Performance Of Protective Coatings Research Articles

Effect of coatings on microstructure and oxidation behavior of the Ni-based single crystal superalloys containing different Ru contents

The element Ru in single crystal superalloy usually plays an important role in inhibiting the mutual diffusion between coating and substate. The MCrAlY coating and PtAl coating were prepared on the fourth and third generation single crystal superalloy, and the isothermal oxidation behaviors of the two superalloys and the two coatings were investigated in static laboratary air at 1200 °C. The oxidation kinetic curves showed that the mass gain of the coated samples was less than the alloys without coatings, which meant the coatings showed more excellent oxidation resistance at high temperature, and the oxidation resistance of the two coatings was slightly enhanced by the addition of Ru during the oxidation tests. Meanwhile, the interdiffusion of elements, such as Al in coating and refractory elements in substrate, was hindered by the addition of ruthenium. The size of γ' phase was also inhibited. As a result, the formation of interdiffusion zone and the precipitation of topological-close packed phase were suppressed, resulting that the DD91 showed more stable microstructure at elevated temperature than the DD90 during the oxidation process. The advantage of Ru in the alloys with coatings will be discussed in detail as well as the protective performance of coatings.

Influence of TiO2 pigment particles on chromate ion transport in epoxy films

Transport of active species (i.e., ions) leaching from pigment particles incorporated in a polymer matrix is the main mechanism behind the anticorrosive performance of protective coatings. Understanding this mechanism is necessary for the effective design of the systems utilizing pigments less toxic than the most efficient chromate salts. It was demonstrated that anticorrosive pigment particles can themselves facilitate the transport of active species via the pathways formed after pigment leaching from a coating. It was also suggested that other paint components, e.g., certain additives, pigments, and fillers can be involved in the formation of transport pathways. Investigation of the possible influence of inert pigment (TiO2) on creating the pathways for chromate ion transport in polymer coatings was the primary objective of this work. In an experiment mimicking the transport of pigment species (i.e., chromate ions), a model epoxy coating containing particles of a single pigment (TiO2) was exposed to a chromate solution (aqueous, or with the addition of acetone as a polymer swelling agent). It was shown that the chromate ions can be transported in the epoxy film preferentially via the TiO2 particles/polymer matrix interface.

Phosphonated and methacrylated biobased cardanol monomer: Synthesis, characterization and application

To create an effective adhesion promotion for different surfaces, specific anchor groups are necessary such as phosphonic groups for metals. Biobased phosphorylated monomer from cardanol was synthesized and polymerized by UV curing or miniemulsion radical polymerization. Phosphonic ethoxy cardanol methacrylate (CMP) was synthesized from cardanol via hydroxyethylation, followed by phosphorylation radical addition of dimethyl phosphite onto the unsaturations of the C15 aliphatic chain of cardanol prior methacrylation of the hydroxyl ethoxy group. Lastly the cleavage of the phosphonate ester groups was made to generate the targeted phosphonic acid moieties as adhesion promoters. Moreover, the development of a phosphonic latex was successfully achieved by miniemulsion radical copolymerization in water with an additional redox termination to ensure quantitative monomer conversions. Phosphonic cardanol and cardanol (as reference) latexes were characterized by dynamic light scattering. The effects of cardanol derivatives on the performance of protective coatings on steel plates were evaluated in UV-cured coatings as well as in latex coatings in terms of contact angle and adhesion effectiveness. In coatings, increased hydrophobic properties were observed in fomulations containing free cardanol or cardanol methacrylate. On the other side, the incorporation of phosphonic acid groups onto cardanol significantly improved the adhesion effectiveness of the coating, whatever the film-making technique.

Performance of Protective Coatings for Aluminum Alloys in the Operating Conditions of Oil Production Equipment

The paper investigates wear resistance and corrosion resistance of protective coatings of D16 aluminum alloy under conditions that simulate operation of drill pipes. The paper also presents microstructure of coatings, electrochemical potential and corrosion rate of D16 aluminum alloy with various coatings. We evaluated adhesion and wear resistance of these coatings. D16 alloy with a tungsten carbide coating has the widest range of service properties and can be used to effectively protect the surface of aluminum drill pipes during operation operation.

