College

College of Engineering (COE)

Date of Last Revision

2020-05-07 11:53:45

Major

Chemical Engineering - Cooperative Education

Honors Course

Honors Project (4250:497)

Number of Credits

3

Degree Name

Bachelor of Science

Date of Expected Graduation

Spring 2020

Abstract

The purpose of this Honors Research Project is to show the effect of sensitization on intergranular corrosion (IGC) on AA5083. Sensitization is the process of a material to experience microstructural phase change, caused by thermal treatment, which promotes precipitation of secondary phases on the grain boundaries. The nitric acid mass loss test (NAMLT), SEM analysis, cyclic potentiodynamic polarization (CPP), and Electrochemical Impedance Spectroscopy (EIS) were performed to find a correlation to the degree of sensitization (DOS) and the pitting and IGC mechanisms. The DOS increased as heat treatment was applied. The SEM images displayed no clear precipitates on the grain boundaries for the as received sample, but after 7 days sensitization at 100°C, AA5083 sample saw β-phase precipitates formation on the grain boundaries, inducing IGC from β-phase dissolution. In addition, the 7 days specimens began seeing pitting due to development of intragranular β-phase precipitates. The CPP plot concluded that as DOS increased, Ecorr decreased. The CPP plot showed that sensitization influenced the pitting potential and resting potential. The sensitized specimen showed an impedance decrease, therefore lower corrosion resistance for the sensitized sample. This work demonstrates a huge weakness for sensitized AA5083 and research into this matter is vital.

Research Sponsor

Dr. Bastidas

First Reader

Dr. Gupta

Second Reader

Dr. Zhou

Honors Faculty Advisor

Dr. Newby

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