An electrochemical method for evaluating the resistance to cathodic disbondment of anti-corrosion coatings on buried pipelines

Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.

Silicone Modified Polyesters Vulcanizable at Room Temperature for Anti-corrosion Coatings on Tinplate

Trimethoxysilyl Polyester(TMOS-PET)was prepared via hydrosilylation of trimethylsilane with acryl-terminated polyester.Copolymerization of TMOS-PET with trimethylmethoxysilane,tetramethoxysilane,and/or dimethyldimethoxysilane give silicone modified polyesters(Si-PET)containing=(SiO_(2))=,-(CH_(3)SiO_(3/2))=,and/or-((CH_(3))_(2)SiO)-units.Coatings from Si-PET were formed on tinplate surface via room temperature vulcanization with applicable curing time(the quickest tact free time and completely drying time are 2 h and 15 h,respectively).Mechanical properties,thermal stability,chemical resistance,and anti-corrosion of coatings were detected.Although the flexibility of the coatings were lowered by=(SiO_(2))=and-(CH_(3)SiO_(3/2))=units,adhesion and thermal stability of coatings were both improved.On the contrary,(CH_(3))_(2)SiOunits seem to improve the flexibility,while decrease the adhesive force for less crosslink points.Generally,the silicone modified polyesters act as an effective shielding for tinplate.According to electrochemical impedance spectroscopy(EIS),the electric resistance of coatings(Rc)were improved about 25 times and open circuit potential(OCP)increased about 0.10 V compared to the control.The chemical resistance and anti-corrosion of the coatings were decreased slightly after=(SiO_(2))=and-(CH_(3)SiO_(3/2))=units were added,but they could be greatly improved by-(CH_(3)SiO_(3/2))=units.Specially,after adding-(CH_(3)SiO_(3/2))=units,coatings give doubled Rc,and its OCP is about 0.20 V higher than the control.

Assessing the corrosion protection property of coatings loaded with corrosion inhibitors using the real-time atmospheric corrosion monitoring technique

The atmospheric corrosion monitoring(ACM)technique has been widely employed to track the real-time corrosion behavior of metal materials.However,limited studies have applied ACM to the corrosion protection properties of organic coatings.This study compared a bare epoxy coating with one containing zinc phosphate corrosion inhibitors,both applied on ACM sensors,to observe their corrosion protection properties over time.Coatings with artificial damage via scratches were exposed to immersion and alternating dry and wet environments,which allowed for monitoring galvanic corrosion currents in real-time.Throughout the corrosion tests,the ACM currents of the zinc phosphate/epoxy coating were considerably lower than those of the blank epoxy coating.The trend in ACM current variations closely matched the results obtained from regular electrochemical tests and surface analysis.This alignment highlights the potential of the ACM technique in evaluating the corrosion protection capabilities of organic coatings.Compared with the blank epoxy coating,the zinc phosphate/epoxy coating showed much-decreased ACM current values that confirmed the effective inhibition of zinc phosphate against steel corrosion beneath the damaged coating.

Preparation technology and anti-corrosion performances of black ceramic coatings formed by micro-arc oxidation on aluminum alloys

In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings. Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface. There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase. And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.

Investigation of anti-corrosion property of hybrid coatings fabricated by combining PEC with MAO on pure magnesium

Novel hybrid coatings on pure magnesium were prepared by combining plasma electrolytic carburizing(PEC)with micro-arc oxidation(MAO)to further enhance the anti-corrosion property in this paper.Scanning electron microscopy(SEM)was used to observe the microstructure of the coatings,meanwhile,energy dispersive spectrometry(EDS)and X-ray diffraction(XRD)were separately used to investigate the elemental as well as phase compositions of the coatings.The anti-corrosion property of the coatings was evaluated by potentiodynamic polarization curves as well as electrochemical impedance spectroscopy(EIS).The results show that PEC process is closely related with the effects of adsorption as well as diffusion of the activated carbon atoms,and it can provide a favorable pretreatment surface with predesigned chemical composition to obtain a new kind of phase,namely Si C with superior corrosion resistance and chemical stability,in the following PEC+MAO hybrid coatings.Meanwhile,PEC preprocessing also can afford an excellent micro-structure to increase the coating thickness as well as to improve the compactness of the PEC+MAO hybrid coatings.During the fabrication process of the PEC+MAO hybrid coatings,an overlapping phenomenon in regard to coating thickness can be observed instead of heaping up layer by layer.Compared with both single PEC surface modification layers as well as single MAO coatings,the PEC+MAO hybrid coatings exhibit more superior anti-corrosion property.Especially,the EIS data reveal that the PEC+MAO hybrid coatings can act as an effective protection system to provide relatively excellent long-range anti-corrosion protection.Note also that employing same MAO technique for both single MAO treatment as well as PEC+MAO combining procedure is the key to this research.

