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Technical Paper

Development of an Improved Cosmetic Corrosion Test for Finished Aluminum Autobody Panels

2005-04-11
2005-01-0542
A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.
Technical Paper

Dent Resistance of Medium Scale Aluminum Structural Assemblies

2001-03-05
2001-01-0757
This work outlines the evaluation of static and dynamic dent resistance of medium scale structural assemblies fabricated using AA6111 and AA5754. The assemblies fabricated attempt to mimic common automotive hood designs allowing for a parametric study of the support spacing, sheet thickness and panel curvature. Closure panels of AA6111, of two thicknesses (0.8, and 0.9mm), are bonded to re-usable inner panels fabricated using AA5754 to form the structural assemblies tested. While normal practice would use the same alloy for both the inner and the outer, in the current work, AA5754 was adopted for ease of welding. Numerical simulations were performed using LS DYNA. A comparison of experimental and numerically simulated results is presented. The study attempts to establish an understanding of the relationship between structural support conditions and resulting dent depths for both static and dynamic loading conditions.
Technical Paper

Crashworthiness of Aluminum-Structured Vehicles

1998-05-31
986018
Today,due to concerns about the emission of greenhouse gases and the Kyoto Protocol, there is increasing interest in the use of aluminum for reducing the weight of passenger cars to reduce fuel consumption and exhaust emissions, particularly CO2. In recent years, several aluminum-structured cars have been developed and are in service in various parts of the world, all of which have met the relevant vehicle safety requirements. However, concern continues to be raised about the crashworthiness of lightweight vehicles. This paper will summarize data on the energy absorption of aluminum automotive materials and structures under impact collapse conditions as well as published information from the automotive industry on the crashworthiness of two aluminum-intensive vehicles.
Technical Paper

Aluminum Wheel Alloy Variants: Effects on Corrosion Performance

1998-02-23
980461
Previous work has shown that variations in wheel alloy chemistry, particularly with respect to copper and iron levels, can have a pronounced effect on filiform corrosion performance. In this study, an examination of A356.2 alloy chemistry variants and their effects on corrosion was carried out in greater detail. The emphasis was on copper and iron variants, both alone and in combination. Copper levels ranged from 0.005 to 0.22% and iron from 0.04 to 0.23%. The effect of manganese additions was also examined, with levels ranging from 0.002 to 0.07%. In addition to the alloying variants, the level of dispersed oxides in the castings was varied to determine any effects on corrosion performance. Although filiform corrosion performance of painted samples was the primary focus of this study, the corrosion behaviour of unpainted samples was also evaluated for comparison purposes.
Technical Paper

Methods for Assessing the Corrosion Behaviour of Heat Exchanger Materials and Components

1997-05-19
971787
To determine the true galvanic compatibility of radiator components a test has been developed using a zero resistance ammeter (ZRA) technique, which measures the magnitude of the galvanic current between different materials, thus allowing specific corrosion rates to be calculated. It is believed that the use of the ZRA technique will help provide a better balance between sacrificial behaviour and thermal performance of fin alloys. In particular, it will be demonstrated that it is not necessary to make additions of zinc to the fin alloys to attain a sacrificial effect, which in the longer term may compromise the recyclability of radiator units.
Technical Paper

Effects of Alloy Composition and Condition on Filiform Corrosion Performance of Cast Aluminum Wheels

1997-02-24
970021
The movement towards extended warranties in the automobile industry has focussed attention on corrosion performance of many components, particularly cast aluminum wheels. Filiform corrosion is of particular concern since it can severely affect the appearance of the wheel. The appearance and the choice of wheel design are the most attractive features to customers. In order to enhance the filiform corrosion resistance of cast aluminum wheels, cleaning, pretreatment, coating and alloy parameters are critical and need to be optimized. In this paper, the effects of alloy composition and condition on filiform corrosion are reviewed. A series of cast discs were prepared with variations in iron, zinc and copper levels around the standard A356.2 alloy composition. Apart from composition, certain specimens were subjected to different heat treatment and ageing conditions. The effects of porosity and different machining procedures were also evaluated.
Technical Paper

How to Weld Bond Aluminium with Structural Adhesives

1997-02-24
970018
Weld bonding of aluminium autobody structures offers automotive vehicle manufacturers the opportunity of achieving significant weight reduction, compared to equivalent steel structures. Further, this is achievable using volume production manufacturing methods. This paper considers all key aspects of the weld bonding process, in particular the equipment requirements and the factors that are important in reliably achieving satisfactory structures. Methods of minimising damage to the adhesive bondline and assessment of spot weld quality are discussed. Using experience gained from extensive weld bonding trials, suitable parameters for robust weld bonding are recommended.
Technical Paper

