|2009 Anodizing Conference Abstracts|
Abstracts for the 2009 Anodizing Conference were organized by General Sessions and the following Focus Sessions: Technical, Technology Forum, and Scientific.
Focus Session 1: Technical
Leonid Lerner, Sanford Process Corporation
Many variations of hard anodizing have been developed to produce coatings for a wide range of applications. The Multifunctional Power Supply is conducted with the help of the low-voltage DC+AC power source supplying DC current with superimposed alternating current. These processes conduct hard anodizing at a very low DC voltage (12-18 volts-average) providing superior coating of anodic oxide. Moreover, alloys with a very high concentration of copper, such as 2011, are easily anodized within short periods of time without burning. The 6061 alloy with specific heat treatment T-6 may be anodized up to thickness of 5-6-7 mils, whereas the DC high-voltage process could only provide thickness not exceeding 2.5-3 mils on the same alloy. A higher copper content alloy such as 2024 can be anodized with the help of low-voltage process up to 6 mils thickness. Power supply is intended to be used for any anodizing processes from conventional anodizing, type II to hard anodizing.
New Nickel-Free Cold Seal
Fabio Vincenzi, Italtecno;
Walter Dalla Barba, Italtecno*
Having an understanding of the different sealing processes available today on the market (nickel-based cold seal, mid temperature seal and hot seal), this presentation will explore a new, ecological, nickel-free cold sealing method. In fact, nickel is a heavy metal with toxic properties and should be banned in many countries of the world in a few years.
The research was performed utilizing the following sealing process:
Research data comparing the new Nickel-Free Cold Sealing Process and standard conventional sealing processes will be presented. The data will prove that nickel-free cold sealing is absolutely possible and will produce sealing quality that is according to, and in some cases greatly exceeds, general aluminum industry standards and the seal quality of commonly used seal products on the market today.
Focus Session 2: Technology Forum
Acid Etch Update
Linda Newman, Houghton Metal Finishing
Since the recent introduction of a new acid etch process to the anodizing industry much new information has been discovered. With many anodizers switching from caustic etch to acid etch, additional questions have arisen. What are the new discoveries of the acid etch process? What are the advantages and disadvantages of both processes? Latest technical updates will be presented.
Enzo Strazzi, Italfinish SpA
Chiara Ferrari, Italfinish SpA
Sabrina Ferri, Italfinish SpA
Onita Crisan-Sintoma, AnodAM*
Everybody is familiar with a sulfuric-acid-based solution when aluminum (and in some cases, titanium) are anodized, but just a few technicians know what happens when an alkaline solution is used. A wide range of amazing options is opened if a proper nontoxic alkaline solution is used with a suitable machine and correct procedure. High-silicon cast aluminum become white and aesthetic and suitable to be used standalone or as a base for high corrosion-resistant powder coating. Any type of magnesium alloy cast or extruded material finds its "natural" and best finishing. Titanium and its family members become pastel colored. Furthermore, if somebody likes black matte tones, a simple modification of the solutions produces aesthetically and technically valuable finishing with opportunities for innovative applications. Practical experiences from industrial plants and wide bibliography will be mentioned.
Advances in the Dyeing of Anodized Aluminum
Pinakin Patel, Techevon LLC
This presentation will review new developments in dyeing anodized aluminum. Newer technologies of manufacturing allow for dyes to be developed with very high light fastness and with purity that was not previously available. Furthermore, black shades can be produced with different undertones depending on the needs of the customer. The presentation will also introduce a new line of dyes that can be sealed using the popular cold sealing methods of today with minimum-to-no bleeding. Additionally, the presentation will cover details of the properties of various dyes along with light fastness and contamination effect studies of various dyes. Some of these products are new molecules made exclusively for use on anodized aluminum.
New OEM Marketing Approach to Promote the Use of Anodized Aluminum
Mark Self and Markus Kleinert, Clariant Corporation
OEMs that outsource their aluminum finishing overseas, while maintaining design and engineering functions onshore, are encountering finish quality and reproducibility problems. Clariant has responded with a centralized OEM support platform, establishing a new product and technology development lab, and partnering with regional distributors. This presentation describes the new business model and focuses on recent product and technology developments in "Green" chemistry, novel colorants, and durable polysilazane coatings for anti-graffiti applications.
Focus Session 3: Scientific
Thin Film Anodizing – Novel Structures & Applications
Mark Jozefowicz, Reliant Aluminum Products LLC
It is well known that the structure of an anodized aluminum coating is related to the process conditions used to create it. To be able to develop new and interesting materials by simply varying electro-chemical parameters while anodizing has intrigued scientists for decades. The Anopore™ membrane is a market successful application which grew out of such a development. Low cost thin film coatings with unique structures can also be created by anodizing aluminum and applied in unusual ways. When combined with chemical metallization to produce vibrant interference colors, an entirely new set of applications are attainable. A discussion on electro-chemical techniques used to create such materials and their application will take place. Prototype examples that have been created on a continuous anodize line will be on display.