Using EIS to evaluate anti-corrosion properties of the SiC_p/5A06 aluminium MMC treated by cerium conversion coatings

This paper evaluated the protection effect of the cerium conversion coatings on the SiCp/5A06 Al composite and the 5A06 Al alloy.Electrochemical impedance spectroscopy(EIS) was employed to examine the variation of the electrochemical variables of the samples treated and immersed in 3.5% NaCl solution at 35 °C for 1 h,which showed the enhancement of charge transfer resistance(Rt) and coating film resistance(Rc),i.e.,the corrosion resistance of the conversion coated samples was improved.The best protection ef...

Influence of graphene on the anti-corrosion performance of epoxy-based coatings

In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.

Modeling and optimization of the parameters affecting the in-situ microencapsulation process for producing epoxy-based self-healing anti-corrosion coatings

Micro/nanocapsules of urea-formaldehyde resin loaded with linseed oil, which are a self-healing agent in glass flake epoxy anti-corrosion paint, were prepared using a combination of ultrasonic homogenization and in-situ polymerization. The main objective of this study was to model and optimize the microen- capsulation process. Five-level central composite design was used to design, model, and optimize the microencapsulation process. A quadratic model was constructed to show the dependency of the per- centage of encapsulated linseed oil and capsule size, as model responses, on the studied independent variables （the rotational speed of the agitator and the power and duration of sonication）. Analysis of vari- ance showed that all of the variables have significant effects on the encapsulated linseed oil percentage, while the rotational speed of the agitator and sonication time is effective variables for controlling the capsule size. Under the determined optimum conditions, a maximum encapsulated linseed oil percentage （ELO%） of 93.9% and a minimum micro/nanocapsule size of 0.574 μm were achieved at 594 rpm agitation, 350 W sonication power, and 3 min sonication time. Validation of the model was performed. The percent- age relative errors between the predicted and experimental values of the ELO% and micro/nanocapsule size are 1.28% and 3.66%, respectively. The efficacy of the optimum micro/nanocapsules in healing cracks in a glass flake epoxy paint and corrosion protection was investigated by the salt spray test and Tafel polarization technique.

Incorporation of nano/micron-SiC particles in Ni-based composite coatings towards enhanced mechanical and anti-corrosion properties

Ni-based composite coatings incorporated with nano/micron SiC particles were fabricated via electrochemical co-deposition in Watts bath,followed by the evaluation of their mechanical and anti-corrosion properties.The micrographic observations suggest that the SiC particles with various sizes can be well incorporated to the Ni substrate.X-ray diffraction(XRD)patterns indicate that SiC particles with smaller sizes could weaken the preferential growth of Ni along(200)facet.In addition,it is found that the incorporated SiC particles with medium micron sizes(8 and 1.5μm)could significantly enhance the micro-hardness of the Ni composite coatings.Nevertheless,electrochemical measurements demonstrate that micron-sized SiC particles would weaken the corrosion resistance of Ni composite coatings ascribed to the structure defects induced.In contrast,the combined incorporation of nanosized(50 nm)SiC particles with medium micron(1.5μm)ones is capable of promoting the compactness of the composite coatings,which is beneficial to the long-term corrosion resistance with negligible micro-hardness loss.

High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Design multifunctional Mg–Zr coatings regulating Mg alloy bioabsorption

Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequate strength limit their applicability.To overcome this,the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium(Zr)content.This approach presents a promising strategy for simultaneously improving corrosion resistance,maintaining biocompatibility,and enhancing strength without compromising osseointegration.By leveraging Mg’s inherent biodegradability,it has the potential to minimize the need for secondary surgeries,thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings,denoted Mg-xZr(x=0–5 at.%).Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content.XRD analysis confirmed the presence of the Mg(00.2)basal plane,shifting towards higher angles(1.15°)with 5 at.%Zr doping due to lattice parameter changes(i.e.,decrease and increase of“c”and“a”lattice parameters,respectively).Mg–Zr coatings exhibited“liquidphilic”behavior,while Young’s modulus retained a steady value around 80 GPa across all samples.However,the hardness has significantly improved across all samples’coating,reaching the highest value of(2.2±0.3)GPa for 5 at.%Zr.Electrochemical testing in simulated body fluid(SBF)at 37℃ revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.%Zr.Compared with the 5 at.%Zr coating which exhibited a corrosion rate of 32 mm/year,these coatings displayed lower corrosion rates,ranging from 1 to 12 mm/year.This synergistic enhancement in mechanical properties and corrosion resistance,achieved with 2.0–3.4 at.%Zr,suggests potential ability for reducing stress shielding and controlled degradation performance,and consequently,promising functional biodegradable materials for temporary bone implants.

