On my way home from a great Aluminium2000 congress with a lot of good and inspiring presentations - also a lot of talks and discussion about secondary aluminium and how we can use more of the recycled aluminium and how we can obtain a quality anodised layer.

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Just invited by Apple to have a presentation about Pulse Anodizing at the Aluminum Anodizers Council´s Annual Anodizing Conference & Expo in Houston, Aluminum Anodizers Council- if you can´t wait you then join me at the Aluminium 2000 world congress where I will have a presentation "Up-date on Pulse Anodizing". hashtagsustainabledevelopment hashtaganodizing hashtagpulsehashtaghashtag

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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,


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.

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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 ┬Ám (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.

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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.

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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.

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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.

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