The Electrochemical Colouring of Austenitic Stainless Steel in Environmentally Benign Solutions
Lead Research Organisation:
Loughborough University
Department Name: Materials
Abstract
The project will address the following issues :
Alternative processes for colouring stainless steel based on benign chemistries
A full understanding of the chemistry/electrochemistry of the colouring processes developed to date including the role played by the stainless steel substrate
To scope the cost of using benign chemistries to determine if they are viable for manufacture on a commercial scale
An investigation of the colouring stages for successful processes in terms of their process parameters i.e. solution compositions, process times and temperatures etc
An investigation of coloured surface properties e.g. colour retention, abrasion resistance, film stability etc
An investigation of scale-up issues of promising colouring systems.
Alternative processes for colouring stainless steel based on benign chemistries
A full understanding of the chemistry/electrochemistry of the colouring processes developed to date including the role played by the stainless steel substrate
To scope the cost of using benign chemistries to determine if they are viable for manufacture on a commercial scale
An investigation of the colouring stages for successful processes in terms of their process parameters i.e. solution compositions, process times and temperatures etc
An investigation of coloured surface properties e.g. colour retention, abrasion resistance, film stability etc
An investigation of scale-up issues of promising colouring systems.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509516/1 | 01/10/2016 | 30/09/2021 | |||
| 1808624 | Studentship | EP/N509516/1 | 01/10/2016 | 30/03/2020 | George Alliott |
| Description | In the 1970's International Nickel developed an electrochemical process for colouring stainless steel, often referred to as the INCO process, which utilises chromic acid and has become well established in industry. It is a multistage process which produces a thin interference oxide film on the surface of the stainless steel. The colour produced is dependent on film thickness. The use of hexavalent chromium (Cr6+) has been subject to scrutiny from the EU in the Registration, Evaluation, Authorisation and restriction of Chemicals (REACh) regulations and the Restriction of Hazardous Substances (RoSH) directive. Restricted use and an eventual ban on the use of Cr6+ for this application has resulted in the need to find an industrial replacement for the INCO process, however, there is currently no industrially established direct replacement. In the present work several new electrochemical processes, which avoid the use of hexavalent chromium have been developed. Candidate processes have been shown to produce a range of interference colours on the stainless steel, some of which have not been previously achievable with the INCO process. The use of advanced analytical techniques, such as transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), have allowed for characterisation of film chemistry and morphology. These analyses aided understanding of the film formation process and identification of how process parameters may be optimised to yield the most significant improvements in film performance. Although development of the most promising and suitable replacement for the INCO process is still in the early stages, investigations to date have yielded encouraging results in terms of aesthetics and physical properties. |
| Exploitation Route | If someone was to continue to pursue an electrochemical alternative to the INCO process, this research could be used as a foundation for further development of the processes outlined within the thesis. Furthermore, if a process appeared not to be suitable for for investigation this has been outlined and would prevent other researchers from using time repeating this work. |
| Sectors | Construction,Environment |