Passivation of low-carbon steel with sodium dodecylphosphonate for protection against atmospheric corrosion

• A.S. Sergienko and G.V. Redkina

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

Abstract: The efficiency of passivation of St3 low-carbon steel in an aqueous solution of sodium dodecylphosphonate (C₁₂PNa) for protection against atmospheric corrosion was studied. In particular, the effect of passivation conditions (inhibitor concentration in the passivating solution, temperature of the passivating solution and subsequent drying, and duration of treatment) on the protective properties of films formed in the presence of alkylphosphonate was studied. The paper presents the results of accelerated corrosion tests under neutral salt spray atmosphere and atmosphere of 100% humidity with daily condensation of moisture on the samples, measurements of the water contact angle (Θ_c). It was found that in an aqueous solution of C₁₂PNa an thin hydrophobic layer with Θ_c=97° is formed on the surface of mild steel, which significantly increases its corrosion resistance in atmospheres of different corrosivity. The protective properties of the alkylphosphonate film are enhanced by increasing the temperature of a solution of C₁₂PNa, the duration of treatment and the drying temperature. The use of the layer-by-layer method of producing thin films allows one to increase the efficiency of passivation of St3 steel with C₁₂PNa without increasing its duration. The protective film obtained on the steel surface in a 2.5 mM solution of C₁₂PNa for 120 minutes at a solution temperature and at temperature of subsequent drying equal to 80°C using the layer-by-layer method has the highest anti-corrosion efficiency under atmospheric conditions.

Keywords: steel, corrosion inhibitor, alkylphosphonic acid, dodecylphosphonic acid, passivation, atmospheric corrosion

Int. J. Corros. Scale Inhib., 2024, 13, no. 3, 1866-1876
doi: 10.17675/2305-6894-2024-13-3-30

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