The study on the corrosion resistance enhancement of cerium-based conversion coatings by adipic acid and phytic acid post-treatment

This study investigates cerium-based conversion coatings enhanced with phytic and adipic acid treatments to improve the corrosion protection of galvanized steel. Optimal coating parameters were identified, including 15 min immersion in a 5 g/L cerium nitrate bath at pH= 3.5. The two-bath phytic acid post-treatment delivered unprecedented corrosion resistance, with an impedance of 11761 Ω.cm2 that markedly exceeds existing literature values. Surface characterization reveals phytic acid forms a more compact, homogeneous coating layer compared to adipic acid. Pull-off tests confirm improved adhesion strength of an epoxy topcoat applied to the phytic acid modified conversion coating. The substantial performance gains quantify the considerable advance this optimized coating system represents for sustainable corrosion inhibition. [Display omitted] •The non-compact and non-uniform layers of Ce-conversion coating were modified by phytic acid post-treatment.•The adhesion strength values increased after the post-treating process with adipic acid and phytic acid.•Ce-conversion coating modified by phytic acid in the two-bath method increased the anti-corrosion performance of the upper layer epoxy coating.