Defects In Coatings Research Articles

Analisa Laju Korosi Pada Plat Baja ASME SA-283 Pada Daerah Splash Zone

Research on the corrosion rate of ASME SA-283 alloy steel has been carried out in the coastal environment. Corrosion is a decrease in the quality of the material that occurs due to the environment, where the coast is a splash zone area which is rich in salt content as a trigger for corrosion. Alloy steel is a material that is used widely as part of the construction of dock buildings on the coast The study was carried out by giving coating defects to ASME SA-283 material and varying the salinity in the splash zone area, where the coating thickness ranged from 350 μm - 410 μm and salt splash testing was carried out for 15 days. The results of the salt splash test show the types of corrosion that occur, namely pitting corrosion and unifrom corrosion. The largest corrosion rate occurred in the area that experienced a coating defect of 1,705 mm / year. The effect of coating on the corrosion rate is very large and the effect of coating defects on corrosion growth is quite high because the coating that functions as a protective specimen has been lost. The aim of this study are expected to become a reference for coating protection data in preventing corrosion growth in coastal environments. Keywords— Coating Defects, Corrosion Rate, Splash zone, Salinity.

Rapid assessment of adhesion of paint coatings by digital image analysis

A program is developed that allows to numerically assess the area of defects in protective coatings by analyzing digital images of surfaces. The program is implemented in Microsoft Visual Studio programming environment. The possibility of estimating the area of flaking of the paint coating from the base layer (%) and determining the adhesion in points, in accordance with the cross-cut test method in the context of paint production is shown. The created program does not require a large computing power of the computer and can reduce the time to obtain calculation results for one plate with a coating from 20 minutes to 1-2 seconds. An example of using the developed program for calculating the area of metal surface areas with different chemical composition is given.

Разработка кремнийорганического декоративного покрытия с кракелюр эффектом

The article analyzes coatings based on organosilicon compounds and presents the results of research on the selection components of compositions that provide protection of painted products from corrosive environments, mechanical and thermal effects. Defects of paint and varnish coatings are investigated. The expediency of modifying organosilicon film-forming compositions with solutions bead polymers of polymethyl methacrylate and polybutyl methacrylate has been substantiated. To obtain a heat-resistant coating, two compositions were developed for the lower and upper layers. The bottom layer was KO-85 organosilicon varnish modified with solutions of bead polymers and PF-060 alkyd varnish. To regulate the wetting and spreading, surfactants were introduced into the bottom layer, which could improve the structural, mechanical and decorative properties of the coatings. The top layer of the coating with the craquelure effect was KO-868 silicone enamel modified with functional additives that increase the surface tension and reduce the spreadability of the resulting composition. Research has been carried out on the physica-mechanical (adhesion, impact strength, elasticity of the film during bending), decorative (change in gloss, color, dirt retention, chalking) and protective (cracking, peeling, weathering, bubble formation, corrosion of metaln, wrinkling, dissolution) properties of a two-layer coating, as well as its resistance to water, gasoline, mineral oil and temperature.

Pulsed Thermography Inspection of Composite Anticorrosive Coatings: Defect Detection and Analysis of Their Thermal Behavior through Computational Simulation.

The use of anticorrosive coatings has been a powerful method to be applied on the surface of metallic materials to mitigate the corrosive process. In this study, the focus is composite coatings that are commonly used on the internal surface of storage tanks in petrochemical industries. The development of non-destructive methods for inspection of faults in this field is desired due to unhealthy access and mainly because undercoating corrosion is difficult to detect by visual inspection. Pulsed thermography (PT) was employed to detect undercoating corrosion and adhesion loss of anticorrosive composite coatings defects. Additionally, a computational simulation model was developed to complement the PT tests. According to the experimental results, PT was able to detect all types of defects evaluated. The results obtained by computational simulation were compared with experimental ones. Good correlation (similarity) was verified, regarding both the defect detection and thermal behavior, validating the developed model. Additionally, by reconstructing the thermal behavior according to the defect parameters evaluated in the study, it was estimated the limit of the remaining thickness of the defect for which it would be possible to obtain its detection using the pulsed modality.