Corrosion beneath a blister with high impedance

In this work, the effect of blisters on the performance of protective coatings was investigated. Artificial blisters were generated by potentiostatic DC polarization of an epoxy-coated aluminum substrate and characterized using optical microscopy, electron microscopy (SEM), scanning electrochemical microscopy, as well as by scanning Kelvin probe (SKP) measurement. Impedance measured above blisters displayed high values, typical of an intact undamaged coating. SKP measurement above the blister identified regions of likely corrosion beneath it, which was verified by SEM. SEM images showed pitting-like corrosion beneath the blisters, implying that high impedance measured on delaminated coatings may correspond to the delaminated polymeric film. SKP was also able to identify regions of invisible delamination.

Evaluation of the protective performance of hydrophobic coatings applied on carbon-fibre epoxy composites

Carbon–fibre epoxy composites are widely used for high-performance structural applications, where they are often exposed to harsh environments. The result of moisture ingress has been extensively studied, causing significant deterioration in the mechanical properties of these composites. This study evaluates the performance of five commercial hydrophobic coatings as protective layers, to inhibit moisture ingress into the composite. The coatings evaluated were NeverWet, HydroBead, SHC, Aculon and LiquidGlass. These coatings were characterised and compared in terms of hydrophobicity, surface energy, roughness and chemical composition. This study also evaluated two atmospheric plasma pre-treatments as a means of enhancing the adhesion performance of these coatings. The pre-treatments involved the use of an air plasma for the activation of the epoxy, as well as the plasma deposition of a nanometre thick SiOx interlayer coating. The durability and protective performance of the coatings, with and without the pre-treatments were then compared using an abrasion test as well as a water immersion study. The use of both plasma pre-treatments was found to enhance the adhesion and the abrasion performance of four out of the five coatings. Of the coatings and pre-treatments investigated, the LiquidGlass in conjunction with a SiOx-coating interlayer was found to exhibit the highest abrasion resistance. This was followed by the composite, which was plasma activated prior to the application of the Aculon coating. Only minor differences were observed when comparing the total moisture ingress (M%) of the epoxy, coated with the different hydrophobic layers. The composite coated with the Aculon and SiOx interlayer exhibited the least amount of moisture ingress, at 0.90%, compared to 1.08% of the uncoated specimen. The shear strength of epoxy composite, coated with the LiquidGlass, NeverWet and the activated Aculon combination, were within the range of the uncoated specimens, therefore the moisture ingress was reversible upon heating and no permanent damage to the epoxy–fibre interface was observed. It is concluded that, of the five coatings investigated, both the Aculon coating and LiquidGlass in combination with a SiOx interlayer coating, exhibit the greatest potential as protective layers for carbon fibre epoxy composites.

Performance and microstructure of bricks with protective coatings subjected to salt weathering

Salt crystallization is the crucial damaging mechanism which affects the durability of porous masonry units like bricks. Improper selection of protective treatments and replacement strategies often degrade the situation further and result in frequent future interventions. In this paper, the role of pore size distribution of the bricks in resisting salt crystallization and its effect on the performance of protective coatings has been discussed. Bricks with different microstructural properties were treated with common water repellent coatings - silicone-based and acrylic siloxane-based and were subjected to accelerated salt weathering tests. The performance of the coatings was studied using standard methods, and the coatings were then evaluated for their compatibility with various bricks with varying microporosity, when exposed to sodium sulphate. Bricks highly prone to salt crystallization have been found to be more sensitive to the properties of treatments over them, as breathability assumes a greater significance.

High protective performance coatings assembled by epoxy-modified furfural-acetone containing polyaniline nanowires for mild steel

High performance protective coatings applied under heavy duty condition will lengthen the structure’s service life, decrease maintenance times, economic and human life loss. Here, high protective performance coatings were prepared by dispersing polyaniline (PANI) nanowires into epoxy modified furfural-acetone (EMFA) resin matrix and then cured with phenalkamine. The protective performance of coatings was investigated by immersion experiments in 12% NaCl solution at 90 °C and Electrochemical Impedance Spectroscopy (EIS) measurements. The coating containing 1.0% PANI nanowires showed high impedance (>1010 ohm·cm2) after 80 days immersion, exhibiting great protective performance. X-ray photoelectron spectroscopy (XPS) surveys verified the formation of passive layer (Fe2O3/Fe3O4) on steel surface beneath the coating with 1.0% PANI. The bending test suggested that both the pure EMFA coating and the EMFA/PANI coating showed excellent flexibility of 2 mm. Here, measurement of water absorption, adhesion strength, pencil hardness and impact resistance were conducted to evaluate coatings performance.

