Performance evaluation of alkyd coatings for corrosion protection in urban and industrial environments

The performance of alkyd based coatings exposed in two different sites in Ecuador, urban and industrial locations, for corrosion protection was evaluated. Atmospheric test sites and corrosion resistance of coatings were examined using mainly ISO and ASTM standards. The alkyd resin degradation was characterized by different methods such as FTIR-ATR, DSC, TGA and SEM.     

Thermal,hydrolytic, anticorrosive,and tribological properties of alkyd‐silicone hyperbranched resins with high solid content

Novel alkyd hyperbranched resins (AHBRs) modified with a Z‐6018 silicone (a polysiloxane intermediate) and with high solid content were synthesized by etherification reaction using an acid catalyst. Different molar ratios of AHBR to silicone were used. Structural, thermal, hydrolytic, anticorrosive, and tribological properties were studied using infrared (IR) analysis, nuclear magnetic resonance (NMR), vapor pressure osmometry (VPO), thermogravimetric analysis (TGA), acid value, electrochemical impedance spectroscopy (EIS), and pin‐on‐disk friction. IR and NMR provide evidence of grafting of the silicone on AHBR; the efficiency of grafting was quantified by TGA. Thermal stability was studied also by acid value analysis. Grafting increases the number average molecular mass, enhances thermal stability, and improves significantly hydrolytic stability. Corrosion resistance on steel is improved by two orders of magnitude, hence our modified materials can be used as highly effective anticorrosion coatings. Grafting lowers dynamic friction dramatically, more so at higher concentrations of silicone. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study of degradation of organic coatings in seawater by using EIS and AFM methods

In this article, electrochemical behaviors and their topography observation for four organic coatings used in seawater, by using both electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) methods to study environment behaviors of different coatings as well as the effects of their film formation, pigments, and fillers on anticorrosion behaviors, were measured. The results show that polyurethane, epoxy, and chlorinated rubber coatings all present one capacitive loop in their tested EIS which contains phenomenally only one time constant, whereas alkyd coating presents two capacitive semicircle arcs. With two capacitive loops, the capacitive semicircle in the high frequency range represents barrier layer property, but the semicircle in the low frequency range represents corrosion reaction of metals under the film. Polyurethane coating used in seawater has well anticorrosion property in seawater immersion test. The appearance features of different layers are visible different between different layers of tested coatings at their surface topography. The property of polyurethane paint film coated on metal is better than other layers, and film of alkyd coating has many pits at its surface by observing the layer's images. AFM photos imaged have also been used to further detail surface topography for four organic coatings, and to approve effects of topography of these coatings on its electrochemical behaviors, from two views of both height and phase modes. It is beneficial to explain deeply the environment behaviors and degradation mechanism of organic coatings. To further study failure of these organic coatings and dynamic processes of corrosion of metal under the film, two equivalent circuit models, according to these tested EIS, have been suggested to explain the corrosive kinetics of these four coatings. To polyurethane, epoxy, and chlorinated rubber coatings used in seawater which have good protection effects for substrate metal, the diffusion process for water, from their layer's surface to interface of film/metal, is mainly controlled factor for degradation. However, the electrochemical reaction process has may become a control procedure for corrosion of alkyd coated metal. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

磺化聚苯胺/硅树脂涂层的制备及防腐蚀性能

分别以十二烷基硫酸钠(SDS)和木质素磺酸钠(LGS)为掺杂剂,通过化学氧化法合成了两种磺化聚苯胺(PANI-SDS和PANI-LGS),并将合成的磺化PANI混入溶胶-凝胶法制备的硅树脂(SiR)中,刷涂在Q235钢表面制备了复合防腐蚀涂层。采用FTIR表征了磺化PANI的结构;对比了PANI-LGS和PANI-SDS的基本性能,考察了SiR、PANI-SDS/SiR和PANI-LGS/SiR复合涂层的耐水性、附着力、机械性能及防腐蚀性能,并分析了复合涂层的防腐蚀机理。结果表明:制备的PANI-LGS/SiR复合涂层疏水性能较好,接触角达到113.0°,吸水率仅为7.58%。电化学测试结果表明,该复合涂层对Q235钢具有良好的防腐蚀性能,腐蚀速率为5.56×10~(-3) mm/a,复合涂层是通过物理屏蔽和阳极保护作用实现对金属的腐蚀防护。     

