Improving Corrosion Resistance of Co Using Silane Coupling Treatment in Neutral Solution

Many products using a magnetic property, a mechanical property and chemical property of the thin metal film of the nm order are developing in the great many fields. The establishment of technology for corrosion prevention under nm level or the atom level is necessary to control corrosion without losing the characteristic of these products. In this study, surface treatments using BTSE, BTSPA, and BTSPS were evaluated from the viewpoint of improving the corrosion resistance of thin cobalt films. Corrosion behavior was evaluated corrosion current density using Tafel plots. Treated cobalt films were characterized by XPS and observed by SEM and AFM. A silane-coupling layer formed on the cobalt as a result of each of these treatments. However, the corrosion resistances offered by the different layers varied significantly. Immersion in BTSE with hydrogen peroxide for one hour did not yield an improvement, whereas immersion for 24 hours resulted in a large improvement. In contrast, immersion in BTSPA with hydrogen peroxide for 24 hours did not lead to a corrosion improvement, whereas immersion for one hour provided corrosion resistance. Immersion in BTSPS with hydrogen peroxide for either amount of time yielded no improvement, because of the poor coherency of the deposit on cobalt. These behaviors can be explained in terms of the hard and soft acid-base principle.