Nineteenth Annual International Anodizing Conference & Exposition

October 5 – 7, 2010 • Montreal, Quebec, Canada

Advancing to the Next Level

Focus Session Abstracts

Technical Track

Process Controls, Documentation & Verification
Kevin Bodily, Metalast

There are various levels of process control that can be implemented in any process line. These systems can range from simple stand-alone controllers that maintain a single process variable to complex programmable logic control (PLC) systems that run automatic process lines. Whatever the degree of complexity, however, the control system must provide a minimum amount of functionality to achieve adequate results. This naturally raises the question, how much complexity does a process line require to achieve desired goals? Is controlling process parameters enough, or should the system also document the process for future verification? How do budgetary constraints affect the complexity of the system? Is the system flexible, expandable? How much maintenance is required? These are some of the questions that will be addressed and answered.

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Innovative, Ecological and Low-Cost Matte Finish

Walter Dalla Barba, Italtecno Srl

Nowadays in the aluminum anodizing industry it is ever more important to obtain new finishes through technologically advanced equipment and plants, as well as through innovative, green-friendly and economical chemical processes. The desired finishing is obtained by means of specifically designed brushing and polishing machines and, when possible, automatic anodizing plants for better control of process parameters. The finishing is then completed by one or more chemical process. An interesting and innovative chemical technology, not yet very well known in the market, is a new type of alkaline etching, specifically formulated to give a matte finish in about half the time compared to traditional alkaline processes, and with a large reduction of caustic soda consumption and a major reduction of dissolved aluminum. From these considerations we can deduce how innovative, ecologically friendly, and “low cost” this process can be.

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Replacement for the Chromic/Phosphoric Acid (CPA) Test for Sealing Quality

Joakin Oxelbark, Sapa

The sealing quality test specified by Qualanod is the Chromic/Phosphoric Acid (CPA) weight-loss test as described in EN 12373-7. This involves the use of chromic acid, which has carcinogenic and allergenic properties. Restrictions for the use of this chemical are anticipated in the near future so it is considered important to identify an alternative. The aim with this work was to investigate some candidates for replacement of the chromic/phosphoric acid test. Four sealing methods were used, because the weight loss is likely to depend on the kind of sealing method used. 

Sealing was made following the recommended working conditions in production given from the chemical supplier but also with a deviation in pH of sealing solution, sealing time, and sealing bath temperature. Samples were also taken from production plants using the four relevant sealing methods. Complementary dye spot and admittance measurements were made. The response in the different weight-loss tests was very different depending on sealing method and will be explored in this presentation.

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Anodizing Difficult Alloys

Fred C. Schaedel, Anodic Technical Services

Numerous Pulse - Step - Ramp Procedures have been developed, modified and improved over the past 50 years with the help of experienced anodizers right on the anodizing line. The most efficient, energy saving and problem solving of these procedures for Type II, 23 and III hard anodize will be presented. Special ramp and run procedures will cover those problem alloys designated as difficult due to burning and quality issues. These procedures will benefit all alloys but there will be special emphasis placed on 2011, 2024, 2219, 5083, 7050, 7075, 7178 and castings including 380 and other high-silicon alloys. Data logger graphs collected and revised over the past 30 years will be presented, which prove time and energy savings of more than 50 percent without burning or powdering of all aluminum alloys (1000 – 8000 Series) for commercial aircraft and military applications.

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Aerospace Anodizing Processes

Gary Kriesch, Walgren Company; W.J. Fullen, Boeing; E.W. Turns, Earl W. Turns & Associates

A number of specialized anodizing processes, including chromic acid anodizing (CAA), phosphoric acid anodizing (PAA), boric-sulfuric acid anodizing (BSAA), and thin-film anodizing, while common to the aerospace sector, are seldom practiced elsewhere. Each method has distinct specification requirements that stipulate controls for facility, process, and chemical constituents; this session provides a valuable introduction to such requirements.

