Environmentally Compliant Novolac Superprimers For Corrosion Protection Of Aluminum Alloys
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Environmentally Compliant Novolac Superprimers For Corrosion Protection Of Aluminum Alloys
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Author :
language : en
Publisher:
Release Date : 2006
Environmentally Compliant Novolac Superprimers For Corrosion Protection Of Aluminum Alloys written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
The Environmental Protection Agency (EPA) in the US has imposed legislations on the use of hexavalent chromium and solvents contributing to emission of volatile organic compounds in primer coatings. This has led researchers to pursue development of alternative environmentally-friendly coatings which would eliminate chromate conversion coatings (CCC). This thesis discusses the work done towards the development of a novel, chromate-free, low-VOC, water-based, organic coating system for corrosion protection of AA 2024-T3 aerospace alloy. These special coatings which can be applied directly to the metal are termed as 'superprimers' and consist of novolac epoxy binder, silanes, polyurethane and non-chromate inhibitors. Coating evaluation tests were employed to compare the performance of the superprimer coatings with controls. SEM, FTIR and NMR were carried out to understand the chemistry of the coatings. The requirement for a conversion coating was obviated and the coating system developed was on par with the chromate-based control coating in terms of performance.
Environmentally Friendly Polyurethane Silane Superprimer For Corrosion Protection Of Aa2024 T3
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Author : Shekhar Bafna
language : en
Publisher:
Release Date : 2007
Environmentally Friendly Polyurethane Silane Superprimer For Corrosion Protection Of Aa2024 T3 written by Shekhar Bafna and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
Chromates used as pretreatments for metals and as anti-corrosive pigments in primers have been found to be a strong carcinogen and hence there is considerable pressure from environmentalists and government agencies for its replacement. Dr. Van Ooij and his research group have developed an array of environmentally friendly hydrophobic silane based pretreatments for corrosion protection of metals. However these coatings are extremely thin, of the order of a few hundred nanometers and hence unable to provide long term corrosion protection like a paint film which has thickness in microns. To eliminate this problem, the idea of Superprimer was conceptualized. "Superprimers" are self-priming coatings containing a mixture of polymer resin and silane as the binder and chromate-free, environmentally friendly corrosion inhibitor make a complete primer formulation. Thus, by adding the right silane to a coating resin, the chromate pretreatment step would be eliminated and the chromate pigment would be replaced by an environmentally friendly anti-corrosive pigment. This research deals with the evaluation of polyurethane-silane superprimer coatings as potential replacement of chromate pretreatment and chromat-containing high VOC primers for corrosion protection of AA 2024-T3 aluminum alloy. The silane chosen was BTSE because of its dipodal structure, hydrophobicity and ability to hydrolyze in water. EIS revealed that the hydrophobicity of the coatings increased considerably due to addition of 4 % BTSE silane improving its impedance and water barrier properties. RAIR and NMR spectroscopy showed hydrolysis and self condensation to siloxanes of the silane molecules. The formation of the siloxane network enhances the tensile strength, Tg and thermal degradation behavior of the coating, as detected by tensile testing, DSC and TGA, respectively. ToF_SIMS and EDXS studies of the interface indicated the presence of siloxane layer at the interface between the metal and coating. It indicated that the silane added to the polyurethane formulation segregated at the interface to form a dense siloxane network below the polyurethane coating. Four different, environmentally friendly corrosion inhibitive pigments were studied by incorporating them separately in the optimized polyurethane-silane formulation and applied them directly over AA2024-T3 without the use of a chromate conversion coating. Corrosion tests such as EIS and salt spray test (ASTM-B117) indicated that calcium zinc molybdate can be a promising replacement to chromates for the system under study.