Non-destructive evaluation of pipes by microwave techniques and artificial neural networks

Near-field imaging based on an electromagnetic sensor has been widely used for nondestructive detection. An approach to detect the near-surface defects in pipeline coatings and dielectric pipelines is proposed. Based on the characteristics of resonant frequency shifts, a novel method using artificial neural network (ANN) is established to quantitatively evaluate circular-section shape defects in pipes, such as air bubbles in pipeline coating layers or qualitative characterize non-circular section-shape defects. The proposed method has three important modules: a new resonator for data acquisition, a signal-processing algorithm for data preprocessing, and an ANN for quantitative imaging. In the designed sensor, we extend the tip of the sensing ring and introduce an appending in the ring gap for high sensitivity. Simulations show that the sensor can detect a defect with a radius as small as 0.7 mm. The raw resonant frequency shifts obtained by the sensor scanning at an angle interval around the specimen first are preprocessed by curve fitting, sampling, and adaptive data interpolation or truncation. Then, using an ANN, the relationships among resonant frequency shifts, external radius of the specimen, and defect size are modeled for imaging of circular-section shape defects. Preliminary simulations and measurements illustrate the efficacy of the method. Consequently, a contactless, high-resolution, near-field imaging measurement based on sensor scanning for inspecting pipe structures is obtained.

Morphology and genealogy of structural defects in vacuum ion-plasma coatings

Introduction. The main work objective is systematization and analysis of structural defects of vacuum ion-plasma coatings; on this basis, their classification principles are developed and given in the paper. Another important part of the work is the experimental study on one of the specific defects of coatings, which the authors propose to call “defect of substructural origin”. Materials and Methods. PVD coatings of various nitride and metal systems 1.5-9.0 μm thick were used as an object of the research. Coatings were applied in vacuum installations using arc and magnetron evaporators. The research results were obtained by high resolution electron microscopy, energy dispersive analysis and indentation. Results. Various types of defects in ion-vacuum coatings are presented as the research results. They include discontinuities, deformation of crystallites, and structural inhomogeneity. The principles of their systematization are validated. It is proposed to classify defects into droplet, substructural, and growth defects (depending on the causes of their nucleation), as well as regular and stochastic ones (depending on their distribution in the coating volume). The study of “substructural defects”, classified by the authors as stochastic, is given special consideration. These micrometric defects are shaped like a cylinder with a conical “head”. Their main axle is oriented perpendicular to the surface of the coating. They can be “extruded” (tore away) by the coating. The paper validates the dislocation mechanism of their nucleation and the helicoid growth principle. Conclusions. The inference is summarized that the proposed systematization of defects in ion-plasma coatings has the character of an intermediate result of research in this scientific area. At this, the “substructural defects” do not have a fatal effect on the structure and properties of the coating due to a small size.

Synergistic lubrication of Ag and Ag2MoO4 nanoparticles anchored in plasma-sprayed YSZ coatings: Remarkably-durable lubricating performance at 800 °C

The high-temperature tribological properties of plasma-sprayed YSZ coatings are enormously weakened by intrinsic cracks and pores, brittleness and lubrication deficiency. Therefore, we are attempting to employ Ag and Ag2MoO4 nanoparticles together, as high-temperature lubricant additives, to chemically modify YSZ coatings. With aid of vacuum impregnation and hydrothermal reaction, Ag and Ag2MoO4 nanoparticles were first anchored in the defects of YSZ coatings. The two nanoparticles dramatically reduced the coefficients of friction and wear rates of YSZ coatings under ultrahigh peak Hertzian contact stress at 800 °C, endowing YSZ coatings with an extremely long lifetime and bringing negligible wear damage to the friction pair. It is liquid lubrication and the formation of stable tribofilm that jointly contribute to the remarkably-durable lubricating performance.

Using an added liquid to suppress drying defects in hard particle coatings

HypothesisLateral accumulation and film defects during drying of hard particle coatings is a common problem, typically solved using polymeric additives and surface active ingredients, which require further processing of the dried film. Capillary suspensions with their tunable physical properties, devoid of polymers, offer new pathways in producing uniform and defect free particulate coatings. ExperimentsWe investigated the effect of small amounts of secondary liquid on the coating’s drying behavior. Stress build-up and weight loss in a temperature and humidity controlled drying chamber were simultaneously measured. Changes in the coating’s reflectance and height profile over time were related with the weight loss and stress curve. FindingsCapillary suspensions dry uniformly without defects. Lateral drying is inhibited by the high yield stress, causing the coating to shrink to an even height. The bridges between particles prevent air invasion and extend the constant drying period. The liquid in the lower layers is transported to the interface via corner flow within surface pores, leading to a partially dry layer near the substrate while the pores above are still saturated. Using capillary suspensions for hard particle coatings results in more uniform, defect free films with better printing characteristics, rendering high additive content obsolete.