Stone/Coating Interaction and Durability of Si-Based Photocatalytic Nanocomposites Applied to Porous Lithotypes.

The use of hybrid nanocoatings for the protection of natural stones has received increasing attention over the last years. However, the interaction of these materials with stones and, in particular, its modification resulting from the blending of nanoparticles and matrices, are yet little explored. In this work, the interaction of two nanocomposite coatings (based on alkylalkoxysilane matrices and TiO2 nanoparticles in water and 2-propanol) with two different porous stones is examined in detail by comparing their absorption behaviour and protection performance with those of the respective TiO2-free matrices. It is shown that the protective effectiveness of both matrices is not negatively affected by the presence of TiO2, as the desired water barrier effect is retained, while a significant photocatalytic activity is achieved. The addition of titania leads to a partial aggregation of the water-based matrix and accordingly reduces the product penetration into stones. On the positive side, a chemical interaction between titania and this matrix is observed, probably resulting in a greater stability of nanoparticles inside the protective coating. Moreover, although an effect of TiO2 on the chemical stability of matrices is observed upon UV light exposure, the protective performance of coatings is substantially maintained after ageing, while the interaction between matrices and nanoparticles results in a good retention of the latter upon in-lab simulated rain wash-out.

A macroscopically nondestructive method for characterizing surface mechanical properties of polymeric coatings under accelerated weathering

The surface of coatings and plastics is the first target in any degradation process initiated by ultraviolet (UV) radiation or mechanical stress (via scratch and abrasion). Surface damage can lead to changes in optical, morphological, and mechanical properties and can result in pathways for ingress of moisture and corrosive agents. Current test methods for monitoring performance of protective coatings focus on chemical properties and optical properties, such as color and gloss measurements, or invasive tests such as abrasion and cross-cut adhesion. In this study, a macroscopically nondestructive performance protocol using nanoindentation metrology via a well-controlled scratch test was applied to evaluate the scratch resistance and monitor the surface mechanical property changes in a protective coating under accelerated weathering. Polyurethane (PU) coatings with different polyol compositions were chosen for this study. Coating specimens were exposed to high-intensity UV radiation at 55°C and 75% RH conditions. Exposed specimens were removed at specified UV exposure times for surface modulus/hardness and scratch resistance characterization via nanoindentation and scratch test. The effect of polyol type and UV radiation dose on the scratch damage (scratch morphology) was investigated and correlated with the surface hardness and modulus of the materials.

Synergistic effect of polyaniline grafted basalt plates for enhanced corrosion protective performance of epoxy coatings

Abstract Polyaniline-graft-basalt plates (PANI-g-BP) were prepared based on γ-aminopropyltriethoxysiliane (APTS)-modified basalt plates via in-situ chemical-oxidation polymerization method. Three PANI-g-BP samples were prepared by varying the ratio of aniline to BP, i.e. 1:2, 1:4, 1:6. The results of Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA) confirmed that PANI was successfully grafted on the surface of basalt plates. Different coatings were prepared by adding the synthesized PANI-g-BPs or PANI, and were coated on the mild steel subsequently. The water-uptake property, the adhesion strength and the passive properties of the coatings were investigated. In addition, the protective performance of the coatings was tested by the electrochemical impedance spectroscopy (EIS) in 12% NaCl solution at 95 °C. The results indicated that the coatings with 10% PANI-g-BP (1:4) exhibited the best protective performance and its impedance at 0.01 Hz is higher than 10 10 after 80 days immersing.

Nanomechanical performance of protective coatings reinforced with core/shell composite materials

Purpose The purpose of this paper is to focus on the investigation of nanomechanical behavior of new types of metal alloys protective coatings. For this purpose, poly(n-butylacrylate) was synthesized via activators regenerated by electron transfer-atom transfer radical polymerization and mixed with epoxy resins, and microcomposites. Design/methodology/approach Multi-layered coatings were applied on hot dip galvanized steel via a baker film applicator. Every layer containing the aforementioned copolymer differs in the proportion of the epoxy resin resulting in the production of a coating with a gradient from hard to soft from the substrate to the top. Nanomechanical performance is accessed via nanoindentation, providing information for structural and mechanical integrity, adhesion and resistance to wear. Findings The results reveal that through trajection of hardness mapping, the resistance is divided in three regions, namely, the polymer (matrix), interface (region close to/between spheres-shells) and spheres-shell regions. Originality/value The structural analysis, adhesion and mechanical integrity of the coatings are clearly demonstrated.

