Abstract
The technology of magnetic recording, which is involved in most aspects of modem life from credit cards to video tapes, is evolving at an ever quickening pace. As the industry strives to produce greater recording capacity and increased information density the demands on the development of improved magnetic storage and recording head materials cannot always keep up with the pace of change. The materials being considered are not only required to have the desired magnetic properties but also to have the necessary corrosion resistance in the operating environment. It is often the latter which can limit the rate of development of new devices since many of the new materials considered for magnetic storage applications consist of very reactive metals with low corrosion resistances. In establishing how research on the corrosion properties of new magnetic materials should be approached, two different experimental routes are explored in this thesis. These studies were a) a combined electrochemical and surface analysis study and b) a novel 'in-situ' SIMS study. The electrochemical study proved to be a very valuable route in obtaining information on the corrosion properties of the magnetically-active alloy FeMn and such a study can be highly recommended for the application to other magnetic materials. The complete electrochemical properties (anodic and cathodic) of FeMn were determined. A region of passivity was revealed through the application of the very sensitive solution analysis technique of ICPMS. The passive layer is associated with a manganese hydroxide rich surface layer. Passivity in the alloy is very vulnerable to corrosion attack by sodium sulphate active ions. The influence of temperature and pH was investigated. Only under low values of pH with the conditions investigated was the corrosion attack increased compared to neutral conditions. The application of sodium chromate inhibitor was found to enhance the passive layer formed. Using the second route the application of a novel 'in-situ' SIMS technique to look at the oxidation properties of magnetic metals and alloys was explored. The interpretation of the SIMS data for the oxidised and unoxidised components of cobalt was achieved and a model for the reaction of cobalt with oxygen at the initial stages of oxidation was successfully produced. At this present stage it is not possible to model the oxidation of more reactive metals than cobalt.