Design and synthesis of bio-based epoxidized alkyd resin for anti-corrosive coating application

Alkyd resins with long aliphatic chain in their backbone are not suitable for high-performance applications. To overcome this limitation of alkyd resins, their backbone structure is usually chemically modified. In this study, an alkyd resin was successfully synthesized from renewable resources, including itaconic acid and linseed oil. Subsequently, the unsaturated backbone of the alkyd resin was converted to oxirane ring through epoxidation reaction in the presence of hydrogen peroxide and acetic acid. The epoxidized alkyd (EA) resin backbone was modified with various amounts of 3-amino propyltrimethoxysilane (APTMS) from 10 to 40 mol percent to enhance the anti-corrosive properties of coatings prepared from the alkyd resins. The structural elucidation of synthesized resins was described by physicochemical analysis and Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The EA resin and APTMS-modified EA resin were cured by itaconic acid in 1:1 stoichiometric ratio on the equivalent weight basis. The differential scanning calorimetric and thermogravimetric analysis results showed that thermal properties improved with increasing APTMS content. The cured coatings were characterized for their mechanical properties, chemical and solvent resistance, gel content, and water absorption. The corrosion-resistance performance of coatings was evaluated by electrochemical impedance spectroscopy and salt-spray test. It was observed that the highly cross-linked structure of the APTMS-modified EA coatings enhanced the corrosion protective property of coating films.     

A novel composite protective coating with UV and corrosion resistance: Load floating and self-cleaning performance

The research in functional materials has been the focus in studying industrial applications, particularly in the field of superhydrophobic functional bionic material. Although many studies of superhydrophobic surfaces have been published at this stage, the performance remain unsatisfactory, especially in a variety of harsh environments in practical applications, such as extremely cold weather, acidic or alkaline environment, prolonged exposure to light, high temperature, or oily wastewater, etc. The mechanical strength and corrosion resistance of coatings in such environments are all mighty challenges. In this study, we propose a fluoro silane-modified zinc oxide (FAS-ZnO) as a nano-filler. A superhydrophobic and oleophobic composite coating was successfully prepared through a single step by spraying suspensions containing attapulgite (ATP), FAS-ZnO, and carboxylated polyphenylene sulfide (PPS–COOH) onto desired substrates. In addition, stearic acid was added as a binder and used to enhance the bonding strength between the filler and the substrate. The composite coatings were characterized by FE-SEM, XRD and FT-IR on substrates, and the corrosion resistance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray chamber experiments. The composite coatings showed excellent corrosion resistance due to the synergistic effect of FAS-ZnO and ATP. It was found that the composite coating had good hydrophobic and oleophobic contact angles of 161 ± 1.5° and 159 ± 1°, respectively, which were mainly attributed to the construction of nano-scale structures. It is worth noting that the composite coating performed excellently in chemical stability, self-cleaning performance, UV resistance, anti-fouling function, mechanical strength, and load-bearing floating ability. The coating maintained its highly hydrophobic surface after being stretched through a universal testing machine. Based on the multiple key properties in the composite coating, it can be expected to be applied to large equipment and instrument surfaces in extreme outdoor environments.     

常温干防腐蚀涂料系用水性树脂

简述了水性丙烯酸乳液、水性醇酸乳液和水性双组分环氧树脂在水性防腐蚀涂料中的应用，并进行了耐湿热性能和耐盐雾性能的比较。     

Room-temperature cured hydrophobic epoxy/graphene composites as corrosion inhibitor for cold-rolled steel

