Alkyd Coatings Research Articles

Improvement of Corrosion Resistance and Solid Content of Zinc Phosphate Pigmented Alkyd Coating by Methacrylated Cardanol

Two cardanol (CO) derivatives, methacrylated cardanol (MACO) and triethoxysilane functionalized cardanol (TSCO) were investigated as the reactive diluents for a zinc phosphate pigmented alkyd coating. It was found that 5 wt% of MACO or TSCO can reduce the dosage of xylene by ∼ 3 wt% while maintaining the viscosity of the alkyd coating system. TSCO presented a negative influence on the drying time and the pull-off adhesion strength of the alkyd coating; however, the addition of 15 wt% MACO decreased the drying time from 12 h to 8 h and increased the pull-off adhesion strength from ∼ 1.73 to ∼ 2.10 MPa, comparing with the neat alkyd coating (without MACO and TSCO). As evidenced by the salt spray test, the addition of TSCO did not show an enhancement of corrosion resistance for the alkyd coating; however, the alkyd coating containing 15 wt% MACO (labelled as M-15) presented superior corrosion resistance to other coating systems. M-15 and the neat alkyd coating were further characterized by electrochemical impedance spectroscopy (EIS). The results of EIS further demonstrated that the corrosion resistance of M-15 is much better than the neat alkyd coating in the 3.5 wt% NaCl solution immersion. Importantly, M-15 can provide an excellent protection of the steel in the corrosive immersion condition for at least 123 days. The improvement of the overall performance was attributed to the homo-polymerization of the methacrylate moiety in MACO. Taken these results together, MACO is an efficient chemical for formulating high solid alkyd coatings with outstanding corrosion resistance.

Effects of zinc oxide filler on the curing and mechanical response of alkyd coatings

The mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content.

Evaluation of the weathering resistance of waterborne acrylic- and alkyd-based coatings containing HALS, UV absorber, and bark extracts on wood surfaces

In this study, tree bark extracts were assessed as functional additives to provide protection in waterborne acrylic- and alkyd-based coatings. Tree bark extracts acted as natural photostabilizers and inhibited UV degradation with high UV absorption capacity. The coating systems comprising bark extracts were compared to the control coating groups comprising ultraviolet light absorbers (UVA) of the hydroxyphenyl-s-triazine (HPT) for acrylic and nonbasic amino ether (NOR) hindered amine light stabilizers (HALS) for alkyd. Scots pine surfaces coated with acrylic and alkyd coatings were exposed to artificial weathering for 2016 h. Three different trees (maritime pine, alder and Calabrian pine) with high antioxidant activity and phenol content were used for this purpose. The chemical structure of acrylic and alkyd coating systems was also examined using ATR–FTIR spectroscopy. The weathering resistance of coating systems containing extracts was evaluated in terms of their color changes and surface roughness through macroscopic evaluation, and they were compared to commercial UV absorber. The lowest color change was observed in the alkyd-based coatings with the bark extract. For the alkyd coatings, the color change (∆E) in the control samples was 24.85, whereas it was found to be 4.68, 5.92 and 7.80 in the test samples containing Calabrian pine, maritime pine and alder bark, respectively. However, color stabilization of the acrylic coatings with UV absorber was found to be much better than the acrylic coatings with extracts. The alkyd coating systems with extracts did not exhibit the same performance for surface roughness. The alkyd coating with the UV absorber provided a smoother surface than that with bark extracts. The acrylic coatings with alder and maritime extracts provided the best results. Acrylic coating may be compatible with (Calabrian) bark extracts. According to the obtained results, it was seen that tree bark extracts in wood coating systems have a potential to substitute commercial UV absorbers as a natural product.

The Evolution of Catalysis for Alkyd Coatings: Responding to Impending Cobalt Reclassification with Very Active Iron and Manganese Catalysts, Using Polydentate Nitrogen Donor Ligands

Autoxidation processes to achieve curing of alkyd resins in paints, inks, and coatings are ubiquitous in many applications. Cobalt soaps have been employed for these applications for many decades and most of the paint and ink alkyd resin formulations have been optimized to achieve optimal benefits of the cobalt soaps. However, cobalt soaps are under increased scrutiny because of likely reclassification as carcinogenic under REACH (Registration, Evaluation, Authorisation, and Restrictions of Chemicals) legislation in Europe. This is critical, since such coatings are available for regular human contact. Alternative manganese- and iron-based siccatives have been developed to address this need for over a decade. They often show very high curing activity depending on the organic ligands bound to the metal centers. Recently, new classes of catalysts and modes of application have been published or patented to create safe paints, whilst delivering performance benefits via their unique reaction mechanisms. Besides the use of well-defined, preformed catalysts, paint formulations have also been developed with mixtures of metal soaps and ligands that form active species in-situ. The change from Co-soaps to Mn- and Fe-based siccatives meant that important coating issues related to radical-based curing, such as skinning, had to be rethought. In this paper we will review the new catalyst technologies and their performance and modes of action, as well as new compounds developed to provide anti-skinning benefits.