Cavitation erosion behavior of ceramic/organic coatings exposed to artificial seawater

The cavitation erosion damage of the materials in seawater is more severe than in freshwater due to the coupling effect of mechanical impact, instantaneous high temperature and seawater corrosion. This study reported that the ceramic/organic coating fabricated by the vacuum pressure impregnation epoxy resin into as-sprayed ceramic coating is introduced. The corrosion inhibition mechanism of the ceramic-based coatings in seawater after introducing the epoxy resin was further clarified. The influence of epoxy resin on the microstructure and mechanical properties of the ceramic coatings were systematically evaluated based on SEM, Vicker hardness and scratch results. The corrosion behaviors of the ceramic-based coatings with/without sealing treatment were evaluated by electrochemical corrosion tester. Their cavitation erosion performance in seawater was comparatively studied using the ultrasonic vibration cavitation testing machine. It was demonstrated by the experimental results that the hardness, compactness and cohesive strength of the ceramic/organic coatings were greatly improved compared with those of the as-sprayed ceramic coatings. The epoxy resin completely filled the defects of the ceramic coatings and effectively prevented the invasion of seawater. Accordingly, the anti-cavitation erosion of the ceramic/organic coatings was significantly improved.

The Effect of Pulsed Electron-Ion Irradiation on Defects in Ceramic-Metal Coatings on Dies for Pelletizing Plastics

In the work, on the example of a coating of a metal-ceramic alloy of 50 vol.% TiC / 50 vol.% (Ni-Cr) of the working part of a die for granulating plastics, the results of the study of the possibilities of using the pulsed electron-ion irradiation method to eliminate continuity gaps in the coating in the form microcracks formed during operation of the die through through the cross section. It has been shown that pulsed electron-ion irradiation makes it possible to restore the integrity of metal-ceramic coatings by filling cracks with a melt of a nickel-chrome binder metal-ceramic composition extending to the surface of the coating of cracks to a depth of more than 100 μm.

237 寒冷地の外装仕上塗工事に関する調査 : その 2 陥について

237 寒冷地の外装仕上塗工事に関する調査 : その 2 陥について

Microstructural, Morphological and Electrochemical Effects of Graphene Oxide Incorporation in Tin-Cobalt Composite Coatings

Effect of incorporation of graphene oxide (GO) on the evolution of morphology, phase constitution, microstructure and corrosion properties of SnCo-GO composite coating was investigated. SnCo-GO composite coatings containing different amounts of graphene oxide were electrodeposited over mild steel substrate using electrolyte with different concentrations of dispersed graphene oxide (0.0625, 0.125, 0.1875, 0.25, 0.3125, 0.5, 0.625 g/L). Morphological examination revealed that lesser additions of GO increased the coating compactness and uniformity whereas higher amounts of GO produced surface defects in the composite coatings. Structural characterization revealed the presence of primarily two different intermetallic phases in the coating microstructure: Co2Sn phase and Co3Sn2 phase. It was observed that the phase fraction of the relatively more inert Co3Sn2 phase increased monotonically with increase in the amount of GO in the coatings. Microstructural investigations revealed that in the pristine SnCo coating the Co2Sn phase is present at the grain boundaries of the Co3Sn2 phase grains. Incorporation of GO altered the coating microstructure considerably leading to the formation of a layered microstructure where the elongated Co2Sn phase grains were present beneath laterally elongated grains of the Co3Sn2 phase. Electrochemical analysis performed using the Tafel polarization and impedance spectroscopy measurements showed that the corrosion properties of the coating were highly sensitive to the amount of GO present in the coating. Initial addition of GO increased the corrosion resistance till an optimum GO concentration for which highest corrosion resistance was achieved. Further addition of GO beyond the optimum lead to monotonic decrease in the corrosion resistance to values which were lower than the pristine SnCo coating. Initial increase in the corrosion resistance was attributed to uniform distribution of GO in the coating, increase in the uniformity and compactness of the coatings, increase in the fraction of the relatively more inert Co3Sn2 phase in the coating microstructure and formation of a layered microstructure in which the exposed coating surface contained the relatively more inert Co3Sn2 phase. Decrease in the corrosion resistance beyond the “optimum” was due to increase in the coating surface defects due to the deposition of agglomerated GO and galvanic coupling due to increase in the cathodic (GO) to anodic (metal) phase area.

