Epoxy Powder Coatings Research Articles

Weathering effect on the wear performance of epoxy powder coatings reinforced with calcium ion-exchanged amorphous silica

Epoxy coatings generally have poor performance when used for exterior applications. After having studied the corrosion benefits obtained with calcium ion-exchanged amorphous silica pigments, the possible weathering advantages they may provide to powder coatings are analyzed in this work for the first time. For that purpose, five epoxy-based powder coatings were studied: the as-received coating (AR), and four epoxy subjected to a hot mixing process with different amounts by weight of silica anticorrosive micropigments (0 %, 1, 2 and 3 %). All epoxy coatings were degraded by ultraviolet radiation with a xenon lamp for 250 h to determine their weathering resistance. The damage suffered by each coating was evaluated quantifying their FTIR spectra, considering the carbonyls and hydroxyls formed during this type of degradation. Subsequently, studies of plastic universal hardness and abrasive and erosive wear were carried out. The results obtained show that these functionalized coatings have better mechanical and wear performance than the commercial coating after xenon light exposure. This is coherent with the fact that the non-reinforced coatings have the greatest degradation both by hydrolysis and photodegradation. After the weathering process carried out, the 3 % coating proves to have the best abrasive and erosive wear performances. Thus, the calcium ion-exchanged silica particles allow the service life of UV exposed epoxy powder coating to be extended, not only because of their anti-corrosive character but also because of their weathering stabilization properties. These findings represent a significant advancement in improving the durability of epoxy powder coatings for exterior applications.

Synthesizing a novel cerium-modified graphene powder to achieve long-term anticorrosion performance of epoxy powder coatings

Synthesizing a novel cerium-modified graphene powder to achieve long-term anticorrosion performance of epoxy powder coatings

Synthesizing a novel cerium-modified graphene powder to achieve long-term anticorrosion performance of epoxy powder coatings

Graphene with extremely large specific surface area possesses great loading capacity for various kinds of corrosion inhibitors to obtain long-term anticorrosion properties. In this study, the corrosion inhibitor cerium nitrate was employed to modify graphene on which the cerium species were loaded. The as-synthesized cerium-modified graphene (Ce-Gr) was introduced into epoxy powder coating to provide long-effective corrosion protection on steel. X-ray photoelectron spectroscopy (XPS) analysis implies that cerium species were successfully loaded on graphene in the form of cerium nitrate and cerium oxide. Scanning electron microscopy (SEM) observation exhibited that Ce-Gr improved structural density and reduced the porosity in coating matrix. Electrochemical measurements demonstrated incredibly high impedance values of 1010.5 Ω cm2 for the epoxy powder coatings containing Ce-Gr after immersion in 3.5% NaCl solution for 45 days. Additionally, the smallest average corrosion propagation width of only 0.60 mm on the substrate at scratch after salt spray test, the shorter cathodic disbondment diameter of 3.49 mm and the fewest corrosion oxidation products with extremely low oxygen content of 3 wt% on substrate after salt solution immersion for 120 days implied that the coating with the addition of 0.05 wt% Ce-Gr possessed the most effective corrosion inhibition property to protect the steel substrate for a long period.

Preparation and anticorrosion performance of graphene-reinforced epoxy powder coating

Existing studies have reported that graphene can enhance the corrosion resistance of solvent-based organic coatings. However, the role of graphene in organic powder coatings remains to be obscure. In the present study, the graphene powder was prepared through liquid-phase exfoliation of graphite followed by freeze drying and the effects of graphene on structures, anticorrosion performance and adhesion strength of epoxy powder coatings were investigated. Scanning electron microscopy (SEM) demonstrated that graphene reduced surface micropores and enhanced structural compactness of the epoxy powder coatings. Electrochemical impedance spectra, Tafel polarization measurement and salt spray test indicated that a small amount (0.0125, 0.025 and 0.05 wt%) of well-dispersed graphene powder would be sufficient to effectively reinforce the anticorrosion performance of the epoxy powder coatings, especially for the coating with 0.025 wt% graphene, of which the impedance modulus maintained the highest values of nearly 107 and 105.8 Ω cm2 after immersion in 3.5 % NaCl solution for 21 and 30 days. Pull-off test confirmed that graphene enhanced the adhesion strength of coatings after salt spray test for 240 h, while the coating with 0.025 wt% graphene exhibited the highest adhesion strength up to 3.88 MPa. In addition, differential scanning calorimetry (DSC) indicated that graphene sheets could improve the thermal conductivity and promote curing reactions of epoxy powder. The mechanism for the reinforcement of epoxy powder coating by graphene has also been proposed.