Development of Anti-Aging and Anticorrosive Nanoceria Dispersed Alkyd Coating for Decorative and Industrial Purposes

This study focuses on nano cerium oxide particles as alternative additives in solvent-based alkyd coatings in order to improve anticorrosive and anti-aging properties. The paint samples were formulated with cerium oxide micro and nanoparticles, and the coating quality characteristics were compared with coating formulated with commercial anticorrosive and UV-aging agents. Formulations were prepared with 3 wt % commercial anticorrosive agent as reference material (RP), 3 wt % cerium oxide microparticles (CER1), 3 wt % and 1% cerium oxide nanoparticles (CER2 and CER3), respectively. The basket milling technique with zirconium balls was used for the preparations of coatings and characterizations were performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle measurements. Improvement in the anticorrosive properties was proven with electrochemical impedance spectroscopy (EIS) and accelerated salt spray tests based on ISO 4628 Evaluation of Degradation of Coatings. Furthermore, physical and mechanical tests were run according to standard test methods for coatings and reported. Results showed that cerium oxide particles provide anticorrosive, UV defender, and self-cleaning effects, besides excellent physical resistance to alkyd coatings. The impact of cerium oxide nanoparticles was found to be stronger than those of the microparticles.

Influence of the Surface Chemical Treatment of D16T Alloy on the Protective Properties of Alkyd Coatings

The application of conversion coatings to D16T aluminum alloy significantly increases its corrosion resistance and weakens its subfilm corrosion under a lacquer coating. In the absence of a lacquer layer, the process of chemical oxidation guarantees higher protective properties as compared with chrome phosphatizing. The specimens made of aluminum alloy with alkyd coatings have almost the same corrosion resistance for chrome phosphatized and chemically oxidized surfaces. The protective effect of chrome-phosphatized coatings can be explained by the interaction of the phosphate layer with functional groups of alkyd resin.

Making alkyd greener: Modified cardanol as bio-based reactive diluents for alkyd coating

With the increase in demand for bio-based coatings with lower volatile organic compound (VOC) emissions, methacrylated cardanol (MACO) and triethoxysilane-functionalized cardanol (TSCO) have been investigated as bio-based reactive diluents for formulating alkyd coatings as a substitute for volatile solvents. The viscosity of the representative alkyd resin was significantly reduced through the use of cardanol-based reactive diluents (over 84% diluent efficiency at 30 wt% loading). Both MACO and TSCO were able to participate in the cross-linked network of the alkyd coating as confirmed by the gel content and cross-link density of the cured coating films. Moreover, the cross-link density of the alkyd coating was significantly improved by using TSCO as the reactive diluent, leading to a significant enhancement in mechanical strength and solvent resistance of the alkyd coating. This work will facilitate the adoption of cardanol as a renewable building block in the coating industry in order to produce greener alkyd coatings.

Synthesis and properties of a high solids triethoxysilane-modified alkyd coatings

Alkoxysilane modified linseed oil alkyds (TESLOA) were prepared using 3-(triethoxysilyl)propyl isocyanate (TESPIC). TESLOA was formulated as a high solids coating substituting up to 40% of an unmodified long oil linseed oil alkyd in increments of 10%. All the resulting high solids alkyds had a viscosity below 5000 cP. Toxicity and volatile organic compounds (VOCs) were reduced using an iron based primary drier and VOC-exempt acetone, respectively. An increase in adhesion was observed when TESLOA was used in formulations. The chemical resistance, appearance, and flexibility were examined using standard coating tests. An increase in chemical resistance and hardness was observed, while maintaining the flexibility and appearance. The surface energy was measured using contact angle. The TESLOA surface energy exhibited a hydrophobic shift in terms of surface wetting. The additional crosslinking sites of the TESLOA alkyds were evident in a higher glass transition temperature and crosslink density. Tensile properties also exhibited an increase in modulus. Fracture toughness testing showed up to a 50% increase in stress intensity factor at fracture, KIC, and the elastic energy release rate, GIC, when 20 wt.% of TESLOA in the formulation. Corrosion protection was studied using electrochemical impedance spectroscopy (EIS). The EIS data suggested that some self-healing properties could be obtained when using TESLOA as an additive.

