Volta potential of clad AA2024 aluminium after exposure to CeCl3 solution

AA2024 clad with AA1050 was immersed in CeCl3 solution to promote deposition of cerium species. The deposition occurs on the entire sample surface for the alkaline etched substrate, while it is very limited for the degreased substrate. The surface potential (Volta potential) was investigated by scanning Kelvin probe force microscopy after different immersion times in CeCl3 solution. The preferential deposition of Ce compounds at Al-Fe intermetallic sites progressively reduces their Volta potential difference relative to the matrix in the alkaline etched substrate. This reduces the susceptibility to localized attack of the intermetallics as proven by potentiodynamic polarization measurements.