Effect of organosilicon surface polymer nanoscale layers on the corrosion and electrochemical behavior of an Al-Mg-Sc alloy

• M.A. Petrunin, L.B Maksaeva, M.A. Agievich and T.A. Yurasova

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31-4, Leninsky prospect, 119071 Moscow, Russia

Abstract: The electrochemical behavior and atmospheric corrosion of a scandium alloyed aluminum–magnesium alloy were studied. The pitting potential of the Al-Mg-Sc alloy was determined in a chloride-containing electrolyte. Corrosion was examined in two natural atmospheres—urban/industrial and marine. In the urban industrial atmosphere, the alloy underwent uniform corrosion and showed satisfactory resistance: the one-year corrosion rate was 0.151 μm·yr^–1 (151 nm·yr^–1). In the marine atmosphere, conditions for localized corrosion were realized and the alloy experienced atmospheric pitting corrosion. On the unmodified alloy, the surface pit density was 1.5–2.5 defects·cm^–2, while the depth based corrosion index reached 336 nm·yr^–1. To form organosilicon layers, samples were immersed in organosilane compositions solutions; as a result, polymeric siloxane layers were formed on the surface. The layer thickness varied from 29 nm to 0.88 μm. Surface organosilicon polymer layers affected both electrochemical behavior and corrosion. Modification with vinylsilane and with a vinyl/aminosilane mixture shifted the pitting potential by +0.10 and +0.17 V, respectively, indicating inhibition of localized anodic dissolution. The siloxane layers were stable under simultaneous anodic polarization (intense metal dissolution) and exposure to corrosive species: electron microscopy confirmed their presence on the surface after recording anodic polarization curves in a chloride electrolyte. Organosilane modification reduced the atmospheric corrosion rate in natural environments. The layer obtained from the vinyl/aminosilane mixture demonstrated the most effective inhibitive properties: in the urban atmosphere, the uniform corrosion rate decreased to 33.6 nm·yr^–1, while in the marine atmosphere, the pit density decreased to 0.5 defects·cm^–2 and the localized corrosion rate declined to 272 nm·yr^–1.

Keywords: scandium-doped aluminum-magnesium alloy, pitting potential, atmospheric corrosion, full-scale corrosion tests, uniform corrosion, localized corrosion, organosilanes, surface self-organizing organosilicon nanolayers, corrosion inhibition

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 2520-2540
doi: 10.17675/2305-6894-2025-14-4-44

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