2023ICERD8-C44 -- Electrochemical Testing of Al-3102 Microchannel Heat Exchanger Tube Sheets in Various Corrosive Electrolytes

The objective of this investigation is to assess corrosion tendency of AA 3102 in general and its pitting vulnerability in aqueous corrosive environments containing low and high concentrations of combination of sodium chloride and ammonium sulfate. Pitting potential, passive potential, and corrosion rates are measured using cyclic polarization tests. Electrochemical Impedance Spectroscopy (EIS) analysis was done on the alloy in same corrosive electrolytes. Results indicate AA 3102 alloy is most vulnerable to electrolyte used sea water acetic acid test (SWAAT) that is ASTM G-85 standard test compared to other less aggressive electrolytes used in this research. Electrolyte used in SWAAT test is highly acidic (pH=2.9) and makes it nonrepresentative of natural atmospheres that has created doubts in validity of ASTM G-85 test results. Electrolytes used in this research has pH values ranging from 4.0 to 5.8 that is closer to nearly neutral environments encountered in many atmospheres. AA 3102 corrosion rates in tested electrolytes were ranging from 13.3 to 44.1 mpy as compared to 86.1 mpy for SWAAT electrolyte. EIS results including Rsol, Rpore, and Rct of AA 3102 with very thin arc evaporated porous Zinc film on AA 3102 along with their equivalent circuit is presented.