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.