Development of methods for inhibiting the corrosion of metals and new options for their application: a review. Part II. Hydrophobization of metal surface as a way to inhibit corrosion

• Yu.I. Kuznetsov and A.M. Semiletov

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

Abstract: The present review discusses the hydrophobization of metal (alloy) surface as a means of slowing down or even suppression of its corrosion in an aggressive environment. The stability of thin layers formed by hydrophobic (HP) treatment depends on the nature of the surface to be protected and the HP reagent and solvent, although hydrophobization of the surface from the gas-vapor phase is also possible. The review is limited to consideration of protection with thinner HP coatings than film-forming inhibited oil formulations, conversion and paint coatings. Examples of metal hydrophobization even from aqueous solutions are given and the importance of chemisorption of a passivator, such as sodium oleylsarcosinate (OSS), is noted. The possibility of increasing the HP stability of AMg6 alloy and passive state of its surface by treatment with an aqueous solution of OSS with addition of aminoethylaminopropyl¬trimethoxysilane is shown. Subsequent water washing increases the HP properties of the alloy surface, i.e. the contact angle (Θ_c) increases to 105°, but the influence of the additional barrier created by physically adsorbed layers removed by water washing should not be underestimated. The cases of hydrophobization of aluminum alloys, including anodized ones, by melted stearic acid where the Θ_c value reaches 110–120° are considered. The advantage of two-stage passivation of zinc using a chemisorbing corrosion inhibitor (CI), sodium dodecyl phosphonate with trialkoxysilanes (TAS), was shown. Laser surface texturing gives phosphonate-siloxane films better adhesion and high stability of their HP properties. Treatment of zinc samples even with aqueous solutions of CIs and TAS, when tested in a heat and moisture chamber, allowed to achieve a high value of the edge angle Θ_c=140°, which was maintained at least 130° during 773 h, and the appearance of corrosion signs was observed after 400 h of testing. The passivation of copper and its alloys by ethanolic solutions of carboxylic acids CH₃(CH₂)_nCOOH (n=4, 8, 12, 16) was considered, of which the best protection against corrosion was shown by acids with n=12 and 16. The HP properties of the copper surface improved with the duration of sample passivation, but even C_in=50 mmol/L and 1 min of treatment (τ_pas) are sufficient to provide Θ_c=114°, while at longer duration of passivation the edge angle increased to 136°. The possibility of copper hydrophobization and its protection by triazoles, thiazoles and mixed CIs based on them, as well as alkanethiols, has been shown.

Keywords: corrosion, corrosion inhibitors, adsorption, passivation, hydrophobization

Int. J. Corros. Scale Inhib., 2024, 13, no. 4, 2515-2542
doi: 10.17675/2305-6894-2024-13-4-34

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