Developing an atmospheric aging evaluation model of acrylic coatings:A semi-supervised machine learning algorithm

To study the atmospheric aging of acrylic coatings,a two-year aging exposure experiment was conducted in 13 representative climatic environments in China.An atmospheric aging evaluation model of acrylic coatings was developed based on aging data including11 environmental factors from 567 cities.A hybrid method of random forest and Spearman correlation analysis was used to reduce the redundancy and multicollinearity of the data set by dimensionality reduction.A semi-supervised collaborative trained regression model was developed with the environmental factors as input and the low-frequency impedance modulus values of the electrochemical impedance spectra of acrylic coatings in 3.5wt%NaCl solution as output.The model improves accuracy compared to supervised learning algorithms model(support vector machines model).The model provides a new method for the rapid evaluation of the aging performance of acrylic coatings,and may also serve as a reference to evaluate the aging performance of other organic coatings.

Functionalized carbon dots for corrosion protection:Recent advances and future perspectives

Metal corrosion causes significant economic losses,safety issues,and environmental pollution.Hence,its prevention is of immense research interest.Carbon dots(CDs)are a new class of zero-dimensional carbon nanomaterials,which have been considered for corrosion protection applications in recent years due to their corrosion inhibition effect,fluorescence,low toxicity,facile chemical modification,and cost-effectiveness.This study provides a comprehensive overview of the synthesis,physical and chemical properties,and anticorrosion mechanisms of functionalized CDs.First,the corrosion inhibition performance of different types of CDs is introduced,followed by discussion on their application in the development of smart protective coatings with self-healing and/or self-reporting properties.The effective barrier formed by CDs in the coatings can inhibit the spread of local damage and achieve self-healing behavior.In addition,diverse functional groups on CDs can interact with Fe^(3+)and H^(+)ions generated during the corrosion process;this interaction changes their fluorescence,thereby demonstrating self-reporting behavior.Moreover,challenges and prospects for the development of CD-based corrosion protection systems are also presented.

Partial regularity and nonlinear potential estimates for Stokes systems with super-quadratic growth

This paper builds a bridge between partial regularity theory and nonlinear potential theory for the following generalized stationary Stokes system with super-quadratic growth and continuous coefficients:-div A(x,Du)+■π=f,div u=0,where Du is the symmetric part of the gradient■u.We first establish anε-regularity criterion involving both the excess functional of the symmetric gradient Du and Wolff potentials of the nonhomogeneous term f to guarantee the local vanishing mean oscillation(VMO)-regularity of Du in an open subset Ω_(u) of Ω with full measure.Such anε-regularity criterion leads to a pointwise Wolff potential estimate of Du,which immediately infers that Du is partially C^(0)-regular under appropriate assumptions.Finally,we give a local continuous modulus estimate of Du.

Photothermal and pH dual-responsive self-healing coating for smart corrosion protection

A novel self-healing coating with photothermal and pH dual-responsive properties has been designed to protect carbon steel against corrosion by loading the stimuli-responsive microcapsules into a shape memory epoxy coating. The sandwich-like microcapsules were based on reduced graphene oxide/mesoporous silica(r GO@MS) assembled with a p H-responsive poly(N,N-dimethylaminoethyl methacrylate)(PDMAEMA) layer, and were loaded with benzotriazole(BTA) inhibitors(abbreviated as rGO@MS-P-BTA). Under near-infrared(NIR) light irradiation, the prominent photothermal effect of rGO could not only elevate the coating temperature to activate the shape memory effect and close the coating scratch, but also facilitate the release of corrosion inhibitors to suppress the corrosion activity. Moreover,the PDMAEMA as a p H-driven “gatekeeper” realized the controlled release of BTA from microcapsules at acid conditions. The surface morphology analysis, electrochemical impedance spectroscopy(EIS), and scanning electrochemical microscopy(SECM) were performed to evaluate the self-healing performance of the composite coatings. The results showed that the combination of NIR light and p H-responsive selfhealing effects endowed the coating with short healing time and prominent healing efficiency.

Microbiologically influenced corrosion of 304 stainless steel by halophilic archaea Natronorubrum tibetense

The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface in the sterile medium.By contrast,the SS exhibited serious pitting corrosion with the largest pit depth of 5.0μm in the inoculated medium after 14 days.The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium.The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+and Cr6+increased in the passive film under the influence of archaea N.tibetense,which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion.Combined with the energy starvation tests,the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N.tibetense was discussed finally.

Multi-action self-healing coatings with simultaneous recovery of corrosion resistance and adhesion strength

In this study, a new self-healing strategy that can simultaneously recover the corrosion resistance and the adhesion strength of coatings was introduced. The coating was based on a shape memory epoxy resin containing ethylene vinyl acetate(EVA) microspheres loaded with Ce(NO_(3))_(3)inhibitors, and was cured at a relatively high temperature to facilitate the fusion of adjacent microspheres for a strengthened self-healing effect. The electrochemical impedance spectroscopy(EIS) and scanning electrochemical microscopy(SECM) results demonstrated that the shape memory effect of epoxy matrix, the filling of molten EVA microspheres as well as the release of Ce(NO_(3))_(3)inhibitors contributed synergistically to suppress the corrosion reaction at the coating damage. After healing, the low frequency impedance modulus of the coatings containing Ce(NO_(3))_(3)-EVA microspheres was three orders of magnitude higher than that of the blank epoxy coating. The adhesion strength of the coatings containing Ce(NO_(3))_(3)-EVA microspheres on the metal substrate was also largely repaired thanks to the strong bonding effect of the EVA microspheres.

Long-term deterioration of lubricant-infused nanoporous anodic aluminium oxide surface immersed in NaCl solution

This study investigated the deterioration of a lubricant-infused anodic aluminium oxide surface in a 1M NaCl solution for~200 days.Direct observation by cryo-SEM and quantitative analyses by UV spectroscopy and EIS revealed that the long-term deterioration of the lubricant-infused surface was divided into two stages:the surface-adhered lubricant layer gradually dissolved at a constant rate until the substrate was exposed;afterwards the lubricant infused in the nanochannels began to diffuse and was depleted after~200 days.The EIS results also revealed that the defects reduced the corrosion resistance of the lubricant-infused surface considerably.