Nanocasting was used to develop epoxy/graphene composites (EGCs) as corrosion inhibitors with hydrophobic surfaces (HEGC). The contact angle of water droplets on a sample surface can be increased from ∼82° (epoxy surface) to ∼127° (hydrophobic epoxy and EGC). It should be noted that EGC coating was found to provide an excellent corrosion protection effect on cold-rolled steel (CRS) electrode. Enhancement of corrosion protection using EGC coatings could be attributed to the following three reasons: (1) epoxy could act as a physical barrier coating, (2) the hydrophobicity repelled the moisture and further reduced the water/corrosive media adsorption on the epoxy surface, preventing the underlying metals from corrosion attack, and (3) the well-dispersed graphene nanosheets (GNSs) embedded in HEGC matrix could prevent corrosion owing to a relatively higher aspect ratio than clay platelets, which enhances the oxygen barrier property of HEGC.     

Fabrication and cytotoxicity assessment of novel polysiloxane/bioactive glass films for biomedical applications

This work evaluates for the first time the cyto-compatibility of silicone (polysiloxane)/bioactive glass composite films produced by dip coating on stainless steel substrates using osteoblast-like (MG-63) cells. With the aim of creating corrosion resistant coatings for biomedical applications, bioactive glass (BG) of 45S5 composition was used as a filler in conjunction with commercial silicones (MK and H62C). Bioactive glass has the property of forming a direct bond to living bone, and polysiloxane is an attractive candidate for protective coatings due to its resistance to oxidation and corrosion. Suspensions based on polysiloxanes (MK/H62C) and micro-sized BG fillers were used for dip coating stainless steel substrates at room temperature, followed by curing in oxidative atmosphere at 260 °C and 500 °C. Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of Si–O–Si, Si–OR, Si–CH₃ and Si–OH groups on the substrate. Field emission scanning electron microscopy showed that the coatings were homogeneous with no obvious cracks or pinholes at relatively high concentrations of both polysiloxane and BG. The cell biology experiments confirmed that the expressed cell-morphology, analyzed on chosen surfaces, was pheno-typical for MG-63 cells after 48 h of incubation. On the film containing the lower amount of polysiloxane/BG the most dense cell layer was formed. Our results indicated that polysiloxane/BG composite films exhibited good cyto-compatibility at 260 °C and 500 °C and showed no toxicity toward MG-63 cells suggesting the potential of this composite for applications in medical implants.     

Elucidation of corrosion failure mechanisms of coated phosphated steel substrates

Coatings are commonly believed to protect metal surfaces from corrosion based on some combination of their barrier properties and electrochemical properties. Various physical and electrochemical tests were performed on seven different coatings (latex, alkyd, 2-PK epoxy, and electrocoat) to determine which properties were the main determinants of corrosion resistance in continuous and cyclic corrosion tests. Physical property tests and AC electrochemical tests were all related to barrier behavior, while DC electrochemical tests were related to electrochemical behavior. DC electrochemical properties are commonly associated with inhibitor chemistry, but can be broadly related to all components of the paint. These test results were compared with corrosion test results from both continuous (B-117) and cyclic (GM9540) accelerated tests. The best correlation was seen with a model emphasizing barrier behavior with a secondary component relating to electrochemical protection. Presented at 2007 FutureCoat! Conference, sponsored by Federation of Societies for Coatings Technology, October 3–5, 2007, in Toronto, Ont., Canada.     

Investigation of the corrosion resistance characteristics of pigments in alkyd coatings on steel

Pigments are added to polymeric coatings for enhancing the protective characteristics of the barrier films that are deposited on metal surfaces to prevent corrosion. Electrochemical impedance spectroscopy (EIS) measurements were performed on carbon steel specimens coated with alkyd primers containing different pigments. Corrosion monitoring was carried out in immersion tests in 3.0 wt.% NaCl solution open to air at room temperature. Changes in the impedance characteristics of the systems were found to occur as a function of the exposure time in all the cases, though their evolution with time showed marked differences which derived directly from nature of the pigments contained in the alkyd primers. The impedance response of the coatings was found to correspond to a porous film presenting localized electrochemically reactive areas, though pigments may facilitate additional resistance to the protective film, the extent of which was found to depend on the nature of the pigment. In this way, the best results were found for the alkyd primer containing aluminium powder.     