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Environmental Track

Integrate Cleaning with the Processing of Aluminum and the Environment

Richard W. Mahn, Houghton Metal Finishing Company

The process of cleaning removes unwanted materials from “something,” which for this presentation is aluminum. The challenge of cleaning is that this chemical process must be done in a manner that completely removes the undesirable material without having a negative impact on that which is being cleaned. However, there must of necessity also be consideration given to the impact cleaning has on the environment. Once we have removed the unwanted materials, what do we do with them? What about the cleaners themselves? The purpose of this presentation is to present some cleaning basics and then to discuss the evolution of the cleaning process as it relates to the environment.

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Non-Chromium Seals for Clear and Hard Anodized Aluminum

Alp Manavbasi, Metalast

Anodized aluminum alloys are required to be sealed for the optimum corrosion resistance. Chemical reaction products formed during the sealing process fill the pores and make the anodized layer stable under a wide range of corrosive atmospheric and environmental conditions. Hexavalent-chromium-based sealers are commonly used for sealing the Type II Sulfuric Acid Anodized and Type IIB Thin Film Sulfuric Acid Anodized aluminum alloys. However, strict environmental regulations, tight waste disposal standards, and very low personal exposure limits (PEL), which are set by OSHA, have made the application of hexavalent-chromium-based seals prohibitively expensive. This presentation will describe a newly developed nonchromium process for sealing anodized aluminum, which has proven to be very effective with outstanding performance on anodic coatings. Corrosion characteristics of the anodized and sealed aluminum were investigated using Electrochemical Impedance spectroscopy (EIS) and Neutral Salt Fog (NSF) techniques.

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Steps to a More Environmentally Sustainable Business Model

Michael Ritzenhoff, Seidel, Inc.

As aluminum’s recyclability supports efforts toward sustainability, anodizing companies also should emphasize sustainability by implementing appropriate procedures and equipment. Financial rewards are seen to support the environmental benefits. The present work reflects efforts of one anodizing company to improve processes such as degreasing, brightening, sealing, rinsing, and heat recovery, to name just a few. Equipment upgrades range from more efficient boiler chillers, and power factor correction, to racking, transformers, and reverse-osmosis apparatus. Further themes include acid recycling, cogeneration, more aggressive water recycling, new wastewater treatment technologies, and general reduction of waste. Audience discussion of ideas will be encouraged.

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Regulatory Initiatives Impacting Surface Finishing Operations

Jeff Hannapel, The Policy Group

This presentation will focus on recent regulatory developments impacting surface finishing operations, including challenges facing the use of hexavalent chromium and long-chain perfluorinated fume suppressants, nickel supply issues, controls for greenhouse gas emissions, and new legislation and regulatory developments for chemical use. In addition, the presentation will also address the emerging trends in regulating industrial processes, chemicals, raw materials, and products containing hazardous substances.

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Environmental Regulations in Ontario

Ross Borthwick, Premier Environmental Services Inc.

The manufacturing sector in Canada is subject to environmental regulation undertaken by all levels of government – federal, provincial/territorial, and municipal. The federal and provincial governments in Canada both have jurisdiction over environmental matters and their environmental statutes often overlap. In addition, municipal governments are traditionally responsible for water and sewage systems and noise issues. The presentation will provide a general overview and update of the current environmental regulations affecting the manufacturing sector in Ontario. It should be noted that Ontario has the largest manufacturing sector in Canada and is a good starting point for the discussion of regulations in Canada. Topics will include air emissions, wastewater and stormwater, solid waste, hazardous building materials and storage.