The effect of structural and energy parameters of glassy melts on the protective performance of coatings made of these glassy melts

We have designed a procedure for calculating strength criterion Kn as a parameter determining the mean strength of structure of silicate glasses and melts. The infrared spectra of silicate glasses used as coatings to protect low-alloy and low-carbon steels against high-temperature gas-phase corrosion in process heating are studied. Aluminum cations in the glasses under study are four-coordinate, while boron ions may be both fourand three-coordinated. The latter fact has a significant effect on the Kn values. The Kn values are calculated at operating temperatures of the studied glassy coatings. The correlation ratio between protective effect Δg of the glassy coatings and their Kn is analyzed. For glassy coatings with an operating temperature that lies within their vitrification range, there exists a nonlinear correlation between Δg and Kn; the correlation ratio between these parameters increases with temperature. Regression equations (significance level p = 0.05) describing the relationship between Δg and Kn are obtained for temperatures of 900 and 1000°C.

Predicting the Long-Term Field Performance of Coating Systems on Steel Using a Rapid Electrochemical Test: The Damage Tolerance Test

Abstract The pace of coatings development is limited by the time required to assess their corrosion protection properties. This study takes a step forward from past studies and correlates the corrosion performance of protective coatings assessed by a series of short-term electrochemical measurements with 18 month and 60 month beachside atmospheric exposure results of coated panels. A series of 11 coating systems on A36 steel (UNS K02600) substrates were tested in a blind study using the damage tolerance test (DTT). In the DTT, a through-film pinhole defect is created, and the electrochemical characteristics of the defect are then monitored over the next 1 to 7 days while immersed in 0.5 M sodium chloride (NaCl). The results from open-circuit potential, anodic potentiostatic polarization, and electrochemical impedance spectroscopy tests were used to characterize the corrosion behavior of the coating systems. The beachside exposure tests were conducted at the Kennedy Space Center (Kennedy Space Center, Flor...

Exposure-Tolerant Imaging Solution for Cultural Heritage Monitoring

This paper describes a simple and cheap solution specifically designed for monitoring the degradation of thin coatings employed for metal protection. The proposed solution employs a commercial photo camera and a frequency-domain-based approach that is capable of highlighting the surface uniformity changes due to initial corrosion. Even though the proposed solution is specifically designed to monitor the long-time performance of protective coatings employed for the restoration of silver artifacts, it can be successfully used also for assessing the conservation state of other ancient metallic works of art. The proposed solution is made tolerant to exposure changes by using a procedure for sensor nonlinearity identification and correction, does not require a precise lighting control, and employs only free open-source software, so that its overall cost is very low and can be used also by not specifically trained operators.

Coatings and surface treatments for protection against low-velocity erosion-corrosion in fluidized beds

Surface coatings and treatments have been used to reduce material loss of components in bubbling fluidized bed combustors (FBCs). The performance of protective coatings in FBC boilers and laboratory simulations is reviewed. Important coating properties to minimize wastage appear to be high hardness, low oxidation rate, low porosity, high adhesion and sufficient thickness to maintain protection for a long period. Economic considerations and criteria for choosing a suitable coating or treatment are discussed for the different types of bubbling FBC. © 1995.

Coatings and surface treatments for protection against low-velocity erosion-corrosion in fluidized beds

Surface coatings and treatments have been used to reduce material loss of components in bubbling fluidized bed combustors (FBCs). The performance of protective coatings in FBC boilers and laboratory simulations is reviewed. Important coating properties to minimize wastage appear to be high hardness, low oxidation rate, low porosity, high adhesion and sufficient thickness to maintain protection for a long period. Economic considerations and criteria for choosing a suitable coating or treatment are discussed for the different types of bubbling FBC.

Thermal-shock performance of evaporated Al2O3, ZrO2, and laminated cermet coatings in an electric-arc plasma source

Measurements have been made on the thermal stability and performance of protective coatings deposited by plasma-gun techniques on copper with an arc heater.

TESTING OF PROTECTIVE COATINGS FOR METALS PART 2

The first part of this paper described scientific principles and methods for practical applications of electrolytic conductance tests on protective films on metals. This second part shows practical methods and procedures for obtaining and recording laboratory test data on the performance of protective coatings and of plastic tape‐wrap coatings applied to steel pipe as primary protection against corrosion.