•Atmospheric corrosion is assessed by fuzzy Kolmogorov–Sinai (K–S) entropy.•Fuzzy K–S entropy for horizontal and vertical orientations are calculated.•Fuzzy K–S entropy decreases as corrosion degree is more and more serious.•There is a linear relationship between fuzzy K–S entropy and weight loss.Fuzzy Kolmogorov–Sinai (K–S) entropy was used to characterize the irregularity of the spatial information distribution in a corrosion image. The fuzzy K–S entropy was measured for horizontal and vertical orientations of corrosion images of steel samples exposed to a marine atmosphere over 191 days. The fuzzy K–S entropy for horizontal and vertical orientations decreased as the corrosion propagated. A relationship between the fuzzy K–S entropy and the weight loss in the steel sample can be presented with a linear mathematical expression. Fuzzy K–S entropy was found to be a semiquantitative and fast method to quantify atmospheric corrosion.Download high-res image (313KB)Download full-size image

A superhydrophobic coating is an outstanding barrier layer isolating the substrate from the corrosive medium, thus enhancing corrosion resistance. In this paper, a superhydrophobic film on the electroless Ni–P plated AZ61 magnesium alloy was fabricated via hydrothermal method and subsequently immersed in stearic acid solution to improve its anti-corrosion properties and self-cleaning performance. The surface morphology, structure, chemical composition and properties were investigated using scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier-transform infrared spectrophotometer (FTIR), micro-Raman spectrometer, optical contact angle meter and electrochemical workstation. The results showed that the plated Ni–P surface was hydrophilic, but it turned superhydrophobic after modification by hydrothermal reaction and stearic acid. We found the temperature and time of hydrothermal reaction could influence the morphology and wettability of the superhydrophobic nature deeply, and the petal-shaped nanosheets resulting at higher temperature had a higher hydrophobicity than the lemongrass-like nanostructures at the lower temperature. The maximum contact angle of 155.6 ± 0.3° and a sliding angle about 2° were obtained under conditions of reaction temperature of 120 °C and reaction time of 15 h. Meanwhile, the chemical stability, mechanical durability and self-cleaning performance of the formed superhydrophobic film were examined. And the potentiodynamic polarization and electrochemical impedance spectroscopy results indicated the corrosion resistance of the AZ61 substrate was improved a lot in 3.5% NaCl.

•Calcination decreases the length-diameter ratio of halloysite nanotubes but retains the basic tubular structure.•550 °C heated halloysite can reach the maximum loading of 8.2 wt% for 2-mercaptobenzothiazole.•Uncoated halloysite after calcination can shorten the release time from 10 to 3 days in neutral water.•550 °C treated halloysite is a worthy container to prepare halloysite/2-mercaptobenzothiazole composite.2-Mercaptobenzothiazole was loaded in calcined halloysite to prepare nanocomposite through vacuum loading and polyelectrolyte layers coating. The microstructure and morphology of treated nanotubes and synthetic composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and automatic gas adsorption analyzer. The total loading and release behavior of 2-mercaptobenzothiazole in tubes with and without polyelectrolyte shell were investigated with the help of UV–Vis spectrophotometer.Results show that calcination keeps the basic tube structure, expands the inner diameter and shortens the tube length. Halloysite treated at 550 °C has the maximum loading of 8.2 wt%. The release time of inhibitor in uncoated halloysite is 3–10 days, which is closely related to the calcination temperature, and the release rules conform to the first order kinetic model. Polyelectrolyte shell makes it controlled and sustained for composite to release 2-mercaptobenzothiazole under the same condition. When the environmental pH changes from neutral to acidic or alkaline to dissociate the polyelectrolyte layers, 2-mercaptobenzothiazole will be released at different rates immediately. It is concluded that 550 °C treated halloysite is a worthy candidate to prepare halloysite/2-mercaptobenzothiazole composite.Download high-res image (223KB)Download full-size image