Microstructure and wear resistance of electromagnetic field assisted multi-layer laser clad Fe901 coating

Thick Fe901 coatings were prepared on Cr12MoV substrates using electromagnetic field (EMF)-assisted multi-layer laser cladding. The effect of the EMF on surface topography, microstructure, multi-layer strategy, phase composition, and wear resistance in the multi-layer laser cladding Fe901 coatings were investigated. The results indicate that the application of EMF decreased the number of defects in coatings produced with laser cladding. Dendrites or cellular crystals oriented perpendicular to the interface were observed in the coatings with and without EMF-assisted growth. The microstructure of the coating formed with the applied EMF gradually transitioned from columnar dendrites to fine dendrites and equiaxed dendrites as the number of cladding layers increased. The coatings with and without an applied EMF primarily contained α-(Fe), α-(Fe,Cr), (Cr,Fe)7C3, CrFeB and FeCrMo phases. The EMF did not affect the phase composition of the coatings, although the intensity of X-ray diffraction peaks from the coating produced in an EMF were changed from those in the coating produced without the field. In addition, the coating produced in the EMF exhibited higher fatigue and abrasion resistance. The coatings prepared in an EMF also displayed narrower, shallower wear tracks, with 78.2% lower mass loss than the conventional coating.

Effect of process conditions (withdrawal rate and coating repetition) on morphological characteristics of sol–gel TiO2 film during dip coating

The effects of the process conditions (withdrawal rate and coating repetition) on the morphological characteristics of sol–gel TiO2 film during dip coating were studied. We carried out dip-coating experiments to observe the effect of the withdrawal rate, coating repetition, and heat treatment on morphological development (homogeneity, thickness, and defects) in coated film. Sol was prepared with acetic acid catalyst and ethyl acetoacetate chelating agent. Withdrawal rate varied between 0.4 and 3.2 mm/s. Multilayered coatings were prepared by conducting 1, 2, 3, 5, and 10 cycles of coating. Heat treatment was carried out for 30 min at 450°C in air. The properties of the TiO2 film were characterized by visual observation, SEM, FIB, FTIR, and electrochemical impedance spectroscopy (EIS). As the withdrawal rate increased, the homogeneity of the film decreased, while the thickness of the film increased to a certain limit without cracking. A homogeneous coating, without edge effect, formed at an intermediate withdrawal rate of 0.1–1 mm/s, conditions under which both viscous drag and capillarity feeding were active. As the number of coatings increased, the coating thickness increased and cracking increased. EIS tests were used to analyze internal defects in coatings. With repeated coating, defects in coatings increased. After a 30-min heat treatment at 450°C in air, pore resistance (Rpore) decreased approximately 20–30% compared to Rpore of specimens without heat treatment. This study confirmed that it is important to control the morphology to obtain optimum properties of TiO2 film as a coating for corrosion barriers, photocatalysts, and photoelectric and optical applications.

Long Array of Microwave Sensors for Real-Time Coating Defect Detection

A real-time, inexpensive, and easy-to-install resonator-based microwave sensor array for coating defect detection on metallic structures is presented. The sensor array is composed of 55 identical rectangular spiral resonators coupled to a 120-cm-long transmission line. The array was simulated, fabricated, and measured. A stopband was created at the fundamental resonant frequency of the resonators. The fabricated sensor array was implemented on the coating to monitor defects beneath the sensor. The proposed sensor array can be used to detect water ingress and coating delamination, which are causes for alarm in metallic structure corrosion and cracking. The proposed structure is a low-cost solution for real-time coating failure identification.

Control of defects in the multilayer dielectric materials and coatings in the microwave range

The development of modern engineering is inextricably linked with the development of the new types of multilayer dielectric materials. Existing radio wave methods for monitoring interlayer defects in such materials exhibit low accuracy in reconstructing the geometric parameters of defects. The results of studying extended interlayer defects in the three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber by the method of surface electromagnetic waves are presented. The method is based on the solution of inverse problems in the reconstruction of the geometric parameters of extended interlayer defects of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. Unlike the methods that make use from the complex reflection coefficient we proposed to increase the accuracy of the reconstruction of the geometric parameters of extended interlayer defects taking into account the linear frequency dependence of the attenuation coefficient as well as reducing the number of fixed measurement frequencies. Moreover, the determination procedure is rather simple, since only the field strength of the surface electromagnetic wave is measured, and there is no need for phase measurements. Experimental data obtained on a multifrequency measuring complex in the range of 10 – 11 GHz were used for reconstruction of the interlayer defects in the coating under study. The developed method provided a relative error of thickness estimation below 10%. The proposed method approach can be used in studying multilayer dielectric coatings on the metal for detection of delamination in the lack of glue or poor adhesion between the layers. The developed method is also suitable for control of the defects in semiconductors, ferrite and composite materials.

