The use of cerium and praseodymium mercaptoacetate as thiol-containing inhibitors for AA2024-T3

•Two rare earth organic compounds were investigated as inhibitors for AA2024-T3.•Mode of inhibition was dependent on concentration and immersion time.•Inhibition behaviour varied depending on which lanthanide cation was used.•Film formation similar to other rare earth organic inhibitors but not fully understood.

The susceptibility of the aluminium alloy, AA2024-T3, to localised corrosion as well as the toxicity of chromate inhibitors are both well known facts. In this paper the effect on the corrosion of AA2024-T3 of the thiol-containing mercaptoacetate, when coupled with cerium or praseodymium is examined. Potentiodynamic polarisation and SEM/EDXS were used to analyse the inhibiting behaviour of the compounds cerium mercaptoacetate and praseodymium mercaptoacetate. Both inhibitors were predominantly cathodic inhibitors with increasing anodic inhibition after 24 h of immersion. A mechanism of film formation and corrosion protection was also proposed.