New Uses for Anodized Aluminum Oxide (AAO)
H. Hau Wang, Argonne National Laboratory
Anodized aluminum oxide (AAO) has attracted significant interest among the nano-science and engineering research community in recent years. AAO consists of highly aligned nanopores “self-assembled” in a hexagonally close-packed pattern. The pore diameter and pore-to-pore distance range between ~10 to 300 nm and 30 to sub-micron, respectively. These nanopores are highly ordered within a domain but do not exhibit intrinsic long-range order. These nanopores can be filled with use of electro-deposition to prepare metallic (Cu, Ag, Au, etc.) or ferromagnetic nanowires (Fe, Co, Ni, etc.). These nanoscaled objects have been studied for their magnetic anisotropic behavior in the laboratory. Complex multi-segmented nanowires have also been developed. The multi-segmented design may be used to enhance self-assembly of these materials. Together with chemical vapor deposition (CVD) and atomic layer deposition (ALD), semiconductive nanowires and nanotubes such as ZnO, CdS, CdSe, GaAs, etc., have been synthesized for photonic devices, transistors, and biological sensing and detection applications. The AAO membrane when coated through ALD technique has been developed into a new membrane catalyst. With precise reaction parameter control, chemical reaction such as dehydrogenation with high selectivity has been demonstrated.
The AAO membrane when coated with ZnO was reported to be a high surface area dye-sensitized solar cell with reasonable power efficiency. With short anodization time, a nanowell structure can be prepared with shallow nanopores. These nanowells have been developed into hydrogen sensors with Pd nanoparticle decoration.
In addition, these nanowells give rise to interference colors and the interference spectra are sensitive enough to pick up one monolayer of explosive molecules such as di- and tri-nitrotoluene. Due to the high aspect ratio (>1,000) in the AAO nanopores, the AAO membranes are reported to lead to highly anisotropic etching and are being developed into various MEMS (micro-electromechanical system) devices such as RF MEMS inductor, microcantilevers, capacitive MEMS humidity sensor, and various gas sensors, etc. The frame work of AAO is very similar to the micro-channel plate (MCP) used in various devices such as night vision goggles and photodetector, etc. It is possible that AAO with proper surface coating may lead to inexpensive large area detector. This presentation will briefly review AAO based research efforts from basic research to energy and security applications.
A Point Defect Interpretation of the Stability of Anodized Aluminum in
Digby Macdonald, Penn State University
All reactive metals that are used for structural, electronic, or decorative purposes, such as aluminum, chromium, nickel, iron, zirconium, magnesium, and many others, and the alloys of these elements, owe their kinetic stabilities to the formation and continued existence of a “passive” oxide film on the surface that effectively separates the reactive metal from the corrosive environment. This film was initially detected by Michael Faraday in 1833 as the result of his famous “iron in nitric acid” experiment. Since that time, numerous models have been devised to describe the properties of the passive film, which commonly forms as a bi-layer structure comprising a point-defective barrier layer and a porous, precipitated outer layer. In the case of aluminum and its alloys, the barrier layer, which grows directly from the metal, has a general formula of Al2+xO3-y, where x and y describe the non-stoichiometry of the phase, with y > 0 for an oxygen-deficient phase, due to the existence of oxygen vacancies, and x > 0 for a metal-rich phase due to the existence of cation interstitials. These two defects dope the barrier layer n-type in electronic character. If x < 0, corresponding to a cation-deficient phase, due to the existence of vacancies on the metal sub-lattice, the oxide is doped p-type in electronic character and hence the electronic properties of the barrier layer can be used to ascertain the dominant defect in the system.
On the other hand, the outer layer forms via the hydrolysis of Al3+ cations that are ejected from the barrier layer and the subsequent precipitation of AlOOH or Al2O3, often in the form of a film that contains pores normal to the surface in a roughly hexagonal array. The outer layer commonly contains species from the solution (e.g., borate) that are co-precipitated with the oxyhydroxide or oxide phase. These species are never found to be present in the barrier layer, whereas alloying elements present in the substrate metal are generally found in both the barrier and outer layers. These observations are consistent with the origins of the barrier and outer layers being direct growth from the metal and precipitation, respectively. The present talk will review what is known about the passive film that forms on aluminum under anodizing conditions and will show that the formation and breakdown of the film is well-described by the Point Defect Model (PDM) that has been developed by the author over the past three decades. The PDM also identifies strategies for producing more corrosion-resistant surfaces via chemical or physical modification of the outer layer. Some of these strategies are already practiced in the anodizing industry (e.g., sealing, chromate conversion coatings), but others are less-well developed. Modification of the barrier layer in terms of interaction of mobile point defects (e.g., cation vacancies) with immobile foreign cations on the cation sublattice is also an attractive strategy, particularly for improving pitting resistance, but it has not been explored in a comprehensive manner.
Electrochemical Kinetics, Transport and Pattern Formation in Anodizing
Dale Barkey, University of New Hampshire
The formation of anodic oxide finish is examined as a far-from-equilibrium electrochemical phase-formation process. In this view, the growth of a highly ordered oxide phase is related to competition among electrostatic and diffusive driving forces, surface kinetics, and spare charges. The framework is compared with published models of oxide growth as well as experimental data from this laboratory.
* indicates presenter
The views expressed and the information, materials, processes and techniques described in the papers and presentations planned for inclusion in the Conference program represent the views and developments of the individual authors and/or the companies or organizations indicated. The Aluminum Anodizers Council (the “Organizer”) makes no representations as to the accuracy or sufficiency of any of the information set forth in the individual papers. The Organizer does not necessarily endorse or approve the views expressed in any of the papers. The Organizer and the individual authors/companies/organizations presenting papers assume no responsibility or liability for the use of any information, materials, processes or techniques described. The Organizer and the individual authors/companies/organizations hereby disclaim any warranties, expressed or implied, in connection with any information included in the presentations made during the Conference or in the papers published in the Proceedings.
The Council reserves the right to alter the program and/or schedule at its sole discretion.