A story of quality and winning choices
The explosion of the phenomenon of filiform corrosion caught many technicians in the sector of painted aluminium processing and applications unprepared, but in aeronautics and island environments it had already existed for several years. It is only recently however that anodic oxidation has started to be discussed as a remedy for the phenomenon, used as an anticorrosive pretreatment before aluminium is painted.
ANOFOR has been working in the field of anodic oxidation since 1967. In 1973, in the earliest days of coloured aluminium, the company also decided to experiment with painted aluminium, perfecting PRE-OX, a special layer of anodic oxide, as a pretreatment before painting, further enhancing the resistance of the layer of anodic oxide to corrosion by anchoring it to a layer of stove-cured paint, using both solvent-based and powder products.
The first task of ANOFOR was to test the already familiar resistance of anodic oxide to corrosion by anchoring a layer of solvent-based paint to it, supplied by US multinational PPG. In 1976, working in collaboration with ISML, a highly experienced light metals experimental centre in Novara, Italy, ANOFOR subjected samples treated with anodic oxidation and painted with PPG’s Duracron Super 630 to atmospheric exposure tests at the Marina di Arenzano test station on the Ligurian coast, at a time when the polyester powder paints capable of guaranteeing the same resistance to corrosion were not yet available.
After 10 years of exposure, ISML Test Report 86/27097 of 18 September 1986 certified the absence of filiform and sub-surface corrosion at the cross-cuts scratched on the samples before exposure. The findings of the ISML report are also confirmed by the following:
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At the ANOFOR headquarters, many years after door and window fittings were painted in 1973, they are still totally free from all traces of filiform and other corrosion, an absolutely outstanding result considering that the doors on the tank platform are in constant contact with humidity and pollution and are exposed to stray and/or electrochemical currents, particularly when the system is at a standstill without forced ventilation for air circulation;
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The black columns of the Hotel Splendid at Bellaria Igea Marina (RN), situated just 150 metres from the sea, were painted in 1980 and are still totally free from corrosion;
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The head offices of the CRA bank in Bellaria Igea Marina, now Romagna Est, are 500 metres from the sea and were painted in 1981, and like many other jobs carried out on the Adriatic coast and elsewhere, have had no problems of any kind over the years.
A necessary choice
In the following years, with the sharp increase in request for painted aluminium, innumerable aluminium painting systems appeared on the market, all with chromate and/or phosphochromate pretreatments and with varying levels of automation and price. Obviously, at this stage ANOFOR decided to align itself with market trends by creating a subsidiary specializing in aluminium painting, in strict compliance with the standards of the time for chromate pretreatments.
However, around 1990, when the first signs of filiform corrosion on aluminium doors and windows were reported, ANOFOR, after scrupulous checks and analyses in collaboration with Granata SpA, our supplier of chromate treatment products, found itself in an absurd situation, as despite having been pretreated and painted in full compliance with all the applicable technical standards, the finished aluminium profile bars still failed to satisfy the expectations of end users, because they had already been attacked by corrosion within the first six months.
The market laws of supply and demand inevitably continued to force prices down, and it would have been too idealistic to think it might be possible to raise market awareness on the problem so that it could be tackled at the root, perhaps by investing a little more money to obtain greater guarantees of product quality. The problem was totally underestimated, and whenever corrosion appeared it was preferred to attempt to solve it by replacing the components believed to be defective. This is why ANOFOR decided to leave the field of painted aluminium profile bars.
The new solution:
PREOXIDATION FOR LASTING QUALITY (PRE-OX)
ANOFOR, firmly believing that painted aluminium door and window fittings, with all their undeniable advantages like excellent visual appearance, practicality, functionality, long lifespan and flexibility in adapting to design needs, should not be totally discarded, attempting only temporary solutions to delay the possible onset of corrosion, such as protective films, waxes, resins and similar solutions, which like an aspirin for toothache have no lasting effect on the basic problem, ANOFOR decided to return to aluminium painting, but only and exclusively after pretreatment with anodic oxidation (PRE-OX) to GUARANTEE resistance against corrosion, as demonstrated by decades of exposure even in particularly extreme conditions, including industrial and coastal areas.
WOOD EFFECTS ON “DECOROX” ANODIZED ALUMINIUM: IMITATING NATURE TO AVOID DESTROYING IT
While anodized aluminium finishes had limitations in their visual appearance in the past, the treatments now available make it possible to perfectly reproduce wood and stone effects, with faithful replicas of precious finishes from briar through to granite and modern abstract designs.
ANOFOR IS THE SOLE LICENSEE OF THE PATENT FOR THE DECOROX PROCESS
developed and patented by Medardo Casadei, which is a special cycle for the production of attractive wood effects on electrolytically coloured anodized aluminium. The process consists in a phase of anodic oxidation and electrolytic colouring of the aluminium, specifically devised to be able to incorporate a subsequent phase of decoration by heat transfer, and then completing the procedure with a layer of special polyester powder that is cured by heat, improving sealing and the surface finish and ensuring outstandingly high resistance against corrosion and weathering.
Today, all users looking for solutions to their problems of product appearance, functionality and durability – from architects and builders to retailers and homeowners – can unite the indisputable properties of anodized aluminium, which include the consolidated certainty of resistance to corrosion, solidity, lightness and an extraordinary range of design options, with the natural beauty of stone and wood, in applications like the construction industry, doors and windows, town centres, transport systems and many others.