The chemical milling condition of 2219 aluminum alloy is investigated in the NaOH + Na2S + triethanolamine + Al3+ alkaline system by the assistance of electric currents. The purpose is to study the influences of electric current densities on both the milling rate and the surface roughness of 2219 alloy under different temperatures, NaOH concentrations and additions of inhibitors. The experiments are carried out under the given requirement that the milling rate is from 0.08 mm/min to 0.14 mm/min and the surface roughness is less than 0.65 μm. The reaction temperature of the chemical milling process can be reduced by 10 °C with the application of current densities in the range of 0–20 mA/cm2. The concentration of NaOH in the alkaline system can be reduced from 180 g/L to 120 g/L with the application of current densities in the range of 0–60 mA/cm2. With the addition of Na2SiO3, Na2CO3 and Na2SnO3 inhibitors in the alkaline system, both the milling rate and the surface roughness of 2219 alloy decrease. The region enclosed with the suitable NaOH concentration and current density expands and moves towards the high current density.Download high-res image (213KB)Download full-size image

•Synthesis of Ni-Co-P-Ce coating by electroless method on silicon substrate.•The Ce content in the coating fluctuated from 0.4 to 1.3 wt%.•The Ce element improves the magnetic properties of Ni-Co-P-Ce coating.•The optimum is the Ce2(SO4)3 of 50 mg/L, Ni2 +/Co2 + ratio of 7/3 and pH value of 9.0.Ni-Co-P-Ce coating was prepared on Si substrate by electroless plating method under different Ce2(SO4)3 concentration, Ni2 +/Co2 + ratio and pH value, and then annealed under different annealing temperature. The surface morphology, thickness, composition, structure and magnetic properties of coatings were observed and determined by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). With the increasing of Ce2(SO4)3 concentration in plating bath, the thickness and saturation magnetization of Ni-Co-P-Ce coating are firstly increased and then decreased. The thickness of coating is raised linearly with the increase of Ni2 +/Co2 + ratio and pH value, whereas too high pH value will deteriorate the plating bath and reduce the adhesion between substrate and coating. The saturation magnetization of Ni-Co-P-Ce coating is improved initially and then reduced with the promotion of Ni2 +/Co2 + ratio, pH value and annealing temperature. The optimum plating conditions and annealing temperature for Ni-Co-P-Ce coating are Ce2(SO4)3 concentration of 50 mg/L, Ni2 +/Co2 + ratio of 7/3, pH value of 9.0, and annealing temperature of 400 °C. The role of Ce element in the plating is to benefit the deposition of Ni ions, promote the formation of Ni(Co) phase during the annealing process, and thus improve the magnetic properties of Ni-Co-P-Ce coating.

•The green calcium alginate gel beads are used as the container of benzotriazole.•Cu-benzotriazole complexes can effectively prolong benzotriazole release time.•Cu-benzotriazole-calcium alginate beads are used to inhibit Q235 steel corrosion.•Cu-benzotriazole-calcium alginate beads own high corrosion inhibition efficiency.Calcium alginate gel beads loaded with benzotriazole (defined as ‘benzotriazole-calcium alginate gel beads’) were successfully prepared by a piercing-solidifying method. Moreover, the insoluble Cu-benzotriazole complexes were introduced on the surface of these gel beads through the interaction between benzotriazole and Cu2 + to obtain Cu-benzoltriazole-calcium alginate gel beads, which act as the barrier to extend benzotriazole release time. The loading amount of benzotriazole in the Cu-benzoltriazole-calcium alginate gel beads was determined by thermo-gravimetric analysis (TGA) and the releasing process of benzotriazole was traced by UV–vis spectrophotometer. The inhibition behavior of Cu-benzoltriazole-calcium alginate gel beads for Q235 steel in 3.5% NaCl solution was investigated by polarization and electrochemical impedance spectrum techniques. The results show that complete release time of benzotriazole from benzoltriazole-calcium alginate gel beads is about 400 min, and further prolonged to dozens of hours by forming a barrier of insoluble Cu-benzotriazole complexes. In addition, Q235 steel in 3.5% NaCl solution + 5.0 g/L Cu-benzoltriazole-calcium alginate gel beads exhibit the lower corrosion current density and higher inhibition efficiency (87.06% at 24 h) than Q235 steel in 3.5% NaCl solution.Download high-res image (237KB)Download full-size image

