Surface World Handbook 2017 Surface World Handbook 2017 - Page 188

QUALICOAT UK & IRELAND ‘QUALICOAT Approved Two Coat Systems for Architectural Aluminium’ by Alan Maginnis – QUALICOAT UK & Ireland Chairman The global powder coatings specification for powder coating over aluminium now in its 14th Edition has its strength in the ‘triple lock’ approval system, firstly, the pretreatment chemistry, secondly the application process, and thirdly the powder used, where for each of these three elements independent approval and inspection is required. For the vast majority of architectural applications, the standard QUALICOAT approved one coat system is perfect, where the strength of weathering is identified by the Class of powder chosen. Environment “So, why two coats!”, I hear the refrain. “Is this a ruse by the industry to charge more for powder coating?”. Well… In more challenging environments (C4/C5) certain aluminium materials and fabrications may be more susceptible to corrosive attack. Two coats, or multi coat systems have been available in the paint industry from the beginning, starting with wet paints. Powder coatings from their inception have penetrated the paint market well often on economic grounds as it is an effective one coat system. For powder coatings, as the technology has improved the use of multi coat systems has become more common place typically for industrial purposes over steel e.g. for plant, machinery and equipment. Materials For the architectural world for powder coating over aluminium a ‘two coat system’ maybe relevant in specific circumstances. What might these be? The corrosion class of the environment where the building is located is the main consideration, followed by the material to be coated, and then 186 from a commercial point of view, for the warranty period to be offered. BUT there are a few occasions where real consideration can be given to the effective use of two coats. QUALICOAT, in recognition of these developments has now approved a number of excellent two coat systems, these can be seen on the approved powder systems list at 2017 - 2018 Environmental corrosion classes from C1 to C5 are outlined and described in ISO12944-2, where C5 is the most corrosive environment. Let us consider perforated aluminium sheets. Probably the weakest area for any paint finish is the sharp edge. Sheets have 4 sides and potentially 4 sharp edges. A perforated aluminium sheet additionally has 100’s of punched, sharp perforations. This multiplies the risk areas considerably. Commercial Warranty QUALICOAT is a specification label and is not involved in such considerations. The approved applicator however and the approved powder supplier are the parties who offer warranties. Where a location is hazardous; where the coated part is challenging; where a long period warrant is required, a two coat system will help. read online: