protection. No clues were given to identify the formula or even the generic make-up of the compound, although it is apparently purely organic, with no silane component. It is said to be a bioremediated cleaner, needing little or no changing, which gives a dry-in-place coating having excellent adhesion measured by either tape or reverse impact test. The process is claimed to be resilient to contamination. No biocides are used in the remediation stage; in answer to a follow-up question apparently no cases of Legionnaire’s disease have been reported! Although we all understand the need for supply houses to protect commercially sensitive information, there was an element of frustration in trying to evaluate this process and its “black box” secret chemistry. Loughborough University’s Dr Gary Critchlow discussed the latest results his group have obtained from an alternative process to chromic acid anodising (CAA) for bonded structures of Al 2000 and 2024 alloys, giving durable bonds with applied epoxy adhesive. CAA apparently gives an order of magnitude higher surface free energy than other standard processes and thus greater wetting. It also gives 25 μm pore diameter compared to eg 10 μm for standard boric sulphuric acid anodising (BSAA), and thus greater primer penetration. Dr Critchlow explained how varying different parameters with BSAA eg deoxidiser and bath temperature, in particular, voltage and electrolyte make-up yielded results close to those of CAA processing. Duplex porous and compact layers were also possible with AC anodising giving porosity and adhesion, and DC (in the same electrolyte) providing compact corrosion resistant layers. Processing time in the modifi ed BSAA is claimed to be about 10x less than that of CAA, 12.5 mins cf 2.5 h. Richard Starkey (Safechem Europe GmbH) has described the continued use of chlorinated solvents recently, particularly in relation to the European Solvent Directive, in this journal1, and his presentation at this meeting followed the same theme of solvents such as trichloroethylene being associated with precision cleaning, and how the name of the game was matching the best cleaning solution with meeting legislative requirements and not compromising quality. One important point made was that waste Trike is now fully recyclable. The slightly mysterious world (to many of us) of abrasive fi nishing and pre-treatment was expertly dealt with by Peter Longstaff of Wheelabrator Group, who explained not only the types of abrasives available – eg ceramics, glasses, plastics – but also their different modes of action, broadly, eroding abrasives which cut and erode by use of angular particles, and peening abrasives which tend to be round and knock contamination from the surface. Different types of bead also give specifi c surface fi nishes eg certain glass beads for satin fi nishes. In addition Peter Longstaff discussed the importance of selecting the abrasive fi nishing equipment carefully to match the customer requirements. Andy Rabbetts (Henkel Locktite Adhesives Ltd) presented a “novel conversion coating technology” as a substitute for tricationic zinc phosphate. Once again little information was given to identify it, but it is claimed to equal or be superior to zinc phosphate in a number of ways: more environmentally friendly, meets OEM specs, reduced process costs – thinner coating (50 nm cf 150 nm) leading to less sludge, ambient operation vs 55°C, no activation or post rinse stages, short treatment times (spray 30–90 s, immersion 30–180 s), price of phosphate increasing drastically, and a robust easy to handle process meaning easier bath control. Ceramic fi ltration, relatively new to paint and plating operations, was discussed by Ray Newell (Power Utilities Ltd). It is apparently ideal for alkaline cleaner baths. A fi ltration rate of about 24 litres per minute is claimed for larger units, and a minimum particle size which can be dealt with of 0.1 μm This one-day meeting, organised by the Organic Finishing Group of the IMF, and held at the Birmingham Medical Institute on 14 October 2008, proved to be very informative and successful, attracting about 60 delegates, exhibitors and speakers. The talks covered a wide spectrum of topics, of both research and industrial bias, and inspired considerable audience participation and questioning.
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Aug 16, 2024
Shuqing Zhang + 5
Open Access