•ZnAlCeMoO4 LDH compound was successfully synthesized by co-precipitation method.•ZnAlCeMoO4 LDH has a better inhibition effect to Q235 steel in 3.5%NaCl solution.•The Cl− ions in solution was partially exchanged with MoO42− ions in host layers.•The passive film and deposition film were formed by the release of LDH compound.ZnAlCe layered double hydroxide intercalated by molybdate (ZnAlCeMoO4 LDH) was successfully synthesized by using co-precipitation method, and the morphology, structure of ZnAlCeMoO4 LDH were observed and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. The inhibition behavior of ZnAlCeMoO4 LDH for Q235 steel in 3.5%NaCl solution was determined by polarization curves, electrochemical impedance spectroscopy (EIS), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray photoelectron spectrometer (XPS) methods. The results shows that the synthesized ZnAlCeMoO4 LDH has a lamellar structure with a particle size of 0.1–2.0 μm, an average thickness of 30 nm, and a basal plane spacing of 0.898 nm. Compared with the addition of ZnAl layered double hydroxide intercalated by nitrate (ZnAlNO3 LDH) and ZnAl layered double hydroxide intercalated by molybdate (ZnAlMoO4 LDH) in 3.5% NaCl solution, Q235 steel in 3.5%NaCl + ZnAlCeMoO4 LDH solution has a lower corrosion current density, larger polarization resistance and a higher inhibition efficiency. The addition of ZnAlCeMoO4 LDH will reduce the chloride concentration in 3.5% NaCl solution by the anion exchanged with molybdate, and improve the corrosion resistance of Q235 steel owing to the formation of passive film with the composition of ferrous or iron molybdate and deposition film with zinc and cerium hydroxides.

The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization. EN data were analyzed using phase space reconstruction theory. With the correlation dimensions obtained from the phase space reconstruction, the chaotic behavior of EN was quantitatively evaluated. The results show that both electrochemical potential noise (EPN) and electrochemical current noise (ECN) have chaotic properties. The correlation dimensions of EPN increase with corrosion extent, while those of ECN seem nearly unchanged. The increased correlation dimensions of EPN during the degradation process are associated with the increased susceptibility to local corrosion.

Chaos theory and the use of phase space reconstruction produce a novel methodology to study electrochemical noise (EN) signals, obtaining novel information to distinguish corrosion types. To evaluate the chaotic nature of electrochemical noise, phase space is reconstructed and the embedding parameter is obtained by the mutual information and Cao's methods. Subsequently, the correlation dimension is calculated. From the correlation dimension, we can conclude that local corrosion shows a higher correlation dimension while passivation shows a lower correlation dimension.Highlights► Chaos theory produces a new methodology to study electrochemical noise (EN) signals. ► Phase space is reconstructed and the correlation dimension is calculated. ► From the correlation dimension we can distinguish different corrosion types.

The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly analyzing the Bode plots of the electrochemical impedance spectroscopy (EIS) data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope (SEM) and scanning probe microscopy (SPM). It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical applications.

MoSx coatings were prepared with an unbalanced DC magnetron-sputtering system by varying the DC power mode, target type and liquid nitrogen trap. The composition and surface morphology were examined by energy dispersive X-ray and scanning electron microscopy; structural characterization was determined by X-ray diffraction. The friction and wear properties were evaluated with a fretting tester in dry (<10% relative humidity) and humid (50% and 90% relative humidity) air. MoSx coatings deposited by simple DC power tended to form rougher surfaces, and had a higher edge orientation of crystallites with worse tribological performance than those by bipolar pulsed DC power. MoSx coatings made by a cold pressed target had a lower deposition rate, and were inclined to form (002) basal orientations parallel to the surface especially at higher argon pressures. The contents of oxygen and carbon in the MoSx coating with the use of liquid nitrogen trap were greatly reduced, but MoSx coatings had lower coefficients of friction and shorter wear life at higher relative humidity. The role of these deposition variables in the formation process is discussed.

Sepiolite/polyacrylic acid (sodium) nanocomposite was synthesized using inverse suspension polymerization method under different sepiolite content, dispersant content and neutralization degree with orthogonal experiments. The surface morphology and structure of sepiolite/polyacrylic acid composite were observed and analyzed, and the humidity controlling properties of composites were determined by absorption and desorption testing. The results showed that sepiolite/polyacrylic acid composite was in a fine particle with rough surface. During the polymerization process, acrylic acid monomer was grafted with hydroxyl on the surface of sepiolite and then intercalated successfully into the tetrahedral silica layers of sepiolite. With the increasing of sepiolite content, dispersant conten, neutralization degree and the humidity controlling behaviors of composite rose initially and then dropped down. The impact of three factors on the humidity controlling behavior of composites increased by the order of sepiolite content, dispersant content and neutralization degree. The optimum preparation parameters are sepiolite content of 4%, dispersant content of 15% and neutralization degree of 90%.