Editorial Magazine 2016/4
New second life for anodizing
THE DEFEAT OF THE “BAD PROPHETS”
The last 30 years in the history of surface finishing have seen the development of painting, considered by some “bad prophets“ as the alternative to anodizing.
I have known prophets of this school. They include those selling paints and painting plants, paint appliers or paint consultants, all of them always ready to trim their sails to suit the prevailing wind.
Well, dear self-appointed prophets, keep your minds on your jobs and stop issuing prophesies, at least for the next thirty years.
In spite of the boom in painting, anodizing is in better health than ever; it is constantly renewing itself, modernizing and setting fashions, but above all it provides quality and is starting to be used as a pretreatment for painting, to prolong its life and stop it falling ill with the filiform corrosion virus. Let’s take a more analytical look at the situation.
Until some years ago, everyone took it for granted that anodizing was going to be swept aside by painting, because of the limited range of colours resistant to outdoor conditions it was able to offer. In response, we have seen the invention of a revolutionary technology able to produce new colours with the guarantee of electrocolouring from grey to blue, green, golden yellow, brick red and also special effects (Aludecor). Many architects are already showing enthusiasm and some leading firms are buying the technology and yet others are starting to prepare the market.
The first problems with painting came to light after years of its unregulated use; so the process has started to be governed by norms, specific control tests and quality label.
The producers of painted elements give guarantees of about ten years, while the purchasing specifi cations for anodized parts indicate up to twenty years, thanks to over 70 years’ experience, and buildings constructed in the 60s or 70s with anodized aluminium frames that are still in excellent condition.
Now we come to the early ‘90s. In various countries worldwide, people were starting to notice an unusual type of corrosion on painted aluminium, known as filiform because of its strange long, narrow, threadlike shape. Filiform corrosion seemed to be unpredictable, appearing in some case but not in others, sometimes after one year, sometimes after five. It was discussed all over the world, at all the congresses. Our journal also carried many technical articles on the topic. Everyone talked about it, but it seemed insoluble.
Then a familiar rabbit popped out of the hat: anodizing, yes anodizing, seems to be the best way of saving painting. Naturally we mean anodizing as pretreatment: 3-6 microns seems to solve the problem perfectly. Users simply have to adopt a specific know-how and the anodic oxide prevents filiform corrosion, also providing an excellent substrate for adherence of the paint.
Anodizing has now started again to be “the fashion” mainly due to its large recent introduction in the automotive market besides the architectural, decorative and mechanical ones.
Walter Dalla Barba,
Editor and Chairman of the 10th Aluminium Two Thousand Congress, Verona 2017
Interall Srl, Via G. Marinuzzi 38, 41122 Modena – Italy