Discoloration of triphenylmethane dyes in ethylene glycol-water coolant medium

Aluminum (Al) alloys find extensive application in vehicle cooling systems due to their favorable strength balance, lightweight properties, thermal conductivity, and corrosion resistance.The combination of AlF 3 -KF, named flux, is crucial in protecting Al surfaces during brazing processes.Despite the prevalent usage of ethylene glycol-based coolant (EG-coolant) due to its costeffectiveness and stability, concerns arise concerning side reactions affecting corrosion resistance.This study investigates the impact of EG coolant and Alflux on the discoloration of a blue-colored coolant with triphenylmethane (TPM) dye through simulated conditions.UV-Vis spectral analysis reveals the interaction between Al and flux, suggesting their synergistic effect on coolant color changes.The discoloration mechanism of TPM dye in the presence of Al is proposed through NMR analysis.Furthermore, XPS and SEM analysis are employed to observe the corrosion phenomena on the Al surface, tracking the corrosion behaviors concerning the interaction with the coolant.The findings indicate that the addition of Al and flux to the coolant leads to Al corrosion, resulting in the formation of Al(OH) 3 and subsequent chemical interactions, which produce KOH within the coolant.Lastly, we explore methods to manage Al corrosion and alleviate TPM color changes by evaluating the effect of additives on the coolant composition.The current findings offer insights into potential modifications in the composition of Al-flux cooling systems, offering valuable insights into system performance without requiring additional instrumentation.