Comparative study of protective coatings for heat resistance

Modern gas turbine engines operate under changing temperature loads. Therefore, one of the important characteristics of the protective coatings used on the turbine blades is their high resistance to the occurrence and development of cracks under mechanical and thermal loads. The applied effective systems of internal heat removal of the cooled turbine blades lead to an increase in their heat stress. At present, cracks arising from thermal fatigue are one of the common defects of the protective coatings used on turbine blades. The heat resistance of coatings at high temperatures is determined by three factors: the shape of the part on which the coating is applied, the thickness of the coating and the phase composition of the surface layers or the maximum aluminum content in the coating. Therefore, when choosing a protective coating for these operating conditions, it is important to know the impact of these factors on the thermal stability of the coating. The paper presents a comparative study of various coatings on their resistance to crack formation under cyclic temperature change. The dependence of the heat resistance of the considered coatings on the method of their application and phase-structural state is established. Especially valuable is the established mechanism of formation and propagation of thermal fatigue cracks depending on the phase composition of the initial coating. It is shown that the durability of protective coatings with cyclic temperature change depends on the chemical composition of the coating and the method of its formation. The dependence of the formation of thermal fatigue cracks on the samples with the coatings under study on the number of cycles of temperature change is established.

Unsaturated carbon linear chains created during bacteria incubation with amorphous carbon thin films produced by a clean technology

Graphene production is usually an expensive process, time-consuming, with low yield and often uses environmental hazardous chemicals during the process. For these reasons, many applications consider the use of graphene based materials (GBM), such as carbon thin films, instead of graphene. In this work, the aim was to produce GBM, by sputtering deposition, from a graphite target. The ability to reduce the defects of the carbon thin films was evaluated by using several bacterial strains to pursue a sustainable practice. The highest reduction of the number of defects of the as-deposited coatings was obtained when the surfaces were exposed to Escherichia coli. The analysis by Raman spectroscopy revealed that the ID/IG ratio reduced from 0.75 to 0.56 which indicate a 75% in defects reduction. The use of different bacterial species also allowed to evaluate the antimicrobial ability of different coatings. For Gram positive bacteria a 95% decrease in colony forming units (CFU) was registered, while for Gram negative bacteria a maximum of 80% decrease of CFU was observed. The Raman characterization after the incubation with bacterial strains indicate that, for one Gram negative bacteria, the antimicrobial activity of the carbon thin films may be related with the formation of linear carbon chains with electronic transport properties similar to metals. During the incubation process the microorganisms effectively reduced the defects of the produced carbon coatings. Moreover, this approach allowed the use of green technology to produce metal-free surfaces with the ability to present different levels of antimicrobial activity against the studied bacterial strains.

Micrometric Growth Defects of DLC Thin Films

Defects in diamond-like carbon coatings deposited on corrosion sensitive 100Cr6 steel have been studied. Diamond-like carbon (DLC) thin films are promising for corrosion protection due to chemical inertness and low electrical conductivity. Nevertheless, the performance of these coating is highly sensitive to the presence of uncoated areas. These defects represent the primary way of substrate degradation in aggressive environments. An in situ optical microscopy coupled to an electrochemical activation was developed to reveal micrometric growth defects and observe that they were at the origin of corrosion. A square wave voltammetry was applied to increase the sensitivity of electrochemical techniques based on the detection of the dissolution of the bare metal surface triggered by the presence of uncoated spots. This method can be utilized to quantify defect density arising from vapor deposition processes.

Detection of Surface Coating Defects using Fuzzy C-Means Clustering with Firefly Optimization

Defect detection in metallic surface images is a challenging task in the image analysis process. The data clustering and optimization techniques have been widely used for image segmentation and the combination of these two approaches improves the output stability as well as convergence speed. In this work developed an automatic, efficient method for the detection and segmentation of coating defects in metal surfaces. The Fuzzy c-means (FCM) and Firefly algorithm (FA) are well-known and popular methods to discover the image information comprising indiscriminate objects and solves many complex problems involved in image segmentation. In this paper, proposed a new technique for the coated metal surface defect detection using the hybridization of two methods, FCM with FA (FCM-FA). The results from experiments verified the efficiency of the developed FCM with FA over comparison with three existing methods in terms of evaluation parameters of defect detection for scanned high resolution images. It can be seen from the experimental results that the incorporated algorithm has the potential to segment and identify the defected regions from the coated surface.