Corrosion behavior of selected Mn+1AXn phases in hot concentrated HCl solution: Effect of A element and MX layer

Reactivity and stability of selected nanolaminated carbides/nitrides (MAX phases) in a concentrated HCl solution are investigated under hydrothermal conditions. The reactivity of the MAX phases strongly depends on the reactivity of A element (Al or Si) with the acid. Al-containing MAX phases suffered severe corrosion, whereas Si-containing Ti3SiC2 survived. For these MAX phases, the reactivity correlates well with the basic structural unit (MX layers). The thicker the MX layers, the less the reactivity is. For carbides, the stability order under hydrothermal condition is TiC > Ti3AlC2 > Ti2AlC. For nitrides, it is TiN > Ti4AlN3 > Ti2AlN. A mechanism is proposed for understanding this interesting phenomenon.

► Hydrothermal acid corrosion of selected MAX phases is investigated.
► The corrosion resistance strongly depends on the nature of A element.
► The corrosion resistance correlates well with the thickness of MX layers.
► The corrosion is initiated by the dissolution of A element.