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Scientific Track

Nanoporous Anodic Aluminum Oxide as a Template for Nanowire Arrays

Beth Stadler, University of Minnesota

Due to its nanoporous structure, anodized aluminum oxide (AAO) is an excellent template for metallic nanostructures that are useful in various magnetic, photonic, electronic, and biological applications. Other popular nano-templates will be briefly discussed and compared to AAO, including block co-polymers and ion-track etched polymers. AAO contains columnar nanopores with diameters of 5-500nm with aspect ratios of 1-104. Ordered pores can be obtained using either 2-step anodization or nano-imprinting of the initial Al metal prior to anodization. Both ordered and non-ordered AAO can be easily integrated with Si. A variety of shapes are also possible, including Y-junctions, antennae, and tree structures. Once the templates are fabricated, the most efficient method of obtaining nanowires is electrochemical deposition of a metal inside the columnar pores. The resulting nanowires can be used for magnetic artificial cilia arrays in biological sensors and actuators. These cilia have resonant frequencies ranging from Hz to GHz depending on their diameters and lengths. Arrays of nanowires also have great potential for high density memory applications, including static applications like hard-drive media and dynamic applications such as heads and random access memory (RAM) with almost 2 Terrabits per-square-inch densities. A third application of nanowires arrays is bio-plasmonic sensors where the photonic resonance of Au nanowires can be controlled using shape. In summary, anodic alumina is an exciting material for the growing field of nanotechnology with a wide range of applications possible.

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Anodized Aluminum Oxide Based Large Area Photo-Detectors

Seon Woo Lee, Ph.D., Argonne National Laboratory

There is a long-existing interest to develop a large-area, inexpensive and fast-response radiation detector. Current photo-detector technology, based on photo-multiplier tube (PMT) is expensive and not easy to scale up. The multi-channel plate (MCP) design uses optical fibers in a hexagonally close-packed array, rendering each optical fiber functioning like a PMT. These optical fibers are made of lead silicate glass. The MCP was made by optical fiber drawing, slicing, and chemically etching to create hollow fiber cores. The lead doped silicate glass has high secondary electron emission coefficient and therefore behaves like a miniaturized PMT. The optical fiber diameter ranges from 40 to ~2 microns. As the fiber diameter decreases, fabrication is becomes more difficult. At present, the state-of-the-art commercially available MCP has pore diameter around 2 microns. In addition to its expensive cost, the mechanical strength also poses a concern for its application. Smaller pores are expected to enhance temporal and spatial resolution. We have taken a new approach: instead of using silicate (SiOx)-based MCPs, we are developing porous alumina (Al2O3) or anodized aluminum oxide (AAO) based MCPs. AAO has several intrinsic advantages. Due to its internal vertically aligned nanopores, the AAO can be etched to create a nearly vertical edge. Aspect ratio of the pores (length/diameter) can be well controlled. The intrinsic nanopore diameter from 20-300 nm also allows MCP pores to be much smaller than the current 2 microns. However, to prepare AAO pores with diameter from 300 nm to ~1,000 nm, direct anodization does not work well. We applied laser writer patterning/photolithography to prepare patterned large pores with diameter from 40 to 4 microns. We plan to prepare pyramidal shaped tip arrays through e-beam lithography. Combined nanoimprint and anodization allows us to develop a new strategy to prepare pore-to-pore distance anywhere between 300 nm to 2 microns and beyond. Therefore, a wide range of AAO- based MCP devices can be fabricated considering hierarchical AAO intrinsic nanopores and lithography-assisted patterning together with anodization. The AAO is inexpensive and large-scale applications are possible. These new results will be presented.

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Formation of Al-based Nanostructured Thin Coatings on Aluminum Substrates Using a Micro-arc Deposition Technique

M. Brochu, J. Milligan and D. Heard, McGill University

Nanostructured materials are known to exhibit superior properties due to their refined grain size, and have a promising future for severe applications. Unfortunately, the cost associated with the fabrication of this technology is often the major drawback for their utilization as a bulk material. Electrospark deposition is a low-cost micro-arc welding process that can achieve cooling rates approaching 105-106°C/sec, allowing for solidification of nanostructure. Consequently, a low-cost nanostructured coating can be deposited on virtually any conductive substrate material, taking advantage of the properties provided by nanometric grains without compromising the manufacturing cost of components. This presentation will demonstrate the feasibility of engineering the surface of bulk Al components with various nanostructured Al alloy deposits, including Al-Si, Al-Ni and Al-Mg alloys. Results on the solidification microstructure and mechanical properties, such as dynamic hardness and impact fatigue, will be presented.

