Date of Award

2012-01-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

Arturo Bronson

Abstract

The investigation focused on the corrosion of galvanized steel embedded in soil. The primary objective of the study was to develop a technique for monitoring the corrosion behavior of samples in the field by measuring the potential and current with respect to time (or electrochemical noise). Electrochemical electrodes were designed to simulate the galvanized steel in contact with a thin-film of electrolytes which are usually generated in soils as they collect and drain rain water depending on soil porosity. The exposure of the galvanized steel to thin-film electrolytes consisted of cycling between two days of wetted soil followed by the removing the water and essentially allowing the soil to dry for five days. The cycled exposure of two-day wet/five-day continued for approximately two years.

To further characterize the corrosion behavior of the galvanized steel, their surfaces were also studied with electrochemical impedance spectroscopy (EIS) to determine the effect of diluted chloride solutions. From the EIS, the corrosion rate was acquired when coupled with a potentiokinetic technique, or polarization scan. The corrosion rate for the galvanized steel reached 81 mils/yr at the high chloride content (i.e., 0.1 M NaCl) and 0.0034 mils/year for the low chloride content (i.e., 0.0001 M NaCl). In comparing the corrosion rates available from field bilogarithmic trends and the acquired laboratory studies, the laboratory corrosion rates of 0.0034 and 81 μm/yr at 0.0001 and 0.1 M NaCl, respectively, corresponded to the field corrosion rate of 20 μm/yr at 200 ppm Cl (approximating 0.0002 M Cl).

The current transients acquired from cycled exposure were linked to EIS measurements by using the conductivity of a NaCl solution. Corrosion rates were calculated for galvanized steel embedded in soil from six sites across the state of Texas. The corrosion rates ranged initially from 820 to 14 µm/year to a plateau rate of 9 to 0.1 µm/year depending on the site.

Language

en

Provenance

Received from ProQuest

File Size

90 pages

File Format

application/pdf

Rights Holder

Jesus F. Hinojos

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