Dip-immersion is simple and cost-effective method for the preparation of
Ce-based conversion coatings (CeCCs), a promising alternative to the toxic
chromate coatings, on the metal substrates. In this work CeCCs were prepared
on Al-alloy AA6060 from aqueous solution of cerium chloride at room
temperature. Effect of immersion time and post-treatment in phosphate
solution on the microstructure and corrosion properties of the coatings was
studied. The longer immersion time, the thicker but nonhomogeneous and
cracked CeCCs. The post-treatment contributed to the sealing of cracks, as
proven by an increase in corrosion resistance compared with as-deposited
coatings. CeCCs prepared at longer deposition time and post-treated showed
much better corrosion protection than those prepared at short deposition
time. A detailed EIS study was undertaken to follow the evolution of
corrosion behaviour of CeCCs with time of exposure to aggressive chloride
environment (3.5 % NaCl). For the sake of comparison, the EIS properties of
bare AA6060 were also investigated. A linear voltammetry was performed to
complete the study. Results confirmed a formation of protective CeCCs on
AA6060 surface. However, even CeCCs prepared at longer deposition time and
post-treated provided a short term protection in aggressive environment, due
to the small thickness.
Effect of Arsenic Alloying on the Microstructure and Corrosion Properties of Mg-Al Alloy