Pyrrole-based silane primer for corrosion protection of commercial Al alloys. Part II. Corrosion performance in neutral NaCl solution

A chromate-free, direct-to-metal treatment using pyrrole-based silane (PySi) was developed for protection against corrosion of as-received commercial Al alloys, following the typical procedure for silane deposition. The protection performance of composite PPySi films, containing polysiloxane linkages and polypyrrole units, was evaluated in near neutral NaCl solution by simple corrosion tests such as single-cycle anodic polarization, corrosion potential monitoring and long-term immersion experiments. Control coatings of polymethylsiloxane (PMeSi) and electrochemically synthesized polypyrrole (Ppy) were also studied. The superior performance of PPySi with respect to PMeSi and Ppy was attributed to highly crosslinked, well-packed and adherent composite films of thickness of the order of microns, manifesting both barrier action and active protection. The use of pyrrole-based silane for corrosion protection of Al alloys constitutes a promising approach for effective replacement of chromium-based treatments in practical applications. Further investigation from the fundamental point of view is deserved.     

Study of epoxy and alkyd coatings modified with emeraldine base form of polyaniline

In this work we examine the ability of the emeraldine base form of polyaniline to impart protection against corrosion when it is used as additive of commercial paints. For this purpose, three paints, which are used as primers in marine environments, were checked: two epoxy coatings that differ in the presence or absence of inorganic anticorrosive pigment (zinc) and one alkyd coating. In a first stage, the rheological, structural, thermal and mechanical properties of the three coatings were characterized using viscosity measurements, infrared spectroscopy, thermogravimetric analyses and stress–strain assays, respectively. Furthermore, we observed that the resulting properties were not altered by the addition of a low concentration of polyaniline (0.3%, w/w). Accelerated corrosion tests were performed to compare the degree of protection of both the modified and unmodified paints. The polyaniline did not affect to the protective properties of the epoxy without inorganic anticorrosive pigment nor the alkyd formulations. In opposition, the polyaniline added to the epoxy paint with inorganic anticorrosive pigment induced the formation of a zinc oxide layer, which promoted the corrosion attack.     

Robust hydrophobicity and evaporation inertness of rare-earth monosilicates in hot steam at very high temperature

Rare-earth oxides are intrinsically hydrophobic, and this characteristic opens new horizons for their design and diverse applications as robust hydrophobic surfaces. Here, we discover some rare-earth (RE) monosilicates (RE₂SiO₅) that are hydrophobic under ambient conditions. Their hydrophobicity is positively correlated with their hot-steam corrosion at 1400°C. RE³⁺ in RE₂SiO₅ is further found to be a hydration prohibitor, and its species can regulate hydration and volatilization at very high temperatures. These results may provide basis for innovative designs of RE silicates in harsh hot-steam environments for robust environmental barrier coatings (EBC) or as ceramic components.     

Synthesis of nano polyaniline and poly-<Emphasis Type="Italic">o</Emphasis>-anisidine and applications in alkyd paint formulation to enhance the corrosion resistivity of mild steel

Protection of oxidizable metals against corrosion has now being intensively investigated, by applying or developing different methods such as coatings and conversion films; however, all reported methods involve environmentally hazardous materials. Conducting polymers have now been used as corrosion inhibitor coatings that are either chemically or electrochemically deposited on the metal substrate. The application of nanotechnology in the corrosion protection of metals has recently gained momentum. Environmental impact can also be improved by utilizing nanostructure particulates in coatings and eliminating the requirement of toxic solvents. We report here the synthesis of nanoparticles of polyaniline (PANI) and poly-o-anisidine (POA) using emulsion polymerization method in micellar solution of SDS and their anticorrosive property has been experimentally checked. The prepared nanoparticles have been characterized by FTIR and TEM. The nanoparticles of the synthesized polymers were dispersed in alkyd paint formulation for coatings on the metal surface (mild steel). The water absorption in the prepared coatings was also studied. The corrosion rate of polymeric film was determined by weight loss measurement and the surface morphology was examined by SEM. The nano PANI/Alkyd coatings showed considerable protection against corrosion than the POA/alkyd coatings.     