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Prediction of the Accumulation of Pitting Damage on Aluminum in Aqueous Solutions

Digby D. Macdonald, Pennsylvania State University

Aluminum and its alloys are used extensively as structural materials in applications ranging from domestic housing (siding and roofing), beverage containers, aircraft, and boats and ships, just to name but a few. In all of these applications, corrosion is a major issue, because corrosion results in degradation of the properties that make aluminum and its alloys attractive for these applications (e.g., high strength-to- weight ratio). Aluminum and its alloys suffer virtually all forms of corrosion, including general corrosion and different forms of localized corrosion. The latter include pitting corrosion, crevice corrosion, galvanic attack, filiform corrosion, stress corrosion cracking, corrosion fatigue, and hydrogen embrittlement. Despite this plethora of degradation mechanisms, aluminum and its alloys are surprisingly durable in service and can provide many years of trouble-free service. This resistance to corrosion can be attributed to anodization, which is the process of forming and sealing a thick oxide film on the surface by electrochemical polarization, to form an impervious barrier between the reactive metal and the corrosive environment. Actually, the anodic oxide film forms as a bi-layer comprising a thin defective barrier layer (typically a few nano-meters thick) that grows directly into the metal and a thick layer (typically a fraction of l micron thick) and which contains species present in the solution at the time of formation (e.g., borate ion when formed in borate buffer solution). This porous outer layer forms via precipitation of AlOOH or Al2O3 (depending upon the anodizing conditions) from Al3+ ions that are transmitted through the barrier layer. The pores are readily sealed by boiling the anodized component in water, which causes dissolution followed by re-precipitation of the outer layer material into the outer layer pores, thereby enhancing the corrosion resistance. Alternatively, oxidizing inhibitors that promote the oxidative repair of the anodic oxide film if ruptured have also been extensively used, particularly in the aircraft industry in the form of chromate conversion coatings. However, chromate is now banned, because of the carcinogenic properties of Cr(VI) and an alternative is now being actively sought.

As with any systems that are fabricated from reactive metals, those manufactured from aluminum are subjected to corrosive degradation that impairs performance and service life. This problem could be effectively managed if methods were available for predicting the rate of accumulation of damage due to corrosion, particularly that due to localized corrosion, such as pitting. Thus, such a tool would allow effective scheduling of maintenance during scheduled outages of the system, the cost of which has been built into the price of the product. Avoidance of unscheduled outages for servicing and repair should provide an enormous incentive for the development of the required technology. We have argued strongly that effective predictions of damage can only be done deterministically, using models whose outputs (predictions) are constrained by the natural laws. These models are discussed in this presentation.

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Metallurgical Assessment of Acid Etch as an Anodizing Pretreatment

Nick Parson, Marc Lebleu, Frederic Savard, Rio Tinto Alcan

A number of anodizing lines in the U.S. and Australia have adopted alternative anodizing pretreatments using fluoride-based etch solutions. The claimed benefits include shorter cycle times and freedom from streaking. The traditional caustic-based etchants are known to be sensitive to the alloy chemistry and microstructure giving rise to the well-known color or shade match problem. This presentation describes a test program conducted to measure the response of the acid etch process to various alloy compositions. The profiles tested included some with deliberately produced extrusion streaks. The impact of acid etch and combined caustic etch times was assessed along with the surface topography produced by these treatments. Comparisons were also made on the same profiles when treated with conventional caustic etching. Significant differences were found between acid etch and caustic etching in terms of the sensitivity of the final finish to alloy composition and also the ability to hide extrusion streaks.

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