Abstract: A systematic approach was adopted to investigate room temperature and elevated temperature corrosion behavior of typical gray cast iron material in an engine coolant containing proprietary combinations of corrosion inhibitors and varying levels of chlorides. Cast iron samples tested in the coolant mixture containing no inhibitors showed no passivity. However, a large passive range of ~1000 mV above open circuit potential (OCP) was observed up to 500 ppm chloride in inhibited coolants at room temperature. Potentiodynamic polarization studies carried out on cast iron samples exposed to 200 ppm chlorides at 90° C for 14 days showed no passivity. Scanning electron microscopic observations of these samples indicated localized pitting attack resulting from micro-galvanic couples created due to graphite flakes and the iron matrix.
Authors: Gaurav Argade, Anusha Chilukuri, Justin Perry, Corey Trobaugh, Randy Schafer, Erica Raisor, Jacob Steenhoek, and Glenia Pena Lugo
Keywords: Cast iron; Potentiodynamic polarization; Corrosion inhibition; Electrochemical impedance spectroscopy