Surface Metallization of Glass Fiber(GF)/Polyetheretherketone(PEEK) Composite with Cu Coatings Deposited by Magnetron Sputtering and Electroplating

Surface metallization of glass fiber(GF)/polyetheretherketone(PEEK)[GF/PEEK] is conducted by coating copper using electroplating and magnetron sputtering and the properties are determined by X-ray diffraction(XRD), scanning electron microscopy(SEM), and electron backscatter diffraction(EBSD).The coating bonding strength is assessed by pull-out tests and scribing in accordance with GB/T 9286-1998.The results show that the Cu coating with a thickness of 30 μm deposited on GF/PEEK by magnetron sputtering has lower roughness, finer grain size, higher crystallinity, as well as better macroscopic compressive stress,bonding strength, and electrical conductivity than the Cu coating deposited by electroplating.

Bio-Based Waterborne Poly(Vanillin-Butyl Acrylate)/MXene Coatings for Leather with Desired Warmth Retention and Antibacterial Properties

This study presents a solvent-free,facile synthesis of a bio-based green antibacterial agent and aromatic monomer methacrylated vanillin(MV)using vanillin.The resulting MV not only imparted antibacterial properties to coatings layered on leather,but could also be employed as a green alternative to petroleum-based carcinogen styrene(St).Herein,MV was copolymerized with butyl acrylate(BA)to obtain waterborne bio-based P(MV-BA)miniemulsion via miniemulsion polymerization.Subsequently,MXene nanosheets with excellent photothermal conversion performance and antibacterial properties,were introduced into the P(MV-BA)miniemulsion by ultrasonic dispersion.During the gradual solidification of P(MV-BA)/MXene nanocomposite miniemulsion on the leather surface,MXene gradually migrated to the surface of leather coatings due to the cavitation effect of ultrasonication and amphiphilicity of MXene,which prompted its full exposure to light and bacteria,exerting the maximum photothermal conversion efficiency and significant antibacterial efficacy.In particular,when the dosage of MXene nanosheets was 1.4 wt%,the surface temperature of P(MV-BA)/MXene nanocomposite miniemulsioncoated leather(PML)increased by about 15℃ in an outdoor environment during winter,and the antibacterial rate against Escherichia coli and Staphylococcus aureus was nearly 100%under the simulated sunlight treatment for 30 min.Moreover,the introduction of MXene nanosheets increased the air permeability,water vapor permeability,and thermal stability of these coatings.This study provides a new insight into the preparation of novel,green,and waterborne bio-based nanocomposite coatings for leather,with desired warmth retention and antibacterial properties.It can not only realize zerocarbon heating based on sunlight in winter,reducing the use of fossil fuels and greenhouse gas emissions,but also improve ability to fight off invasion by harmful bacteria,viruses,and other microorganisms.

Bonding strength of graded anti-corrosive coatings of fluoroethylenepropylene (FEP)/polyphenylene sulfide (PPS)

Fluororesin-based anti-corrosive coatings including graded FEP/PPS were prepared on carbon steel by melt powder coating, the bonding strength of all coating systems was determined by the pull-off test. It is found that the poor adhesion of fluororesin coatings to metallic substrates is improved obviously by the graded coating structure of FEP/PPS, and the bonding strength reaches up to 11.8 MPa for the five-layer system. Examination by electron probe microanalysis （EPMA） verifies that the distribution of main components is graded in the five-layer system, which is responsible for the enhancement of the interfacial bonding.

Experimental study on the microstructural and anti-corrosion behaviour of Co-deposition Ni-Co-SiO_2 composite coating on mild steel

Mild steel is commonly used in the construction of Pipeline. The major problem of this Pipeline is corrosion. Effort is make my researchers to combat this problem. In this work Co-deposition of Ni-CoSiO_2 composite coating on mild steel was reported with the view to reduce this problem. The SiO_2 was varies from 5 to 25 wt% in the deposition. The microstructure, hardness values and potentiodynamic polarization in simulated sea water were determined. The results show that XRD pattern of the Ni Co deposited mild steel revealed the presence hard phases of NiO, Co_5Ni, Co_2Ni_3, Ni Co5 while that of Ni-CoSiO_2 deposited mild steel revealed the presence harder phases of NiOSiO_2, CoNi_7Si_2, Co_5Ni_2Si_3. The NiCo-25 SiO_2 deposited sample has smaller particle size than Ni-10 Co coating. Coating thickness of 110.7 mm was obtained for Ni-10 Co coating, while coating thickness of 135.7, 157.7, 165.0 mm were obtained at Ni-10 Co-x SiO_2(x=10, 15, 25 wt%). 99.90% corrosion resistance was achieved at Ni-Co-25 SiO_2. This improvement in corrosion resistance after composites coating could be attributed to the hard and fine structure obtained after coating.

