Special USF Vacu-Blast Ventus® machine chosen for controlled surface preparation prior to precious metal coating

Citation

(2003), "Special USF Vacu-Blast Ventus® machine chosen for controlled surface preparation prior to precious metal coating", Anti-Corrosion Methods and Materials, Vol. 50 No. 4. https://doi.org/10.1108/acmm.2003.12850dad.006

Special USF Vacu-Blast Ventus® machine chosen for controlled surface preparation prior to precious metal coating

Special USF Vacu-Blast Ventus^® machine chosen for controlled surface preparation prior to precious metal coating

Keywords: Surface preparation, Coatings, Metals

One of the world's leading specialists in chemical control, water treatment and purification systems, Chemfeed Ltd (part of Vivendi Water), has recently commissioned a new, purpose-built facility at its Tonbridge, Kent site, for the precious metal coating of alloy tubes used as anodes in the company's process equipment. The coatings employed are based on platinum, ruthenium and iridium (Plate 4).

Surface coating of the anodes with the company's specially formulated process, allows the transmission of an electrical current through brine to turn it into a sodium hypochloride solution (bleach).

Plate 4 The USF Vacu-Blast "Ventus^® 150P AXT" machine installed by Chemfeed Ltd for the precision surface preparation of anode tubes prior to a special precious metal coating process, showing the purpose-designed rotating jig with a tube in position

Controlled surface preparation of the tubes forms a vital part of the overall coating process in order to ensure optimum coating adhesion and integrity – an operation which is achieved using a special automatic "Ventus^® 150P AXT" machine, designed and manufactured by USF Vacu-Blast International, Slough. The surface preparation operation follows an initial acid wash and water rinse.

The Vacu-Blast machine uses 30 mesh aluminium oxide media to precision etch both the internal and external tube surfaces. The tubes – which can measure up to 1.5 m in length and up to 60 mm in diameter – are retained on a specially designed fixture and rotated under a traversing blast nozzle which provides external surface etching. Internal etching is achieved using a blasting lance that extends progressively through the internal bore, again as the tube rotates. The whole process is governed automatically and takes place in an hermetically sealed 1.5 m wide × 1.4 m deep × 1.2 m high blast enclosure. Processing parameters such as blast pressure and duration and speed of rotation are programmable according to the size and type of tube being processed. The tubes are loaded and unloaded manually through a safety-interlocked access door.

During the etching operation, discharged media is recovered, along with dust and debris, via a hopper and pneumatic conveyor to the machine's generator-reclaimer system. The latter separates out reusable media, cleans it in a high integrity reverse-jet pulse unit and recycles it back to the pressure-fed blast nozzle system. Degraded media and debris are directed to a dust collector. Together with automatic control of the surface preparation process, this continuous media regrading process ensures a reliable and consistent surface etch at all times.

The "Ventus 150P AXT" is one of an extensive range of manual, semi-automatic and automatic cabinet machines available from USF Vacu-Blast International, with processing enclosure sizes up to 2 m × 2 m × 2 m.