Recycling as a hot topic at the Aluminium - World Trade Fair and Conference in Dusseldorf


9 years ago I wrote the first post about The good and the bad about recycled aluminium. Since then recycled aluminium has become a hot topic and this year´s Aluminium - World Trade Fair in Dusseldorf - Aluminium 2018 has dedicated a lot of energy into this subject.

One of the articles in their news room is about recycled aluminium,

RECYCLING: CHALLENGES FOR ALUMINIUM AS AN INDUSTRIAL MATERIAL

A short informative note about challenges, mentioning that there are no qualitative differences between aluminium alloys made from the primary and those made from recycled aluminium.

Is this always true - not really, especially when looking at the result obtained when anodizing aluminium.

Here you have to be aware of the following:

  • Heavy metals
  • Metallurgical structure
  • Traceability
  • Repeatability/Consistency
  • Consistent recycled stock

So it should not be difficult to use more recycled aluminum for anodizing. It only requires a minimum amount of adjustment to arrive at the present alloy composition, which works well for anodizing. So this should not be the reason for not using recycled aluminum when anodizing.

From an environmental viewpoint, anodizing is a very unique process. It does not require the use of organic solvents, which may cause unwanted atmospheric emissions and the amount of sludge can be diminished by using new processes as the acid etch.

Finally anodized extrusions and castings can be readily recycled without the need for special emission control equipment, so no VOC or other hazardous chemicals are emitted to the air.


If you find this article useful and you would like to know more please contact me blog@aluconsult.com 
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Introduction to hard anodizing

The main purpose of hard anodizing is to form a thick and dense oxide layer with a high wear resistance with thicknesses above 25 µm (1 mil). A dense oxide layer is an oxide layer with narrow pores and very thick cell walls.

The figures show the differences in structure of type II Anodizing compare to type III Anodizing. The anodized layer is seen from the top and down into the porous hexagonal structure.

The structure of the porous aluminium oxide layer is highly ordered as explained in an earlier post with the great slide from a hard coat presentation by Mr. Leonid Lerner from Sanford Process Corp. at International Hard Anodizing Association symposium in Las Vegas.


The slide show the two different directions of external stresses in the anodized oxide layer depending on if we test it or use it in normal applications.

According to MIL-A-8625F shall type III coatings be a result of treating aluminium and aluminium alloy electrolytically in a sulfuric acid based electrolyte to produce a uniform, hard anodic coating, often called Hard Coat in US and Hard Anodized.

This can be done by a low electrolyte temperature and a low concentration of the electrolyte in order to slow down chemical dissolution of the oxide layer. Production of very thick coatings will usually involve very high voltages and/or high current densities, which lead to high local temperatures therefore agitation of the electrolyte is most important.

According to MIL-A-8625F the hard-anodized coatings are characterized by their layer thickness and the coating weight of the formed layer. These types of coatings are named Type III coatings. Usually these coatings are used in the engineering industry for components such as pistons, cylinders and hydraulic gear, where a severe abrasive wear is found.

Apart from the wear resistance of the oxide layer, the hard-anodized oxide layer has other properties. Properties such as low friction and non-stick are very important. These hard coatings are usually unsealed to maintain a high wear resistance, but can be impregnated with different materials such as waxes and silicone.

If sealed in hot water the wear resistance will decrease with 20 - 50 % depending of the sealing process used.

If the corrosion resistance is the most important property for the surface, a sealing will enhance this property. The sealing will normally be in hot water or dichromate, which increases the corrosion resistance remarkably.

If you find this article useful and you would like to know more please contact me
 blog@aluconsult.com 

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More about Hard Anodizing

Due to my presentation at 17th Technical Symposium in Seattle about the History of Hard Coat - Hard Anodizing I am about to refreshing my previous posts with new links and more information.

 The Hard Anodizing Symposium will take place in the middle of September, the International Hard Anodizing Associtations webpage for more information regarding the Symposium and the people registered so far.
If you find this article useful and you would like to know more please contact me blog@aluconsult.com 

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IHAA 17th Technical Symposium in Seattle


Come join the International Hard Anodizing Association 17th Technical Symposium in Seattle and get a lot of new knowledge, network and talks about hard coat / hard anodizing.

