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What is QUALICOAT Seaside ?
As the name suggests , an architectural powder coating to be used in coastal applications , but what does this additional endorsement mean for QUALICOAT licensed applicators ?
BY CHRIS MANSFIELD - QUALICOAT CHAIR
An architectural powder coating finish relies on its ability to adhere to the aluminium substrate . If there is no ‘ key ’ to adhere to , as is the case for untreated aluminium , the powder coating is prone to chipping or flaking off in over time . Powder coating is porous at the molecular level and a coating on an untreated aluminium substrate , subject to weathering , will continue to oxidise under the coating . So , no matter the quality or thickness of the powder coating that is applied , it will not offer the anticipated life expectancy . Crucially , a thin ‘ conversion coating ’ on the base metal , which is part of the pretreatment process , offers the vital seal the metal surface and a key for the powder coating to adhere to .
The surface of extruded fenestration aluminium also carries contaminants from the extrusion process which , if left on the surface of the aluminium , will reduce the performance of the ‘ conversation coating ’. Removing these contaminants from the extrusion is part of the pretreatment process undertaken by either dipping or spraying an acid or alkaline solution which etches the surface of the aluminium removing a minimum of 1g / sm of aluminium . Without this surface etch potential corrosion could form around the contaminants on the aluminium substrate once coating has been completed . Given that the pretreatment process is undertaken correctly , in accordance with the QUALICOAT Specification , architectural powder coated products will offer an extensive life expectancy in most locations . The pretreatment process is actively monitored by members of the Association and third party inspected by IFO , QUALICOAT UK & Ireland ’ s independent test house .
Introduced in 2008 , QUALICOAT also offer a ‘ Seaside ’ class of powder coating where the minimum removal of aluminium surface is increased to 2g / sm using a dip or spray process of either an acid or a combination acid / alkaline etch . This deeper etch removes more contaminants and therefore offers a more robust pretreatment for areas where atmospheres carry corrosive salts ( chlorides ) and other aggressive pollutants .
QUALICOAT licensed applicators who wish to offer ‘ Seaside ’ class coatings need to apply for an additional licence . The applicator needs to demonstrate that they can remove the 2g / sm by process and
monitoring , plus the applicator must offer a coated ‘ Seaside ’ sample for an additional filiform corrosion test carried out in the IFO laboratory . Licensed coaters who are licensed to offer ‘ Seaside Class ’ are clearly identified on the Associations website . Filiform corrosion is a spider like blistering that creeps under the powder coating and runs along the aluminium grain boundaries . A deeper acid or alkaline etching removes more trace elements from these areas making the grain boundaries more resistant to corrosion . Statistically , with this greater etch of 2g / sm , filiform resistance is increased significantly . The following pretreatment conversion coating can then be applied using any of the QUALICOAT approved systems .
Another method of increasing resistance to filiform corrosion is by using a ‘ pre-anodisation ’ process , sometimes referred to as PREOX or Flash Anodising . A more expensive pretreatment , this thin anodising film of just 4-8 µ m ( microns ) totally removes all the grain boundaries ,
56 NOVEMBER 2024 CLEARVIEW-UK . COM