Abstracts

The global Trade system on shifting sands, implications for the European Aluminium industry

Responsible society, sustainability, circular economy are terms that appears in many publications today. The climate changes we observe make us think differently and force us to take a responsibility for choices we make. One way to add to circular economy is to use recycled materials. Aluminium is a good example of material that can be endlessly recycled. However, that would be only possible if its really recycled, and not downcycled. In order to keep aluminium in the loop for a long time it is necessary to produce products with the same quality as the original ones, as for example window to window.

Closing recycling loop – powder coated profiles made of recycled aluminium for building application

Responsible society, sustainability, circular economy are terms that appears in many publications today. The climate changes we observe make us think differently and force us to take a responsibility for choices we make. One way to add to circular economy is to use recycled materials. Aluminium is a good example of material that can be endlessly recycled. However, that would be only possible if its really recycled, and not downcycled. In order to keep aluminium in the loop for a long time it is necessary to produce products with the same quality as the original ones, as for example window to window.

Thanks to new sorting technologies it is possible to get an aluminium scrap with very low level of other metals. The aluminium ingots with as high as 70-80 wt% of EOL scrap can be produced today. There is however a concern in the industry how the slight increase of trace elements like Zn and Cu influence the corrosion and surface appearance of powder coated and anodized profiles.

In this paper we will focus on the corrosion resistance of powder coated profiles for building application. We will present the filiform corrosion test results from the latest studies done on the profiles made of aluminium coming from recycling. Good etching, desmutting and conversion treatment play an important role in avoiding FFC. We will discuss importance of the appropriately controlled pretreatment and paint process in assuring filiform corrosion- free powder coated profiles. In addition to FFC test, GDOES and SEM/EDX analysis of the studied alloys will be presented, specially focusing on effect of enrichment of copper through the pretreatment and the role of the conversion coating.

FOX – Flash Oxidizing

Flash Oxidizing is a new technology which allows the pre-anodizing process to take place along a vertical coating line for aluminium extrusions, and which makes it possible to operate the pre- anodizing of a huge amount of aluminum profiles without manual handling and without any delay between the pre-anodizing process and the coating phase.

Cast Aluminum Alloys for Anodizing Applications; Overcoming the Negative Impact from Alloy Intermetallics

Silicon is added to aluminum as an alloying element for increasing its castability with die casting processes. Cast aluminum components are becoming more important due to their excellent weight to strength ratio in meeting weight reduction requirements; a key metric for the future of electric vehicles is a focus on the weight reduction. Anodization is one of the most efficient ways for corrosion protection for aluminum alloys however, presence of high amount of silicon create problems in anodization by causing the discontinuity of the anodic oxide film, inhomogeneous thickness distribution, low hardness and decreased seal quality.

This study aims to create optimum conditions to anodize cast aluminum parts with high silicon content, mainly by taking into account the morphology/distribution of the intermetallics and their contribution to the anodic oxide film quality. The corrosion protection ability of the anodized alloys are quantified by using potentiostatic methods, salt spray, acidic dissolution tests. Morphological features of the alloys are investigated both by optical microscopy and SEM.

Advanced experimental and modelling approaches to understand and predict better corrosion of metals

In the advanced materials industry, there is a clear trend towards more sustainable concepts, and this is certainly also the case for metals. They take a prominent position in the materials market thanks to their multifunctionality and structural and mechanical properties. However, metals are prone to corrosion, and therefore often organic coatings are applied to extend their lifetime. The search for organic coated metals with higher multifunctionality and extended lifetime goes together with the search for more sustainable material concepts in the context of the REACH regulation. Nowadays, materials are developed for providing components with a lifetime ranging from 10 to 25 years. The lifetime of a material highly depends on its exposure to the environment inducing ageing processes. In the current state of the art, lifetime and ageing assessment are performed by means of experiments, combining accelerated and field testing. The limitation of the first is that the conditions of the accelerated tests are not representative for the real environmental conditions and that there is no proven relationship between accelerated laboratory tests and field performance data. The limitation of the second is that it takes several years (5 to 10 years).

The only way to realise a substantial decrease in the development time of new materials is to introduce modelling in the design cycle. What is needed to realize a breakthrough in this field is a tool that can predict quantitatively and dynamically the corrosion behaviour of (organic coated) metals. The long term scientific motivation of our research is to build a knowledge and technology platform to enable the prediction of durability behaviour and the estimation of lifetime of (organic coated) metals under long-term environmental ageing and corrosion conditions. This requires advanced research because corrosion of a (organic coated) metal is the result of an intense interplay between several physical phenomena that need to be characterized in real conditions and modelled. Within VUB and TUDelft research we try to focus on both aspects bringing in new advanced combined electrochemical & in situ surface analysis, advanced finite element electrochemical modelling and more recently quantum chemical modelling. During the lecture an overview will be given on our state of the art in the different domains, emphasizing some success but also bringing bottlenecks when it really comes to predictions of corrosion.

