PPA-containing layered double hydroxide (LDH) films for corrosion protection of a magnesium alloy

Abstract In this study, Mg alloys coated with four kinds of MgAl-layered double hydroxide (LDH)-based films with and without PPA were fabricated. PPA, as a small-molecule corrosion inhibitor, can be introduced into the LDH interlayer by virtue of in situ growth and anion exchange methods. Comparisons of the anti-corrosion performance of the LDH films were conducted by means of EIS, potentiodynamic polarization and endurance measurements. The introduction of PPA into LDH films provides more effective corrosion protection on a Mg alloy due to the blocking effect of the LDH film and the corrosion inhibition of PPA. Moreover, the different PPA introduction methods show significant differences in surface morphology, impedance behaviour and durability. Herein, the MgAl-PPA LDH film, which is obtained by introducing PPA in the in situ growth process, displays an excellent anti-corrosion ability due to its stable film structure. Although PPA-containing LDH films obtained via the anion-exchange method initially present a relatively good anti-corrosion performance, their susceptible film structure displays their low durability.