Corrosion Behavior of Alloyed Cast Iron in Ethylene Glycol-Based Engine Coolants at Elevated Temperature

Abstract

For enhanced engine performance, corrosivity of the engine coolants would play a significant role. In this work, corrosion investigation was performed on cast iron material in pre-mixed engine coolant environment to understand the threshold limits of contaminants. The pre-mixed coolant contained combination of organic additives viz. sebacate (SA), 2-ethylhexonate (2-EH), and tolyltriazole (TTA) with varying concentrations of chloride contaminant. Constant immersion of cast iron samples in engine coolant with different chloride levels at 90 °C was followed by room temperature electrochemical tests. The potentiodynamic polarization tests showed no instability until 100 ppm chloride additions exposed up to 28 days. At lower frequencies in electrochemical impedance spectroscopy (EIS) spectra, inhibition layer characteristics changed from highly capacitive to highly resistive and concurrently a sharp decrease in charge transfer resistance was observed with time for samples exposed to >100 ppm chloride levels. In the longer duration corrosion tests, higher pit depths with increased number density of attacks were observed for cast iron samples exposed to engine coolants containing >100 ppm chloride. For elevated temperature exposures a threshold limit of <200 ppm chloride was established for cast iron samples.

The Crystal Structure of Calcium Sebacate by X-ray Powder Diffraction Data

“…Sodium sebacate is the more widely used derivative in the aqueous environment, being rather soluble (198 g L −1 ). A typical application is as a self-healing promoter in coolant liquid formulation [5,6]. Conversely, calcium sebacate, produced by an ion exchange in calcium-rich environments, shows a much decreased solubility (2 g L −1 ), and thus, its formation and precipitation can be detrimental for the systems where sodium sebacate is used in water-based solutions.…”

Study ability of protection effect of organic acids for multi-metallic anti-corrosion additive system in ethylene glycol-water coolants

“…-Polarization curve: measuring range ± 0.15 V vesus to open circuit potential (OCP); scan rate 0.001 V/s. The corrosion inhibition efficiency (IE) was calculated according to the following formula: (1) where, and are current density (A/cm 2 ) in the absence and presence of inhibitors, respectively.…”