Many industries today use foil coatings on aluminum surfaces for temporary protection against damage, especially for architectural applications. However, if film or adhesive residues remain on coated or anodized aluminium, they not only have a negative effect on the visual appearance, but can also reduce the adhesion properties of the surface. The Verband für die Oberflächenveredelung von Aluminium e. V. (VOA), together with its member companies and relevant specialist companies from its extensive network, has been working intensively on this complex topic and has carried out extensive tests with various films on finished aluminum surfaces. Based on its cross-industry expertise, the association has now summarized the accumulated specialist knowledge in the new leaflet A 09 B 07 "Protective foiling of aluminium surfaces", which is aimed at anodizers, coaters and all interested parties.
The final inspection of a new building is imminent: At the last moment, the employees remove the protective films from the building elements that have served them well during transportation or assembly. But there is a nasty surprise waiting underneath: if the film remains on the surface for too long, if it is exposed to sunlight or strongly fluctuating temperatures or if an unsuitable adhesive is used, adhesive residue remains on the surface after removal. This does not look good and may also impair the properties of the surface. Different influencing factors can interact here and produce different defect patterns. Correcting them is not only annoying - especially in a newly constructed building - but also requires unplanned measures that are usually time-consuming and costly.
To ensure a successful surface in the construction sector, it is also important to protect the surfaces accordingly so that they are not damaged. This applies to all companies in the surface finishing industry. In addition, the licensees of the international quality marks Qualanod for anodized and Qualicoat for coated aluminium, for which the VOA acts as general licensee in Germany, know that customers expect particularly high quality here. At the suggestion of VOA member companies, the interdisciplinary project group "Foiling" was founded, in which various companies from the fields of anodizing and coating, manufacturers of profile systems, powder coatings, chemicals and foils as well as experts and testing institutes work together. The aim: to gather all practical experience, expand it by simulating different adhesives on the surfaces and record it in a VOA leaflet in order to provide practical tips for companies in the surface finishing industry.
The VOA project group carried out extensive tests on foil and adhesive residues on finished aluminum. A total of four powder coatings from two manufacturers were used. The coated workpieces were provided with four different protective films - designed for the architectural sector - also from two manufacturers, one of which was applied smoothly and the other with folds. For an even more meaningful result, the VOA used protective films with different adhesive characteristics. Two tests followed: one was the so-called QUV-B test 313 nm over 350 hours with alternating irradiation at 60 °C and moisture exposure at 40 °C and the other was the climate change test based on the Volkswagen factory standard VW PV 1200. In the end, depending on the pairing of the four different powder coatings and films, the results were sometimes very different. The tests therefore make it clear that many aspects play a role in the selection of suitable protective films, which the VOA addresses in its new information sheet.
The conclusion of the project group: there is no simple standard solution in the sense of a universally applicable film for all applications and substrates for surface-finished aluminum. This was also repeatedly made clear by the film manufacturers. It is therefore advisable for VOA member companies and customers to have comparative tests carried out in advance by various suppliers in order to find the optimum film for the respective application, taking into account the most important powder coatings.
With its leaflet series, the VOA provides its members and interested groups of people with broad, well-founded information for day-to-day work in the company. On average every four years, the VOA project group "Updating the information sheets" reviews them with regard to the current state of the art and the standards and literature references listed.
