Evaluating the effect of Si and Mg addition on the corrosion performance of gravity-cast Al-12Ce alloys in NaCl solutions

Abstract

The present investigation assesses the immersion and electrochemical corrosion performance of gravity-cast Al12Ce and Al-12Ce-X alloys (X = 0.4Mg, 4.0Si, and 4.0Si+0.4Mg, all in wt%) targeted for diesel engine applications in 0.1 M and 3.5 wt% NaCl solutions for the first time. The findings revealed that the Al-12Ce-4Si alloy exhibited highest weight loss (+107 %), while Al-12Ce-0.4Mg alloy illustrated the lowest weight loss (-26 %) compared to Al-12Ce alloy in both solutions. With increasing exposure time from 0 to 168 hours, the open circuit potential (OCP) of the alloys increases, being lower in 3.5 wt% NaCl compared to 0.1 M NaCl. Among all the alloys, the Al-12Ce-0.4Mg alloy displayed the lowest double layer capacitance, highest charge transfer resistance, and highest film resistance in both NaCl solutions, indicating its superior corrosion resistance. The current density and electrochemical corrosion rates were the highest for Al-12Ce-4Si alloy and lowest for Al-12Ce-0.4Mg alloy, highlighting the highest corrosion resistance of Al-12Ce-0.4Mg alloy. Corrosion rates of all the alloys were higher in 3.5 wt% NaCl than in aqueous 0.1 M NaCl. Cracking and pitting was most severe in Al-12Ce-4Si alloy and least in Al-12Ce-0.4Mg alloy. The alpha-Al phase adjacent to the CeAlSi2 phase in Al-12Ce-4Si alloy was highly corroded, while the alpha-Al phase adjacent to Al11Ce3 in Al-12Ce-0.4Mg alloy was less corroded.