Performance Of Organic Coatings Research Articles

Evaluation of surface tortuosity on the corrosion resistance of organic coatings using laser texturing process

Surface tortuosity is a quantitative measure of the complexity of a material's surface. It is commonly defined as the ratio between the real length of the surface over the shortest distance between two points on the surface. An increase in surface tortuosity has been found to have advantageous effects on the durability of coated parts when exposed to corrosive and humid conditions. Laser surface texturing, a versatile process, can be used to modify the surface tortuosity by creating various structure patterns on the surface of steel. This study aims to investigate the impact of V-shaped groove dimensions on the resistance against corrosion creep of an organic coating applied to textured surfaces. Comparative surface tortuosity measurements were obtained for different groove dimensions while keeping the aspect ratio and textured areas constant. V-shaped grooves with an aspect ratio of 1 and sizes of 50, 100, and 200 μm were machined on carbon steel AISI-A36. The distance between adjacent grooves was varied to achieve different textured areas, ranging from 10% to 60%. The surface roughness (Sa) and surface tortuosity were characterized. The performance of the coating was evaluated using an accelerated corrosion test based on ISO 12944-9. The results indicate that V-shaped grooves with dimensions of 100 μm and a textured area of 40% exhibit the lowest coating delamination. It is worth to mention that the performance of organic coatings is enhanced up to a certain optimal point by an increase in surface tortuosity. However, beyond this optimal point, further increases in tortuosity do not lead to an increased resistance to the propagation of corrosion.

Performance of organic coatings upon cyclic mechanical load

Performance of organic coatings upon cyclic mechanical load

The effect of size and distribution of inert pigment on the performance of organic coatings

ABSTRACT The paper aims to show how the performance of paint coatings is affected by their composition. Samples of two paint coatings, which had delaminated in service, were compared with the same type of paint applied to samples for the purposes of certification. The particle size distribution of the filler materials (inert pigments) affected the flow of resin and wetting of the particles. In both failed samples, large particles sizes had agglomerated creating voids and crevices, resulting in poor wetting by the resin. This poor wetting and inherent lack of bonding had resulted in their premature failure. Both equivalent laboratory samples had a much better particle size distribution, with a lower maximum particle size, resulting in inert pigment being well distributed through the paint layer. The paper concludes that tighter control over the sizes of additives in paint such as inert pigments within Standards is needed to ensure better performance.

Performance of organic coatings upon cyclic mechanical load

A number of engineering structures fail due to the fatigue damage resulting from cyclic mechanical stress. However, as far as organic coatings are concerned this degradation factor remains underestimated. In the paper the authors propose a methodology combining global electrochemical impedance spectroscopy and local atomic force microscopy measurements for evaluation of coating resistance to an impact of repetitive mechanical stress. Typical epoxy coating designated for ship hull protection has been tested in as-received state as well as after pre-exposure to elevated temperature. Application of atomic force microscopy-based approach helped to reveal and spatially localize the spots of organic coating degradation onset. The mechanism and process of defect formation and propagation has been shown on a microscopic scale.

Simulation of dirt pickup performance of organic coatings

Simulation of dirt pickup performance of organic coatings

Evaluation of Surface Preparation Techniques for Steel Substrates Prior to Coating Application

The performance of organic coatings on steel substrates is strongly affected by substrate cleanliness and anchor patterns. During present research work, Surface pre-treatments were applied to remove contaminants from steel surfaces. Electrochemical Impedance Spectroscopy (EIS) was used to characterize such surfaces in terms of electrochemical parameters to find out the extent of activeness of prepared surfaces, and electrochemical processes are modeled into corresponding electrical equivalent circuits (EECs). Surface roughness parameters were evaluated to find out the extent of mechanical interlocking between prepared surface and the coating to be applied over it. The optimum surface preparation technique prior to application of organic coating was characterized.

