Hot-dip galvanized steel dip-coated with ureasilicate hybrid in simulated concrete pore solution: Assessment of coating morphology and corrosion protection efficiency

• Electrochemical study of U(230) sol–gel coatings on HDGS in contact with SCPS.
• The thickness of the coating film was found to be in a range between 3 and 15 μm.
• The use of several steps to coat the HDGS does not improve the barrier protection.

The barrier effect and the performance of an organic–inorganic hybrid (OIH) sol–gel coating are highly dependent on the coating deposition method as well as processing conditions. In this work, studies on the influence of experimental parameters using the dip coating method were performed. Factors such as residence time (Rt), a curing step between each dip step and the number of layers of sol–gel OIH films deposited on HDGS to prevent corrosion in highly alkaline environments were studied. These OIH coatings were obtained using a functionalized siloxane, 3-isociantepropyltriethoxysilane that reacted with a diamino-functionalized oligopolymer (Jeffamine® D-230). The barrier efficiency of OIH coatings in simulated concrete pore solutions (SCPS) was assessed in the first moments of contact, by electrochemical impedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings in SCPS was monitored during eight days by macrocell current density. The morphological characterization of the surface was performed by scanning electronic microscopy before and after exposure to SCPS. Glow discharge optical emission spectroscopy was used to obtain quantitative composition profiles to investigate the thickness of the OIH coatings as a function of the number of layers deposited and the influence of the Rt in the coating thickness.