Processes for the Recycling of Sheet and Other Wrought Alloys from Aluminum Intensive Vehicles

1997-02-24
970017
This paper will describe the main features of two newly-developed enabling technologies for the future establishment of an integrated system to recover the full value of the aluminum from scrapped aluminum intensive vehicles. These technologies are fluidized bed decoating and alloy sorting using analysis by laser induced optical emission spectroscopy. Aluminum Intensive Vehicles will employ substantial quantities of sheet material, most of which will have fairly heavy paint coatings and possibly adhesives. While it may be possible to remove and segregate some of the closure panels and the major aluminum castings, the main body structure will need to be shredded to facilitate both the separation of the various aluminum and other materials and also the subsequent thermal decoating of paint films and adhesives. The decoating is necessary to ensure complete pyrolysis of the coatings and to avoid the excessive dross losses encountered when as-painted scrap is remelted.
Technical Paper

Composition Based Sorting of Aluminum Scrap from Aluminum Intensive Vehicles

1996-02-01
960163
The feasibility of applying laser induced optical emission spectroscopy to the high speed sorting of mixed-alloy aluminum scrap from automobiles has been established. The basic spectroscopy for analysing aluminum alloys for the major alloying elements is reviewed and key technical issues solved in developing the total sorting system are highlighted. Opportunities to apply this technology to the recycling of scrapped automobiles are discussed.
Technical Paper

The Properties and Characteristics of Two New Aluminum Automotive Closure Panel Materials

1996-02-01
960164
The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing. The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings.
Technical Paper

Reduced Finishing Costs for Aluminum Intensive Vehicles

1996-02-01
960170
Due to the inherently superior corrosion resistance of aluminum compared to automotive steels, phosphating and electrocoating are not necessarily required to provide good corrosion protection to aluminum intensive vehicles. This allows the potential for significant cost savings in the overall finishing process by eliminating these steps. Advantage can also be taken of the movement towards the use of powder primer surfacers to reduce solvent emissions in that the powder coating can be applied directly to a suitably pretreated aluminum surface. Pretreatments which are optimized for aluminum and much simpler to control than phosphating were chosen for trials based upon discussions with chemical suppliers. In this paper, the adhesion and corrosion characteristics of these selected pretreatment/powder primer systems were compared to standard phosphated and electrocoated AA6111 automotive closure sheet.
Technical Paper

The Lincoln Mark VIII Cast Aluminium Suspension Control Arm (Parallel Development)

1994-03-01
940874
An A356T61 cast aluminum lower suspension control arm has been put into production for the Lincoln Mark VIII. The mechanical requirements which drive the design for a critical part like this are discussed, together with some of the background knowledge needed to address the issues surrounding alloy and process selection. Particularly as it must be realized that the process impacts the degree to which the potential of the alloy can be realized. With this in mind, some of the research activities which have been spawned in parallel with the production activities are briefly covered. The sequence of events involved in the design and prototyping of the part itself are outlined, as is the implementation of a specialized low pressure casting line to produce the part. Part performance to date has been excellent and the quality controls and test methods which have been put in place to see that this remains so are also covered.
Technical Paper

NOCOLOK™ Sil Flux - A Novel Approach for Brazing Aluminum

1994-03-01
940502
The need to reduce the weight of automobiles has favored the widespread use of aluminum in automotive ventilation and cooling systems. Space, weight restrictions, the need for increased thermal efficiency, and recycling legislation have all contributed to new designs for heat exchangers. In many cases there has been a move to using extruded tube rather than seam-welded tube, leading to a reliance on the relatively more expensive clad fin. A new process, NOCOLOK™ Sil flux brazing, offers the potential for materials cost savings through the use of “in-situ” filler metal generation. This eliminates the need for using clad brazing materials. It can be applied to a number of alloy systems and product forms. This new technology is firmly rooted in the well established NOCOLOK™ non-corrosive aluminum brazing flux system.
Technical Paper

Development of an Understanding of the Critical Factors Influencing Waterside Corrosion Behaviour of Brazed Aluminium Radiators

1994-03-01
940499
The application of aluminium alloy materials for automotive heat exchangers, including engine cooling and air conditioning systems, is now widespread. To meet the industry demands of both extended service life and improved reliability for heat exchanger components, it is important that the critical factors influencing corrosion behaviour are properly understood, particularly with the trend towards downgauging of materials. To maximise resistance to waterside corrosion, manufacturers have adopted the approach of using an internal cladding, commonly a high purity or zinc - containing alloy, to provide sacrificial protection of the core material. Recent studies have shown that the presence of an internal cladding can, under certain conditions, promote rapid localised attack of the core alloy.
Technical Paper

