Effect of the composition of alkylphosphonic acid solutions and the initial surface morphology on the anticorrosion efficiency of phosphonate–siloxane films formed on zinc

• G.V. Redkina and A.S. Sergienko

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Effect of the solvent nature in solutions of alkylphosphonic acids (C_nPs), as well as the structure of their molecules, namely the alkyl length (n_c), on the protective and hydrophobic properties of films formed upon layer-by-layer passivation together with octyltrimethoxysilane (OTES) on a zinc surface with different morphologies was studied. The paper presents the results of the study by scanning electron microscopy, profilometry, contact angle measurements and accelerated corrosion tests in atmospheres of high humidity and salt spray. It was shown that zinc passivation in ethanol solutions of dodecylphosphonic acid is more effective than in aqueous solutions of its sodium salt, both when they are used individually and upon two-stage passivation together with OTES. The inhibiting properties of C_nPs with n_c=12, 16, 18 in relation to zinc increase with increasing their n_c, including when they are used together with OTES. Preliminary laser treatment of the zinc surface enhances the hydrophobic and protective properties of thin phosphonate–siloxane films formed. Layer-by-layer passivation of laser textured zinc surface at a low scanning speed in ethanol solutions of octadecylphosphonic acid and OTES is most effective for its anticorrosion protection in atmospheres of different corrosivity.

Keywords: zinc, corrosion inhibitor, alkylphosphonic acid, trialkoxysilane, superhydrophobization, laser treatment

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 2265-2281
doi: 10.17675/2305-6894-2023-12-4-44

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