Date of Award

2002

Degree Type

Thesis

Degree Name

Master of Science in Ocean Engineering

Department

Ocean Engineering

First Advisor

Richard Brown

Abstract

The corrosion behavior of Cr2O3 and TiO2 based surface treatments in 0.5N NaCl solution was investigated. These surface treatments are used for adhesive bonding of SS3 l 6L both to itself, other metals and non-metals. In order to quantify corrosion behavior and determine their ability to passivate in a chloride environment, a poteniodynamic test was employed.

To measure the adhesive strength of bonds using the different surface treatments, a standard test method, ASTM D 1002, was used. This measured the apparent shear strength of single lap joints made by adhesively bonding metals specimens together. A general-purpose epoxy adhesive was used in the experiments.

To investigate the effect of marine exposure, lap joints samples were placed in salt spray apparatus for different exposure periods and the residual shear strength measured. Results indicated that the shear strength of adhesive joints coated with Cr2O3 decreased in strength to a value less than joints treated with TiO2, even though the initial strength was higher.

Adhesive and cohesive failure of joints was noticed. In order to examine the surface conditions of the samples after failure, a scanning electron microscopy (SEM) was employed. The surface treatments did not change the surface features markedly.

It is suggested that the decrease in bond strength for the Cr2O3 treatment was due to crevice corrosion between the SS316 and the adhesive. The TiO2 treatment did not show the same degree of crevice corrosion. The potentiodynamic data supported this theory as the Cr2O3 treatment showed a tendency to localized corrosion while the TiO2 treatment did not.

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