Toward high glass-transition temperatures in epoxy powder coatings based on BTDA®

Toward high glass-transition temperatures in epoxy powder coatings based on BTDA®

Effect of GO and diamond wax on morphology and properties of epoxy powder coatings

Effect of GO and diamond wax on morphology and properties of epoxy powder coatings

Unique catalyst for low temperature cure epoxy powder coatings

Unique catalyst for low temperature cure epoxy powder coatings

Rubber-Composite-Nanoparticle-Modified Epoxy Powder Coatings with Low Curing Temperature and High Toughness.

In this study, a rubber-composite-nanoparticle-modified epoxy powder composite coating with low curing temperature and high toughness was successfully fabricated. The effects of N,N-dimethylhexadecylamine (DMA) carboxy-terminated nitrile rubber (CNBR) composite nanoparticles on the microstructure, curing behavior, and mechanical properties of epoxy-powder coating were systematically investigated. SEM and TEM analysis revealed a uniform dispersion of DMA-CNBR in the epoxy-powder coating, with average diameter of 100 nm. The curing temperature of the epoxy-composite coatings had reduced almost 19.1% with the addition of 1phr DMA-4CNBR into the coating. Impact strength tests confirmed that DMA-CNBR-modified epoxy-composite coatings showed significant improvements compared with the neat EP coating, which was potentially attributed to the nanoscale dispersion of DMA-CNBR particles in epoxy coatings and their role in triggering microcracks. Other mechanical properties, including adhesion and cupping values, were improved in the same manner. In addition, thermal and surface properties were also studied. The prepared epoxy composite powder coating with the combination of low curing temperature and high toughness broadened the application range of the epoxy coatings.

The effect of additions of anticorrosive pigments on the cathodic delamination and wear resistance of an epoxy powder coating

The cathodic delamination and wear resistance of epoxy powder coatings were evaluated after adding 3 % (by wt.) of calcium ion exchanged micropigments from amorphous synthetic silica. The materials were manufactured through the innovative and economical hot mixing method, and three different coatings were considered: commercial epoxy, epoxy without micropigments submitted to the hot mixing treatment, and epoxy with micropigments. The curing kinetics of the powder coatings was studied in order to evaluate the possible effects of the micropigments on the epoxy, using differential scanning calorimetry (DSC). In addition, mechanical properties of coatings (hardness and scratch resistance) and their wear resistance (reciprocal tribometer tests) were assessed. After provoking a controlled mechanical failure in the coatings, their delamination resistance was analyzed by scanning Kelvin probe (SKP). The delamination front was calculated after adding a drop of 3.5 % NaCl solution and taking measurements for 26 days. The results show that the corrosion attack progresses through a cathodic delamination mechanism. The addition of corrosion inhibitors in epoxy powder coatings has not only allowed a considerable improvement in delamination resistance, but has also led to greater mechanical and wear resistance. At the same time, it has simultaneously reduced the chances for mechanical failure of the coating and decreased the progression rate of damage, if it occurs. The study has also been completed with electrochemical impedance spectroscopy and polarization measured of fully-immersed defective coatings in 3.5 % NaCl.

Graphene-reinforced epoxy powder coating to achieve high performance wear and corrosion resistance

The corrosion and wear resistance of organic coatings are the key factors to maintain their good function. Graphene-based polymer composites have attracted incredible attention owing to their superior physicochemical properties than polymers. In this study, the effect of graphene nanosheet (G) additives on the microstructure, adhesion behaviors, anti-wear performance and corrosion resistant of epoxy powder coatings (EP) were systematically investigated. Field emission scanning electron microscope (FESEM) results verified that the mild addition of G could enhance the compactness of EP and reduced microstructure defects such as cracks, cavities, and voids. The adhesion and tribological results confirmed that the graphene-contained epoxy powder composite coatings (G/EP) could demonstrate significant improvement compared to the EP, which potentially attributed to the high mechanical and self-lubrication properties of G nanoflakes. In particular, the electrochemical and salt spray evaluation revealed that the enhanced physical barrier protection performance and outstanding anti-corrosion capacity of the G/EP composite coating containing 0.4 wt% G. The current study provides a promising metal protection strategy for the development of graphene-enhanced organic powder coatings applied in mechanical-corrosion coupling environments. This article reveals for the first time that graphene nanosheets enhance the interfacial adhesion strength of organic powder coatings, as well as the effect on wear and electrochemical performance.

