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The effects of multiwalled carbon nanotubes (MWCNTs) on the adhesion strength and corrosion resistance of the acrylic nanocomposite coatings were evaluated on Q235 substrates via pull-off tests and electrochemistry measurements (EIS, LEIS). Addition of MWCNTs to the acrylic resulted in an up to ∼50% increase in the adhesion strength. After 36 h of immersion in 3.5 wt% NaCl, the coating resistance of the native acrylic coating was 235.8 Ω cm 2 , whereas those of the nanocomposite coatings containing 0.5 and 1 wt% MWCNTs were 1.36 × 10 5 and 9.27 × 10 7 Ω cm 2 , respectively. LEIS analysis indicated that the addition of MWCNTs increased the adhesion strength and retarded the delamination. The results demonstrated the positive effects of the incorporation of MWCNTs on the anticorrosive ability of the coatings. [ABSTRACT FROM AUTHOR]

• The EIS technique combined with LEIS technique was used to study the failure process of waterborne acrylic coating. • The effects of defect size, chloride ion concentration and resin type on failure process of waterborne acrylic coating were investigated. • The key factor in the failure process of the waterborne coating were studied by compared two types of waterborne acrylic coating during immersion. Cathodic delamination—weakening or loss of adhesion between the coating and the metal—is one of the major failure processes of organic coatings. Generally, it is almost inevitable to introduce defects to the coating during processing and operation. In this work, the delamination process of coatings around defects and the corrosion in defective coated metals was elucidated using immersion and electrochemical impedance tests. Two types of coatings (styrene-acrylic coating and terpolymer coating) were compared. The effects of defect size, chloride ion concentration and resin type on cathodic delamination were investigated. A small defect may affect the metal corrosion. Increasing the chloride ion concentration can promote the corrosion of metal but may not accelerate the delamination of the coating. The resin type is the key factor in the failure process of the coating. [ABSTRACT FROM AUTHOR]

Highlights • The stage and regularity of corrosive media transporting in different waterborne coatings are investigated. • The morphology of different waterborne coatings is studied by atomic force microscopy. • The effect of different structures of waterborne coating on the transport of corrosive media is determined. Abstract In this study, gravimetric method and electrochemical impedance spectroscopy combined with atomic force microscopy (AFM) and contact angle measurement were used to study the transport of corrosive medium in waterborne thermosetting and thermoplastic coatings with different structures. Three typical kinds of resin membrane of waterborne coatings (waterborne acrylic, waterborne fluorocarbon, and waterborne epoxy coatings) were analyzed. Results show that the transport of corrosive medium in waterborne thermoplastic coatings and waterborne thermosetting coatings is consistent. The transport in these two kinds of coatings can be divided into three stages. In the first stage, transport is primarily affected by the water concentration in the coating and the medium content is linear with t 1 / 2 , which satisfies the Fick diffusion law. Then, medium transport deviates from Fick diffusion and the medium content reaches saturation over time. During condensation of polymer particles in thermoplastic waterborne acrylic coating and waterborne fluorocarbon coating, the intermolecular diffusion of molecular segments on the particle interface is limited. The presence of microstructural defects leads to limited densification of coating and easier formation of medium channels. The waterborne fluorocarbon coating contains symmetric fluorocarbon bonds, resulting in low surface energy, and the hydrophobic properties result in a slower medium transport rate. During coagulation of the latex particles in the waterborne epoxy coating, the crosslinking and curing reaction of the particle interface greatly reduces the microstructural defects, thereby increasing the compactness and resulting in the slowest medium transmission process. [ABSTRACT FROM AUTHOR]