Mechanism of Corrosion Product Growth on Nickel Aluminum Bronze/Ammonia or Seawater Interface: Modeling Based on Chemical Reaction Kinetics: Part-2
Abstract
In order to develop a model of the corrosion process based on the chemical reaction kinetics in materials, this investigation was undertaken. A mathematical model relating the process parameter (viz. the weight change, the measured open circuit potentials (versus SCE) and the change in the structure of the material) and the reaction time was developed. This model was tested with nickel aluminum bronze samples in NH4OH solution and seawater, and the kinetics parameters such, as the rate constant and the order of reaction, were determined. The nickel aluminum bronze (NAB) samples were exposed to seawater and 10%, 20% and 50% NH4OH solutions for up to 46 days. The weight change, the open circuit potentials (versus SCE) were measured, and the x ray diffraction patterns were obtained from all the corroded samples. The weight change data and the open circuit potentials were fed into the reaction kinetics based model and the oxide characteristics were determined. The results suggest that the kinetic parameter such as the order of reaction for the corrosion process that was predicted by feeding all three sets of data conclude that the corrosion of NAB in NH4OH solution or seawater is a diffusion controlled process. The kinetics of the fast reaction stage is controlled by the availability of NAB sample surface for corrosion. The slow chemical reaction stage is very complex. The complexity is perhaps due to the nucleation and growth of complex and mixed oxides/hydroxides. During the corrosion process the rate of corrosion of iron is the highest and the corrosion of the nickel is the slowest.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2007
- Accession Number
- AD1068249
Entities
People
- A. S. Rao
Organizations
- Naval Surface Warfare Center Carderock Division