Developing multi-wall carbon nanotubes/Fusion-bonded epoxy powder nanocomposite coatings with superior anti-corrosion and mechanical properties

The aim of the study is to achieve homogeneous dispersion quality of multi-wall carbon nanotubes (MWCNTs) within fusion-bonded epoxy (abbreviate FBE) powder coatings by co-processing methods of the ball milling and hot melt extrusion. The surface of the MWCNTs is modified with polyvinylpyrrolidone (m-MWCNTs) before utilization as nanofiller in the FBE powder coatings. The structure and morphology of the MWCNTs and m-MWCNTs are investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. The dispersion quality of the m-MWCNTs in the epoxy coatings is evaluated by scanning electron microscopy. The corrosion resistance and mechanical properties of the FBE powder coatings containing various amounts of m-MWCNTs are studied by salt spray, electrochemical impedance spectroscopy, and pull-off adhesion tests. The results indicate that the corrosion resistance and the adhesion strength of the nanocomposite coating have improved by adding 0.2 wt% m-MWCNTs. The uniform dispersion of the nanofiller as well as increasing the pathway of the corrosive electrolytes into the coating matrix are the main reasons of improving the coating resistance. The tensile strength of the nanocomposite coating has improved by almost 53.7% through loading 0.2 wt% m-MWCNTs into the coating. The enhanced tensile strength indicates that the load-transfer has enhanced due to the better interfacial bonding. The results of this paper reveal that the combination of ball milling with hot melt extrusion is a promising approach for preparing nanocomposite powder coatings with enhanced corrosion resistance, mechanical performance, and thermal properties.

Hindering the decrease in wear resistance of UV-exposed epoxy powder coatings by adding nano-SiO2

Hindering the decrease in wear resistance of UV-exposed epoxy powder coatings by adding nano-SiO2

Thermal properties and curing kinetics of epoxy powder coatings containing graphene nanoplatelets

Thermal properties and curing kinetics of epoxy powder coatings containing graphene nanoplatelets

Hindering the decrease in wear resistance of UV-exposed epoxy powder coatings by adding nano-SiO2 through ball milling

The wear resistance of organic coatings has an important role in order to extend their in-service life. Epoxy powder coatings were mixed with nanosilica through ball milling to study their effect on the wear performance after ultraviolet (UV) exposure. Two types of SiO2 nanoparticles were added: hydrophilic (HL) and hydrophobic (HB) at different percentages (0.25–1% by wt.). Modified powders were applied by electrostatic spraying gun on carbon steel sheets. After curing, coatings were exposed to a xenon lamp for 500 h. The surface of coatings was analyzed by scanning electron microscope (SEM). Reciprocating sliding wear tests were performed at room temperature and dry conditions, under 5 N load and 10 Hz frequency. The countermaterial was a 6 mm-stainless steel ball. Wear tracks were analyzed by an optoelectronic microscope and SEM. In order to analyze possible chemical changes, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was performed. Finally, universal hardness was evaluated to study mechanical properties. Results reveal that small amounts of both types of nanosilica, make the epoxy-matrix coatings chemically degrade less than non-reinforced ones under irradiation, increasing their mechanical behavior and thus wear resistance. The 0.75-1HL and the 0.75HB coatings exhibit the best wear performance after UV exposure.

Anhydride-Cured Epoxy Powder Coatings from Natural-Origin Resins, Hardeners, and Fillers

Carbon-neutral policy and technological race on the powder coatings market force to develop more advanced, safer, cheaper, and naturally sourced products. To meet the market needs, powder coating compositions and coatings were prepared from safe and natural-origin hardeners, resins, and fillers prepared from rosin, bio-diols, bio-epichlorohydrin, and halloysite, to investigate their thermal, mechanical, and functional properties in comparison with petroleum-based references: cross-linking behavior, glass transition temperature, thermal stability, hardness, cupping resistance, adhesion, chemical resistance, gloss, color, and anti-corrosive behavior in salt chamber. As a result, compositions containing up to 83 wt.% of natural resources, and showing comparable or better properties, as compared to references, were successfully prepared. Their application includes binders for future ecological powder paints for demanding protection of steel substrates.