The electrochemical behavior of nanocomposite organic coating based on clay nanotubes filled with green corrosion inhibitor through a vacuum-assisted procedure

In this study, the clay nanotubes were loaded with green corrosion inhibitor obtained from the basil aqueous extract through a vacuum-assisted procedure. The nanocontainers with long-term inhibitive performance were synthesized and introduced to the alkyd coating for corrosion protection of mild steel substrates against the saline solution. The basil loaded halloysite nanotubes (BHNs) were characterized by thermogravimetric analysis, field emission scanning electron microscopy, ultraviolet–visible spectroscopy, X-ray diffraction (XRD), and Fourier transformation infrared spectroscopy analyses. Results showed that the successful loading of basil molecules in the halloysite nanotubes (HNT) was achieved under vacuum condition. Active corrosion inhibition performance of BHNs was investigated by electrochemical and visual tests in saline solution (NaCl 3.5 wt%). The results of electrochemical impedance spectroscopy (EIS) and polarization tests revealed the considerable inhibitive action of the synthesized nanocontainers in 3.5 wt % NaCl solution. Also, scanning electron microscopy, XRD, and energy dispersion spectrometer results confirmed the deposition of a surface inhibitive film on the samples which dipped in the BHNs extract solution. The corrosion inhibition performance of nanocomposite alkyd coatings based on HNTs and BHNs was investigated by EIS and visual tests. The best corrosion resistance was observed in the presence of 0.5 wt % HNTs in the nanocomposite coating. Also, it was found that BHNs significantly improved the corrosion resistance of nanocomposite organic coating over time. The barrier and active performance of BHNs were proposed as the protective mechanism of nanocomposite coating in the presence of the nanocontainers.

Synthesis of melamine formaldehyde cured castor oil based hydroxyl functional alkyd for coating application

The legislation pertaining to air pollution has led the paint and coating industries to develop ways to reduce the volatile organic content (VOC) of the solvent-borne coatings without compromising the film performance and application characteristics. This resulted in the emergence of solvent-free alkyd coatings which are the most potential solutions to reduce environmental problems. In the present work, hydroxyl functional castor alkyd (CA) was synthesized using a solvent-free process and cured with Melamine Formaldehyde (MF) resin. Structures of the formed product were confirmed by Fourier Transform Infrared (FTIR) spectroscopy and 1H and 13C Nuclear Magnetic Resonance (NMR) analysis. Thermal properties of the cured film samples were determined using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis which showed that Tg and degradation temperature values increased as the amount of MF increased. Also, the corrosion performance of the coating films was studied by using a salt spray test which revealed that the best corrosion resistance was shown by 70:30 ratio of MF: CA. All the results including mechanical properties of the coating film showed that the eminent role was played by the MF in the performance of CA.

Mussel-Inspired Self-Healing Coatings Based on Polydopamine-Coated Nanocontainers for Corrosion Protection.

The mussel-inspired properties of dopamine have attracted immense scientific interest for surface modification of nanoparticles due to the high potential of dopamine functional groups to increase the adhesion of nanoparticles to flat surfaces. Here, we report for the first time a novel type of inhibitor-loaded nanocontainer using polydopamine (PDA) as a pH-sensitive gatekeeper for mesoporous silica nanoparticles (MSNs). The encapsulated inhibitor (benzotriazole) was loaded into MSNs at neutral pH, demonstrating fast release in an acidic environment. The self-healing effect of water-borne alkyd coatings doped with nanocontainers was achieved by both on-demand release of benzotriazole during the corrosion process and formation of the complexes between the dopamine functional groups and iron oxides, thus providing dual self-healing protection for the mild steel substrate. The coatings were characterized by electrochemical impedance spectroscopy, visual observations, and confocal Raman microscopy. In all cases, the coatings with embedded benzotriazole-loaded MSNs with PDA-decorated outer surfaces demonstrated superior self-healing effects on the damaged areas. We anticipate that dopamine-based multifunctional gatekeepers can find application potential not only in intelligent self-healing anticorrosive coatings but also in drug delivery, antimicrobial protection, and other fields.

