This project aims to develop technology for the surface treatment of a range of metals and alloys in order to eliminate the use of hexavalent chromium compounds. These chemicals are widely used throughout Europe and elsewhere to deposit conversion coatings on many metals and articles. However, their application has serious risks, since they are carcinogenic, and are a fire hazard. Disposal of spent solutions is also costly, since reduction to the trivalent state, which is non-toxic, is generally required In general terms, the technical programme will proceed along four main lines, i.e.
(a) Development of immersion baths based upon permanganate.
(b) Anodising in the presence of manganous ions.
(c) Deposition of chromium trioxide films from trivalent chromium baths.
(d) Extension to zinc coated steel and other active metals.
Processes based on routes (a) - (c) have been described in previous studies, with particular success being achieved on oxide covered metals such as aluminium, and will be subjected to more complete development and assessment. Similar techniques will be applied in (d) to obtain a suitable method for use on zinc coated steel. Various metals, in sheet form, and small commercially produced articles will be used as test pieces throughout.
After treatment the results will be assessed by several methods including rapid electrochemical tests of corrosion resistance, salt spray tests, and paint adhesion. The involvement of many SMEs will ensure that the choice of work pieces, and their subsequent appraisal after coating, are relevant to the needs of industrial users.
In the later stages of the project, on line coating of articles in the work place environment will be demonstrated. Pilot trials of the more complex innovative routes will also be carried out. The participation of a large number of SMEs in the project will ensure that the final evaluation, and the subsequent exploitation are carried out in a realistic manner.
Funding SchemeCRS - Cooperative research contracts
402 72 Goeteborg
NE21 5AB Blaydon-on-tyne
B1 3LF Birmingham
4794 SN Heijningen
20009 San Sebastian
2404 CD Alphen Aan Den Rijn
WF13 3JW Ravensthorpe
LS9 0NY Leeds
TW8 8HU Brentford - Middlesex
B1 1NQ Birmingham