Analysis of Wear and Strength Behaviour of SiO2 Nanoparticles Mixed in Epoxy Powder Coating on Mild Steel Material

Analysis of Wear and Strength Behaviour of SiO2 Nanoparticles Mixed in Epoxy Powder Coating on Mild Steel Material

Performance of ultraviolet exposed epoxy powder coatings functionalized with silica by hot mixing

The effect of hydrophilic nanosilica additions on the (1–3% by wt.) mechanical performance of epoxy powder coatings after UV exposure was investigated in this study. The epoxy coatings were prepared by mixing a commercial epoxy powder with nanoparticles in a hot mixer, an alternative method that is simpler than extrusion. Powders were electrostatically applied on carbon steel and cured to obtain coatings. The epoxy-based coatings were exposed to a xenon lamp with an irradiance of 550 W·m−2 for 500 h. Chemical structure of coatings was characterized before and after xenon exposure, using an attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Glass transition temperature (Tg) was measured with differential scanning calorimetry (DSC). Mechanical and wear tests were performed in order to study the difference among the coatings without and with silica nanoparticles after UV exposure. Surface of the coatings was analyzed with scanning electron microscopy (SEM), as well as the wear tracks to assess the wear mechanism. Finally, aesthetic properties (gloss and color) were also evaluated. The results confirm that the use of SiO2 nanoparticles in amounts up to 2% allows less chemical and physical degradation of the surfaces and better wear resistance than the plain epoxy coatings after xenon exposure was found for 1% coating.

Corrosion Protection in Chloride Environments of Nanosilica Containing Epoxy Powder Coatings with Defects

This paper describes the use of innovative, nanosilica containing epoxy powder coatings for the corrosion protection of steel. Two types of nanosilica particles (hydrophilic -HL- and hydrophobic -HB-) were mixed by ball milling with the powders (0.75 wt.%). The adequate homogeneity and embedding of nanoparticles were verified by transmission electron microscopy. The corrosion performance of the coatings as-received, and with HL and HB additions, were analyzed in 3.5 wt.% NaCl solutions. The mechanism and rate of delamination of defective coatings under drops simulating atmospheric conditions were analyzed by Scanning Kelvin Probe measurements for 30 d. The results show that the corrosion attack progresses through a cathodic delamination mechanism. Besides, fully-immersed samples, with and without defects, were monitored by electrochemical impedance spectroscopy. In defective coatings under these conditions, the occurrence of anodic undermining is proved. The results obtained reveal that the corrosion driven coating failure is delayed in the case of the epoxy coatings containing nanosilica. This delay is larger in the case of HB additions than HL additions in both atmospheric and immersion conditions. The corrosion mechanism observed is dependent upon exposure conditions. It is proposed that the nanoparticles delay water absorption, thus delaying corrosion attack.

Functionalizing organic powder coatings with nanoparticles through ball milling for wear applications

Epoxy powder coatings were functionalized with nanosilica to improve wear resistance. Ten different organic coatings were studied: 0.25–1% (by wt.) of SiO2 nanoparticles (both hydrophilic -HL- and hydrophilic -HB-) were added to epoxy powders. The homogeneity of the distribution of the silica nanoparticles in the epoxy powder matrix was achieved with an innovative ball-milling mixing method. This homogeneity was confirmed through transmission electron microscopy (TEM) observations. Powder coatings were sprayed and cured on steel sheets. The wear resistance of the coatings was evaluated in reciprocating wear equipment, measuring the depth and the width of the wear tracks obtained by an optoelectronic microscopy. Results reveal very significant improvement in wear resistance, with the best wear performance being observed for the epoxy reinforced with 0.75%HB SiO2 nanoparticles. This is related to the enhanced crosslinking of the matrix in the coatings due to SiO2, as shown by the mechanical properties. The curing kinetics of the functionalized epoxy powders was studied by non-isothermal differential scanning calorimetry (DSC). Activation energies (Ea) calculated from DSC are related to in the diffusion-controlled reactions.

Influence of cathodic polarization on the properties of epoxy powder coatings

The article discusses the effect of cathode polarization on the protective properties of powder epoxy coatings, assesses their operational reliability, statistics of failures and describes the problems found during their operation. In the process of applying commercially available pipes with epoxy powder coating on the existing gas pipeline, a not previously manifested defect was observed - the formation of dome-shaped swellings. This led to some restrictions on the use of epoxy powder coatings. With the advent of a new generation of epoxy materials, as well as in connection with the revision of the regulatory documentation GOST R 51164-98, the issue of removing these restrictions on their use for insulating large diameter pipes (up to 1,420 mm). Without additional protection has become topical. As a result, it became necessary to estimate the probability of the appearance of defects of this type when using modern powder coatings. We carried out laboratory studies of the effect of cathode polarization on the properties of modern two-layer epoxy coatings after exposure to them of shock loads of a certain size. The results indicate that the impact of such a mechanical load may cause the appearance of microdefects of the coating, which are not determined by the existing methods of control. Due to the penetration of electrolyte under the coating and the occurrence of certain physicochemical and electrochemical processes that are enhanced by imposing the potential of cathodic protection and increasing the operating temperature, these microdamages can serve as active centers for the formation of a cupola-shaped swelling.