Calcareous scales deposited in the organic coating defects during artificial seawater cathodic protection: Effect of zinc cations

In this work, the effect of Zn2+ cations on the calcareous scales during the cathodic protection of mild steel was studied. The Zn2+ cations were introduced into the epoxy and alkyd coatings in the form of zinc chloride. Also, the influence of Zn2+ cations was investigated in the zinc -rich primer coated mild steel. The study was conducted in the electrolyte and coating phases. In the first stage, pure calcareous scales deposited from artificial seawater (AS) were compared with zinc containing calcareous scales deposited from the zinc containing AS solution. For this purpose, scanning electron microscopy equipped with the energy dispersive spectroscopy and X-ray diffraction analyses were used to characterize the calcareous scales. Also, chronoamperometric, electrochemical impedance spectroscopy, and potentiostatic polarization were conducted to investigate the effect of Zn2+ cations on the calcareous scales. Results indicated that the Zn2+ cations have influenced the calcareous scales through altering calcareous deposited phases and phase proportions. Moreover, according to the electrochemical results, with increase in the Zn2+ cations concentration, an increase in calcareous scales inhibition was observed. In the coating phase, the effect of Zn2+ cations presented in the organic coatings and zinc-rich primer was studied. To evaluate this effect, the coated samples with an artificial defect were exposed to AS. Results showed that the presence of Zn2+ cations in the coatings led to a decrease in the brucite content of the scales and stabilization of the hydrated calcium carbonate phases over aragonite phases. Furthermore, presence of the Zn2+ cations in the form of zinc-rich primer leads to the brucite phase elimination in the calcareous scales.

Iron(II) complex with modified bispidine ligand: Synthesis and catalytic alkyd drying

Modified iron(II) bispidine complex was synthesized and characterized by analytical methods including crystal structure determination on single crystal. Catalytic activity of the title compound toward autoxidation process was established on alkyd resin of long oil length. The standardized mechanical tests as well as kinetic studies, performed on thin layers of alkyd coatings, revealed high activity at considerably lower concentrations than usual for commercial cobalt(II) 2-ethylhexanoate. Due to high solubility in non-polar solvents, title compound is applicable without necessity of pre-dissolution in a polar organic solvent as in case of parent [Fe(bispi)Cl]Cl.

The influence of quantity and nature of bortitan-containing modifier on the properties of the alkyd protective coatings

The influence of quantity and nature of bortitan-containing modifier on the properties of the alkyd protective coatings

Sucrose octaesters as reactive diluents for alkyd coatings

Sucrose octasoyate (SS8) was investigated as a reactive diluent for a medium oil alkyd (MOA). SS8, which is derived from sugar and soybean oil, is 100% biobased, nontoxic, and biodegradable. As a result of its unique molecular architecture, it was expected that SS8 would be an excellent reactive diluent for alkyd coatings. The experiment conducted basically involved the incremental replacement of the MOA with SS8, while maintaining essentially equivalent solution viscosity. The properties of cured coatings were determined using industry standard methods. In general, it was found that SS8 could be used to reduce volatile organic compound content of the coatings, while also reducing drying time (i.e., tack-free time), increasing solvent resistance, and increasing impact resistance. Of the properties measured, the only cured film property that was negatively affected by the use of SS8 was the Konig pendulum hardness. However, the reduction in Konig pendulum hardness was only observed when the amount of MOA replaced by SS8 was greater than 10 wt%. Overall, these initial results suggest that SS8 is a very good reactive diluent for alkyd coatings.

Acrylated Alkyds Synthesized via Quasi‐Living Radical Polymerization: ATRP and RAFT

AbstractA new method for the synthesis of autoxidatively curable acrylated alkyds is demonstrated. Acrylic block is grafted onto the backbone of the alkyd chain via atom transfer radical polymerization (ATRP) polymerization. The acrylated ATRP copolymers are compared to RAFT copolymer and both are characterized using quantitative 1H NMR, 13C NMR, and 2D‐NMR spectroscopy. In particular, the autoxidative curing of ATRP polymerized acrylated alkyd is compared to the RAFT polymerized acrylated alkyds using Fourier transform infrared spectroscopy (FTIR) spectroscopy. The analysis finds that the autoxidation of the RAFT acrylated alkyds is inhibited. It is postulated that the thiocarbonyl functionality hinders the autoxidative reactions. The performance of autoxidatively cured ATRP polymerized acrylated alkyd coatings is evaluated using tensile, viscoelastic, and general coating properties. Alkyd‐acrylic copolymer coatings show improved hardness, glass transition temperature, and drying time. General coating properties such as cross‐hatch adhesion, methyl ethyl ketone (MEK) resistance, and impact resistance are maintained except at higher acrylic concentrations.

