During the pretreatment process of aluminium, prior to the application of powder coating, metal surfaces are thoroughly cleaned and chemically etched. A pre-treatment 'chemical conversion coating' is then applied that offers both corrosion protection and a substantial ‘key’ for the final finish. For many years ‘chromates’ have been used, but now they are soon to be replaced with safer solutions. Non-chromate systems have been commercially available for a number of years now, and Qualicoat has evaluated and issued formal Qualicoat Approvals for some of these non-chromate systems to ensure they meeting its rigorous requirements. Approvals from Qualicoat ensure these Chrome free systems meet the quality demands of specifiers and end users.
Chromium in its hexavalent/chromate form is a hazardous substance and is on the ECHA (European Chemical Agency) candidate list to come under very stringent regulation from September 2017, chromate processes are scheduled with this ‘sunset date’. Over half of the current Qualicoat UK and Ireland applicators are already using, or now in the process of changing to, chrome-free alternatives well ahead of the due date.
Chromate pre-treatment is still being used by some Qualicoat members as it is a resilient and easy to apply conversion layer for aluminium that has been tried and tested for over 60 years. Once the process is complete, the finished aluminium profile, sheet or casting, carries no chrome (VI) and so is safe to use and recycle within the construction supply chain. Applicator employees are protected under the guidance of the COSHH regulations (Control of Substances Hazardous to Health) when working with these pretreatment systems.
Chrome-free systems may require additional production equipment and certainly a professional level of process control, both of which are an investment in future production for the applicator. Early adopters of chrome-free pretreatment systems now have a range of systems available and the experience to select systems that suit their plant and throughput. When applied correctly, chrome-free pretreatment systems are as effective as their chrome bearing counterparts.