System Design and Operation: Sulfide-Induced Corrosion

Project Lead: Vivian Merk, Ph.D.
Affiliated Home Campus: Boca Raton
Affiliated Department: Ocean and Mechanical Engineering & Chemistry and Biochemistry
REU Scholar: Gabriela Laboy
REU Scholar Home Institution: University of Puerto Rico Mayaguez

For the last couple of years, in the coast of West Florida, sulfides are becoming more and more common in seawaters due to the Red Tides and the Harmful Microalgal Blooms; these are causing a major corrosion problem in the marine environment and consequently economic losses. Therefore, throughout the summer a Sulfide-Induced Corrosion Research held by Dr. Merk, was partially completed by investigating the fundamental mechanisms of mild steel that was incubated in hydrogen sulfide-amended seawater. Five pieces of steel platelets were incubated in two solutions: one with potable water and 3.5% of NaCl added, which simulates artificial seawater, and another with the same solution, but with 0.010M of sodium sulfide in air added in representation of the sulfide the algae blooms produce. To investigate some of the causes of this corrosion and find a possible solution, these samples that eventually underwent corrosion were tested and analyzed weekly using the following techniques: Light microscopy to identify and document macroscopic color and texture changes in sulfide-corroded steel, Scanning Electron Microscopy (SEM) to study the surface of the steel and the morphological changes, the Atomic Force Microscopy (AFM) for surface topography images that would be down to the nanometer scale, and a software called Gwyddion to analyze the data collected using the AFM. With the SEM corrosion is supposed to appear as a bright white color; iron oxide is a poor conductor of electricity and when the electrons hit the sample, it will charge itself. Also, using the AFM and Gwyddion the change in depth of the sample could be determined. Nevertheless, due to the short amount of time, there was not any corrosion that one could see at plain sight, but there were some microscopical changes throughout the weeks.