Exploring the corrosion inhibition of aluminium by coatings formulated with calcium exchange bentonite

Enviromentally friendly calcium-exchange derived from naturally occurring sodium-bentonite clays (Wyoming) are shown to significantly enhance resistance to corrosion protection in organic coatings applied on aluminium under aggressive environment typical from industrial areas. Two pigments classified as ion-exchange were also studied for comparison (Shieldex® and Al-Zn-vanadate hydrotalcite) together with zinc chromate as reference corrosion protection pigment. Electrochemical impedance spectroscopy (EIS) is used to study the corrosion protection in the metal/coating interface of pigmented alkyd coatings and a blank coating (without corrosion inhibitor pigment) in combination with visual inspection. The protection performance of these specimens was studied using outdoor exposure (two atmospheres with different aggressiveness) and accelerated tests (condensing humidity, salt spray and Kesternich tests, respectively). Results have shown strong dependence of the coating performance with the aggressive environment (e.g. Cl−, H+, SO2) for all coatings formulated with ion-exchange pigments. The corrosion protection of the underlying aluminium substrate provided by calcium-exchange bentonite coating was shown under the presence of cationic aggressive agents in accelerated corrosion tests (specifically in Kesternich test). However, poor performance was observed for this coating using chlorides as an aggressive agent. Therefore, the presence of bentonite pigment improves the corrosion protection due to the cation-exchange mechanism.

Influence of polyaniline/multiwalled carbon nanotube composites on alkyd coatings against the corrosion of carbon steel alloy

AbstractPolyaniline (PANI) and its composites with multiwalled carbon nanotubes (MWCNTs) were synthesized by chemical oxidative polymerization. High-resolution transmission electron microscopy (HR-TEM), thermogravimetric analysis (TGA), and Raman spectroscopy were used to characterize the investigated compounds. The synthesized composite is formulated as pigments in alkyd resin with different pigment-binder (P/B) ratios and investigated as anticorrosive coatings on carbon steel in 1mHCl using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The protection mechanism of PANI occurred through the barrier and passivation effect on the carbon steel surface. The encapsulation and dispersion of MWCNTs into the PANI matrix promoted the anticorrosive efficiency of the alkyd coating.

The influence of calcium and zirconium based secondary driers on drying solvent borne alkyd coatings

Cobalt based driers are the most commonly used primary catalysts in alkyd coatings as they promote fast drying and lead to hard coatings. However, several studies have suggested potential reclassification of cobalt-based alkyd driers. Therefore, cobalt based driers are being replaced by alternatives, e.g. based on iron or manganese. In practice primary driers (Co, Mn, or Fe) are used in combination with secondary driers (e.g. Ca, Zr) to enhance drying of the film. Coating formulators aim for a high drying speed and hardness development. However, each combination of primary and secondary driers leads to a different oxidative drying pattern resulting in variations in the crosslink density and hardness development. In this study we have systematically investigated the effect of two secondary driers, Calcium (Ca) and Zirconium (Zr), on curing behavior when added to different primary driers (Co, Mn, and Fe) using a high spatial resolution NMR set-up. As expected, we observed increased drying speed and higher crosslink densities when adding these secondary driers. While calcium showed to promote the front speed, zirconium showed to increase the measured crosslink density. The behavior seems to be generic as this was seen for all three the primary driers.

Preparation and transparent heat insulating properties of aqueous acrylic–amino–alkyd coatings with CuS nanoplates

A novel aqueous transparent heat insulation coating (C–X–Y) with CuS nanoplates as solar heat insulating functional nanomaterial and acrylic-amino-alkyd baking varnish (AAA) as coating-forming material was prepared. The C–X–Y coating was applied to the surface of ordinary glass substrates. Those C–X–Y coated glass substrates have good transparency in the visible region (390–780 nm) and strong absorption in the near-infrared region (780–1750 nm). For instance, a 150 μm-thick C–X–Y coating with 1.0 wt% CuS nanoplates (C–1.0–150) can transmit 60% visible light and shield 80% near-infrared light. The stable temperature inside the box covered with the C–X–Y coating C–1.0–150 was 12.0 °C lower than that with the reference coating (without nano-CuS) under the irradiation of a 250 W infrared lamp. Based on their special characteristics, such as selective transparency in the visible region and selective shielding in the near-infrared region of solar light, the CuS nanoplates based transparent heat insulation coatings might have a potential application in architectures and vehicles for energy saving and environmental protection due to the unique optoelectronic properties of the CuS nanoplates.