Development Of An Environmentally Benign Anticorrosion Coating For Aluminum Alloy Using Green Pigments And Organofunctional Silanes
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Author : Zhangzhang Yin
language : en
Publisher:
Release Date : 2009
Development Of An Environmentally Benign Anticorrosion Coating For Aluminum Alloy Using Green Pigments And Organofunctional Silanes written by Zhangzhang Yin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Current protection measurement employs substantial use of chromate and high VOC organics, both of which are identified as environment and health hazards. The approach of this study is to utilize a combination of organofunctional silanes and a compatible inhibitor integrated into high-performance waterborne resins. First, an extensive pigment screening has been done to find replacements for chromates using the testing methodology for fast corrosion inhibition evaluation and pigment. Zinc phosphate and calcium zinc phosphomolybdate were found to have the best overall performance on Al alloys. Some new corrosion inhibitors were synthesized by chemical methods or modified by plasma polymerization for use in the coatings. Low-VOC, chromate-free primers (superprimer) were developed using these pigments with silane and acrylic-epoxy resins. The developed superprimer demonstrated good corrosion inhibition on aluminum substrates. The functions of inhibitor and silane in the coating were investigated. Both silane and inhibitor are critical for the performance of the superprimer. Silane was found to improve the adhesion of the coating to the substrate and also facilitate corrosion prevention. Addition of zinc phosphate to the coating improved the resistance of a scratched area against corrosion. The microstructure of the acrylic-epoxy superprimer coating was studied. SEM/EDAX revealed that the superprimer has a self-assembled stratified double-layer structure which accounts for the strong anti-corrosion performance of the zinc phosphate pigment. Zinc phosphate leaches out from the coating to actively protect the scratched area. The leaching of pigment was confirmed in the ICP-MS analysis and the leaching rate was measured. Coating-metal interface and the scribe of coated panels subjected to corrosion test was studied. ToF-SIMS studies confirmed the presence of silane at the interface and the hydrolysis of the silane. The abundant presence of silane was believed to improve the adhesion and also facilitate the corrosion prevention. The protection mechanism of the acrylic-epoxy superprimer was proposed. The self-assembled double-layer structure of the acrylic-epoxy superprimer consist of a less-penetrable hydrophobic layer (epoxy-dominated) on the top and a hydrophilic layer (acrylic-dominated) accommodating the inhibitors underneath. This unique structure of the acrylic-epoxy accounts for the good protection of the coating. Furthermore, the inhibition mechanism of zinc phosphate was explored and compared to those which have been reported. Based on the protection mechanism of the superprimer, electrodeposition was explored in order to achieve a more organized coating with a better engineered metal/coating interface. The electrodeposited coatings were found to have higher barrier property and anticorrosion performance.
Organic Inorganic Hybrid Sol Gel Coatings As Eco Friendly Surface Pretreatment For Corrosion Protection Of Aluminum Alloy
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Author : Mahshid Niknahad
language : en
Publisher:
Release Date : 2016
Organic Inorganic Hybrid Sol Gel Coatings As Eco Friendly Surface Pretreatment For Corrosion Protection Of Aluminum Alloy written by Mahshid Niknahad and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Alloys categories.
Pretreatments are thin, adherent, and protective layers deposited directly on cleaned metal surfaces to enhance the performance of the multi-coat finishing system on metal and alloy substrates. Regulatory and environmental considerations dictate that industries replace the extant toxic and hazardous chromate-based pretreatments used for aluminum alloys with more sustainable ones. Two new families of organic-inorganic hybrid (OIH) pretreatments for aluminum alloys have been developed using customized silane-type sol-gel precursors--Epoxy-silane and Bis-ureasil--as primary components. Two series of sol-gel compositions varying in concentrations of silane precursor, organic corrosion inhibitor, and nano-silica particles have been prepared and used to deposit OIH pretreatments on aluminum alloy substrates (AA-2024-T3). The corrosion resistance performance of these OIH pretreatments has been studied by electrochemical impedance spectroscopy (EIS), direct current (DC) polarization resistance, and neutral salt spray test and compared with the resistance performance conventional hexavalent chromium-based pretreatment, as a benchmark and industry standard for Al alloys. This research specifically investigates the effects of key components of sol-gel compositions on the corrosion performance of the OIH pretreatments on Al-2024-T3. Using the Box-Behnken Design of Experiment (DoE) methodology and Minitab software for analysis, the key factors affecting corrosion performance have been identified and sol-gel compositions optimized. This study revealed that for both families of OIH pretreatments, the film deposited in the sol-gel bath containing 25% by weight of precursor provided the best performance. Furthermore, incorporation of nano-silica particles to an optimum level of 5% by weight led to a remarkable improvement of the corrosion-resistance performance of the pretreatments for both families. This study has also very clearly shown that the use of the organic corrosion inhibitor mercaptobenzthiazole is effective in enhancing the corrosion-resistance performance of both families of pretreatments when used at the optimum level of 3% by weight. A comparison of the corrosion-resistance performance of the two families of OIH pretreatments with chromate conversion coating (control) showed that pretreatments based on epoxy-silane precursor when used at optimum compositions clearly outperform chromate conversion coatings used as a control in this study. Furthermore, OIH based on a bis-ureasil precursor, while showing a slightly lower performance than its epoxy-silane counterpart, is comparable or slightly superior to the commercial conversion coating when used at optimum compositions.
