employing the Gr as the inner template to synthesize the PANI. The protective properties and electrochemical behavior of coatings with artificial defects were investigated by monitoring the free corrosion potential versus time and by using localized electrochemical impedance spectroscopy (LEIS). A synergetic enhancement of the physical barrier role of the coating and the zinc sacrificial cathodic protection was achieved in the case of ZRP including PANI/Gr nanosheets. In addition, the ZRP mixed with the PANI/Gr at a content of 0.6% exhibited the best anticorrosion performance across the range of investigated PANI/Gr contents. [ABSTRACT FROM AUTHOR]

Waterborne coating has recently been paid much attention. However, it cannot be used widely due to its performance limitations. Under the specified conditions of the selected resin, selecting the function pigment is key to improving the anticorrosive properties of the coating. Zinc phosphate is an environmentally protective and efficient anticorrosion pigment. In this work, zinc phosphate was used in modifying waterborne acrylic coatings. Moreover, the disbonding resistance of the coating was studied. Results showed that adding zinc phosphate can effectively inhibit the anode process of metal corrosion and enhance the wet adhesion of the coating, and consequently prevent the horizontal diffusion of the corrosive medium into the coating/metal interface and slow down the disbonding of the coating., Competing Interests: We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.