A new conversion coating process for electrogalvanized (EG) steel based on a cerium nitrate (Ce[NO3]3) solution with some additives has been developed that reduces the total treatment time to 70 s. The corrosion current densities of untreated and treated EG samples have been monitored during exposure to 0.5 N sodium chloride (NaCl) for 7 days using polarization and impedance data. The chemical composition of the coating layer has been determined as a Ce-C-O-Si film layer using scanning Auger microscopy (SAM). The treated EG sample passed the 72-h salt spray test without white rusting. The results of these tests suggest that the newly developed Ce-based conversion coating process is a promising candidate for replacing the conventional chromate treatments used presently for galvanized steel.

Subject
Electrochemical impedance spectroscopy, Zinc rich coatings, Sodium chloride, Impedance, Silanes, Silica, Film formation, Salt spray corrosion testing, Corrosion protection, Corrosion resistance, Polarization, Chemical conversion coatings, Samples
Keywords:
cerium nitrate, conversion coating, electrogalvanized steel
NACE International
2006
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