Corrosion inhibition of AA6060 by silicate and phosphate in automotive organic additive technology coolants

Coolant corrosion inhibitors are paramount for the durability of automotive heat exchangers. The novel generation of “hybrid coolants” consists of inorganic inhibitors added to an OAT (Organic Additive Technology) backbone. This investigation appraises the corrosion inhibition provided by OAT, phosphate and silicate (separately and combined) on AA6060 exposed to antifreeze coolant at 75 °C. The effects of hard water cations and temperature are also discussed. Linear Polarization Resistance provided a time-resolved assessment of inhibition, and potentiodynamic polarisation extrapolated the corrosion behaviour to more severe scenarios. Supported by SEM-EDX analysis, schematic diagrams of the inhibition mechanisms were elaborated for the coolant systems.