Joint venture on greener chromium electroplating

Poeton Industries is part of a joint initiative to develop 'green' electrolytes to deposit chromium by electroplating.

Poeton Industries is part of a joint initiative to develop 'green' electrolytes to deposit chromium by electroplating.

Chromium metal is inert to virtually any other chemical and its low surface friction and bulk hardness makes it a particularly unique and useful coating, servicing virtually every sector of industry.

That hard or bright chromium plated surfaces are perfectly safe is demonstrated by the many well-established applications in industries such as medical equipment and food production.

However, although metallic chromium is a safe non-toxic material, some chemicals used in its production, such as electrolytes containing chromic acid, are not.

Which is why a project, partly funded by the sustainable technologies initiative (STI) from the DTI and EPSRC, addresses the replacement of chromic acid for chromium electroplating with a new benign and sustainable technology based upon Cr(III) containing ionic liquids.

The project involves close co-operation between a number of academic and industrial partners.

The University of Leicester is developing the new methodologies.

Poeton Industries will develop and test the technologies on a pilot industrial scale.

Smiths Aerospace Actuation Systems will apply and validate the techniques on high-tech aircraft components.

And Whyte Chemicals will formulate the novel ionic liquids and supply them to end-users.

Scionix, a joint venture company between the University of Leicester and Genacys, manages the whole project.

The major disadvantage of the current process of chrome plating is that it requires the use of chromic acid-based electrolytes comprising hexavalent chromium - Cr(VI).

The toxicity and carcinogeneity associated with Cr(VI) has resulted in wide-ranging environmental legislation in the USA and Europe to reduce its use.

The novel chromium deposition process being developed uses Cr(III) salts, which are significantly less toxic than the Cr(VI) species.

In addition, the process will operate with around 90% current efficiency.

As these are not aqueous solutions, there is also a dramatic reduction in hydrogen evolution, which means that more crack-free, highly corrosion resistant deposits should be possible.

This may also allow thinner deposits, thus reducing overall material and power acid vapours.

The working conditions for operators are also dramatically improved.

Further benefits will include the minimising of required effluent treatment and elimination of air pollution control measures.

It is anticipated that the development of ionic liquid-based chromium plating processes will have a significant impact on industrial sustainability for chromium plating.

Another important part of the project is the life cycle assessment for the re-use of the ionic liquids.

Formulation of the ionic liquid does not require organic solvent, high pressure, high temperature or extended reflux conditions.

Vapour pressure characteristics mean that losses to the atmosphere are negligible, and the resulting potential for re-use and recycling of ionic liquid materials is high.

The materials employed are far less toxic than those currently used and energy requirements for electroplating processes will be significantly reduced.

As the technology developed by this project is generic to most metal plating systems, it also represents a significant advancement for the environmental sustainability of major industrial processes.

The significance of this project is summed up by Dr Gregor Rozenberg, business development manager for Scionix, who says: "All the benefits that ionic liquids inherently bring can now be applied to large scale processes.

The process is revolutionary because it introduces a completely new range of electroplating electrolytes - and the advantages are very apparent.

Not only is the process environmentally benign - it is also cheaper, easier and safer to use than comparable alternatives".

(This was Engineeringtalk's Top Story on 9 October 2002).

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