Spectroscopic Nondestructive Evaluation of Environmental Barrier Coating Failure on Silicon-Based Ceramics

Environmental barrier coatings (EBCs) are external ceramic coatings on silicon-based ceramic components to protect them from water vapor attack in combustion environments. A spectroscopic nondestructive technique to monitor the degradation of environmental barrier coatings was investigated. Lithium oxide was selected as a spectroscopic marker material after an extensive screening of various materials for their emissivity in simulated combustion environments. Spectral response of excited lithium atoms from mullite doped with 0.025–1 wt% lithium oxide was examined under an oxy-acetylene flame. A three-layer EBC (Si/Li₂O-doped mullite/BSAS) on a silicon carbide substrate, which had fine simulated cracks, showed significant lithium emission on exposure to the oxy-acetylene flame, which demonstrated the potential of emission spectroscopy as a nondestructive evaluation tool to monitor EBC degradation.     

Corrosion protective performances of commercial low-VOC epoxy/urethane coatings on hot-rolled 1010 mild steel

The protective properties of low-VOC epoxy/urethane paint systems of commercial grade have been investigated using a variety of techniques such as electrochemical impedance spectroscopy (EIS). One epoxy-polyamide mastic/urethane, three high-solid epoxy-amine/urethane coatings, one solvent-free epoxy-amine/urethane, one water-based epoxy-amine and one high-VOC alkyd paint system (used as paint reference system) were applied on hot-rolled 1010 mild steel panels and exposed for up to 2000 h in the salt spray cabinet (SSC) or for 1 year at an outdoor marine test site. These paints were tested for their barrier properties, corrosion-induced adhesion loss and visual defects, as well as for their flexibility and resistance to direct impact. The barrier properties increased in the following order: alkyd相似文献   

Synthesis and characterization of novel silicone acrylate–soya alkyd resin as binder for long life exterior coatings

A polymeric binder on soya alkyd, silicone intermediate and 2-hydroxyethyl metacrylate has been synthesized for formulation of long life exterior coating. Initially silicone acrylate monomer (SAM) was prepared by reacting hydroxyl-terminated silicone and 2-hydroxyl ethyl methacrylate (HEMA) and characterized by Fourier transformer infrared spectroscopy (FTIR) and carbon nuclear magnetic resonance spectroscopy (¹³C NMR). SAM was used in varying concentrations to synthesize novel soya alkyd resin. The unpigmented polymer film obtained from silicone acrylate–soya alkyd resin exhibits excellent mechanical properties and good exterior durability compared to silicone modified alkyd resin.     

纳米二氧化硅-有机硅复合涂层防护性能的研究

利用电化学阻抗谱(EIS)技术对纳米二氧化硅含量为5%的有机硅复合涂层的防护性能进行了研究,试验结果与有机硅清漆涂层和微米二氧化硅含量为5%的有机硅复合涂层的实验结果进行了比较。结果表明,纳米氧化硅粒子的填加有效的阻挡侵蚀介质的渗透和腐蚀,纳米氧化硅-有机硅复合涂层比有机硅清漆涂层和微米二氧化硅-有机硅复合涂层具有更好的防护性能。     

Corrosion resistant polymer derived ceramic composite environmental barrier coatings

Corrosion resistant coatings are a promising solution to protect structural metals in harsh environments. Ceramic composite coatings made from polymer-derived ceramics are highly attractive due to the ease of their processing and the ability to work in various environments. This paper is focused on the performance of a TiSi₂-filled SiOC ceramic composite coating system on 316 stainless steel (SS) substrates as a corrosion resistant coating. The best-performing quadruple-dip coatings were shown to be able to reduce the weight loss due to hot sulfuric acid (95+%, 104–107 °C) corrosion by 85% over a 30-day period. Coatings from the same system were also examined under 800 °C static (100 h) and cyclic (10 cycles) oxidation. Our results indicate that the coatings perform well under both conditions of prolonged high temperature oxidation and thermal cycling, suggesting the strong potential of this system as an environmental barrier coating (EBC).