Corrosion inhibition of galvanized steel by thin superhydrophobic phosphonate–siloxane films

• A.S. Sergienko¹, G.V. Redkina¹, A.S. Rozhkov^1,2 and Yu.I. Kuznetsov¹

¹ A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation
² Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation

Abstract: The work suggests an environmentally friendly and efficient method of galvanized steel passivation for protection from atmospheric corrosion, which can serve as an excellent alternative to toxic chromate treatment. In particular, an important advantage of such passivation is the use of aqueous solutions of corrosion inhibitors (or those containing no more than 10% ethanol) to obtain superhydrophobic nanoscale anticorrosion films, which makes it a fire safe method. The method is based on laser and heat treatment of galvanized steel surface followed by layer-by-layer chemisorption of sodium dodecylphosphonate (SDDP) and vinyltrimethoxy¬silane (VTMS) or n-octyltriethoxysilane (OTES). A comparative assessment of the thickness, protective, hydrophobic properties and stability of thin coatings formed by layer-by-layer adsorption of the alkylphosphonate and trialkoxysilanes on the surface of galvanized steel with different morphology was carried out. It was shown that preliminary modification of the galvanized steel surface using laser exposure and heating enhances the protective and hydrophobic properties of the nanoscale phosphonate-siloxane films formed and increases its corrosion resistance in corrosive atmospheres. The polymodal morphology of the galvanized steel surface obtained using a laser promotes strong adsorption of the lower phosphonate layer, which in combination with the barrier properties of the siloxane network in the top layer, provides high protective and hydrophobic properties of phosphonate–siloxane films and their stability in corrosive atmospheres. The most effective method involves the layer-by-layer passivation of laser textured surfaces of galvanized steel with SDDP and OTES, which allows one to obtain stable superhydrophobic coatings with high anticorrosive properties in corrosive atmospheres of high humidity and salt spray.

Keywords: galvanized steel, passivation, corrosion inhibitor, alkylphosphonates, trialkoxysilanes, laser treatment, superhydrophobicity

Int. J. Corros. Scale Inhib., 2022, 11, no. 1, 322-338
doi: 10.17675/2305-6894-2022-11-1-19

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