Robustα-Fe_(2)O_(3)/Epoxy Resin Superhydrophobic Coatings for Anti-icing Property

α-Fe_(2)O_(3)/epoxy resin composite superhydrophobic coating was prepared withα-Fe_(2)O_(3) nanoparticles and epoxy resin by spin coating method.The coating without epoxy resin has higher contact angle(CA)and lower ice adhesion strength(IAS),but the mechanical properties are poor.Theα-Fe_(2)O_(3)/epoxy resin composite superhydrophobic coating exhibits good mechanical durability.In addition,compared with the bare aluminum substrate,the Ecorr of the composite coating is positive and the Jcorr is lower.The inhibition efficiency of the composite coating is as high as 99.98%in 3.5 wt%NaCl solution.The difference in the microstructure caused by the two preparation methods leads to the changes in mechanical properties and corrosion resistance of composite superhydrophobic coating.

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.

Pulse electroplating of Ni-W-P coating and its anti-corrosion performance

Ni-W-P coatings were electrodeposited on copper substrates by pulse electroplating.Effects of electrolyte pH(1-3),temperature(40-80°C),average current density(1-7A/dm2)and pulse frequency(200-1000Hz)on deposition rate,structure and corrosion resistance performance of Ni-W-P coatings were studied by single factor method.Surface morphology,crystallographic structure and composition of Ni-W-P coatings were investigated by means of scanning electron microscopy,X-ray diffractometry and energy dispersive X-ray spectroscopy,respectively.Corrosion resistance performances of Ni-W-P coatings were studied by potentiodynamic polarization and electrochemical impedance spectroscopy in3.5%NaCl solution(mass fraction)and soil-containing solution.It was found that the pulse electroplated Ni-W-P coatings have superior corrosion resistance performance and the electroplating parameters significantly affect the structure and corrosion resistance performance of Ni-W-P coatings.The optimized parameters of pulse electroplating Ni-W-P coatings were as follows:pH2.0,temperature60°C,average current density4A/dm2,and pulse frequency600Hz.The Ni-W-P coating prepared under the optimized parameters has superior corrosion resistance(276.8kΩ)and compact surface without any noticeable defect.

New Problems of Boiler Corrosion after Coupling Combustion of Coal and Biomass and Anti-Corrosion Technologies

This study explores the corrosion issues arising from the coupled combustion of coal and biomass and proposes potential solutions.Biomass,as a renewable energy source,offers advantages in energy-saving and carbon reduction.However,the corrosive effects of alkali metal compounds,sulfur(S)and chlorine(Cl)elements in the ash after combustion cannot be underestimated due to the high volatile content of biomass fuels.We investigate the corrosion mechanisms,as well as the transfer of Cl and alkali metal elements during this process.Comparative corrosion analyses are conducted among coal-fired boilers,pure biomass boilers and boilers with coupled combustion.Various biomass types in co-firing are studied to understand different corrosion outcomes.The main factors influencing corrosion include the physicochemical properties of biomass feedstock,furnace temperature and heating surface materials,with the chemical composition and ash content of biomass playing a dominant role.Currently,the methods used for anti-corrosion include water washing pretreatment of biomass feedstock,application of novel alloys and coatings and the development of additives to inhibit fouling,ash deposition and corrosion.Efficient inhibitors are economical and easy to produce.Additionally,biomass can be converted into biomass gasification gas,although challenges related to tar still need to be addressed.

Multiscale Simulation of Microstructure Evolution during Preparation and Service Processes of Physical Vapor Deposited c-TiAlN Coatings

Physical Vapor Deposited(PVD)TiAlN coatings are extensively utilized as protective layers for cutting tools,renowned for their excellent comprehensive performance.To optimize quality control of TiAlN coatings for cutting tools,a multi-scale simulation approach is proposed that encompasses the microstructure evolution of coatings considering the entire preparation and service lifecycle of PVD TiAlN coatings.This scheme employs phase-field simulation to capture the essential microstructure of the PVD-prepared TiAlN coatings.Moreover,cutting simulation is used to determine the service temperature experienced during cutting processes at varying rates.Cahn-Hilliard modeling is finally utilized to consume the microstructure and service condition data to acquaint the microstructure evolution of TiAlN coatings throughout the cutting processes.This methodology effectively establishes a correlation between service temperature and its impact on the microstructure evolution of TiAlN coatings.It is expected that the present multi-scale numerical simulation approach will provide innovative strategies for assisting property design and lifespan prediction of TiAlN coatings.