Electrochemical Studies of Passive Film Formation and Corrosion of Friction Stir Processed Nickel Aluminum Bronze.

摘要

The Navy currently uses Nickel-Aluminum Bronze (NAB) for its propellers. Friction stir processing (FSP) is a proposed method of improving the mechanical properties of NAB, and it is believed to improve the corrosion- resistive properties of NAB. This thesis used multiple techniques to compare the corrosion resistance of as-cast NAB with FSP NAB. Passive films were grown on the as-cast (AC) and FSP samples and modeled in order to relate the impedance data to changes in phase and microstructure resulting from FSP of NAB. Impedance modeling provides a way of measuring the passive film that forms on a metal and protects it from corrosion. In addition, cyclic polarization data was taken in order to study the stability of the films over a range of potentials. This data was then compared with SEM images to link the changes in the passive films with the changes in microstructure that occurred due to FSP.