Photo from last Symposium in Dusseldorf, 2016.
If you find this article useful and you would like to know more please contact me blog@aluconsult.com
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Review of the Aluminium Surface Science and Technology Symposium in Denmark, May 2018

By the end of May 146 people from more than 20 countries from all over the World were gathered to the 8th Aluminium Surface Science & Technology Symposium in Denmark – www.asst2018.com.
Since its first edition in 1997, the mission of the symposium has been maintained intact: to create a high-level international platform where science meets the industry. To do so, the symposium offers a very nice environment for a mixture of academics, PhD students and industrial colleagues.
The venue this year was set at the beautiful coast of northern Sealand – Elsinore in Denmark at Hotel Marienlyst.
The 8th Aluminium Surface Science and Technology Symposium follows the previous years’ symposium at 2015 (Madeira, Portugal), 2012 (Sorrento, Italy), 2009 (Leiden, The Netherlands), 2006 (Beaune, France), 2003 (Bonn, Germany), 2000 (Manchester, U.K.), 1997 (Antwerp, Belgium).
The Symposium series has been a unique and key event on aluminium surface science and technology bringing together industries, universities, and research institutions involved with aluminium.
Today the ASST symposium has become a common platform and net-work for aluminium surface science and technology in Europe and the rest of the world. This time gathering aluminium surface science people from countries like Germany, France, Japan, England, Alger, China, Belgium, Brazil, Denmark, Korea, Australia, Sweden, Norway, The Netherlands, Italy, Portugal, Spain, US, Chile and Poland.
The goal of the Symposium is to offer the participants a high-level meeting with attractive presentations and an interesting social program.

This year the program offered scientific topics, such as:
  • Heat Exchangers
  • Joining methods
  • Chemical conversion coatings
  • Electrolytic conversion coatings
  • Plasma Electrolytic Oxidation
  • Other Surface Treatments for aluminium
  • Inorganic and organic coatings for aluminium
  • Structure-Property correlations
  • Aluminium science, Technology, and characterization methods
  • Lithography techniques and Etching
  • Corrosion properties and performance
  • Thermo-Mechanical Processing
  • Multi-materials design and performance
  • Environmental free aluminium surface treatments
  • Architectural design and performance
  • Modelling of aluminium microstructure and corrosion

You can read the whole summary when the August number of Light Metal Age are on the street, or check back to see the upcoming posts regarding some of the presentations.
If you find this article useful and you would like to know more please contact me blog@aluconsult.com
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Galvanic corrosion = Bi-metallic corrosion on Aluminum

One of my most read articles on Anodizing World is the one about galvanic corrosion, therefore I have decided to dwell a little bit more about galvanic corrosion on aluminum.

When two dissimilar metals are in direct contact in a conducting liquid, experience shows that one of the two will corrode - hereby the name - Bi-metallic Corrosion or also called Galvanic Corrosion.

If two metals, e.g. aluminum and copper, are placed in sea water both metals will start to corrode. If the two metals are connect with a wire a current will flow, and aluminum will corrode faster and the copper will stop corroding. This is like a sacrificial anode of zinc on a boat, but here the anode is the aluminum.

Aluminum is a reactive (un-noble) metal compared to most of the metals used. Aluminum will therefore almost always be the anode, the part which corrodes, in contact with other metals.

The two main factors are the severity of the environment and the potential difference between the two materials, e.g. aluminum and copper.

The more aggressive the environment and the larger the difference in potential between the two metals are the more sever is the corrosion attack.

The bible "Surface Treatment and Finishing of Aluminum and its Alloys" by S.Wernick, R. Pinner and P.G. Sheasby shows the following table.

General guide to galvanic influence of various metals on aluminum.

Metal
Comment
Cadmium
Slight effect
Chromium
Small to negligible
Copper and copper alloys 
Severe
Graphite
Severe
Lead
Negligible except in severe marine environments
Stainless steel
Negligible except in severe marine environments
Steel and Iron                               
Slight except in severe environments
Tin
Negligible except in salt solutions
Titanium
Negligible except in severe marine environments
Galvanised steel
No effect until zinc coating is destroyed

If you find this article useful and you would like to know more please contact me blog@aluconsult.com
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Troubleshooting Aluminum surface issues!

Send me your surface finishing issue per. email, preferably with a photo, then I will ask detailed questions which you answer before the call, during the call we will clear out your questions together, coming up with ideas, new opportunities and results. After this call if you have any follow-up questions about the topic, you can sent an email, which I answer within in 48 hours.

Your investment?


An e-mail and one hour, and $495. Money you've earned into multiples when you can reduce your time used on this specific issue, and know what to expect of your product and what your requirements are.


Payment is easily done by PayPal using any major credit card.


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Troubleshooting Aluminum Surface Issues!

Send me your surface finishing issue per. email, preferably with a photo, then I will ask detailed questions which you answer before the call, during the call we will clear out your questions together, coming up with ideas, new opportunities and results. After this call if you have any follow-up questions about the topic, you can send an email, which I answer within in 48 hours.

Your investment?

An e-mail and one hour, and $495. Money you've earned into multiples when you can reduce your time used on this specific issue, and know what to expect of your product and what your requirements are.


Payment is easily done by PayPal using any major credit card.

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