Interpretation of EIS data from accelerated exposure of coated metals based on modeling of coating physical properties

Electrochemical studies on the accelerated weathering of corrosion protective coatings systems in this laboratory have yielded time series data in the low frequency portion of the spectrum that can be fit by a simple exponential decay function in time. A description of how this can be empirically used for lifetime prediction for coatings has already been presented. Attempts have been made to use other parts of the EIS spectrum for analyzing coating performance in accelerated exposure, but these have not yet yielded a predictive model for the effects of exposure on the structure and performance of organic coatings. First, a simple model which considers only loss of coating thickness by UV-induced ablation is applied to the interpretation of EIS time series results from coatings systems undergoing accelerated weathering. Next, more complete models which include a diffusion front of electrolyte that moves with either Fickian or Type II diffusion kinetics are applied to the same problem. Incorporating these models for degradation as a simple RC equivalent circuit representation of a coating gives predictions of EIS performance that have reasonable agreement with experimental data. Further, using a two layer representation of coating changes due to water intrusion and known effective medium theories for dielectric and resistivity changes due to water intrusion allow prediction of the changes in EIS spectra seen in immersion or other accelerated testing of coating films. These results provide further evidence of the power of modeling physical processes in interpreting EIS data and predicting coating protective lifetimes.

The role of ions diffusion in the cathodic delamination rate of polyester coated phosphatized steel

A very important mechanism of organic coating deterioration is the cathodic delamination. The basic knowledge about the diffusion mechanism of ions, oxygen and water through the coatings and through the defects in the coatings is not yet sufficient to improve the performance of organic coatings by developing more resistant coatings, and more research is necessary. In this study a particular electrochemical cell has been developed in order to keep separated the solution in contact with an artificial defect (inner solution) and the solution in contact with the rest of the intact organic coating (outer solution). In this way it is possible to polarize the sample in the cathodic region and to control the environment (ions and their concentration, oxygen, water activity) in the defect and around the defect. With this cell samples of polyester coated phosphatised steel were studied. The cathodic delamination was measured, in different solutions, by measuring the distance of delamination from the artificial defect after different times of exposure to cathodic polarisation. The experimental results are discussed in terms of two parameters: the induction time (time necessary to notice the beginning of delamination) and the delamination rate (mm2 of delamination per hour). On comparing the experimental data it was possible to obtain new and interesting information on the delamination mechanism and to determine also the rate controlling step of the phenomenon for our materials, which is found to be the cation diffusion through both the coating and the defect. The proposed mechanisms were confirmed also by SEM observation and surface analysis.

Erratum

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/03699420210420350. When citing the article, please cite: Niki Kouloumbi, Petros Moundoulas, (2002), “Anticorrosive performance of organic coatings on steel surfaces exposed to deionized water”, Pigment & Resin Technology, Vol. 31 Iss 2 pp. 74 - 83.

Effect of Micron-Scale Surface Deformation on the Corrosion Behavior of Coil-Coated Aluminum Alloy 5182

Abstract An investigation of the corrosion behavior of coil-coated AA5182 (UNS A95182) can ends revealed directional underfilm corrosion during immersion in 0.6 M sodium chloride (NaCl) solution. Corrosion occurred preferentially within ∼ 10 mm wide bands that were dull in appearance. Microscopic examination revealed that these dull bands were a result of small dimples ≈ 10 μm deep and 100 μm wide. Regions that had a higher dimple density had a lower pitting potential than regions with fewer dimples. Subsequent investigation determined that dimples were introduced into the coil-coated sheet by feed rollers during can end manufacturing. Oxide damage and second-phase precipitation at dislocations resulting from micron-scale surface deformation were proposed as the mechanisms of increased corrosion susceptibility. The present study showed the importance of manufacturing protocol in the determination of corrosion performance of organic coatings on alloy substrates. More specifically, the importance of the sub...

Performance of Organic Coatings in Tropical Environments★

Abstract Seven-, six-, three-, and one-year exposures have provided quantitative data on the ability of organic coating systems to protect metals from the five corrosion environments characteristic of tropical latitudes. Data are reported on the performance of more than 350 coating systems in which alkyds, epoxys, synthetic rubbers, phenolics, vinyls and bitumens were used singly or in combinations and mixtures. 2.2.5

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有機質塗裝の耐曝露性に及ぼす鋼の組成の影響

有機質塗裝の耐曝露性に及ぼす鋼の組成の影響

Effect of Composition of Steel On the Performance of Organic Coatings In Atmospheric Exposure

Abstract The investigation provides at least a partial answer to the question as to whether improved atmospheric corrosion resistance of alloy steels is advantageous when they are painted. Steels s...