Environmentally Compliant Corrosion Resistant Electrically Conductive Inorganic Coatings For Aluminum Alloys
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Author :
language : en
Publisher:
Release Date : 2001
Environmentally Compliant Corrosion Resistant Electrically Conductive Inorganic Coatings For Aluminum Alloys written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
The objective of this project was to develop an environmentally compliant conversion coating for use on aerospace aluminum alloys (e.g., AA2024-T3). This conversion coating was to replace the current chromate conversion coating processes in both mode of application (bath or spray applied in the depot) and function (stand alone corrosion protection, adhesion to organic layers, self-healing, and low electrical contact resistance). Hydrotalcite (HT) was developed within this program as a replacement to chromate conversion coatings. HT coatings are formed by exposure of aluminum and its alloys to alkaline lithium salt solutions. The coating chemistry used to form these conversion coatings has many processing variables (e.g., time, temperature, anion, etc.). A Fractional Factorial Design was used to determine that temperature was one the more critical processing variables. The FFD study also determined that HT coatings formed from nitrate-based chemistries had consistently better stand-alone corrosion protection properties. Through the use of additional oxidants within the coating bath, HT coatings with the ability to withstand 168 hours of salt spray could be formed in less than 6 min. HT conversion coatings could also be post-treated (e.g., hydrothermally aged, surfactant) to revert the hydrotalcite to aluminum oxide, or augmented to include high valence-state rare earth cations (e.g., cerium). Hydrothermal aging allowed a procedure to chemically anodize aluminum, while incorporation of cerium into the molecular gallery of the hydrotalcite structure provided a means to develop self-healing characteristics, a highly sought property characteristic of chromate-based coatings. Self- healing was indeed demonstrated by the cerium doped HT coatings. The adhesion of epoxy coatings to the hydrotalcite coating was studied in detail. The Lewis-base nature of HTs makes them intrinsically less able to be wet by the Lewis- base nature of epoxy.
Environmentally Compliant Coatings Using Non Chromated Systems
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Author :
language : en
Publisher:
Release Date : 2001
Environmentally Compliant Coatings Using Non Chromated Systems written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Conversion coatings and primers used for the corrosion protection of aluminum alloy components in aircraft are based, almost exclusively, on chromate systems that are on the Environmental Protection Agency List of hazardous materials. Chromium is targeted for elimination from the workplace. This effort is part of a research program to develop a suitable replacement for chrome in coatings technology. This effort focused on the use of cerium chemistry to provide the corrosion inhibition for aluminum alloys used in the aircraft industry. The primary tasks were the development of a non-chromated conversion coating and surface treatment and a non-chromated primer coating system for military aircraft. This report presents the development, characterization, and evaluation of inorganic coatings that can serve as potential replacements for current chromate coatings. This effort was performed by the Materials Research Center at the University of Missouri-Rolla and the Boeing Corporation.
Self Healing Materials
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Author : Martin D. Hager
language : en
Publisher: Springer
Release Date : 2016-07-06
Self Healing Materials written by Martin D. Hager and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-07-06 with Technology & Engineering categories.
The series Advances in Polymer Science presents critical reviews of the present and future trends in polymer and biopolymer science. It covers all areas of research in polymer and biopolymer science including chemistry, physical chemistry, physics, material science. The thematic volumes are addressed to scientists, whether at universities or in industry, who wish to keep abreast of the important advances in the covered topics. Advances in Polymer Science enjoys a longstanding tradition and good reputation in its community. Each volume is dedicated to a current topic, and each review critically surveys one aspect of that topic, to place it within the context of the volume. The volumes typically summarize the significant developments of the last 5 to 10 years and discuss them critically, presenting selected examples, explaining and illustrating the important principles, and bringing together many important references of primary literature. On that basis, future research directions in the area can be discussed. Advances in Polymer Science volumes thus are important references for every polymer scientist, as well as for other scientists interested in polymer science - as an introduction to a neighboring field, or as a compilation of detailed information for the specialist. Review articles for the individual volumes are invited by the volume editors. Single contributions can be specially commissioned. Readership: Polymer scientists, or scientists in related fields interested in polymer and biopolymer science, at universities or in industry, graduate students
Handbook Of Adhesive Technology Revised And Expanded
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Author : Antonio Pizzi
language : en
Publisher: CRC Press
Release Date : 2003-08-06
Handbook Of Adhesive Technology Revised And Expanded written by Antonio Pizzi and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-08-06 with Science categories.
