Mechanism of Corrosion Product Growth on Nickel Aluminum Bronze/Ammonia or Seawater Interface: Modeling Based on Chemical Reaction Kinetics
Abstract
The open circuit potentials (versus SCE) were measured for nickel aluminum bronze (NAB) samples after exposure to seawater and 90 percent -10 percent, 80 percent-20 percent and 50 percent-50 percent water ammonia solutions for up to 34 days, in order to model the electrochemical reaction. The results suggest that the normalized open circuit potentials (versus SCE), can be used to determine the reaction kinetics. The results also suggest that the data (normalized potentials) obtained for up to 10 days shows significant scatter and this scatter is probably due to selective corrosion of different metals and/or the induction period for the corrosion process. The data obtained after 10 days shows a specific trend. The overall reaction for the corrosion of NAB in 90 percent-10 percent and 80 percent-20 percent water - ammonia solution is primarily diffusion controlled process. The order of reaction during the fast oxide growth suggests that only the concentration of the metal is changing with time. The overall reaction for NAB in 50 percent-50 percent water ammonia solution is controlled both by the diffusion process and also a change in concentration of metal. In order to compare the data obtained from open circuit potentials with the data obtained from structural analysis during the corrosion process, the electrochemical kinetics parameters were determined from earlier data on the change in the structure of nickel , nickel - copper alloy due to cathodic and anodic electrochemical reaction in KOH and seawater for reaction up to 24 hours. The results suggest that the kinetic processes are dominated by selective chemical reactivity of copper and nickel.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2006
- Accession Number
- AD1068207
Entities
People
- A. Strinivasa Rao
Organizations
- Naval Surface Warfare Center Carderock Division