Development of a Long Life Aluminium Brazing Sheet Alloy with Enhanced Mechanical Performance

1994-03-01
940505
The use of aluminium alloys for automotive heat exchangers has increased considerably in the last 15-20 years and, in parallel, new alloys have been developed to meet the increased demand for strength and improved corrosion resistance. A non-heat treatable Al-Mn alloy, X800, has been developed by Alcan to significantly increase the corrosion resistance of radiator tubes when subjected to typical service environments. The alloy development employed considerable microstructural understanding to provide heat exchanger manufacturers with an improved product that readily attained enhanced performance during any brazing cycle. A similar philosophy has been adopted to address the issue of increased mechanical performance, higher intrinsic sheet strength, both during and after brazing, provides the opportunity for sheet downgauging and thus lightweighting of components.
Technical Paper

Galvanic Corrosion Prevention of Steel-Aluminum Couples

1993-10-01
932357
Efforts towards weight reduction are leading towards increasing use of aluminum components on automobiles. Although aluminum on its own has inherently superior corrosion resistance to steel, galvanic action between the aluminum and steel or galvanized parts can lead to severe corrosion. Straightforward and effective methods of preventing galvanic corrosion from the subject of this paper. Since many aluminum components are connected to steel structures by mechanical fasteners, protective coatings on fasteners were evaluated as well. Galvanic test couples were prepared in a manner simulating typical automotive assembly conditions while incorporating features which would lead to enhanced corrosion. A variety of chemical treatments and coatings on the fasteners as well as barriers between the dissimilar metals were evaluated for corrosion prevention between the aluminum and cold rolled or galvanized steel. Comparison between neutral salt spray and cyclic corrosion tests is provided.
Technical Paper

Effects of Surface Texture on the Appearance and Corrosion of Painted Aluminum Body Sheet

1993-03-01
930702
Studies have indicated that enhanced corrosion resistance and appearance after painting can be obtained on automotive steels by texturing the sheet surface. To determine whether these same improvements could be obtained on aluminum, paint performance and appearance were evaluated on heat treatable alloys that had been given shot dulled and laser textured finishes. Corrosion performance was measured by filiform and SCAB tests and paint appearance by distinctness of image (DOI). Profilometry was used to characterize the roughness of the sheet surface at various stages of paint application. Experiments demonstrated that corrosion performance was not significantly affected by surface texture. However, the DOI of painted textured surfaces varied with the extent of reduction of the sheet when rolled and, in particular, with the paint system. Mill finish aluminum was shown to have DOI equivalent to that achieved on cold rolled or electrogalvanized steels.
Technical Paper

The Recycling and Reclamation of Metal-Matrix Composites

1993-03-01
930182
The recycling and reclamation of metal-matrix composites (MMC's) are critical aspects of the commercialization process. By recycling, we mean the economic processing of MMC scrap for reuse as composite. Reclamation refers to the separation and recovery of the individual components of the composite, i.e., the various aluminum alloys and ceramic particles. Three forms of MMC wrought alloy scrap have been considered; i.e., D. C. (direct chill) cast log ends, extrusion butts, and cut extrusion scrap. Recycling each of these forms of scrap back into D. C. cast extrusion billet has been demonstrated. This has been accomplished by recycling the scrap back through the basic mixing process. Various ratios of scrap to virgin composite have been explored and optimum blends are being studied. Similarly, for MMC foundry alloy (high silicon) gates and risers produced in shape-casting, fluxing and degassing techniques have been developed so these may be recycled back into useful castings.
Technical Paper

Alternatives to Electrocoating Aluminum in Automotive Applications

1992-02-01
920280
The inherent corrosion resistance of aluminum is much greater than automotive steels. To demonstrate this principle in a fashion acceptable to the automotive industry, a test program was run which incorporated lab, test track and real life trials on both unpainted and painted aluminum and painted steel. The lab program consisted of neutral salt and cyclic corrosion tests. Having demonstrated that aluminum does not need electrocoating for good corrosion integrity, alternatives to electrocoating which would allow primers to be applied only where necessary for esthetic purposes were sought. Several primers were selected for study based upon current automotive usage. Factors such as the degree of pretreatment prior to primer application and the presence of residual lubricant on the metal were evaluated.
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