The Handbook of Adhesive Technology, Second Edition exceeds the ambition of its bestselling forerunner by reexamining the mechanisms driving adhesion, categories of adhesives, techniques for bond formation and evaluation, and major industrial applications. Integrating modern technological innovations into adhesive preparation and application, this greatly expanded and updated edition comprises a total of 26 different adhesive groupings, including three new classes. The second edition features ten new chapters, a 40-page list of resources on adhesives, and abundant figures, tables, equations.
Handbook Of Smart Coatings For Materials Protection
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Author : Abdel Salam Hamdy Makhlouf
language : en
Publisher: Elsevier
Release Date : 2014-02-22
Handbook Of Smart Coatings For Materials Protection written by Abdel Salam Hamdy Makhlouf and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-02-22 with Technology & Engineering categories.
A smart coating is defined as one that changes its properties in response to an environmental stimulus. The Handbook of Smart Coatings for Materials Protection reviews the new generation of smart coatings for corrosion and other types of material protection. Part one explores the fundamentals of smart coatings for materials protection including types, materials, design, and processing. Chapters review corrosion processes and strategies for prevention; smart coatings for corrosion protection; techniques for synthesizing and applying smart coatings; multi-functional, self-healing coatings; and current and future trends of protective coatings for automotive, aerospace, and military applications. Chapters in part two focus on smart coatings with self-healing properties for corrosion protection, including self-healing anticorrosion coatings for structural and petrochemical engineering applications; smart self-healing coatings for corrosion protection of aluminum alloys, magnesium alloys and steel; smart nanocoatings for corrosion detection and control; and recent advances in polyaniline-based organic coatings for corrosion protection. Chapters in part three move on to highlight other types of smart coatings, including smart self-cleaning coatings for corrosion protection; smart polymer nanocomposite water- and oil-repellent coatings for aluminum; UV-curable organic polymer coatings for corrosion protection of steel; smart epoxy coatings for early detection of corrosion in steel and aluminum; and structural ceramics with self-healing properties. The Handbook of Smart Coatings for Materials Protection is a valuable reference for those concerned with preventing corrosion, particularly of metals, professionals working within the surface coating industries, as well as all those with an academic research interest in the field. Reviews the new generation of smart coatings for corrosion and other types of material protection Explores the fundamentals of smart coatings for materials protection including types, materials, design, and processing Includes a focus on smart coatings with self-healing properties for corrosion protection
Modern Aspects Of Rare Earths And Their Complexes
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Author : Vinny R. Sastri
language : en
Publisher: Elsevier
Release Date : 2003-12-09
Modern Aspects Of Rare Earths And Their Complexes written by Vinny R. Sastri and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-12-09 with Science categories.
In order to use rare earths successfully in various applications, a good understanding of the chemistry of these elements is of paramount importance. Nearly three to four decades have passed since titles such as The Rare Earths edited by F.H. Spedding and A.H. Daane, The chemistry of the Rare Earth Elements by N.E. Topp and Complexes of the Rare Earths by S.P. Sinha were published. There have been many international conferences and symposia on rare earths, as well as the series of volumes entitled Handbook of Physics and Chemistry of Rare Earths edited by K.A. Gschneidner and L. Eyring. Thus, there is a need for a new title covering modern aspects of rare earth complexes along with the applications. The present title consists of twelve chapters. 1. Introduction2. General aspects3. Stability of complexes4. Lanthanide complexes5. Structural chemistry of lanthanide compounds6. Organometallic complexes7. Kinetics and mechanisms of rare earths complexation8. Spectroscopy of lanthanide complexes9. Photoelectron spectroscopy of rare earths10. Lanthanide NMR shift reagents11. Environmental ecological biological aspects12. Applications The authors studied in schools headed by pioneers in rare earth chemistry, have a combined experience of one hundred and fifty years in inorganic chemistry, rare earth complex chemistry, nuclear and radiochemistry of rare earths and supramolecular chemistry. The present monograph is a product of this rich experience.