Influence of buffering on the spontaneous deposition of cerium conversion coatings for corrosion protection of AA2024-T3 aluminum alloy

Cerium-based conversion coatings were spontaneously deposited on AA2024-T3 alloy at 60 °C using buffered and non-buffered CeCl3 solutions in the presence of H2O2. Malonic acid or amino-acetic acid (glycine) was used as buffering additives. The deposition process and the properties of the coatings obtained were followed by linear voltammetry and electrochemical impedance spectroscopy. The surface morphology was studied by scanning electron microscopy. It was found that buffering complicates the conversion process and hampers the deposition rate. The coatings deposited using buffered baths had lower barrier ability and corrosion durability in 3.5 % NaCl corrosive medium compared to those deposited in the absence of buffers.