2022 Annual Meeting

Comparing Corrosion Rates of Bio-Graphene Coated Metals Using Electrochemical Analysis and Experimental Weight Loss Testing

Graphene consists of a repeating pattern of hexagonally arranged carbon atoms that form a thin carbon sheet, usually one to five atoms thick. In recent years, graphene has been heavily researched due to its great strength, thinness, and electrical conductivity. In this study, graphene was synthesized onto metal (iron and cobalt) substrates using biochar (from biomass model compounds) as a precursor to test its corrosion-resistant properties.

One way corrosion resistance can be measured is by using an electrochemical cell (E-cell). Micro-galvanic corrosion occurring at the metal surface can be measured when a sample is placed into the E-cell with a 3.5 wt% NaCl electrolyte solution, mimicking seawater. Electrochemical Impedance Spectroscopy (EIS) is then performed using a potentiostat to measure the metal’s corrosion at different voltages. This is a “forced” corrosion method where results are obtained within hours. Linear Polarizing Resistance tests can then be performed to generate a Tafel plot from which the corrosion current density can be extrapolated and used to calculate the metal sample’s corrosion rate in millimeters per year.

A more “traditional” method for testing corrosion resistance is to place the metal samples directly into the electrolyte solution and determine the mass loss of metal with time, which may take days. Using the mass loss data and time immersed, the corrosion rate can be calculated to determine if graphene provides a significant decrease in a metal’s corrosion rate.

Comparing the results of both methods will help determine which technique is more reliable and can be used to report corrosion data. Determining the corrosion rate will provide the consumer with necessary information on its durability and lifespan. In order to test the difference between the two methods of determining corrosion rate, iron and cobalt foil samples are prepared in three different ways: pure metal only, graphene-coated metal obtained by coating one side of the metal with biochar before beginning dissolution in the furnace, and graphene-coated metal obtained by placing a weight on top of the biochar and metal to increase contact between the biochar and metal. Each type of sample is then tested for corrosion in the electrochemical cell or immersed in the electrolyte solution. For each sample, corrosion rates obtained by each method were compared.