Sol–gel coatings doped with organosilane and cerium to improve the properties of hot-dip galvanized steel

• Tetraethyl orthosilicate sol was roll coated on hot-dip galvanized steels.
• Organosilane doping eliminated cracks on tetraethyl orthosilicate coating.
• Organosilane doping improved the corrosion resistance of tetraethyl orthosilicate coating.
• The hybrid sol–gel doped with cerium salts exhibited self-healing capability.

An inorganic sol–gel coating and an inorganic/organic hybrid sol–gel coating without and with cerium nitrate were made on hot-dip galvanized steel via a roll coating process. Results showed that the corrosion resistance of the hot-dip galvanized steel was improved with the inorganic coating; however, cracks were present in the coating. Cracks were effectively eliminated and paintability of the sol–gel coating was enhanced while doped with organic precursor. The corrosion resistance and self-healing capability were further enhanced when cerium cation was doped. Finally, the corrosion protection mechanism of the various coatings was discussed in detail.