Self-lubrication effects on corrosion and tribological properties of anodized aluminium surfaces

Recently, lubricant-infused surfaces (LIS) have emerged as a prominent class of surface technology for antifouling, anti-icing and anticorrosion applications. However, long-term corrosion exposure and mechanical damages may deteriorate the practical performance of LIS during application. In this study, a robust LIS was fabricated by the vacuum impregnation of mineral oil into anodized aluminum oxide (AAO) nanochannels with a depth of 50 μm. The impregnation of the lubricant was visualized under cryo-scanning electron microscopy (cryo-SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests showed that the deep nanochannels of LIS can provide excellent corrosion protection during long-term immersion.

Furthermore, the as-prepared LIS demonstrated superior resistance to mechanical attack due to self- healing by the lubricant. As shown by cryo-SEM observation and PDP tests, the micro-cracks formed on the LIS can be instantaneously repaired by the in-flow of the oil from the surrounding surface. In the tribological tests, the LIS also presented high wear resistance and superior mechanical durability. Obviously I can also prepare a presentation more focused on self-healing or active protective coatings etc, but thought the above may be of interest as well.

Environmentally-friendly pretreatment of aluminum profiles prior to coating and anodizing

Development of chromate and fluoride-free substitutes for the chromate treatment as pretreatment of aluminum alloys prior to painting and anodizing has been a significant challenge. This study investigates the present state-of the-art in economically-feasible applications for 6xxx-series extruded profiles.

Surface cleaning has become of increasing importance in the absence of chromate. The reasons for this will be explained. The simplest and most effective approaches, involving immersion without applied current, in particular deep alkaline and acid etching options, are compared. The latter option is based on phosphoric acid-water solution at elevated 80℃. Exposure of the Al(Fe,Mn)Si intermetallic particles (α-phase) and their enrichment of the of their nobler components Fe, Mn and Si by alkaline etching is undesirable because of their role as pinholes through the anodized layer and cathodic sites in the event of filiform corrosion of the coated surface. Furthermore, alkaline etching causes nonuniform dissolution of the grains in the presence of the elements Zn and Cu, resulting in topographies undesirable for the appearance of the anodized finish. The cause of this behavior will be discussed.

The advantages of using (fluoride-free) acid etching will be discussed next in the light of the above. Acid etching by dipping alone, such as in phosphoric acid solution at 80℃, neatly removes the problematic α-phase particles because all of its metallic components are electrochemically more active than Al at low pH, with the exception of Cu if it is present at 0.1 wt% or higher. Possible challenges for Cu enrichment of the oxide-Al extrusion interface will be discussed for the anodized and painted surfaces.

Nickel-free cold sealing: Characterization and industrial implementation

Hot sealing or hydrothermal sealing has been used for years as the reference procedure to seal aluminum anodized in sulfuric acid. However, hot sealing involves a high-energy consumption. As alternative, cold sealing with nickel allows carrying out the process at low temperatures, but toxic nickel salts are incorporated in the anodic layer, giving a greenish aspect to anodized aluminum. In this paper, we present a new and non-toxic cold sealing, which meets QUALANOD directives and has been successfully implemented in several anodizing lines.

By means of different electrochemical and spectroscopic techniques, we will characterize the anodic layers sealed with this new process. Besides we will compare the performance of this nickel-free sealing with the classical cold sealing in terms of sealing quality, corrosion resistance, admittance and alkali resistance.

The guide to Hard Anodising

This presentation will go through the Hard Anodising process and give an overview of how the various process parameters influence the final surface finish.

There are some general perspectives on how the process work, and some disparity between the Hard Anodising process and Conventional Anodising (type II) which will be included and commented.

To produce a proper hard anodic layer on aluminium some consideration about the alloys must be incorporated in the presentation, plus comments about the equipment for the process and the various standards for the Hard Anodising process.

Finally the properties of the Hard Anodising coating will be discussed and a simple guide to "where to use" will be included.

New techniques versus classical ones to interpret corrosion processes in coating profiles of architectural use.

DECOTEC is developing simple tests in order to be used by the laboratories of the coating factories for understanding the corrosion processes produced in their extruded aluminium profiles. The results obtained with these techniques will be equivalent to the results obtained by the most current techniques used in specialized laboratories and Universities, which are not at disposition of the laboratories of the coating extruded profiles factories.

Adding value to aluminum upgrading surface treatment for special request or new alloys

Market drivers in aluminum surface treatment are industrial generic ones as sustainability, environmental legislation request or adaptation to the circular economy and more specific ones as the increase of use of post-consumer recycled aluminum and introduction of new alloys for specific new industrial request. Chemical suppliers for aluminum surface treatment have to provide the aluminum finishing industry with products to deal with all these market drivers. This presentation shows some examples of it from Henkel’s perspective.

The development of a very good seal.

The main shortcoming of the conventional sealing treatments until today has been not to provide adequate protection to aluminium automotive parts to alkaline agents in general so consequently limiting the possible uses.

Cars bodies with anodized aluminium outside in general are subject to heavy corrosion stress mainly due to car wash with alkaline cleaners.

Lately, the market is more and more often requesting new features and new performances to anodized aluminum in order to open new developments for new applications to ensure the competitiveness of the anodized aluminum vs other materials and/or types of treatment. In particular, the requests received were:

- Resistance to alkaline agents

- Improved performance to sealing tests

- Anti-print treatment and sweat resistant

- Ecological process

- A process easy to use, easy to analyze, not very sensitive to pollutants and not too affected by small changes in the operating parameters used on the plants.

Based on these requirements a new super seal has been developed. The study for the research of a special super seal for automotive industry has also included the development of a nickel-free seal (cold seal) suitable for architectural anodizing. Also this interesting development is analyzed in details.

Coloring of Anodized Aluminium for long-lasting outdoor applications

Adsorptive dyeing of aluminum has a proven record in architectural and other outdoor applications.

Compared to electrolytic coloring adsorptive dyeing with organic dyes offers the great advantage of a much wider color gamut with more brilliant and vibrant colors. Even a combination of electrolytic and adsorptive dyeing is possible. Unlike powder coatings the aluminum surface still maintains its typical and unique metallic "look and feel". However, the durability of dye-based coloration is often questioned when compared to electrolytic coloring or powder coating.

Practical examples around the world show that when all parameters in this multi-step process of coloring anodized aluminum are considered the color remains stable for years or even decades. Crucial is the selection and the application of these dyes as weather and light fastness of such dyed surfaces

This presentation will give an overview of suitable chromophores for architectural and other outdoor applications. Furthermore, various sealing options are demonstrated with respect to their influence on the durability of colored anodized aluminum surfaces with specific focus on long lasting outdoor applications. Some surprising effects have been observed especially when using environmentally friendly nickel free sealing processes.

Anodic E-coating on anodized aluminium: What is it?

Not be confused with electrostatic spraying, electrophoretic painting – or electropainting, as it is frequently called – bears some similarity to electroplating. This modern method of paint application relies on the effect of E-coating and involves the migration of colloidal particles in a solution, such as water-based paint, under the action of an applied electric field.

The E-coating process has existed for many years but has been, until now, scarcely used on aluminum mainly due to the complexity of the plant equipment necessary for its application. Over the last few years, however, improvements have been recorded both from the chemical point of view and from the plant point of view.

From the chemical point of view there is the introduction of new resins, in particular for Anodic E-coating that can guarantee better performance both as regards the aesthetic aspect, both for corrosion protection and light resistance.

From a plant engineering point of view, there was a significant qualitative improvement that led to a reduction in prices at the same time. The new systems are more efficient, simpler to use and more automated and with significantly reduced amortization times.

The advantages of innovative technology, in particular of Anodic E-coating, on aluminum are the following:

- Compared to powder coating, it is a high adhesive coating film which is not easy to fall off and aging

- Compared to anodizing, E-coating coating is a higher hardness coating film with great impact resistance

- Colorful and metallic luster

- Protective layer with higher corrosion resistance than anodizing and powder coating

- Resistant to cement, mortar acid rain invasion

- Better wear resistance, weather and chemical resistance than anodizing

- Short processing time: as it works in water-based E-coating tank, it could finish the painting in several minutes which is easy to achieve the automated assembly line work.

- High utilization of painting: Because the painting has low viscosity and the E-coating workpiece could be washed with water, the utilization of electrophoretic coating could be up to 95% or more by recovery equipment.

Anodic E-coating finish is based on the anodizing finish, thus the quality would be better than anodizing finish.

An Unbridgeable Contradiction: Quality Improvements and Cost Savings in the Anodising Process

It is not any overstatement to say that the supply chain for surface finishing of aluminium will witness greater consolidation. For anodizing applicators, the past decades that were characterized by routine and repetitive task are already replaced by increasingly competitive and globalized market environments where value added services often appear undifferentiated.

The outcome is that applicators start to and/or are forced to compete by dividing existing demand and focus on trying to outpace one another in delivering the minimum standard quality at lowest possible cost.

In such a competitive market companies often search for new ideas and innovations that can give them a competitive advantage.

Like the pioneers of ‘blue ocean thinking’ central to the narrative of this paper is ideas are often are not from innovating in terms of technology or science, but by looking at familiar ‘standard’ processes from new perspectives.

This paper will present some ideas for improvement and/or significant cost savings in the anodizing process step and use case study results of customer experiences collected globally.

With references to practical experiences it will be shown that demands that the industry has assumed and taken as granted in the anodizing process steps could in future be eliminated or substituted – additionally some process standard could even be created that the industry has never offered.